Production of 1,000 Gallons of 

Certified Biojet Fuel through 

Biochemical Conversion of 

Softwood Forest Residues

Robert Wooley

J.Y. Zhu

Roland Gleisner

Andrew Hawkins

Paul Starkey

Johnway Gao

United States Department of Agriculture

Forest

Service

Forest Products

Laboratory

General Technical Report

FPL–GTR–278

July

2020

Tom Spink

Joe Ley

Kent Evans

Mike Wolcott

Gevan Marrs

John Sessions

Fermentation via Gevo 

microorganism, 

recovery of iBuOH

Enzymatic 

saccharification

Pretreatment using 

NARA/SPORL process

Procure and process 

feedstock

Convert to biojet via

Gevo technology

Pretreated solids

56% moisture

Samples of

liquid co-product

Biojet

Nearly pure

iBuOH

LIGHTFIELD STUDIOS – stock.adobe.com
July 2020

Wooley, Robert; Zhu, J.Y.; Gleisner, Roland; Hawkins, Andrew; Starkey, 

Paul; Gao, Johnway; Spink, Tom; Ley, Joe; Evans, Kent; Wolcott, Mike; 

Marrs, Gevan; Sessions, John. 2020. Production of 1,000 gallons of 

certified biojet fuel through biochemical conversion of softwood forest 

residues. General Technical Report FPL-GTR-278. Madison, WI: U.S. 

Department of Agriculture, Forest Service, Forest Products Laboratory. 

105 p.

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Abstract

Approximately 1,050 gal of certified biojet fuel was 

produced utilizing feedstocks of softwood forest slash 

from the Pacific Northwest and pulp mill reject material 

from a mill in Washington State, USA. These feedstocks 

were collected and processed by the team of Northwest 

Advanced Renewables Alliance (NARA) using technologies 

developed by NARA partners. This investigation found 

these feedstocks to be economically sustainable.

Keywords: Biojet fuel, forest residue, biorefinery, SPORL, 

enzymatic saccharification and fermentation, iso-butanol, 

iso-paraffinic kerosene
1

Currently Senior Scientist/Engineer, International Paper Company, Memphis, Tennessee, USA

Production of 1,000 Gallons of Certified 

Biojet Fuel through Biochemical Conversion 

of Softwood Forest Residues

Robert Wooley, Manager

Biomass ad infinitum, LLC, Cedar Key, Florida, USA

J.Y. Zhu, Research General Engineer 

Roland Gleisner, Engineering Technician 

USDA Forest Products Laboratory, Madison, Wisconsin, USA

Andrew Hawkins, Director, Laboratory Services

Paul Starkey, Process Engineer

Gevo, Inc., Englewood, Colorado, USA

Johnway Gao,1 Senior Scientist/Senior Research Engineer 

Weyerhaeuser, Seattle, Washington, USA

Tom Spink

Thomas Spink Incorporated, Wilsonville, Oregon, USA 

Joe Ley, Senior Scientist

Kent Evans, Fermentation Team Leader 

Gevo, Inc., Englewood, Colorado, USA 

Mike Wolcott, Regents Professor

Washington State University, Pullman, Washington, USA

Gevan Marrs, Bio-Fuels Feedstocks Consultant 

Gevan Marrs, LLC, Puyallup, Washington, USA

John Sessions, University Distinguished Professor 

Oregon State University, Corvallis, Oregon, USA
Contents

Executive Summary..................................................................................................... 1

Project Objective.......................................................................................................... 1

1. Vetting Potential Toll Facilities................................................................................ 2

2. Feedstock Procurement and Processing................................................................... 4

3. SPORL Pretreatment................................................................................................ 9

4. Enzymatic Hydrolysis............................................................................................ 21

5. Filtration, Concentration, and Storage ................................................................... 28

6. Fermentation .......................................................................................................... 28

7. Product Isobutanol ................................................................................................. 35

8. Saccharification of Cosmo Reject Pulp—Part 1.................................................... 38

9. Saccharification of Cosmo Material—Part 2 and Fermentation............................ 40

10. Production of Biojet from Isobutanol .................................................................. 55

11. Conclusions.......................................................................................................... 59

Literature Cited .......................................................................................................... 60

Appendix A—Daily Historical Summary of the ZeaChem Run ............................... 61

Appendix B—Chemical Analyses Performed at Weyerhaeuser for 

Magnesium-Bisulfite-Pretreated Douglas-fir Forest Residuals................................. 67

Appendix C—Stream Ladder .................................................................................... 72

Appendix D—Daily Historical Summary of the ICM First Campaign—0290 ......... 73

Appendix E—Composition of Cosmo Rejects and Fermentation Residuals............. 82

Appendix F—Daily Historical Summary of the ICM Second Campaign—0310 ..... 85

Appendix G—Final Fuel Certificate of Analysis..................................................... 104

Acronyms

AF aerobic fermenter

API American Process, Inc.

BDT bone-dry ton

CHF combined hydrolysis factor

CIP clean in place

CSKT Confederated Salish and Kootenai Tribes

DO dissolved oxygen

FPL Forest Products Laboratory

GC gas chromatograph

HFM hollow fiber membrane

HPLC high-pressure liquid chromatography

NREL National Renewable Energy Laboratory

RDVF rotary drum vacuum filter

SHR South Hampton Resources

SIP steam in place

SPORL sulfite pretreatment to overcome the

recalcitrance of lignocelluloses

VB viscosity break tank

YC yeast conditioning tank

Conversion table

English unit Conversion factor SI unit

gallon (gal) 3.785412 liter (L)

inch (in.) 2.54 × 101 millimeter (mm)

pound, mass (lb) 4.535924 × 10–1 kilogram (kg)

pound per square inch 

(lbf in–2)

6.894757 kilopascal (kPa)

ton (2,000 lb) 9.071847 × 10–1 metric ton (t)

T°F T°C = (T°F – 32)/1.8 T°C
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

Executive Summary

Approximately 1,050 gal (3,975 L) of certified biojet fuel 

was produced utilizing feedstocks of softwood forest slash 

from the Pacific Northwest and pulp mill reject material 

from a mill in Washington, USA. These feedstocks were 

collected and processed by the team of Northwest Advanced 

Renewals Alliance (NARA) using technologies developed 

by NARA partners. This investigation found these 

feedstocks to be economically sustainable.

This project was sponsored by a US$40 million U.S. 

Department of Agriculture, National Institute of Food 

and Agriculture (USDA–NIFA), Coordinated Agriculture 

Project (CAP). The project had no large capital equipment 

to accomplish such a task, so toll processers across the 

country were investigated to find locations that could 

(1) perform the NARA partners’ technologies, (2) have 

sufficient capacity to handle this large volume, and (3) be 

available for contracting at a fair cost. Some compromises 

were required by NARA because available equipment was 

not necessarily what would be designed for this process and 

due to the fact that there are multiple toll processers located 

at far distant locations.

Forest residues were collected by NARA from 

Weyerhaeuser’s Siuslaw site in Oregon, USA, from 

Muckleshoot Tribal lands in Auburn, Washington, USA, 

and from CSKT Flathead Tribal lands in Lone Pine, 

Montana, USA. All material was brought to Lane Forest 

Products in Junction City, Oregon, USA, where it was 

screened and rechipped. Overall, 272 green tons (GT) of 

material was received and 66 bone-dry tons (BDT) was 

used for further processing.

The pretreatment facility of ZeaChem, Inc., in Boardman, 

Oregon, USA, was selected to perform the pretreatment 

of forest residues using sulfite pretreatment to overcome 

recalcitrance of lignocellulose (SPORL). The SPORL 

technology was developed by the USDA Forest Products 

Laboratory in collaboration with the University of 

Wisconsin–Madison. Most of the SPORL development 

work to date was at the Forest Products Laboratory (a 

NARA partner) in a batch mode; ZeaChem’s process 

was continuous. ZeaChem’s pretreatment equipment was 

supplied by Andritz, Inc. (Canonsburg, Pennsylvania, USA), 

so a short trial at Andritz’s pilot plant in Springfield, Ohio, 

USA, seemed the best way to transition to a continuous 

operation. A two-day trial was conducted to understand the 

conditions that should be used at ZeaChem and to verify 

the kinetic-based reaction severity scale-up factor, the 

combined hydrolysis factor (CHF), developed at the Forest 

Products Laboratory. Various adaptations were required, 

including using Mg(HSO3)2 and H2SO4 to make HSO3

– and 

SO2 in the reactor rather than feeding SO2. Additionally, 

the residence time and reaction temperature were adjusted 

to accommodate the equipment based on CHF. Another 

compromise was to not transport the sugar-containing liquid 

hydrolyzate from the process. This material is low pH and is 

therefore a hazardous material for shipping.

The facility of ICM Biofuels, Inc., in St. Joseph, Missouri, 

USA, was selected to carry out enzymatic saccharification 

of the pretreated woody material from ZeaChem and the 

rejected pulp from the Cosmo Specialty Fibers mill in 

Cosmopolis, Washington, USA. The Cosmo facility uses 

a sulfite pulping process very similar to SPORL, but at 

high sulfite loadings, longer reaction times, and a low 

temperature and uses softwood (hemlock) as their feedstock. 

Cosmo is interested in the possibility of valorization of 

their rejected pulp material through this project. In addition 

to enzymatic saccharification, the resulting sugars were 

fermented to isobutanol at ICM using Gevo’s proprietary 

microorganism (Gevo, Englewood, Colorado, USA).

Enzymatic saccharification of the SPORL-pretreated forest 

residue at ZeaChem and Cosmo materials went well at ICM 

with expected yields. However, issues associated with the 

filtering of residual solids caused sugar loss, and the storage 

of sugars induced sugar contamination led to the production 

of less isobutanol than expected. Approximately 900 gal of 

isobutanol was produced, about half the amount needed to 

make 1,000 gal of jet fuel.

A second campaign was conducted at ICM, this time 

using only Cosmo rejected pulp. Approximately 60 BDT 

of Cosmo material was obtained. Process changes were 

implemented at ICM, such as not filtering the solids 

after saccharification and running low-concentration 

fermentations. As a result, an additional 1,000 gal of 

isobutanol was produced.

The lack of a complete distillation system at ICM for the 

removal of any ethanol in the product limited how much 

water could be removed by distillation as well. Therefore, 

another toll processer (Whitefox) was used to remove the 

water via a membrane process.

Finally, the purified isobutanol was converted to biojet fuel 

in the Gevo design pilot facility owned and operated by 

South Hampton Resources in Silsbee, Texas, USA.

The ASTM-certified (ASTM D7566) biojet fuel was 

blended with Jet A by Alaskan Airlines and flown in their 

regularly scheduled commercial flights AS04 from Seattle 

(SEA) to Washington DC (DCA) on November 14, 2016.

Project Objective

The purpose of this project was to demonstrate that 

conversion technologies developed and researched in the 

NARA project can indeed convert the woody feedstock 

selected by NARA to biojet fuel as a blend stock in fuel for 

commercial airlines. In addition to simply showing that jet 

fuel could be produced, a quantity needed to be produced 

that would allow a commercial airline to fly one of their jets 

on a meaningful flight.
General Technical Report FPL–GTR–278

2

To use the fuel produced by NARA in a commercial flight, 

the process and final fuel needed to be accepted by the 

industry. Gevo accomplished this by being instrumental in 

developing an ASTM certification approved by essentially 

the entire aviation industry (airline manufacturers, engine 

manufacturers, airline operators, and many others) (ASTM 

International 2016). Without this certification process 

in place, commercial flights with this fuel would be 

impossible. In addition to spearheading the certification 

process, Gevo teamed with Alaskan Airlines to fly more 

than one flight using biojet fuel produced from their 

corn-based isobutanol. The certification is for biojet 

from isobutanol in any blend up to 30% with commercial 

aviation fuel. Given this, and in conversations with airline 

representatives, a 20% blend of NARA biojet (5,000 gal 

total) was determined be an appropriate quantity for a 

significant demonstration flight. For example, an airline 

company indicated that a Boeing 737 could be flown from 

Seattle, Washington, USA, to Washington, D.C., USA, with 

approximately 5,000 gal of blended fuel.

Having established that the original amount of fuel, 

1,000 gal, was appropriate, the priorities of making this fuel 

were also established (for example, whether to insist that 

the NARA configuration of their member’s processes be 

followed exactly and that engineering scale-up information 

be developed, or that we produce and collect the various 

by-products envisioned for the commercial process). To 

get everyone associated with this project in agreement on 

boundary conditions, a meeting in Seattle of the various 

technology stakeholders within the NARA project was 

convened in January 2015. Included in the meeting were 

those responsible for all technical aspects of the NARA 

project. Out of that meeting came a list of five guiding 

principles for this project:

1. A quantity of 1,000 gal was chosen to enable a blended 

jet fuel trial by a commercial airline plus useful 

performance, quality, and composition tests.

2. Several key aspects from the NARA project are to be 

utilized in production:

• Feedstock: softwood forest residues from the Northwest 

region of the United States, primarily Douglas-fir and 

hemlock

• Pretreatment: SPORL process as developed by FPL 

using CHF as the scaling-up factor (Zhu et al. 2012)

• Enzymatic saccharification: utilizing commercial 

enzymes from Novozymes and as utilized by 

USDA–FPL and Gevo on this pretreated material

• Isobutanol production: via fermentation using Gevo 

patented organisms and fermentation protocols

• Jet fuel conversion: via Gevo process

3. Efforts will be made to accommodate the production of 

representative co-products, but it will not be a priority.

4. Cost and availability of suitable demonstration scale 

equipment will dominate decisions, so the production 

process conditions adopted are not optimal.

• Efforts will be made to determine representative or 

scalable yields as opportunities present themselves 

(for pretreatment generally). Specifically, when

available, scalable demonstration equipment and 

procedures will support TEA studies (that is, data for

specific scenarios defined by the demonstration will be

available to the TEA).

5. An overall optimized yield from wood to biojet fuel is 

not expected and the overall yield of the trial will be 

considered NARA confidential.

With these guiding principles, then project could be moved 

forward knowing what is important to address or include 

and what is not.

1. Vetting Potential Toll Facilities

Producing 1,000 gal of biojet is a large operation. Even with 

a production facility operating at peak efficiency, it would 

require over 20 BDT of wood feedstock to be processed. 

For this project, we needed to lower yield expectations 

because the equipment being used was the best available 

and not specifically designed for the technologies adopted 

by NARA. In addition, the various processing steps took 

place at multiple physical sites, further reducing the 

efficiency of the operations. Neither the NARA project nor 

the primary developers of the technology generally owned 

or operated facilities for all parts of the process at this scale 

of operation. The exception were the Gevo-built isobutanol 

recovery process at ICM and an isobutanol to biojet fuel 

demonstration plant at South Hampton Resources (SHR, 

Silsbee, Texas, USA). However, the rest of the process was 

not readily available; even the two assets that Gevo built 

were not available for Gevo to operate themselves.

In an effort to determine what (if any) facilities were 

available in the country to handle the needs of this project, 

a comprehensive list of organizations that potentially had 

equipment suitable for this project was developed. A crude 

flowsheet showing the various steps in the process was 

established (Fig. 1.1). Each of these processes likely took 

place at a different location, as opposed to a commercial 

operation where most of or all the operations would be on a 

single site.

Table 1.1 summarizes the possible toll processers identified 

for each of the processing steps. Feedstock procurement 

and processing are each a separate large task within 

NARA. They took on the task of supplying feedstock to the 

pretreatment facility per specification developed with the 

selected toll processer (see Section 2).

Two of the unit operations have several potential toll 

processers. A two-step review was conducted: first, 

examining the suitability of available equipment and 

comparing to the size and needs of the NARA process; 

second, conducting site visits of the short list to better 

understand process equipment available, operating 

characteristics, cost, and availability of the unit to meet 

project needs.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

3

1.1 Pretreatment Toll Processers 

Several possible pretreatment toll processers were quickly 

eliminated. The main factor in eliminating the FPL was 

that it was too small to process the volume needed. The 

National Renewable Energy Laboratory (NREL) pilot plant 

was almost too small, but they and the University of Florida 

pilot plant had not used SO2 (a key reactant in the SPORL 

process), and both informed us that obtaining approval to 

use SO2 would be a long process with an unknown outcome. 

The ICM facility in St. Joseph was also eliminated due to 

concerns about using SO2 in their facility.

This left Cosmo, American Process, Inc. (API, Atlanta, 

Georgia, USA), Andritz, and ZeaChem. Cosmo and API 

routinely handled SO2, whereas Andritz had used SO2 and 

was confident that they could do so. The Andritz facility, 

although essentially the same size as ZeaChem, was limited 

to operating only 8 h per day, 5 days per week. This led to 

their elimination because it would take too long to process 

enough feedstock to meet the requirement of the project. 

It should be pointed out that most of these facilities charge 

by time, so the smaller the throughput the more difficult it 

is for them to be price competitive. Cosmo is a production 

facility, and although they are interested in the possibility 

of someday running a sulfite-based process like SPORL 

commercially, the logistics of separating out one of their 

digesters to use a different feedstock (NARA’s slash grade) 

without risk of contaminating their expensive commercial 

pulp products was too great. In addition, Cosmo was 

probably too large because it would have taken only about 

two digester batches to process all the NARA feedstock. If 

something went wrong with one of these batches, it would 

be a major problem.

The two remaining facilities were visited, and “fitting” 

the NARA process into their equipment was considered. 

API had the advantage of operating with SO2, with the 

facilities and procedures already in place to accommodate 

this. Regarding through-put, they were bigger than Andritz 

but smaller than ZeaChem, and the process could have 

Figure 1.1—General process flow for production of 1,000 gal of NARA biojet fuel.

Fermentation via Gevo 

microorganism, 

recovery of iBuOH

Enzymatic 

saccharification

Pretreatment using 

NARA/SPORL process

Procure and process 

feedstock

Convert to biojet via

Gevo technology

Pretreated solids

56% moisture

Samples of

liquid co-product

Biojet

Nearly pure

iBuOH

Table 1.1—Potential process tollers

Pretreatment Andritz, Inc., Pilot Facility, Springfield, OH

American Process International (API) 

Development Plant, Thomaston, GA

ZeaChem Development Plant, Boardman, OR

Cosmo Specialty Fiber, Cosmopolis, WA

Forest Products Lab (FPL), Madison, WI

ICM Biofuels, Inc., St. Joseph, MO

University of Florida Pilot Plant, Perry, FL

Enzymatic saccharification 

and fermentation

ICM Biofuels, Inc., St. Joseph, MO

American Process International (API) 

Development Plant, Thomaston, GA

NREL Biomass Pilot Plant, Golden, CO

Isobutanol conversion 

to jet

South Hampton Resources (SHR), 

Silsbee, TX
General Technical Report FPL–GTR–278

4

been accomplished in a reasonable amount of time. They 

were more expensive per operating day than ZeaChem and 

did not have the liquid–solid separation system that would 

make moving the product solids to the next location easier. 

There was the option of doing an enzymatic saccharification 

on their site and concentrating the resulting sugars for 

shipment; however, their saccharification reactor was poorly 

agitated and would have required many dilute runs and a 

considerable concentration of the resulting sugars afterword. 

ZeaChem could handle a higher through-put and could 

separate the resulting solids for a wet-cake only product to 

ship to the next step. They did not have prior experience 

in handling SO2, but they were willing to consider design 

modifications to their system for that purpose.

It will be covered in more detail in the section on ZeaChem, 

but the issues of handling and feeding SO2 at ZeaChem 

were eliminated to a large extent by utilizing Mg(HSO3)2

and H2SO4, as demonstrated in initial practice of SPORL 

at FPL (Zhu et al. 2009; Wang et al. 2015), such that SO2

would be generated only within the digester and would not 

need to be purchased and handled on site as a feed chemical. 

The vent of the digester would contain SO2, and that was 

accommodated by converting a vent clean in place (CIP) 

system to a scrubber using a dilute caustic solution.

1.2 Enzymatic Saccharification and 

Fermentation

Several locations could have accomplished these tasks 

if it were not for the need to recover isobutanol from 

the fermentation broth while the fermentation was in 

process to avoid the toxicity of isobutanol to the GEVO 

microorganism. In addition, enzymatic saccharification, 

which produces sugars at conditions nearly optimal for 

fermentation but also avoids contamination (depending 

on the microorganism), should be done only on site with 

fermentation. This minimizes the risk of contamination 

in shipping sugar solution a long distance or storing for 

any length of time. Only the NREL and ICM locations 

had suitable enzyme saccharification and fermentation 

facilities at the same site (API’s enzymatic saccharification 

capabilities were limited). The NREL facility was much 

smaller (2,500-gal saccharification tanks) than ICM 

(35,000-gal saccharification tanks) and did not have 

any way to effectively recover the isobutanol from the 

fermentation broth. ICM houses the Gevo pilot GIFT (Gevo 

Integrated Fermentation Technology) system for isobutanol 

recovery, which could easily be connected to the ICM pilot 

fermentation tanks. For these reasons ICM was the only 

viable option for these steps.

1.3 Conversion of Isobutanol to Biojet

Gevo built a demonstration facility at South Hampton 

Resources in Silsbee, Texas, USA, to convert isobutanol to 

jet fuel in 2011. This process has the capacity to produce 

1,000 gal in a short time and so is the appropriate size 

for this project. Gevo continues to utilize this facility for 

jet fuel and other operations (through contract to South 

Hampton Resources (SHR)). In addition, Gevo is a partner 

in the NARA project and has a vested interest in seeing the 

success of NARA producing biojet fuel from forest residue. 

Therefore, this was a logical choice and maybe the only 

choice to make the final jet fuel. Gevo was willing to work 

with NARA to allow this project time in the facility, which 

would otherwise be used by Gevo. Before Gevo built the 

SHR facility, they looked for other locations that might have 

all the equipment available as a tolling operation. Although 

the unit operations are common in the hydrocarbon 

processing industry, no one had all the units available for 

use together and certainly not in a size appropriate for 

Gevo’s need then or NARA’s now. Most combined units 

are lab or small pilot plant size for feasibility or proof 

of concept testing. That drove Gevo’s initial decision to 

build. NARA was then in a position to capitalize on Gevo’s 

investment.

The geographical locations of all considered toll processers 

are shown in Figure 1.2.

2. Feedstock Procurement and 

Processing

2.1 Feedstock

The feedstock utilized in the NARA project was softwood 

residue material left in the forest after logging operations in 

the Pacific Northwest region of the United States. A separate 

task within the NARA project, managed by Gevan Marrs 

and John Sessions, was responsibility for researching what 

feedstock would be used and where it would be sourced for 

the entire NARA project and specifically for the 1,000 gal 

biojet fuel production. The quantity of material needed for 

this operation was vastly larger than that of the rest of the 

NARA project.

Various mixtures of feedstock had been collected and 

tested in the labs associated with NARA (Weyerhaeuser, 

Catchlight Energy, Washington State University, USDA 

Forest Products Laboratory, Gevo). In the end the feedstock 

mixture FS-10 was chosen as a typical and suitable 

reference feedstock. Therefore, it was determined that a 

“FS-10 like” feedstock would be used for this project. As 

explained below, materials from three locations (designated 

as FS-17, FS-18 and FS-19) were blended into FS-20, which 

was used in the 1,000-gal biojet fuel task through SPORL 

pretreatment. The individual and combined materials are 

compared to FS-10 in Table 2.1.

2.2 Feedstock Sourcing

The largest source of feed material (FS-17) was from 

Weyerhaeuser’s western Oregon Siuslaw 900 site (Lat 43 

50 46 N x Long 123 22 14 W). Forest residues were from a 

45-year-old Douglas-fir stand that had been shovel logged. 

Lane Forest Products used a Peterson 4710B horizontal 
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

5

Whitefox

ZeaChem

Muckleshoot

WI Bioproducts

SEATAC

Cosmo

WY

Lane

CSKT

Gevo

ICM

SHR

Figure 1.2—Various processing sites involved with the NARA 1,000 gal biojet production.

grinder with 3-in./4-in. grates to grind (Fig. 2.1) 317 GT 

(2,000 lb) (approximately 180 BDT, 13 truckloads) of 

Douglas-fir forest residuals in the woods to roughly 

1.5- to 2-in average particle size with 6- to 8-in. maximum 

particles. This material was hauled to the Lane Forest 

Products Yard in Junction City, Oregon, USA.

Two Native American tribes also supplied feedstock. 

The Muckleshoot Tribe, from their lands east of Auburn, 

Washington, USA, supplied material from their Tee-Off 

timber sale (FS-19). The Tee-Off Unit is a 45-year-old 

Douglas-fir stand at about 1,400 ft elevation (Lat 47 11 

21 N, Long 121 56 40 W). Species mix was Douglasfir 95%, western hemlock 2%, red alder 2%, and other 

hardwoods (such as cottonwood) 1%. It was shovel logged. 

Piles (Figs. 2.2, 2.3) were prepared by the logger as part 

of logging operations using the same shovel. The unit 

was logged and piled from January through April 2014. 

Approximately 23 GT of feedstock was collected from the 

Tee-Off site for NARA. Material was ground by Rainier 

Wood Recyclers using a horizontal grinder with 3-in./4-in. 

grates and hauled to Lane Forest Products in Junction City, 

Oregon, USA.

The second tribal source of material (FS-18) was from the 

Confederated Salish and Kootenai Tribes (CSKT) Flathead 

Indian Reservation, near Lone Pine, Montana (T23N R23W, 

sections 14-15-16-23). Their slash piles were primarily 

Douglas-fir tops and residues from log manufacturing 

(Fig. 2.4). The majority of the residues are large diameter 

(Fig. 2.5). CSKT sorted out the larger diameter residues 

from the branches with green needles, which were the 

upper part of the piles (Fig. 2.6) and sides of some piles 

(Fig. 2.7). Grinding was done by John Jump Trucking using 

a Peterson HC 2410 horizontal grinder with 5-in. grates. 

Two truckloads (approximately 38 GT) were hauled to Lane 

Forest Products in Junction City, Oregon, USA.

2.3 Tribal Land Material

The Muckleshoot Tribe material, from their lands east of 

Auburn, Washington, USA, was 5% of the total FS-20 

blend. A similar amount was supplied by the Confederated 

Salish and Kootenai Tribes from the Flathead reservation, 

near Lone Pine, Montana. This was approximately 13.6 tons 

from each site, or 27.2 GT, added to Siuslaw 900 feedstock, 

for a total of approximately 272 GT. Total original Siuslaw 

900 was approximately 317 GT, but some of this was lost in 

pile storage and yard movements.

2.4 Feedstock Processing

Feedstock processing is depicted in Figures 2.8–2.10. The 

material was reground at Lane Forest Products, put through 

a 1.5-in. grate, and then screened with 1-in. top, 1/8-in. 
General Technical Report FPL–GTR–278

6

Table 2.1—Characteristics of NARA feedstocksa

FS-10 FS-20 FS-17 FS-18 FS-19

Chemical composition (wt %)

Total polysaccharides 57.9 59.7 60.4 60.6 64.2

C6 polysaccharides 52.8 52.2 52.0 54.4 59.8

C5 polysaccharides 5.1 7.5 8.3 6.2 4.4

Ash-free lignin, acid insoluble (Klason) 27.0 30.2 29.3 31.2 29.6

Acid-soluble lignin 2.0 3.0 2.95 2.0 1.7

Hot water extractives 6.1 2.43 3.47 6.14 4.57

Ethanol extractives 0.6 0.94 0.74 1.93 1.21

Ash 0.1 0.60 0.47 0.48 0.06

Acetyl 1.8 —b — — —

Total 95.5 96.9 97.3 102.4 101.3

Polysaccharides detail (wt % of total wood)

Glucan (C6) 40.30 39.8 40.67 40.0 45.3

Mannan (C6) 2.39 9.14 8.48 11.2 12.3

Galactan (C6) 0.49 3.22 2.88 3.19 2.23

Xylan (C5) 4.61 6.55 7.49 4.94 3.7

Arabinan (C5) 10.10 0.98 0.84 1.28 0.65

Total 57.89 59.69 60.35 60.61 64.18

Species composition (wt %)

Douglas-fir 64 68 64 97 97

Hemlock 15 5 9 1 1

Cedar 1 1 1 0 0

Pine 1 3 3 0 1

Spruce 3 4 3 1 1

True fir 1 0 1 0 0

Hardwood 15 19 19 1 0

Total 100 100 100 100 100

a

NARA FS-10, Douglas-fir forest residual accepts.

NARA FS-20, 1,000-gallon biojet feedstock blend accepts.

NARA FS-17, Siuslaw 900 Douglas-fir residuals accepts.

NARA FS-18, CSKT Montana Int Douglas-fir and pine FHR accepts.

NARA FS-19, Muckleshoot Enumclaw WA FHR accepts.

b

Not measured.

Figure 2.1—Grinding feedstock at the Weyerhaeuser Siuslaw site.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

7

Figure 2.7—Other side of pile of branches and 

needles.

Figure 2.2—Lower pile on Tee-Off site.

Figure 2.3—Larger residues above road on Tee-Off site.

Figure 2.4—Piles of feedstock at CSKT.

Figure 2.5—Forest residue from log 

manufacturing.

Figure 2.6—Slash piles of branches and needles.

Figure 2.8—FS-17 Weyerhaeuser Siuslaw 

900 site.

Figure 2.9—FS-18 CSKT site.
General Technical Report FPL–GTR–278

8

bottom screen. Oversized materials were reground with a 

1.5-in. screen, and fines were disposed of. This allowed 

stringers as long as 2 in. and some fines greater than 1/8 in. 

to stay in the accepted mix (Figs. 2.11, 2.12).

This was unacceptable for use at ZeaChem, and size 

specification was changed to a 1/4 in. Several different top 

screen sizes (1, 3/4, and 5/8 in.) were tried. All the material 

was ground through a 1.5-in. grate, and part of it was 

screened, but there was still too much oversized material, 

so it was ground through a 1-in. grate. A sample was 

screened, but it did not meet the specification. All fines 

were disposed of.

To produce material for the Andritz trial (using the same 

particle size specification as for ZeaChem), approximately 

7 GT was sent to Forest Concepts (Auburn, Washington, 

USA) to be screened and crumbled to get approximately 

1 BDT to Andritz. Forest Concepts used a “muncher” to 

give a first shot and keep rocks out of the Crumbler (Forest 

Concepts). Next the Crumbler was set at 3/16 in. followed 

finally by the oribital screen with a 3/8-in. round hole 

punched plate top deck and a very small bottom screen 

(about 16 mesh, or approximately 1.5 mm clear opening) 

(Fig. 2.13). The screen oversized materials were batch 

Figure 2.10—FS-19 Muckleshoot Tribal site.

Figure 2.12—NARA FS-20 at Lane Forest Products before 

resizing.

Figure 2.11—FS-20 blended and screened. Figure 2.13—“Crumbled” FS-20 from Forest Concepts.

recycled into the feed material, so that >3/8-in. oversized 

particles got many passes through the Crumbler and a 

chance to be sized as accepts.

This process made an acceptable product to feed to the 

Pressafiner and digester at Andritz or to the digester at 

ZeaChem. However, the size of equipment available at 

Forest Concepts was so small that processing the entire 

FS-20 blend would have been time and cost prohibitive.

An alternative to the Forest Concepts Crumbler process 

was found in a full-scale portable Peterson microchipper 

at Lane Forest Products that could produce an acceptable 

size material. All FS-20 material was run through the 

microchipper and rescreened 3/8-in. top, 3/16-in. bottom. 

This gave approximately 40 BDT of accepts, 40 BDT 

of oversized, and 40 BDT of fines. Because our target 

was to have at least 60 BDT, we microchipped the overs 

and screened using one section of 1/2-in. top and 3/16-in 

bottom, which gave approximately 20 BDT of accepts and 

approximately 15 BDT of overs. Because this would be 

our last opportunity with the microchipper (Lane Forest 

Products had other projects needing the microchipper), 

the 15 BDT of oversized material was run through the 

microchipper again and screened, giving us 65–66 BDT of 
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

9

sized FS-20 accepts. The 1/2-in. top was chosen to make 

sure we had enough accepts. Only one (the middle) 3/8-in. 

top screen section was replaced with a 1/2-in. screen (3/8 to 

1/2 to 3/8 in.).

Thus, starting with approximately 272 GT, we ended with 

approximately 108 GT of accepts, or approximately 66 BDT 

plus a small pile of oversized material (15 GT).

3. SPORL Pretreatment

3.1 Overview

The NARA team decided to use SPORL pretreatment (Zhu 

et al. 2009) at the ZeaChem Boardman, Oregon, USA, 

facility. As explained earlier, this facility had a large enough 

throughput, a reasonable tolling cost, and limited residence 

time in the reactor to no greater than 45 min. The SPORL 

process is versatile, operating over a range of residence 

time. The resident time and temperature can be scaled using 

a CHF (Zhu et al. 2012; Zhou et al. 2013); for example, 

a short residence time can be compensated by a higher 

temperature, although a higher temperature might cause 

more degradation of the solubilized sugars. For this work, 

the decision was made to forego use of the majority of the 

pretreatment liquid hydrolyzate for at least three reasons: 

(1) the pretreatment liquid hydrolyzate would be low pH 

and therefore a hazard and cost prohibitive for shipping 

half way across the country; (2) the liquid hydrolyzate 

could potentially be high in fermentation inhibitors for 

pretreatment at high temperatures; and (3) the sugar yield 

loss could be made up for with additional pretreated solids. 

Because the solids were not washed but only filter pressed, 

only the portion of hydrolyzate squeezable from the solids 

was lost with some of the liquid retained in the solids.

To be able to use the ZeaChem facility, we had to come 

up with an alternative method of making the pretreatment 

liquor. Normally in a commercial sulfite pulping process, 

SO2 is mixed with water slurry of CaO (or MgO). These 

will react to form Ca++ (or Mg++) and HSO3

–

, and/or SO3

2–

depending on pH. An excess of SO2 is added so that there 

will be free SO2 in solution. At ZeaChem, this would require 

the purchase and handling of SO2. Because ZeaChem was 

not already set up to handle and purchase SO2, it would 

be complicated and expensive. The alternative was to 

purchase a solution of Mg(HSO3)2, mix that with the wood 

and then add H2SO4 in the reactor to adjust the pH of the 

sulfite solution (Zhu et al. 2009; Wang et al. 2015). This 

resulted in a solution containing Mg++, SO2, and HSO3

–

 at 

pH of approximately 2. When the pH is finally adjusted 

to the targeted pH of 2.0 with H2SO4 the proper amount 

of free SO2 will be present in solution. SO2 concentration 

in a bisulfite (HSO3

–

) solution is an equilibrium reaction 

driven by pH (Fig. 3.1). The SO2 is formed only in the 

digester, so none had to be purchased. However, there would 

be SO2 in the vent. ZeaChem added a caustic scrubber to 

accommodate removing SO2.

One of the benefits of selecting ZeaChem was that the 

manufacturer of their equipment, Andritz, had a large-scale 

demonstration unit with which we could conduct a short 

test. This is the Andritz Springfield, Ohio, USA, test facility 

that we initially considered as the location for our whole 

production. They were too small for our 1,000-gal biojet 

production, but were an excellent place to do a short test 

to determine if the continuous, shorter time would work 

the same as the longer batch times typically conducted in 

the lab.

3.2 Andritz Piloting

The digester unit available at Andritz was exactly the same 

design as that at ZeaChem, but there were some differences 

in the impregnation system and the maximum pressure at 

which it can operate (Andritz was lower). ZeaChem had a 

lock hopper plus an inclined steam mixing conveyor to mix 

the chemicals and the heating steam with the wood. The 

Andritz unit had a screw press feeder to push the feedstock 

into the digester “T” mixing section, where chemicals 

and steam are added. To simulate the ZeaChem’s steam 

mixing conveyer, Andritz suggested that we use their 560 

Pressafiner (Fig. 3.2) to mix Mg(HSO3)2 solution with the 

wood before feeding to the digester (Fig. 3.3). This was 

a separate unit and open to the room. If we mixed only 

the Mg(HSO3)2, there would be no SO2 formation. 

We then used the digester’s screw feeder to feed the 

100

80

60

40

20

0

0 2 4 6

pH

8 10

Mole percentage

HSO3

– SO3 SO 2– 2

Figure 3.1—Calculated equilibrium concentration of SO2

at 25 °C as a function of pH in a bisulfite/sulfite solution 

for scale-up SPORL using the equipment at ZeaChem. 

Although using a mixture of Mg(HSO3)2 and H2SO4 had been 

practiced at FPL extensively (Zhu et al. 2009; Wang et al. 

2015) and proven robust for pretreating softwood forest 

residue, these SPORL experiments had been run only at 

lab scale at batch mode. Because ZeaChem’s facility is 

continuous, with fixed residence time of 45 min, a higher 

temperature had to be used. A combined hydrolysis factor 

(CHF), a kinetic-based reaction severity factor developed 

by FPL (Zhu et al. 2012; Zhou et al. 2013, 2014; Zhang et al. 

2014), was used to design the desired reaction temperature 

to achieve good pretreatment. The design conditions had 

been tested at pilot scale (Zhu et al. 2015).
General Technical Report FPL–GTR–278

10

wood/Mg(HSO3)2 mixture to the “T” piece contained H2SO4

to make SO2, along with the addition of steam for heating.

Another difference between the pilot operations at Andritz 

and a full-scale operation at ZeaChem was the size and 

character of the wood chips. Large digesters that can 

accommodate hundreds of tons per day of feedstock can 

be designed to handle larger chips than a 10-BDT/day 

unit. ZeaChem wanted a “chip” that was approximately 

1/4 by 1/4 by 1.5 in., so the feedstock processing group 

ground the forest residue material collected to the desired 

specification (see Section 2, Feedstock Procurement and 

Processing). Two alternatives were used to produce properly 

sized material. One was to use a Forest Concepts Crumbler, 

which resulted in the desired material for the run at Andritz 

(Fig. 3.4). However, the lab or pilot unit at Forest Concepts 

was too small to accommodate the large quantity of material 

that would be needed for the run at ZeaChem. Another 

process called a microchipper was developed at Lane Forest 

Products, Junction City, Oregon, USA. Lane Forest Products 

was handling the sorting and screening of the material as 

Figure 3.2—560 Pressafiner at Andritz.

Figure 3.3—Continuous digester at 

Andritz.

Figure 3.5—Feedstock prepared with Forest Concepts 

Crumbler.

Figure 3.4—Crumbler feedstock 

at Andritz.

received from the forest, so they were a logical location to 

process it further to small chips. The final feedstock was 

designated as FS-20 (Figs. 3.4, 3.5).

An experimental plan was worked out among the Andritz 

engineers, FPL scientists (FPL being the inventor of the 

SPORL process), and other NARA team members. The 

tests needed to be conducted within two days so as to 

make optimal use of resources. The first day focused on 

processing the wood through the Pressafiner to mix in the 

Mg(HSO3)2 solution: the second day focused on processing 

that material through the digester while adding H2SO4

and steam. The desired SPORL reaction temperature 

and time were calculated based on the scaling-up CHF 

of approximately 22.5, or lab-optimal condition of Top = 

165 °C for top = 75 min for similar feedstock (Leu et al. 

2013) using the following equation (Zhu et al. 2015) with 

activation energy E = 100,000 (J/mole). This resulted in a 

residence time of 45 min for reaction pressure of 130 psig 

(pounds per square inch gauge) or temperature 173 °C. 

Mg(HSO3)2 and H2SO4 loadings on wood were 12 and 

2.2 wt%, respectively (Leu et al. 2013).
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

11

(3.1)

(3.2)

where α, β, γ are the adjustable parameters; CA, CB are the 

molar concentration of the reaction chemicals (i.e., H2SO4, 

and Mg(HSO3)2), Top and top are optimal temperature and 

time based on laboratory study, and Tup and tup are desired 

temperature and time for the scale-up run.

The Andritz unit was limited to a maximum pressure of 

approximately 125 psig. The pressure limits the maximum 

temperature at which that the reactor could be run. So, the 

experimental conditions listed in Table 3.1 were design for 

the trial runs at Andritz.

Each test was designed to be about 1.5 h, which was at least 

two residence times. The lower residence time was included 

because the ZeaChem unit has a higher throughput with 

shorter residence time. The tolling fees at ZeaChem were 

based on the length of running time, so a shorter residence 

time could reduce tolling fee charge.

Highlights of the Andritz runs included the following:

1. The pressure in the digester was limited to 113–115 psig, 

even though they thought they could hold a higher 

pressure and their steam supply was 150 psig. This 

limited the temperature at which the digester could be 

operated. There was no temperature gauge in the digester 

because normally the Andritz facility was operated with 

mainly steam, so the temperature could be determined 

from the pressure of the digester. Back calculating the 

pressure contribution of the SO2 in the system, 115 psig 

would be 170 °C, so runs at the higher temperature of 

173 °C were not possible.

2. It was not possible to make three runs in an 8-h day as 

planned. Because we were limited in temperature, only 

two runs at the residence times of 35 and 45 min were 

carried out.

3. The material from the 45-min run had the appearance 

(dark color) of being considerably more digested 

than that from the 35-min run. Saccharification and 

fermentation testing (below) at Gevo would confirm the 

digestion.

4. There was also a desire to evaluate how easily the 

pretreated material could be dewatered. Although 

ZeaChem had a filter press, Andritz had only the 

Pressafiner; but Andritz thought the Pressafiner would 

give an indication of the ease of filtration. The 45-min 

material was too fine to attempt in the Pressafiner. 

The feeding of the 35-min material failed. Therefore, 

no information was obtained regarding filtering the 

pretreated material at Andritz.

) g g q() gy 

(J/mole). This resulted in a residence time of 45 min for reaction pressure of 130 

 per square inch gauge) or temperature 173 °C. Mg(HSO3)2 and H2SO4 loadings on 

2 and 2.2 wt%, respectively (Leu et al. 2013).

( ) CHF ( ) E RT C C A B

A B e C Ct α βγ − ++ = + (3.1)

up ( )( up op ) op T T ER T T 1 1

te t − = (3.2)

are the adjustable parameters; CA, CB are the molar concentration of the reaction 

e., H2SO4, and Mg(HSO3)2), Top and top are optimal temperature and time based on 

udy, and Tup and tup are desired temperature and time for the scale-up run.

Leu et al. 2013) using the following equation (Zhu et al. 2015) with activation energy 

0 (J/mole). This resulted in a residence time of 45 min for reaction pressure of 130 

s per square inch gauge) or temperature 173 °C. Mg(HSO3)2 and H2SO4 loadings on 

12 and 2.2 wt%, respectively (Leu et al. 2013).

( ) CHF ( ) E RT C C A B

A B e C Ct α βγ − ++ = + (3.1)

up ( )( up op ) op T T ER T T 1 1

te t − = (3.2)

γ are the adjustable parameters; CA, CB are the molar concentration of the reaction 

i.e., H2SO4, and Mg(HSO3)2), Top and top are optimal temperature and time based on 

tudy, and Tup and tup are desired temperature and time for the scale-up run.

Table 3.1—Designed test conditions at Andritz

SPORL 45 min 40 min 35 min

170 °C (~115 psig) x x x

173 °C (~130 psig)a x x x

a

Or maximum pressure, e.g., 173 °C is ~125 psig. 

psig, lb/in2 (gauge).

Andritz supplied a supplemental report (Codner and Joshua 

2015) providing the detailed material balance for the 560 

Pressafiner operations. They briefly mentioned the second 

day operation through the 418 System (their digester).

Gevo conducted enzymatic hydrolysis and fermentation 

tests on the two sets of materials that we produced at 

Andritz. The material from the run with 45-min residence 

time gave results similar to those obtained earlier from 

pretreated material made at FPL in a batch system. The 

35-min material appeared to be under-pretreated, as 

expected.

3.3 ZeaChem Runs

A demonstration plant built by ZeaChem to process 

plantation-grown and harvested hardwood using a 

dilute acid technology was used to conduct the SPORL 

pretreatment of the NARA-collected softwood forest 

residuals. The plant has a nominal capacity of approximately 

10 BDT/day at the maximum digester residence time of 

45 min.

To produce 1,000 gal of biojet fuel, it was estimated that 

approximately 75 BDT of forest residuals would need to 

be processed, given the designed inefficiencies inherent in 

using equipment not optimized for this process and in using 

toll processers that are located at multiple sites. To that 

end, approximately 71.6 BDT of feedstock (Table 3.2) was 

processed at ZeaChem, producing approximately 52 BDT of 

processed solids that were sent to ICM. Section 2, Feedstock 

Procurement and Processing, indicated that approximately 

66 BDT of process material meeting the specifications 

of ZeaChem were prepared. It also mentioned that an 

additional 15 BDT of oversized materials were available. 

Approximately 7 BDT of those oversized materials were 

utilized as the last material used at ZeaChem, without issue. 

Five different “runs” were made at ZeaChem (Table 3.3). 

Based on original material balance estimates, this amount of 

feedstock would produce 1,000 gal or more of biojet fuel.

The ZeaChem process (Fig. 3.6) was slightly modified. 

An additional line was added to feed Mg(HSO3)2 solution 

along with a dilute solution of H2SO4 to the digester just 

about where the solids were fed. The Mg(HSO3)2 feed tank 

was one of their existing large liquid hydrolyzate tanks. 

A 30% Mg(HSO3)2 solution was purchased in 300-gal 

totes and loaded into the storage tank with an appropriate 

amount of dilution water before starting up. The second 

modification to the ZeaChem process was to scrub the 
General Technical Report FPL–GTR–278

12

Table 3.2—NARA feedstock received at ZeaChem, 

Boardman Demonstration Plant

Date

Weight 

delivered 

(lb)

Weight 

delivered 

(ton)

Moisture 

(%)

Weight 

(BDT)a

8/14/2015 49,040 24.5 26.7 18.0

8/17/2015 51,300 25.6 31.9 17.5

8/24/2015 50,520 25.3 26.6 18.5

8/31/2015 16,200 8.1 28.2 5.8

8/31/2015 26,960 13.5 12.5 11.8

Total 194,020 97.0 71.6

a

BDT, bone dry ton.

Table 3.3—Hydrolysis cake generated at 

ZeaChem, Boardman Demonstration Plant

Run No. sacks

Weight (wet) 

(lb)

Weight (dry) 

(BDT)a

NR01 27 12,860 2.5

NR03 68 57,340 11.2

NR04 96 76,720 17.0

NR05 35 29,900 7.2

NR06 44 40,150 9.6

Total 270 216,970 47.5

a

Based on an average 39% for NR01 and about half of NR03; 

the rest averaged 48% solids content.

Inline

mixer

Lock

hopper

feed

NP 

steam

3× steam

for blow

Steam mixing 

conveyor 

(SMC)

Pretreatment reactor 

(PTR)

Feed

hopper

Wood chips

Live

bottom

bin

H2SO4

Mg(HSO3)2

solution

LP 

steam

Blow

line

Figure 3.6—Flow arrangement at ZeaChem.

blow tank vent of SO2 gas that evolved when the digester 

pressure was reduced through the blow tank. To accomplish 

this, a continuously recirculating stream of dilute caustic 

was added through the CIP system of the vent condenser. 

This spray of caustic into the vent stream was effective in 

reacting with and removing the venting SO2.

Laboratory SPORL runs with batch digestions (Zhu et al. 

2009; Wang et al. 2015) had no “blow” or rapid reduction 

in reactor pressure that tends to explode the pretreated solid 

material. Therefore, it was necessary to run the pretreated 

material through a disk refiner to further reduce the particle 

size in lab batch operation. Initially the disk refiner was 

used at ZeaChem to further reduce the size of the material as 

carried out at the Andritz trial. Because the ZeaChem system 

was equipped with a significant “blow” or rapid pressure 

reduction that the pretreated material is subjected to, it was 

concluded that disk refining might not be necessary.

The NARA-prepared forest residual feedstock, designated 

as FS-20 (Fig. 3.7), was delivered by a self-unloading 

tractor–trailer from Junction City, Oregon, USA (Fig. 3.8). 

The NARA team had prepared the feedstock at Lane 

Forest Products using a microchipper, which produced 

material with essentially the same size characteristics as the 

Crumbled-produced chips used at Andritz.

Two quick tests ultimately determined whether the 

pretreatment was being conducted properly. First was the 

compositional analysis showing unsolubilized cellulose. 

It is desirable to preserve as much of the starting cellulose 

as possible because the majority of the glucose solubilized 

in pretreatment is lost when the liquid is removed. 

Second was the digestibility of the pretreated solids, that 

is, the amount of unsolubilized cellulose that could be 

converted into fermentable glucose through enzymatic 

saccharification. Both tests were difficult and require several 

days to complete. However, the FPL developed a “quick 

saccharification” test that gave a relative indication of the 

digestibility of solids within a few hours. With the reference 

materials of the two runs at Andritz, we would be able to 

determine if the ZeaChem material was more similar to the 

good run (45-min run) at Andritz or to the poor run (35-min 

run) at Andritz (Table 3.1).
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

13

Based on the Andritz trial runs, the initial conditions for 

Mg(HSO3)2 loading were 12% bisulfite to wood, H2SO4 was 

0.35% v/v, L:S was 4.0 (including all liquid with feedstock 

and condensed steam), temperature was set to 175 °C, and 

an expected pressure of 132 psig (steam pressure alone at 

175 °C is 114.7 psig, overpressure is due to dissolved SO2).

3.3.1 Operation at ZeaChem

After various initial delays (such as Mg(HSO3)2 not 

delivered on time, issues with three pumps, agitator “key” 

found in flushing out blow tank), the process was started 

very early in the morning of August 19, 2015. The running 

temperature was 175 °C, but the pressure was at only 

119–120 psig, which was below the expected pressure of 

130 psig, accounting for the partial pressure of the SO2

generated from the levels of Mg(HSO3)2 and H2SO4 added. 

The pretreated material was lighter in color than either of 

the runs at Andritz. Furthermore, the quick saccharification 

test resulted in a concentration of only 4.13 g/L glucose 

after 6-h saccharification, or approximately 45% glucan 

conversion in enzymatic hydrolysis, compared with the 

result from the 45-min run at Andritz (Table 3.4). The 

system was not pretreating the feedstock properly. The 

results were also poorer than the 35-min run (6.31 g/L) 

at Andritz (Table 3.4), even though the amount of sulfur 

making its way to the vent condenser was about what 

would have been expected for the design amount of SO2

in the vent. We quickly identified that the most probable 

cause of poor pretreatment was loss of SO2 throughout the 

continuous reactor, especially at the discharge.

At this point we encountered more operational difficulties, 

such as hot slurry being fed to the filter press even though 

interlocks should have prevented this. As a result, one of the 

filter frames was destroyed, as was part of the filter cloth; 

this allowed solids to enter the liquid filtrate tank, where 

they had to be laboriously cleaned.

H2SO4 loading was increased to increase SO2 concentration. 

Additional acid lowered the pH and increased the amount 

of SO2 (Fig. 3.1), which was verified by the pressure in the 

system. Pressure was approximately 15 lb/in2 higher than 

just pure steam at process temperature. We also increased 

the amount of liquid being added. The feedstock was only 

about 27% water, compared with an estimated value of 50%, 

so the resulting L:W in the digester was very low. Increasing 

the system temperature should also help the digestion as 

expected based on the scale-up design CHF (Eq. (3.1)) (Zhu 

et al. 2012), so temperature was increased to 180 °C and 

then 185 °C from the initial 175 °C.

With temperature increased to 185 °C, the SO2 overpressure 

was slightly increased. We also achieved a L:W ratio 

of about 5 by increasing the water flowing in with the 

chemicals (diluted the Mg(HSO3)2). However, the system 

was shut down on August 20 due to a blow line plug.

The system down time provided the opportunity to 

determine the cause of SO2 loss, which had been identified 

as the cause of poor pretreatment. We began investigating 

how the steam was entering the system. Because of the 

small size of the ZeaChem unit (smaller than a production 

unit), the blow line was designed based more on being large 

enough to avoid plugging and availability of standard pipe 

sizes than on desired pressure drop for the designed flows. 

A higher steam flow than required for the thermal heating 

Table 3.4—Results of FPL “quick” saccharification 

test on Andritz trial material (as reference)

Enzymatic hydrolysis time 

(h)

Glucose by YSI analyzera at 

two digester residence times

(g/L)

35 min 45 min

0 0.06 0.06

1 2.43 3.06

2 3.66 4.95

4 5.41 7.51

6 6.31 8.73

8 6.96 9.58

a

YSI 2700 Biochemistry Analyzer, YSI Inc., Yellow Springs, OH.

Figure 3.8—NARA feedstock at ZeaChem.

Figure 3.7—ZeaChem-accepted feedstock.
General Technical Report FPL–GTR–278

14

of the system was needed to avoid frequent plugging. As 

much as 1,500 lb/h of excess steam was swept through the 

reactor to maintain the pressure drop through the exit blow 

line, compared with less than 500 lb/h needed to maintain 

the temperature of the system. We calculated that as much 

as 150 lb/h of SO2 could be removed from the system 

with that much steam sweeping through the digester. The 

required flow of SO2 through the system was only about 

20 lb/h. Consequently, most of the SO2 being generated was 

not remaining in the solution but was being stripped out by 

the excess steam. This large steam flow through the blow 

line is needed to operate the ZeaChem reactor. However, 

this steam flow does not need to sweep through the entire 

reactor and can be added just before the discharge. One of 

the lead operators conveyed that they had operated this way 

at various times (Fig. 3.9).

The change was made to have the excess “blow” steam for 

blow (Fig. 3.9) added at the digester discharge. We were 

able to maintain 158 psig at 185 °C. This is about a 

10 lb/in2 over the pure steam pressure but was still lower 

than we would expect due to SO2 loss by the steam for 

heating the reactor (Fig. 3.9). After these changes, the 

enzymatic test results for the pretreated solid was now 

similar to those between the 35-min and 45-min runs at 

Andritz, a definite improvement.

From this point forward, various stops and starts occurred 

due to mechanical and other issues (for example, Fig. 3.10 

shows material that collected in a progressive cavity pump 

and in the blow-line). However, in general, the system 

continued to run fine and produce material that was 

digestible (Table 3.5). The historical summary of the run 

is provided in Appendix A. When the process was running 

or shut down can be ascertained from Figure 3.11. When 

Inline

mixer

Lock

hopper

feed

NP 

steam

Steam for 

heating

Steam mixing 

conveyor 

(SMC)

Pretreatment reactor 

(PTR)

Feed

hopper

Wood chips

Live

bottom

bin

H2SO4

Mg(HSO3)2

solution

LP 

steam

Blow

3× steam for blow line

Figure 3.9—Modified steam flow arrangement.

Figure 3.10—Material from pump and blow line.

the line was flat, the process was shut down; when it was 

increasing, the process was running. The slope of feedstock 

usage was the feed rate of the system. From about 9/4/2015 

until 9/15/2015, the plant was shut down for repairs; from 

9/18/2015 to 9/21/2015, the plant was again experiencing 

mechanical issues but finally came up on the 9/21/2015 

and ran the rest of the feed material, completing the run on 

9/24/2015.

3.3.2 Run Designations

During the course of the ZeaChem operation, different 

“runs” were identified. Generally, each time a major process 

change was made, the run designation was changed. The 

bags of product solids were marked as to the run number, 

the sequential filter press dump (the filter press is a batch 

process and a single discharge cycle would be several 

bags full), and the sequential bag within that dump. Such 

as NR01-2C would be run 01, filter press dump 2, and 

bag C, or the third bag filled from that dump. The runs are 
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

15

Table 3.5—ZeaChem run designations

Run Start time Stop time Description

NR01 8/18/2015 3:30 AM 8/21/2015 7:40 PM Steam feeding to inlet of digester stripping SO2

NR03 8/22/2015 3:00 AM 8/24/2015 11:59 PM Excess steam moved to discharge of digester

NR04 8/25/2015 00:01AM 9/3/2015 10:15 PM Refiner off (off for remaining two “runs” as well)

NR05 9/3/2015 10:27 PM 9/17/2015 8:10 PM Lower Mg(HSO3)2 to match unexpected lower wood flow

NR06 9/21/2015 1:30 PM 9/23/2015 5:40 PM Switched to a coarser wood chip

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

8/14/15 8/19/15 8/24/15 8/29/15 9/3/15 9/8/15 9/13/15 9/18/15 9/23/15 9/28/15

Accumulated feed (lb)

Figure 3.11—ZeaChem accumulated wood feed.

as shown in Table 3.6 (there was never a NR02 run, we 

skipped from 01 to 03).

3.3.3 Pretreatment Yields

ZeaChem conducted an 8-h material balance study on liquid 

accumulating in the blow tank. This gave a reasonable 

accounting for the yield of glucose and xylose in the 

pretreatment hydrolyzate stream (Table 3.7). ZeaChem 

did not analyze mannose for this analysis, so we have no 

accounting of how much mannose was solubilized. By 

ZeaChem analysis, 8% of the feedstock glucose and greater 

than 100% of all the xylose was solubilized. It was not 

possible to utilize the pretreatment hydrolyzate that was 

pressed out of the pretreated solids through dewatering 

due to hazardous shipping required with the multiple 

tolling sites for the present project. The sugar stream in the 

pressed-out portion of pretreatment hydrolyzate was lost 

to the production of isobutanol but will be reclaimed in a 

commercial operation.

3.3.4. Solids Yields

The overall solids yield from the run can be determined 

from the total amount of feed and total amount of waterinsoluble solids. A few bags were analyzed at ZeaChem 

for moisture (Fig. 3.12). Many bags were analyzed for 

solids composition by NARA partner Weyerhaeuser. Those 

analyses are presented in Appendix B. The most difficult 

aspect of assessing yield was accurate determination of 

moisture content of both feedstock and pressed product. 

The feedstock was held in a pile in the open air in the very 

dry climate of eastern Oregon and was continuously losing 

moisture, so we added water by running a hose into the feed 

drag line. This moisturized material was weighed.

In general, early bags averaged about 39% consistency, or 

61% moisture of filter-pressed product, whereas later bags 

were about 48% consistency, or 52% moisture.

Using the moisture data from analyses and interpolating for 

the bags that were not analyzed, we estimated the overall 

yield. In summary, 47.5 BDT of solids were produced 

from 71.6 BDT of feedstock, or an overall solids yield of 

66%. This solids yield is higher than typical laboratory 

washed solids yield of 62.6% from equivalent feedstock 

(Leu et al. 2013). These were not quite washed solids, but 

rather were pressed solids with a substantial amount of 

the dissolved solids gone with the filtrate, so a significant 
General Technical Report FPL–GTR–278

16

Table 3.6—Summary of enzymatic saccharification quick assaya

YSI glucose (g/L)

Sample 0 h 1 h 2 h 4 h 6 h 6.5 h 8 h 16.5 h 17 h 24 h 48 h 72 h 94 h 115 h

Andritz 

35 min

0.06 2.43 3.66 5.41 6.31 6.96 9.46 10.10 10.40

Andritz 

45 min

0.06 3.06 4.95 7.51 8.73 9.58 12.80 13.30 13.50

NR01-FP1 0.12 1.65 2.52 3.53 4.13 6.24 6.68 6.92

NR01-FP3 0.09 1.73 2.65 5.79 6.26 6.64 7.11

NR01-FP3 

2X enzy

2.70 4.40 4.66 7.32 7.91

NR03-FP1 0.16 2.59 4.30 6.48 7.67 10.90 11.80

NR03 FP2 0.21 2.52 4.25 6.52 11.60 12.40

NR03 FP5 0.29 2.38 4.17 6.59 8.13 13.20

NR03 FP6 0.30 2.47 4.20 6.45 8.19 13.50

NR03 FP6 

2X enzy

4.39 7.49 10.60 12.00 14.10

NR03 FP8 0.51 2.66 4.52 11.30 14.10 16.20

NR03 FP9 2.43 4.76 6.99

NR04 FP4 0.20 2.61 4.51 11.70 13.50 15.40

NR04 FP6 0.23 2.68 4.71 12.50 14.80 15.60

NR04 FP8 0.29 2.58 4.69 12.10 14.30 15.30

NR04 FP10 0.24 2.29 4.18 11.50 13.70 15.00

NR04 FP12 0.28 2.66 5.15 13.50 14.20

NR04 FP14 0.32 2.22 4.53 13.60 14.70

NR04 FP16 0.25 2.40 4.59 13.60 14.80

NR04 FP18 0.21 2.51 4.57 7.23 9.35 13.10 14.00 14.20

NR04 FP20 0.24 2.35 4.40 6.71 9.58 13.40 14.40 14.60

NR04 FP22 0.23 2.25 4.11 7.17 8.89 12.90 14.00 14.20

NR04 FP24 0.33 2.25 4.23 12.70 12.40 14.30 14.60

NR04 FP25 0.27 2.14 4.03 12.60 13.50 14.50 14.50

NR05 FP1 0.30 2.31 4.21 12.30 13.20 14.30 14.00

NR05 FP2 0.25 2.41 4.31 12.10 12.90 14.20 14.20

NR05 FP3 0.39 3.02 12.95

NR05 FP4 0.36 2.57 13.45

NR05 FP4 

(duplicate)

0.21 2.29 4.08 13.10 14.60

NR05 FP5 0.30 2.51 4.38 12.60 14.10

a

3% solids loading, 5% Ctec3 loading, pH 5.5, 50 °C.

amount of solublized sugars was retained, and therefore 

a slightly higher solids yield was reasonable. This solids 

yield was lower than pilot scale unwashed solids yield of 

88.8% (Zhu et al. 2015) from equivalent feedstock FS10 

using a much lower pretreatment temperature of 145 °C for 

240 min at equivalent severity CHF. The solids yield from 

the ZeaChem runs being lower than that from the pilot-scale 

run could be due to the higher temperature (185 °C) used at 

ZeaChem than the substantially lower temperature (145 °C) 

at pilot scale, in addition to the improved filter press at 

ZeaChem.

We also calculated solids yield from the rate of feed addition 

and product solids collection during periods of constant 

operation. Figure 3.13 shows two periods of consistent 

continuous operation, the first from about 8/21/2015 to 

8/23/2015. There was a lag between counting feedstock and 

product. The calculated dry solids yield for that period was 

64% (Table 3.8). A second period from about 8/31/2015 to 

9/4/2015 gave the result of 67%.

Full solids composition measurement was time consuming 

and can be costly. Weyerhaeuser measured the compositions 

of samples from 39 product bags (from a total of 270). The 

results of selected samples are summarized in Table 3.9; 

glucan and total carbohydrate analyses are given in 

Figure 3.14. Additional data are included in Appendix B.

Solids composition measurements were not made for 

Run NR01 (Fig. 3.14) because Run NR01 was sub-optimal 

in terms of pretreatment. Average glucan composition of 
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

17

Table 3.7—ZeaChem 8-hour mass balance experimenta

Initial value Final value

Blowtank level 11,855.0 L 24,297.0 L

Blowtank fill rate 1,493.0 L/h

Total condensate 1,213.8 L/h

Hybrid poplar chips fed to system 2,137 BDkg

Hydrolyzate glucose concentration 5.08 g/L 5.66 g/L

Hydrolyzate xylose concentration 12.31 g/L 13.15 g/L

Hydrolyzate formic acid concentration 0.00 g/L 0.00 g/L

Hydrolyzate acetic acid concentration 1.34 g/L 2.16 g/L

Hydrolyzate levulinic acid concentration 0.00 g/L 0.54 g/L

Hydrolyzate HMF concentration 1.49 g/L 1.80 g/L

Hydrolyzate furfural concentration 0.16 g/L 0.44 g/L

Condensate glucose concentration 0 g/L

Condensate formic acid concentration 0 g/L

Condensate acetic acid concentration 1.29 g/L

Condensate furfural concentration 0.06 g/L

Blowtank glucose produced 72.2 kg

Glucose yield 8.0%

Blowtank xylose produced 162.1 kg

Xylose yield 102.2%

a

Run NR03 single fill mass balance, 9/2/2015 from 6:00 to 14:20. Hydrolyzate refers to the 

liquid portion of the pretreated slurry.

0

0.1

0.2

0.3

0.4

0.5

0.6

8/14/2015

8/19/2015

8/24/2015

8/29/2015

9/3/2015

9/8/2015

9/13/2015

9/18/2015

9/23/2015

9/28/2015

Consistency (% solids)

Process run date

Figure 3.12—Moisture analyses of filter press cakes.
General Technical Report FPL–GTR–278

18

Table 3.8—Solids yield calculated from 

continuous operationa

Product start 8/22/2015 3:30 AM 2.62 BDT

Product finish 8/24/2015 6:05 AM 9.82 BDT

Feed start 8/21/2015 10:12 PM 7.07 BDT

Feed finish 8/23/2015 8:48 PM 18.38 BDT

Total feed 11.3 BDT

Total product 7.2 BDT

Average solids yield 64%

a

Feed moisture ~30%, product moisture ~60%.

Table 3.9—Summary of Weyerhaeuser solids composition measurements

Run

Total 

bags

Bags 

samples

Solids content (weight % ± standard deviation)

Glucan Mannan Galactan Xylan Total

NR01 27 0

NR03 68 2 48.47 ± 1.6 1.54 ± 0.22 0.35 ± 0.07 1.54 ± 0.22 51.28 ± 1.91

NR04 96 16 50.87 ± 1.37 1.46 ± 0.1 0.23 ± 0.04 1.46 ± 0.1 53.55 ± 1.33

NR05 35 9 46.47 ± 1.78 1.22 ± 0.04 0.24 ± 0.04 1.22 ± 0.04 48.7 ± 1.82

NR06 44 12 47.82 ± 1.23 1.23 ± 0.21 0.29 ± 0.07 1.23 ± 0.21 50.07 ± 1.14

Total 270 39 48.79 ± 2.22 1.34 ± 0.19 0.26 ± 0.06 1.34 ± 2.22 51.24 ± 0.14

0

10

20

30

40

50

60

8/17

8/18

8/19

8/20

8/21

8/22

8/23

8/24

8/25

8/26

8/27

8/28

8/29

8/30

8/31

9/1

9/2

9/3

9/4

9/5

9/6

Cumulative dry tons

Cumulative dry tons – Feed

Cumulative dry tons – Product

Figure 3.13—Accumulated feedstock and product at ZeaChem.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

19

0

10

20

30

40

50

60

NR03 8E 9A

NR

O3 FP18

C

NR

O4 FP10

C

NR

O4 FP11

C

NR

O4 FP12

C

NR

O4 FP13

C

NR

O4 FP14

C

NR

O4 FP15

C

NR

O4 FP16

C

NR

O4 9D/10

A

NR

O4 FP17

C

NR

O4 FP19

C

NR

O4 FP20

C

NR

O4 FP21

C

NR

O4 FP22

C

NR

O4 FP23

C

NR

O4 FP24

C

NR

O4 FP25

C

NR05 FP-1CNR05 FP-2CNR05 FP-3D

NR05 FP-04NR05 FP-05

NR

O5 FP-7

NR

O5 FP-8

NR

O5 FP-9

NR

O5 FP-10

NR

O6 FP-1

NR

O6 FP-2

NR

O6 FP-3

NR

O6 FP-4

NR

O6 FP-5

NR

O6 FP-6

NR

O6 FP-7

NR

O6 FP-8

NR

O6 FP-9

NR

O6 FP-10

NR

O6 FP-11

NR

O6 FP-12

Glucan and total polymer sugar 

(%, wt/wt on pretreated biomass)

Sample ID

Glucan Total

Figure 3.14 —Carbohydrate composition of selected filter cake samples analyzed by Weyerhaeuser.

48.8% compares with 57.3% in the washed pretreated solids 

or 44.1% in the unwashed pretreated solids from a pilotscale experiment using similar feedstock and Ca(HSO3)2

(Zhu et al. 2015).

Total glucan recovery from 8/31/2015 to 9/3/2015 is 97% 

(Table 3.10); Zhu et al. (2015) showed a glucan recovery 

of 95.5%. This does align with the 8% glucose that the 

8-h ZeaChem liquid material balance showed as being 

solubilized (Table 3.7). Suffice it to say the recovery of 

glucan was very good.

3.3.5 Saccharification Yields

In addition to the “quick” saccharification test that FPL 

developed and conducted, Weyerhaeuser ran several 

saccharification tests using conditions more reflective of the 

large-scale enzymatic saccharification (that is, 15% solids, 

no buffer solution, and relevant enzyme loadings). The 

elevated pH 6.5 can reduce nonproductive cellulase binding 

to lignin, as discovered by Lou et al. (2013) and Lan et al. 

(2013), which was especially important for the present study 

Table 3.10—ZeaChem run solids and 

glucan yield from 8/31/15 to 9/4/15

Product start 9/1/2015 6:10 AM 19.94 BDT

Product finish 9/4/2015 6:34 AM 31.34 BDT

Feed start 8/31/2015 8:32 PM 31.81 BDT

Feed finish 9/3/2015 11:01 PM 48.90 BDT

Solids Glucan

Feed 17.1 BDT 7.0 BDT

Product 11.4 BDT 6.8 BDT

Yield 67% 97%

using unwashed solids. The glucose yields of three typical 

samples from the ZeaChem runs are given in Table 3.11.

All the saccharification yields after 72 h were excellent, 

greater than 88%. The primary difference between the three 

ZeaChem runs was that NR03 was disk milled, whereas the 

other two, NR04 and NR05, were not. Furthermore, NR05 

had a lower Mg(HSO3)2 dosage than NR03 and NR04. The 

differences in yields seem to be contrary to what might be 

expected, that is, highest yield with high Mg(HSO3)2 and 

disk refiner (Table 3.11). Disk milling apparently did not 

result in enhanced saccharification as expected, because the 

materials were well pretreated and the hot blow was able 

to substantially reduce the size of the pretreated material 

(Zhu et al. 2010). A higher Mg(HSO3)2 loading might have 

increased the pH of the pretreatment liquor, which reduced 

hemicellulose removal even though it increased lignin 

dissolution, which can reduce saccharification (Zhu et al. 

2009).

In total, 270 supersacks of pretreated solids, pressed to 

40% to 50% solids were produced (Fig. 3.15). Given 

the composition (moisture and glucan) and enzymatic 

saccharification test results, we could predict how much 

biojet fuel can be produced from this material. An expected 

amount of biojet fuel that could be produced was calculated 

from the amount of filter cake produced (Table 3.3), the 

average amount of glucan in that material (Table 3.9), a 

conservative saccharification yield based on Table 3.11, 

but reduced by 5% to account for processing loss, and 

some reasonable yield expectations for fermentation and 

jet production. That amount of jet fuel expected was over 

1,250 gal (Table 3.12). The goal was at least 1,000 gal.
General Technical Report FPL–GTR–278

20

Table 3.11—Weyerhaeuser saccharification results

Sample ID Refiner

MgBS 

on wood 

(%)

Glucan 

in solid 

(%)

Enzyme 

dose

24-h hydrolysis 48-h hydrolysis 72-h hydrolysis

Glucan 

titer 

(%)

Glucan 

yield 

(%)

Glucan 

titer 

(%)

Glucan 

yield 

(%)

Glucan 

titer 

(%)

Glucan 

yield 

(%)

HMF 

titer 

(%)

Sugar yields by high enzyme dosage for solid hydrolysis from three pretreated conditionsa,b

NR03 

8E/9A

Yes 17 47.33 High 6.90 87.80 7.60 96 7.50 95 0.07

NR04

9D/10A

No 17 53.00 High 7.40 84.30 8.10 91 8.30 94 0.04

NR05 

FP3D

No 15 46.27 High 6.80 88.70 7.60 98 7.60 98 0.05

Sugar yields by low enzyme dosage for solid hydrolysis from three pretreated conditionsa,c

NR03

8E/9A

Yes 17 47.33 Low 5.80 73.00 7.00 73.00 7.10 90 0.07

NR04 

9D/10A

No 17 53.00 Low 6.30 70.80 7.30 70.80 7.80 88 0.04

NR05 

FP3D

No 15 46.27 Low 6.10 79.20 7.20 79.20 7.40 96 0.05

a

Solids concentration: 15%; initial pH 6.5, ending pH ~5.0 without base addition during hydrolysis. Glucan yield is based on glucan in 

pretreated solids.

b

High enzyme dose: 10% Cellic Ctec3 and 1% HTec3 on solid.

c

Low enzyme dose: 5% Cellic Ctec3 and 0.5% HTec3 on solid.

Figure 3.15—Supersacks of pretreated forest residues produced at ZeaChem.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

21

4. Enzymatic Hydrolysis

4.1 ICM Run C0290

Two campaigns were executed at ICM’s Facility in St. 

Joseph, Missouri, USA, to produce isobutanol from 

pretreated solids. The first in November and December 

2015 was referred to by ICM’s run number C0290. A second 

campaign (C0310) was conducted in March through May 

2016. ICM operates multiple pilot plants at this location 

in addition to a corn-ethanol production facility. The pilot 

plants include a cellulosic pretreatment and enzymatic 

saccharification facility and a fermentation facility. 

In addition, they house the Gevo GIFT pilot plant for 

recovering isobutanol from fermentation and purifying it.

The overall plan for enzymatic saccharification in run 

C0290 at ICM was to utilize the best or prime ZeaChemproduced solids of approximately 45 BDT and saccharify 

in two batches in the 35,000-gal saccharification tanks 

available in ICM’s cellulosic biomass pilot plant. In 

addition, some reject pulp from the Cosmo Specialty Fiber 

mill in Cosmopolis, Washington, USA, was also used in 

C0290 to evaluate the suitability of commercial sulfite 

pulp mill rejects for biofuel production. The Cosmo mill is 

a magnesium bisulfite pulping process that uses hemlock 

wood to produce a high-quality dissolving pulp. The process 

is similar to the SPORL process used at ZeaChem, at a 

much higher SO2 dosage (three to four times) and longer 

Table 3.12—Expected jet production from 

the pretreated forest residue material 

produced at ZeaChem

Parameter Value

Filter cake, NR03–NR06a 45 BDT

Average glucanb 49% wt

Glucan 44,100 lb

Saccharification yieldc 85%

Glucose 41,608 lb

Processing lossesd 5%

Glucose to fermentation 39,528 lb

Isobutanol yielde 0.32 lb/lb glucose

Isobutanol produced 12,649 lb

Isobutanol produced 1,879 gal

Isobutanol lossesd 5%

Biojet carbon yieldf 86%

Max theoretical jet yield 0.766 lb jet/lb iBuOH

Actual jet yield 0.659 lb jet/lb iBuOH

Jet density 6.31 lb/gal

Final jet 7,916 lb

Final jet 1,255 gal

a

Table 3.3.

b

Table 3.9.

c

Table 3.11 (less 5%).

d

Estimated losses.

e

Typical Gevo yield.

f

Gevo yield (this is with C8 production minimized).

cooking time of 4 to 6 h but at a much lower temperature of 

140 °C (Gu et al. 2016). Cosmo was interested in exploring 

the opportunities to produce sugars from their rejected pulp 

stream, which was burned at the mill only for its heating 

value. It was planned that the Cosmo material would be 

hydrolyzed in a small third hydrolysis batch.

As described in Section 3, Pretreatment, pretreated solids 

from ZeaChem were delivered to ICM in supersacks 

(Fig. 4.1). The supersacks were stored in the feedstock tent, 

and as needed, they were dumped onto the relatively clean 

concrete floor of the feedstock tent. A front-end loader was 

used to fill the feed hopper (Figs. 4.2, 4.3) that conveyed 

them into a slurrying tank. From the slurrying tank, the 

material was pumped to the saccharification tanks located 

across the street in the cellulose pilot plant area. This is a 

distance of about 280 ft plus the vertical runs to get up to the 

second floor (Fig. 4.4).

Pumping a slurry of targeted concentration of 15% solids 

had not been done at ICM. ICM’s usual feed to their 

cellulose pilot plant was a dry untreated material, like 

chopped or ground corn stover or switchgrass. Their 

normal conveying system over this distance is pneumatic, 

which works well for dry solids. There were difficulties 

in pumping this slurry, but generally it was accomplish by 

going into a second slurry tank (Fig. 4.5) at about half the 

distance and using a second pump (large diaphragm pump) 

to get the slurry from the second tank to the hydrolysis tank.

4.2 C0290 Saccharification

With ICM’s four 35,000-gal saccharification tanks, it was 

possible to fill two and even three tanks in sequence and 

start the saccharification by adding enzyme as each tank 

was full. (The alternative would be filling one tank, running 

the saccharification to make sure it worked properly, and 

then filling the second.) ICM wanted to push through all the 

solids transfer as quickly as possible to get that problematic 

operation completed and not have to start and stop the solids 

transfer. As we saw in C0310, starting and stopping the 

solids transfer a few times was not an issue.

As each tank was nearly filled, Cellic CTec3 cellulase 

enzyme cocktail (complimentarily provided by Novozymes) 

was added, and saccharification was started. All the prime 

ZeaChem material (ZeaChem batches NR03, NR04, NR05, 

and NR06) was not able to fit into two saccharification 

tanks, because maintaining the targeted 15% solids in the 

feed slurry was not possible due to difficulties in pumping 

slurry at high solids. Therefore, the third tank, rather than 

being exclusively for saccharifying the Cosmo material, 

would be a mixture of prime ZeaChem material and Cosmo 

rejected pulp. All the ZeaChem sub-prime material (NR01) 

was also added to the third tank because there was spare 

volume in the third tank and the saccharification run in 

third tank was already a mixture. This would produce some 

additional sugar overall.
General Technical Report FPL–GTR–278

22

Figure 4.1—CM facility in St. Joseph, Missouri, USA.

Dump supersacks 

and bulk load solids

Saccharification in 

35,000-gallon tanks

Ferment to 

isobutanol

Fuel-grade 

isobutanol

Concentrate sugars 

in evaporate

Recover isobutanol 

through GIFT® system

Add water to form 

slurry and pump to 

saccharification 

tank(s)

Filter solids out with 

filter press or rotary 

drum filter

Discard solids

Figure 4.2—Overall process at ICM.

Figure 4.3—Loading of dumped supersacks into feed hopper.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

23

Feedstock

tent

Truck

delivery

Saccharification

tanks

Figure 4.4—Location of feedstock and enzymatic digestion tanks at ICM. Figure 4.5—Intermediate slurry 

pumping tank.

Figure 4.6 and Tables 4.1 and 4.2 indicate the time required 

to fill and empty the saccharification tanks. It took between 

30 and 50 h to fill each tank. The filling process was 

plagued with various line plugging issues due to the high 

solids concentration, but there were also problems in the 

centrifugal pumps with small rocks that seemed to have 

carried through with the feedstock. These could have 

come from the dumping of the supersacks on the floor of 

the feedstock tent, but that was cleaned. These were more 

likely from the original feedstock, as was experienced at 

ZeaChem. A very small amount of enzyme, approximately 

5 gal, was added during the fill of tanks 2 and 3 to help 

reduce viscosity and improve mixing for pH adjustment 

through neutralization. The pH of the tanks was low, 

about 3.5 to 4, before being neutralized with KOH, so it 

was expected that all the initial enzyme applied for initial 

reduction of viscosity may had been lost.

Batch 601 began on 11/16/2015. Filling the saccharification 

tank took 50 h. After filling, the pH (target 5 to 5.5) and 

temperature (target 122 °F, 50 °C) were adjusted. The CTec3 

enzyme was added on 11/18/2015 at the dosage of 7% based 

on the biomass solids. This was significantly higher than 

generally used in the laboratory (4%), but the objective 

here was to maximize yield of sugar. This enzyme loading 

equates to approximately 250 gal of enzyme cocktail based 

on the solids in the tank. Lactrol (~400 g) was added at 

the same time to control any possible contamination. The 

bulk of the saccharification was completed within 24 h and 

0

10

20

30

40

50

60

70

80

90

100

Tank level (

% full)

Hydro tank 2 (501)

Hydro tank 3 (502)

Hydro tank 4 (503)

11/14/2015

11/16/2015

11/18/2015

11/20/2015

11/22/2015

11/24/2015

11/26/2015

11/28/2015

11/30/2015

12/2/2015

12/4/2015

12/6/2015

Figure 4.6—Filling and emptying the enzyme saccharification tanks with slurry.
General Technical Report FPL–GTR–278

24

Table 4.1—Hydrolysis composition, volume and fill times

Batch

Glucose 

(g/L)

Total 

solids

(%)

Volume 

(gal)

Project time (h) Hours

Start Full Drop End Fill Filter Duration

601 67.2 14.2 32,718 6 56 97 236 50 139 230

602 69.7 15.2 32,751 53 88 245 310 35 65 257

603 61.9 13.1 27,137 88 121 316 418 33 102 330

Table 4.2—Enzyme addition timed for saccharification tanks

Batch

Enzyme 

added

Saccharification 

time 

(h)

Heat-up for 

pasteurization

Start drain 

to filter Finish drain

Drain 

time 

(h)

601 11/18/2015 20:00 60–121 11/24/2015 1:00 11/21/2015 11:00 11/26/2015 4:00 113

602 11/21/2015 02:30 91 11/24/2015 22:00 11/26/2015 14:00 11/29/2015 7:00 65

603 11/22/2015 12:00 72 11/25/2015 12:30 11/29/2015 11:50 12/3/2015 5:30 90

peaked with peak glucose concentration of 67.2 g/L. The 

slurry was mixed thoroughly after the enzyme was added. 

Shortly after the filtering process began for batch 601, lactic 

acid began to accumulate in the tank (Fig. 4.7). The cause 

of the contamination was the techniques used during the 

filtering process (see Section 5, Filtration, Concentration, 

and Storage).

Batch 602 began on 11/18/2015, shortly after the filling 

of batch 601 was completed. It took hours to fill the 

saccharification tank. Again, a small amount of enzyme was 

added to the tank during filling to reduce slurry viscosity. 

The enzyme addition improved mixing and created a small 

amount of glucose. The full dose of enzyme, 250 gal, was 

added at 2:30 AM on 11/21/2015. Batch 602 produced 

a peak glucose concentration of at 69.7 g/L. Lactic acid 

0

1

2

3

4

5

6

7

8

0

10

20

30

40

50

60

70

80

11/16/2015

11/17/2015

11/18/2015

11/19/2015

11/20/2015

11/21/2015

11/22/2015

11/23/2015

11/24/2015

11/25/2015

11/26/2015

11/27/2015

11/28/2015

Acetic, lactic, EtOH (g/L)

Glucose (g/L)

Glucose (biomass)

Glucose (Gevo)

Acetic acid

Lactic acid

EtOH

Figure 4.7—Batch 601 tank compositions.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

25

0

1

2

3

4

5

6

7

8

0

10

20

30

40

50

60

70

80

11/18/2015

11/19/2015

11/20/2015

11/21/2015

11/22/2015

11/23/2015

11/24/2015

11/25/2015

11/26/2015

11/27/2015

11/28/2015

11/29/2015

11/30/2015

Acetic, lactic, EtO

H (g/L)

Glucose (g/L)

Glucose (biomass)

Glucose (Gevo)

Acetic acid

Lactic acid

EtOH

began to appear at about 96 h after filling began, or about 

48 h after the application of the main enzyme dose when 

saccharification was completed (Fig. 4.8). After additional 

antibiotics were added and the temperature was raised 

to approximately 160 °F, the contamination seemed 

to be controlled. There was no obvious cause for the 

contamination.

Batch 603 began on 11/19/2015, shortly after the filling 

of batch 602 was completed. Batch 603 was a composite 

of ZeaChem material and Cosmo pulp rejects. ZeaChem 

fiber was pumped in with the same hydroconveyor system 

that was used to fill 601 and 602. Cosmo fiber was slurried 

in a cut off tote with hot city water and pumped a few 

feet into the side of the hydrolysis tank. Solids content in 

batch 603 was slightly lower than 601 and 602, largely 

due to difficulties in pumping the Cosmo fiber slurry, 

which was nearly impossible to pump at about 10% solids. 

At about noon on 11/22/2015, 190 gal of enzyme was 

added. The tank started showing some contamination 

shortly after the addition of enzyme. Antibiotics did not 

stop the contamination. Increasing the temperature of 

the tank to 160 °F (71 °C) during 11/25/2015 stopped 

the contamination. However, approximately 7 g/L lactic 

acid had been produced (Fig. 4.9). The high temperature 

also denatured the enzyme. Fortunately, the system 

had completed 72 h of saccharificationand the glucose 

concentration had been leveled off.

4.3 Saccharification Yield

The yield of enzymatic saccharification is dependent on 

the solids concentration in the tank, which was difficult 

to measure accurately due to the poor mixing in the tank 

at the beginning of saccharification. Table 4.3 shows a 

yield calculation based on the final (peak) concentration 

of glucose in the tank and the solids concentration. The 

composition of the starting solids (see Section 3) was 

determined. The maximum theoretical glucose is the amount 

of glucose that would be generated at 100% yield from 

the feed solids loaded. The final glucose concentration of 

the liquid in the saccharification tank was adjusted for the 

amount of insoluble solids remaining at the end. Batch 602 

appears to have a lower insoluble solids concentration 

(10.9%) than does batch 601 (12.7%) (Table 4.3; Fig. 4.10). 

This is puzzling because batch 602 has higher total solids, 

and these are essentially the same prime ZeaChem material. 

The yield for batch 602 appears unrealistically high. 

However, if the percentage insoluble solid is adjusted to be 

a similar ratio to total solids as that of batch 601, the yield is 

more in line with that of the other two batches (see modified 

line in Table 4.3). With the adjustment to batch 602, the 

yields for all three batches range from 84% to 87%.

Figure 4.8—Batch 602 tank compositions.
General Technical Report FPL–GTR–278

26

0

1

2

3

4

5

6

7

8

0

10

20

30

40

50

60

70

80

11/18/2015

11/20/2015

11/22/2015

11/24/2015

11/26/2015

11/28/2015

11/30/2015

12/2/2015

12/4/2015

12/6/2015

Acetic, lactic, EtOH (g/L)

Glucose (g/L)

Glucose (biomass)

Glucose (Gevo)

Acetic acid

Lactic acid

EtOH

Figure 4.9—Batch 603 tank compositions.

Table 4.3—Saccharification batch yields

Batch

Final 

glucose 

(g/l)

Total 

solids 

(%)

Starting 

insoluble 

solids 

(%)

Ending 

insoluble 

solids 

(%)

Soluble 

solids 

(%)

Tank 

volume 

(gal)

Final 

glucose 

(lb)

Initial 

glucose 

in solidsa

(lb)

Max 

theoretical 

glucoseb,c

(lb)

Yield

(%)

601 67.2 14.2 12.7 5.50 7.90 32,717 17,360 126 19,686 87.5

602 69.7 15.2 10.9 6.00 8.20 32,740 17,923 138 16,908 105.2

602d 69.7 15.2 13.6 6.00 8.20 32,740 17,923 138 21,087 84.3

603 61.9 13.1 12.2 5.00 7.30 25,859 12,706 91 14,947 84.4

a

Glucose dissolved in liquor coming in with the solids. 7% glucose in ZeaChem liquor.

b

Batch 601 and 602 have a solids glucan composition of 48.8%, Prime ZeaChem material. c

Batch 603 is a mix of Prime and sub-Prime ZeaChem and Comos. Glucan assumed to be same at 48.8%.

d

Insoluble solids concentration for batch 602 adjusted to be more like batch 601—result is a more realistic yield.

4.4 Potential for Biojet Production

It is worth noting how much isobutanol could be produced if 

the rest of the process went as planned. Table 4.3 illustrates 

the production of 47,989 lb of glucose based on the 

volumes of the hydrolysis tanks and their respective glucose 

concentrations. This was more than expected because more 

solids (that is, the sub-prime ZeaChem and Cosmo solids) 

were processed; furthermore, the actual yields appeared 

to be slightly better than expected. At this point we would 

have expected to have enough sugar to produce 1,450 gal of 

biojet (Table 4.4).

5. Filtration, Concentration, and 

Storage

Fermentation can be accomplished with much higher 

sugar concentrations that are realized from enzymatic 

saccharification. By fermenting at high sugar concentrations, 

the total number of fermentation runs (or full tanks) is 

minimized, which also minimizes the amount of yeast and 

nutrients required overall. The isobutanol was continuously 

removed by the GIFT system, so its concentration was 

maintained at a low level in the fermenter, regardless of 

sugar concentration. Before concentrating the sugars by 
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

27

Solids profiling,

percent

 suspended solids

15

10

5

0

0 24 48 72 96 120 144 168 192 216 240 264 288 312

Time point

Solids profiling,

percent

dissolved solids

15

10

5

0

Solids profiling,

percent

total solids

15

10

5

0

Batch ID 601 602 603

Figure 4.10—Solids concentration in the saccharification tanks.

Table 4.4—Project biojet production amount 

given the sugar produced in saccharification

Parameter Value

Glucose from saccharificationa 47,989 lb

Processing lossesb 5%

Glucose to fermentation 45,590 lb

Isobutanol yieldc 0.32 lb/lb glucose

Isobutanol produced 14,589 lb

Isobutanol produced 2,167 gal

Isobutanol lossesd 5%

Biojet carbon yieldb 86%

Max theoretical jet yield 0.766 lb jet/lb iBuOH

Actual jet yield 0.659 lb jet/lb iBuOH

Jet density 6.31 lb/gal

Final jet 9,130 lb

Final jet 1,448 gal

a

See Table 4.3, amount of glucose produced in 

saccharification.

b

Gevo yield (this is with C8 production minimized). c

Typical Gevo yield.

d

Estimated losses.
General Technical Report FPL–GTR–278

28

evaporation, the insoluble solids must be removed by 

filtration. ICM has two filtration systems that could be 

used. The first, a plate and frame pressure filter, is preferred 

because it is more automated and does not usually introduce 

a foreign filtering aid. The plate and frame filter has the 

ability to wash the solids to maximize sugar recovery. The 

second unit operation available is a rotary drum vacuum 

filter (RDVF). This system uses diatomaceous earth as a 

coating on the drum, which should act to trap fine particle 

and prevent the filter from plugging. It has the ability to 

rinse the solids and therefore should result in high sugar 

recovery. Its primary drawback is that the solids become 

mixed with the diatomaceous earth and are no longer 

useable. For this project, that was not an issue, because 

we were not going to further process lignin solids. For 

a production process, this would be a problem because 

the lignin has value, which is significantly diminished by 

mixing it with foreign material.

A test was conducted during the filling of batch 601. 

Approximately 1,800 gal of slurry was diverted to a smaller 

tank (yeast conditioning tank) and dosed with enzyme. 

Once saccharification was completed, it was filtered using 

the filter press. The results were not promising. The loss 

of sugar was substantial. The resulting cake was higher in 

moisture than other hydrolyzed materials, and the filter cloth 

plugged quickly. One cycle of 1,200 gal took 3 h, which 

would calculate to 80 h for the full batch 601. A choice was 

made to start batch 601 filtering with the RDVF.

Filtering of batch 601 began on 11/21/2015 with the 

RDVF. The RDVF operates by drawing liquid through a 

thick layer of a diatomaceous-earth- (DE-) coated drum by 

vacuum. The drum rotates through a pool of slurry, picking 

up hydrolyzate solids on the drum. Liquids pass through 

the DE. Solids (biomass and some portion of the DE) are 

scraped off one side of the drum.

The RDVF turned out to be very slow for filtering the 

hydrolyzate. Filtering began at 11:00 AM 11/21/2015 with 

32,729 gal in batch 601. At 08:00 AM 11/23/2015, after 45 h 

of filtering, the tank level was 18,975 gal; 13,750 gal had 

been filtered in 45 h, for a filtering rate of 5.1 gal/min. This 

ultimately diminished to an average of 2 gal/min.

In the course of filtering with the RDFV, saccharification 

slurry was drained from the open pool in the filter back 

to the saccharification tank each time the filter needed to 

be recoated with DE. This introduced contamination to 

batch 601, which was controlled by adding more antibiotics 

and raising the temperature to 160 °F. The operation of 

returning hydrolyzate from the open filter to the main tank 

was stopped, and a small tank was used to store the recycle.

After two days of filtering with the RDVF, we considered 

the possibility that if the DE were premixed as a filter aid 

with the slurry, it might filter better in the filter press. So 

we moved the hydrolyzate from the hydrolysis tank to a 

6,000-gal tank, where it was mixed with DE. Hydrolyzate 

with DE filtered more quickly than hydrolyzate without 

DE on the filter press. Over a 21-h period of filter 

pressing, 9,800 gal of hydrolyzate was filtered, yielding 

approximately 7.8 gal/min; 51,300 gal of hydrolyzate was 

filtered in five days, averaging approximately 7.1 gal/min.

On 11/21/2015, evaporation of the filtered sugar solution 

began. There was some initial foaming in the evaporators, 

but it was controlled with a small amount of antifoam. The 

evaporators generally ran without issue and at a much faster 

rate than the filters.

The original intent was to concentrate the filtered 

hydrolyzate to >150 g/L sugar and store it in one of the 

unused ethanol fermenters at a reduced temperature of 

40 °F. By 11/24/2015, it was evident that the cooling system 

was not adequate to reduce the temperature of the sugar to 

40 °F; it had only cooled to 56 °F. After consulting with 

Gevo, we decided to store the sugar hot, so the temperature 

of the storage tank was raised to 140–160 °F. The 

hydrolyzate was ultimately concentrated to 191 g/L, with 

measurement of 174 g/L in the two storage tanks (ethanol 

fermenters EF3 and EF4).

Because sugar loss in the filter press was excessive (as 

much as 25%), batch 602 was filtered using the RDVF 

again. The RDFV initially ran at approximately 11 gal/

min, dropping off to approximately 7 gal/min and then 

approximately 4 gal/min with batch 603. Filtering was 

finished on 12/4/2015.

6. Fermentation

Fermentation of the concentrated sugars using a Gevo 

proprietary organism was conducted at the ICM site using 

three 6,000-gal aerobic fermenters connected together 

in series to act as a single fermenter. Some years before, 

Gevo had installed a pilot GIFT isobutanol recovery and 

purification system in the ICM pilot facility. The GIFT unit 

was piped up to the three aerobic fermenters and used to 

remove isobutanol during the course of fermentation and to 

strip residual isobutanol remaining in the fermentation broth 

after the fermentation finished (Fig. 6.1).

6.1 Fermentation 501

The aerobic fermentation tanks were emptied and prepared 

for steam-in-place cleaning (SIP) on 12/2/2015. SIP was 

conducted and the tanks cooled (Fig. 6.2).

After SIP of the tanks was completed, the concentrated 

sugar was added (Fig. 6.3). In the course of adding the 

concentrated sugar, it was discovered (twice) that there was 

a leak on the dissolved oxygen (DO) probe port in tank 2. To 

fix it, the tank was emptied back to the storage tank. Finally, 

once the tanks were full of about 15,000 gal, fermentation 

nutrient was added, and SIP was started at 

3:00 AM on 12/3/2015.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

29

GIFT AF3 AF2 AF1

Figure 6.1—Aerobic fermenters and GIFT recovery 

system arrangement.

The temperature in the fermenters was raised to 250 °F, 

held for 60 min, then cooled. Fermentation temperature 

was reached about 6:00 PM on 12/3/2015, and additional 

fermentation nutrients were added.

The next step was to add the yeast. The original plan was to 

use an IKA blender-pump that could be completely steam 

sterilized. However, during SIP, the seal was blown, which 

resulted in seal water (nonsterile) being pushed backed 

into the yeast tote when pumping was started. In addition, 

the yeast tote had been sitting without mixing for about 

3 weeks, which caused substantially more settling of solids 

than expected. The material seemed to be not pumpable. 

We decided to use a large diaphragm pump. The pump was 

sanitized with 4-Quat and a recycle loop set up. This was 

able to pump the yeast. All the yeast was unintentionally 

0

50

100

150

200

250

300

12/2/15

12:00 AM

12/2/15

12:00 PM

12/3/15

12:00 AM

12/3/15

12:00 PM

12/4/15

12:00 AM

12/4/15

12:00 PM

Temperature (°F)

Aerobic tank 1

Aerobic tank 2

Aerobic tank 3

Cooling time 8 hours

Empty tank SIP

Figure 6.2—Fermentation 501 sterilization temperature profile.

sent to one tank rather than distributing it among the three 

tanks. The yeast would be distributed over time due to the 

normal circulation between the individual tanks and the 

GIFT system. Yeast addition was completed at 4:30 AM 

12/4/2015.

The target isobutanol broth concentration was higher than 

planned because the GIFT system was not able to maintain 

the design pressure. All efforts were made to determine if 

there was a leak, and none could be found. There could have 

been an issue with too much dissolved CO2 and an inability 

of the vacuum jets to remove all the noncondensables. No 

resolution was found. Because the G-Column was operating 

at a higher pressure than design, the boiling point was also 

higher, which lowered the temperature differential on the 
General Technical Report FPL–GTR–278

30

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

12/2/15 2:24 PM

12/2/15 7:12 PM

12/3/15

12:00 AM

12/3/15 4:48 AM

12/3/15 9:36 AM

12/3/15 2:24 PM

12/3/15 7:12 PM

12/4/15

12:00 AM

12/4/15 4:48 AM

Tank volume (gallons)

Aerobic tank 1

Aerobic tank 2

Aerobic tank 3

Figure 6.3—Batch 501 aerobic tank volume during fermentation.

reboiler and reduced the amount of isobutanol that could 

be removed. The isobutanol titer peaked at about twice the 

intended level. As an aside, without fermentation operating, 

the G-Column was able to hold the design pressure.

In this first batch, the sugar was consumed slowly and 

the fermentation was continued for over 100 h (Figs. 6.4, 

6.5). It was hypothesized that the extremely long storage 

of the concentrated sugar at high temperature (to avoid 

contamination) created inhibitors and retarded the 

fermentation. This was confirmed later when fermentations 

performed well using sugars that did not have long heat 

histories (see Section 7.1).

No contamination was seen in the fermentation until about 

94 h into the run. At that time, the concentration of both 

acetic acid and lactic acid (typical products of contaminating 

bacteria) started to increase (Fig. 6.6). We decided about 8 h 

later to end the fermentation.

The amount of isobutanol produced was calculated using 

the flow of broth through the GIFT and the concentration 

differential (amount removed). Figure 6.7 shows the profile 

of isobutanol production during the run.

The yield of isobutanol from the first run was lower than 

expected, given the planned starting sugar concentration. 

This can be attributed to the high temperature and long 

duration that the sugar was stored due to issues with 

filtration. There were certainly various toxic compounds 

during this storage that resulted in yields lower than 

measured in the lab with the same saccharified biomass but 

without a storage history.

6.2 Fermentation 502

At the end of the first fermentation the aerobic fermenters 

were emptied to a storage tank to wait on determining 

their final disposition. The aerobic tanks were rinsed and 

sterilized by SIP (Figs. 6.8, 6.9). Upon finishing the tank 

SIP, the tanks were partially cooled and the stored sugar and 

fermentation nutrient were added. The volume of remaining 

sugar was less than needed to fill the fermenters so it was 

decided to add dilution water to help dilute out the inhibitor 

concentrations that built up during the >250-h at >140 °F 

sugar storage. All the contents were then sterilized by SIP. 

The cooling was improved and accomplished in 10 h in this 

second batch.

The pressures in the GIFT and G-Column were no better 

during this run, hovering higher than the design pressure.

The isobutanol titer actually peaked a little higher in this 

run compared to run 501. This was primarily due to a faster 

production rate in the fermenter coupled with the reduced 

ability (due to pressure) of the GIFT to remove isobutanol.

Sugar concentration was significantly lower in this batch 

than the previous one, 63 g/L compared with 126 g/L, but 

the consumption rate was much higher. The fermentation 

was completed in 40 h and consumed all the sugar 

(Fig. 6.10).
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

31

124

0

2

4

6

8

10

12

14

16

18

20

0

20

40

60

80

100

120

140

0 8 16 24 32 40 48 56 64 72 80 88 96 104 112

g/L arabinose, mannose, galactose

g/L glucose, xylose

EFT (h)

Glucose

Xylose

Lab average glucose

Arabinose

Mannose

Galactose

Average glucose 

consumption rate 

~1.1 g/L/h

17

86

87

88

89

90

91

92

93

94

95

5.0

5.2

5.4

5.6

5.8

6.0

6.2

6.4

6.6

6.8

7.0

12/3/15

12:00

12/4/15 0:00

12/4/15

12:00

12/5/15 0:00

12/5/15

12:00

12/6/15 0:00

12/6/15

12:00

12/7/15 0:00

12/7/15

12:00

12/8/15 0:00

12/8/15

12:00

12/9/15 0:00

Temperature (°F)

pH

AF1 pH

AF2 pH

AF3 pH

AF1 temperature

AF2 temperature

AF3 temperature

Figure 6.4—Fermentation 501 sugar profile.

Figure 6.5—Fermentation 501 pH and temperature profiles.
General Technical Report FPL–GTR–278

32

0

5

10

15

20

25

30

–2 6 14 22 30 38 46 54 62 70 78 86 94 102 110

Acetate, lactate, ethanol (g/L)

EFT (h)

Acetic acid

Lactate

Ethanol

Figure 6.6—Fermentation 501 contamination profile.

0

50

100

150

200

250

300

350

400

450

0 8 16 24 32 40 48 56 64 72 80 88 96 104

Gallons

EFT (h)

Gallons iBuOH estimate – GIFT method

Figure 6.7—Fermentation 501 isobutanol production profile.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

33

0

50

100

150

200

250

300

12/9/15 7:12 PM

12/10/15

12:00 AM

12/10/15 4:48 AM

12/10/15 9:36 AM

12/10/15 2:24 PM

12/10/15 7:12 PM

12/11/15

12:00 AM

12/11/15 4:48 AM

12/11/15 9:36 AM

Temperature (°F)

Cooling time 10 hours

Aerobic tank 1

Aerobic tank 2

Aerobic tank 3

Figure 6.8—Fermentation 502 sterilization temperature profile.

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

12/9/15

12:00 PM

12/10/15

12:00 AM

12/10/15

12:00 PM

12/11/15

12:00 AM

12/11/15

12:00 PM

12/12/15

12:00 AM

12/12/15

12:00 PM

12/13/15

12:00 AM

12/13/15

12:00 PM

12/14/15

12:00 AM

12/14/15

12:00 PM

12/15/15

12:00 AM

Tank volume (gallons)

Aerobic tank 1

Aerobic tank 2

Aerobic tank 3

Figure 6.9—Batch 502 aerobic tank volume during fermentation.
General Technical Report FPL–GTR–278

34

0

1

2

3

4

5

6

7

8

9

0

20

40

60

80

100

120

140

0 8 16 24 32 40 48 56 64 72 80 88 96 104 112

g/L arabinose, mannose, galactose

g/L glucose, xylose

EFT (h)

B501 average glucose consumption rate = 1.1 g/L/h

B502 average glucose consumption rate = 1.9 g/L/h

Glucose

Xylose

Lab average glucose

501-glucose

Arabinose

Mannose

Galactose

126

17

63

3

1

Figure 6.10—Fermentation sugar profile, runs 501 and 502.

0

2

4

6

8

10

12

14

16

18

20

–2 6 14 22 30 38 46 54 62 70 78

Acetate, lactate, ethanol (g/L)

EFT (h)

Acetic acid

Lactate

Ethanol

Figure 6.11—Fermentation 502 contamination profile.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

35

Contamination was also low in this run. Lactic acid 

increased slightly toward the end of the run (Fig. 6.11). 

Considerable background of lactic acid was noticed in the 

sugar from saccharification and storage. It is well known in 

the fuel ethanol industry that 0.8% w/v or 8 g/L lactate can 

lead to yeast inhibition or even death. The tolerable level 

of acetate is even lower, at 0.05% w/v or 0.5 g/L. Both of 

these byproducts were above this threshold in the first and 

second fermentations and likely led to lower than optimal 

performance.

Isobutanol production in this batch nearly matches the 

previous batch with only about half the sugar that was 

present in the first batch (501) (Fig. 6.12). A plausible 

explanation of the difference between these two batches is 

that the second batch of sugar was not held for hundreds 

of hours at elevated temperatures. Thus, the generation of 

inhibitors may have been lower in 502.

The yield of isobutanol from the run was encouraging. 

Overall, production of isobutanol was much better in this 

run and was not that far from results realized in the lab 

with these feedstocks that did not have the storage and heat 

history.

7. Product Isobutanol

Fermentation 502 fairly well completed all the sugars. 

However, run 501 left some sugars unconsumed, at 

approximately 17 g/L. ICM had transferred the contents to a 

storage tank. After run 502 was completed, they transferred 

it back to the aerobic tanks and attempted to complete the 

fermentation. Unfortunately, in the transfer process, the 

broth picked up an ethanol-producing organism. The ethanol 

0

50

100

150

200

250

300

350

400

450

0 8 16 24 32 40

Gallons

EFT (h)

Gallons iBuOH estimate – GIFT method

Figure 6.12—Fermentation 502 isobutanol production profile.

contaminated some portion of the remaining isobutanol that 

had not been completely dehydrated yet.

At the end of operations, there were three partial totes that 

met water specifications and one tote that was contaminated 

with ethanol and could not be dehydrated by distillation. 

Table 7.1 summarizes the materials produced and their 

compositions. Samples from two of the totes were sent 

to Midwest Laboratories to test for acid. The isobutanol 

specification for acid was 70 ppm, or 0.007%. The 

results for the two totes tested were 0.529% and 0.165%, 

considerably over the specification.

In total, 627 gal of isobutanol met the specifications for 

water and isobutanol but failed in acid. In addition, 380 gal 

of isobutanol containied too much ethanol to be dehydrated 

by distillation. Roughly 296 gal of potentially recoverable 

isobutanol was in that high ethanol material. The total 

possible isobutanol would then be 923 gal if all could be 

recovered and finally purified.

In addition, the appearance of the product was not waterwhite; it looked more like “swamp water” (Fig. 7.1). Twice 

during the operation, operator error caused a considerable 

amount of isobutanol to be dumped on the floor: the first 

was a valve position error and the second caused a relief 

valve to open. This material was put back into the recovery 

system, but it contained dirt and contaminants from the 

floor and the floor trenches. The isobutanol was a bottoms 

product from the recovery system, so there was no way to 

remove heavy components (it would need to be sent through 

the entire GIFT to do that). This is probably where the 

adverse color came from. Fermentation broth was carried 
General Technical Report FPL–GTR–278

36

Table 7.1—Isobutanol quantity and composition from Campaign 1

Tote

Volume 

(gal)

Watera

(%)

Acid 

weightb

(%)

Content (%)

EtOH 1-PrOH iBuOHc 3M1BuOH 2M1BuOH 2PhEtOH Unknown Other

901 82 0.4939 0.084 0.027 95.677 3.338 0.764 0.055 0.032 0.023

902 274 0.4117 0.529 0.031 0.015 97.531 1.617 0.291 0.111 0.397 0.007

903 272 0.4017 0.165 0.072 0.026 97.046 2.209 0.446 0.074 0.12 0.007

Total iBuOH 627

Hi ethanol totes

Hi EtOH-1 170 29.6 2.4 67.3 0.5 0.1 0.1

Hi EtOH-2 210 9.5 3.6 86.4 0.3 0.1 0.1

Potential iBuOH 296

Total potential 

iBuOH

923

a

Specification for water is <1.0%.

b

Specification for acid (expressed as acetic) is <0.007% or 70 ppm.

c

Specification for isobutanol is >97%.

overhead in the GIFT multiple times due to pressure upsets 

in the G-Column. This would cause organic acids that would 

otherwise be left in the fermenter to end up in the product. 

A daily historical summary of the first campaign at ICM to 

produce isobutanol is given in Appendix D.

The result of the first campaign was disappointing. 

The amount of isobutanol produced was only enough 

to potentially make 515 gal of jet fuel, whereas we had 

expected to have enough isobutanol to make well more than 

the goal of 1,000 gal of jet fuel.

Multiple processing issues occurred. Filtration to remove 

residual solids after saccharification was unsatisfactory. A 

very limited amount of preliminary testing indicated that 

there might be a problem with filtration, but it was not 

deemed to be as serious as it turned out.

For unexplained reasons, filtration rates through both 

the filter press and the rotary drum vacuum filter were 

extremely low. The excessive sugar loss in both units 

Figure 7.1—Product isobutanol samples.

was alarming. Sugar losses through the filter press were 

estimated to be 25% at one point. We had expected about 

a 3% sugar loss through the filter press based on ICM’s 

previous experience separating residual biomass solids after 

saccharification.

The very slow filtration led to very long storage times 

for the resulting sugar. To avoid contamination (which 

did occur during saccharification and initially in storage), 

the concentrated sugar (and impurities) were held at high 

temperatures, initially at 160 °F but then mostly at 140 °F. 

We believe that this long storage at high temperature 

created even more inhibitors for the yeast, leading to a low 

yield of isobutanol in the first fermentation. The second 

fermentation, which was diluted and not stored as long, 

performed much better.

Figure 7.2 illustrates the potential for production of jet fuel 

and where the “normal” flow of carbon would go. Figure 7.3 

attempts to show where the carbon actually went and how 
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

37

0

500

1,000

1,500

2,000

2,500

3,000

Actual Expected

1,370

2,800

420

71

567

337

Jet fuel (gallons)

Saccharification loss

Filtration loss

Contamination in filtration

Fermentation maintenance

Stillage/contamination loss

Jet conversion loss

Net produced

35

100% conversion of all 

carbon; not practically 

possible in any process

Expected jet fuel production 

when finished at SHR

Figure 7.2—Potential for jet fuel production from material delivered to ICM.

0

500

1,000

1,500

2,000

2,500

3,000

Actual Expected

1,370

2,800

420

71

567

337

127

2,800

700

399

386

326

346

515

Jet fuel (gallons)

Saccharification loss

Filtration loss

Contamination in filtration

Fermentation maintenance

Stillage/contamination loss

Jet conversion loss

Net produced

35

100% conversion of all 

carbon; not practically 

possible in any process

Expected jet fuel production 

when finished at SHR

Figure 7.3—Losses during the processing at ICM.
General Technical Report FPL–GTR–278

38

we got from a potential of over 1,300 gal of jet fuel to about 

500. These figures make reasonable assumptions about the 

conversion yields of isobutanol to biojet.

8. Saccharification of Cosmo 

Reject Pulp—Part 1

As described in Sections 5, 6, and 7, the processing of 

pretreated forest residue at ICM produced significantly less 

isobutanol than expected because of a variety of issues. 

The amount of isobutanol produced was less than 900 

gal, which when processed to biojet, would result in only 

approximately 500 gal of finished biojet fuel. The goal of 

the project was to produce 1,000 gal of biojet fuel.

8.1 What Could Be Done?

When the second fermentation was completed at ICM 

in mid-December 2015, about 25% of a tote of Gevo 

proprietary yeast remained unused. The first thought was to 

quickly obtain some additional Cosmo reject pulp and run 

an additional enzymatic saccharification and fermentation to 

isobutanol before the holiday season. Cosmo was contacted 

and was willing to supply NARA with more reject material, 

but time ran out with respect to the availability of the ICM 

facility.

The next window of availability at the ICM facility was 

March 1, 2016. In the intervening time, the NARA team 

was able to assess some of the issues encountered in the first 

campaign and develop a new operating plan to improve the 

operation.

The Gevo organism had performed well. The yeast dosage 

could be less than what was used in the first campaign, in 

which two totes were used. We calculated that we could 

potentially do four fermentations with only one tote. NARA 

requested that Gevo sell the project one tote and keep one of 

the two totes usually produced in a batch at the vendor.

8.2 Pretreated Feedstock Material

As mentioned, Cosmo Specialty Fiber was willing to 

donate additional material to the project. Using material 

from Cosmo would be the only way a second campaign 

could be accomplished. The time and cost required to go 

back and procure additional wood slash and process it at 

ZeaChem were prohibitive. Cosmo was generous enough to 

contribute their rejected pulp material (which has a positive 

fuel value to them) to NARA for no cost. It was described 

earlier how the Cosmo process uses wood from the Pacific 

Northwest and a sulfite pulping process similar to the 

SPORL process. In addition, Cosmo is interested in the 

potential for producing fermentable sugars from this stream. 

About 15,000 lb of Cosmo material had been combined with 

ZeaChem pretreated material in the third saccharification 

batch of the campaign with no noticeable impact on results. 

Based on these positive factors, it was decided to use Cosmo 

reject pulp as the enzymatic saccharification substrate 

for the second campaign. A total of 319,000 lb wet or 

121,000 lb dry of Cosmo material was shipped to ICM. 

A detailed chemical analysis for the Cosmo rejected fibers

and the subsequent fermentation solids is provided in 

Appendix E.

8.3 Process Changes at ICM

The biggest issue in the first campaign at ICM was the 

liquid–solid separation after enzymatic saccharification. 

This separation was required to enable concentrating of the 

sugars by evaporation, thus allowing for fewer fermentation 

batches. There is no reason to expect that the fermentation 

would not perform well with the solids present. Processing 

with the solids is how cellulosic ethanol simultaneous 

saccharification and fermentations are run. Corn ethanol 

dry mills operate with the solids present as well, but corn 

solids are quite different. The primary issue of running these 

fermentations with solids might be the operation of GIFT. 

The GIFT loop includes a plate and frame heat exchanger 

through which the fermentation broth with solids must pass. 

That heat exchanger was reconfigured to a “wide gap” on 

the process side to help minimize plugging due to solids.

The basic concept for the start of Campaign 2 at ICM was as 

follows:

1. Procure rejected pulp from Cosmo in bulk. This required 

transporting about 23 wet tons per load using a moving 

bed truck that could self-unload at the ICM feedstocks 

tent.

2. Load the solids into a 32,000-gal saccharification tank 

at about 13% solids. In Campaign 1, Cosmo solids were 

loaded by dumping the cardboard boxes they arrived 

in into a plastic tote, adding water to make a slurry and 

pumping directly into the tank. This resulted in only 

about 10% solids, which was being mixed with higher 

concentration ZeaChem material. For this run, mixing 

the solids with partially saccharified slurry from the 

tank might enable pumping and increase the solids 

concentration.

3. Add enzyme and allow the saccharification to go to 

completion.

4. Transfer about half or 16,000–17,000 gal of slurry 

directly to the fermentation tanks, sterilize, and add 

yeast.

5. Run the fermentation and recover the isobutanol through 

the GIFT.

6. Clean the fermenters and transfer the remaining 

saccharified slurry, sterilize, and add yeast

7. Run the fermentation and recover the isobutanol through 

the GIFT.

8. Repeat for a second load in the enzymatic 

saccharification and subsequently two more 

fermentations.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

39

The general flowsheet for this scheme is illustrated in 

Figure 8.1.

8.4 Batch 605

The first saccharification batch was run using the procedure 

described above. Loading the saccharification tank began 

on March 3, 2016, at an initial rate of approximately 650 lb 

solids per hour.

The as-received Cosmo material (Fig. 8.2) was hammer 

milled in the feedstock tent at ICM. The material could not 

be air lifted from the mill, so it was allowed to drop on the 

floor (Fig. 8.3). This was particularly cumbersome for ICM 

because it could not be easily picked up by the front loader 

and mostly had to be shoveled into the front loader scoop by 

hand.

The material was loaded into a portable bin and shuttled 

from the feedstock tent to near the saccharification tank, 

where it was laboriously scraped out through a 12- by 12-in. 

hole in the bottom of the bin into an open tote. Initially they 

added water in the tote to slurry the solids and then pumped 

it into the 32,000-gal saccharification tank.

Novozymes Cellic CTec3 enzyme was added to the 

saccharification tank, first 10 gal and then 50 gal, while 

the tank was being filled to help reduce the viscosity of the 

slurry. Two bags of lactrol (antibiotic) were also added. At 

some point early in the filling, they switched from using 

only fresh water to using partially saccharified slurry 

(reduced viscosity) from the tank and some water to mix 

with the new solids, with the hope of increasing the solids 

content. An additional 40 gal of enzyme was added on the 

third day. The solids content was measured at 11.5%, with 

26,000 gal in the tank. The tank was running a little hot, so 

3,500 gal of water (at 45 °F) was added to cool.

While attempting to adjust the pH in the tank, they overshot 

to about 6.7. There was no capability to add acid to bring the 

pH down. They finally added some acid manually to bring 

the pH to 6.0. At that point the rest (250 gal) of enzyme was 

added. It was hoped that as the saccharification continued, 

Load tote

in tent Moved by 

fork truck

Mix solids with slurry from 

saccharification tank

Three 

fermentation 

tanks

GIFT iBuOH 

recovery

Transfer 1/2 of 

saccharification tank 

to fermentation

Hold 1/2 for second 

fermentation

Figure 8.1—ICM campaign 2 initial flowsheet.

Figure 8.2—Cosmo feedstock as received at ICM.

Figure 8.3—Hammer mill discharge of Cosmo 

material.
General Technical Report FPL–GTR–278

40

the solids at the bottom would break up and that the pH 

would come down naturally.

When the saccharification broke up the solids in the bottom 

of the tank, the pH shot up to 7. There must have been a 

pocket of KOH trapped in the solids. Generally, people with 

enzyme experience at ICM felt that the enzymes would 

recover after the pH had been adjusted back to 5.5.

Saccharification did not recover after the pH was lowered. 

Additional enzyme was added to a sample from the large 

tank in the lab and saccharification restarted, indicating 

that the enzymes in the large tank had been denatured. The 

lactic acid was also climbing even though a significant 

amount of lactrol had been added. A dose of chlorine-based 

disinfectant Fermasure was added, but it did not stop the 

lactic acid. Additional saccharification did occur after more 

enzyme was added.

The lactic-acid-producing contaminant seemed to have 

taken over the tank and all efforts to stop it did not work 

(Fig. 8.4). The decision was made to abandon the batch.

0

5

10

15

20

25

30

0

10

20

30

40

50

60

70

80

90

100

3/2/2016

3/3/2016

3/4/2016

3/5/2016

3/6/2016

3/7/2016

3/8/2016

3/9/2016

3/10/2016

3/11/2016

3/12/2016

Saccharification tank (% full)

Glucose and lactic acid (g/L)

Fermasure added

Dilution caused by 

water addition

50 gal 

enzyme 

added

10 gal 

enzyme 

added

Additional 

enzyme 

added

Run 

abandoned

Tank volume (% full)

Lactic acid concentration

Glucose concentration

250 gal enzyme added

Figure 8.4—Batch 605 volume and production profile.

9. Saccharification of Cosmo 

Material—Part 2 and Fermentation

9.1 What Next?

The scheme described in Section 8 seemed to be 

unworkable due to contamination risk. It was not clear if 

the contamination was caused by recirculating partially 

saccharified slurry with free sugars outside the tank and into 

the open slurrying tank and back or if the contamination was 

inherently in the feedstock. During Campaign 1, the tank 

with Cosmo material did have an unexpected contamination 

event, which was controlled. Whether that came from the 

feedstock was undetermined.

ICM came up with a scheme to more easily transport the 

solids from the feedstock tent, get them into a slurry of high 

solids and get it pasteurized as soon as possible before fully 

saccharifying and fermenting (Fig. 9.1). That procedure is as 

follows:

1. Mix the Cosmo solids as received in the feedstock tent 

with water to make 2% to 5% solids slurry. (This is the 

approximate solids concentration that Cosmo uses when 

pumping this material in their plant.)
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

41

2. Pump this dilute slurry (as a hydro conveyor) to a rotary 

press mounted on top of a 3,000-gal “viscosity break 

tank” (VB1). The press produced a solids cake of 18% 

to 25%, which fell into the tank with high agitation. 

Enzyme was continuously added to help reduce the 

viscosity. A second tank (YC1) of approximately 

6,000 gal was added in series to allow a longer residence 

time for viscosity reduction. The water removed with the 

press was recycled to mix with fresh solids.

3. Pump the high solids, but lower viscosity, to the aerobic 

fermenter and heat to pasteurization (190 °F). The 

original plan was to pump through the ICM pretreatment 

reactor to heat pasteurize, but this proved to be unwieldy. 

The enzymes added earlier would be denatured. More 

would be added after cool down.

4. Cool the aerobic fermenters, and add the appropriate 

level of enzyme to saccharify.

5. Run a saccharification at 55 °C for 2–3 days.

6. Add nutrients and sterilize the sugar and nutrients.

7. Cool the fermenter; add yeast and ferment, recovering 

the isobutanol through the GIFT. The recovery of 

isobutanol was later changed to be after the fermentation 

was completed because of plugging issues with the GIFT.

8. Repeat for four fermentations.

This procedure was intended to minimize the possibility of 

contamination because there were only a few hours before 

the partially saccharified material was pasteurized. Because 

the solids were being dewatered to a cake at the slurry tank 

and enzyme was being added to break the viscosity, higher 

solids slurry should be possible.

Load from bulk pile 

into feed hopper

Add recycled water to 

make ~5% slurry

Continuously add 

KOH and low level 

of enzyme to 

reduce viscosity

Pump dilute slurry 

to rotary press and 

dewater to 18–25% 

solid

Transfer to fermenter for 

enzyme saccharification 

and fermentation

Recover iBuOH with 

GIFT—during or after 

fermentation

Figure 9.1—ICM campaign 2 final flowsheet.

9.2 Operation of the Solids Transfer and 

Rotary Press

The hydro conveyor (pump) used large volumes of water to 

move the solids from the feedstocks tent, across the street to 

a rotary press on the viscosity break tank (VB1). The rotary 

press removed the water, making a wet cake that dropped 

into the tank. Warm water (140 °F) was pumped from a 

holding tank to a slurry tank in the feedstocks tent. In this 

tank, solids were added at a rate that would result in slurry 

of about 5% solids. That slurry was pumped to the rotary 

press, where the solid was dewatered. The solids fell into 

the VB1 tank. Water pressed out was returned to the water 

holding tank.

The rotary press for dewatering the hydroconveyor slurry 

used a restriction gate to maintain a condensed fiber plug, 

which prevented water from passing with solids into the 

tank. Water was forced through screens by the compression 

of the fibers. In the hydroconveyor system, the water was 

recycled and pumped back to the hydroconveyor slurry tank. 

Compressed fibers were slowly ejected from the press and 

fell into the VB1 tank.

The mechanism for adding solid fibers to the slurry was 

not optimal. Sometimes large amounts and sometimes 

very small amounts of fiber would be added to the slurry. 

The hydroconveyor slurry solids content would swing 

between about 2% and 7% because of the rate at which 

the fibers were entering the slurry tank. High solids in the 

hydroconveyor would tend to form plugs in the line. Low 

solids in the hydroconveyor would tend to allow water to 

pass through the rotary press into the VB1 tank. The rotary 

press was configured so that fiber cake exiting the press 

was damp at around 18% total solids. Damp fiber cake, 

15% to 18% total solids, would sink into the slurry. With 

the settings to provide 15% to 18% solids, the condensed 

fiber plug in the rotary press occasionally would be pushed 
General Technical Report FPL–GTR–278

42

through, allowing copious amounts of water to enter the 

VB1 tank. The resulting slurry in VB1 rarely contained 

more than 15% solids.

Conversely, drier fiber cake, 20% to 25% total solids, 

tended to float on top of the slurry in VB1. If the liquid 

level in VB1 was above the top agitator, dry fiber cake 

would pile up and form a raft. When this happened, the 

hydroconveyor would need to be stopped until the fiber raft 

was incorporated into the slurry.

In the 3,000-gal VB1 Tank, solids were combined with 

water and enzyme. The pH was maintained by metering in 

potassium hydroxide (KOH). Temperature was maintained 

at 130 °F in VB1 by adjusting the temperature of the water 

in the hydroconveyor. Enzyme was added to the slurry to 

begin the liquefaction process. Residence time in the tank 

allowed the material to liquefy enough to make the slurry 

pumpable for a short distance.

One goal of the VB1 tank was to increase slurry solids 

content to about 15%. Due to the varying concentration 

of solids in the hydroconveyor slurry, there were periodic 

failures of the solid fiber plug at the outlet of the filter, 

allowing copious amounts of water to enter the tank. The 

resulting slurry typically averaged 10% to 13% (Fig. 9.2).

From the viscosity break tank, fiber slurry was pumped 

with a diaphragm pump to a 6,000-gal liquefaction tank, 

which provided longer residence time. In the liquefaction 

tank known as “yeast conditioning tank 1” (YC1), the 

slurry continued to liquefy for several hours. Continuous 

pumping from the liquefaction tank to the hydrolysis tank 

did not provide the velocity through the pipe needed to 

Figure 9.2—Solids profiles during different runs of enzymatic hydrolysis.

20

15

10

5

0

0 12 24 36 48 60 72

Time point

Solids profiling with solids bias (% total solids)

606

612

607

613

608

614

609

615

610

616

611

617

Batch ID

prevent settling of solids, which would allow clogs to form. 

Periodically, the liquefaction tank was pumped to a 6,000-

gal aerobic fermenter. Higher velocity in the line between 

the tanks reduced plugging.

Liquefaction of the fibers resulted in the release of glucose 

from the fibers. Typically, slurry leaving the liquefaction 

tank contained 20 to 40 g/L glucose. This is the initial 

point on Figure 9.3. Only one hydrolysis batch, batch 608, 

developed more than 2 g/L lactic acid during liquefaction. 

This is the initial point on Figure 9.4.

During run 7, batches 615, 616, and 617 had the rotary press 

set so that the cakes were dry enough to float. The liquid 

level in the secondary slurry tank was maintained just below 

the top agitator, which allowed cakes to be hit with agitator 

blades and not form a raft of dry fibers. Relatively dry fiber 

cake allowed the rotary press to maintain the solid fiber plug 

needed to force the water through the rotary press screens 

instead of allowing the water to pass through the rotary 

press and into the secondary slurry tank. This allowed the 

slurry to contain higher solids in run 7 than in previous runs.

9.3 Enzymatic Saccharifications

Hydrolysis was conducted in the same tanks as 

fermentation. The 6,000-gal aerobic fermenters provided 

temperature control, mixing, pH control, and a sterile 

environment. The tanks were first sterilized. The tanks 

were heated to 190 °F as fiber slurry was pumped into the 

tanks. Fiber slurry was pasteurized to 190 °F to eliminate 

contamination as was seen in batch 605 (run 3). After 

pasteurization, enzyme was added to complete hydrolysis 

of the fibers. Aerobic fermenters were filled sequentially. 
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

43

90

70

80

40

20

0

0 12 24 36 48 60 72

Time point

10

30

60

50

Biomass analysis—HPLC (g/L) glucose

606

612

607

613

608

614

609

615

610

616

611

617

Batch ID

Figure 9.3—Glucose profile during enzymatic saccharification.

5

4

2

0

0 12 24 36 48 60 72

Time point

1

3

Gevo—HPLC (g/L) lactic acid

606

612

607

613

608

614

609

615

610

616

611

617

Batch ID

Figure 9.4—Lactic acid profile during enzymatic saccharification.
General Technical Report FPL–GTR–278

44

Slurry in aerobic fermenter 1 (AF1) typically hydrolyzed for 

24 h longer than slurry in aerobic fermenter 3 (AF3).

Because the fiber slurry was pumpable through a 2-in. pipe 

for several hundred feet, the fiber slurry was at a viscosity 

that would allow for thorough mixing. Fiber slurry had 

hydrolyzed and liquefied in VB1 and YC1 for several hours 

before it was pumped to the aerobic fermenters. However, 

controlling pH was problematic. The particulate nature of 

the slurry tended to blind over the pH probe, separating 

the probe from the majority of the volume. Because the 

pH probe reading was unreliable, the tanks were checked 

periodically through sampling and measurement with a lab 

pH probe.

Sampling was problematic in run 4. The sample ports on 

the aerobic fermenters were designed for liquids that were 

largely free from suspended solids. The suspended solids in 

the hydrolyzate would quickly blind over the sample port 

opening. As a result, new sample ports were fabricated. 

During run 4, AF1 and AF2 had sample ports installed on 

the top of the fermenter. Because AF3 had not been filled 

when this problem was discovered, AF3 had a 1-in. sample 

port installed where the pH probe opening was. After run 4, 

similar sample ports were fabricated and installed on AF1 

and AF2. All ports were equipped with steam to allow sterile 

sampling.

Solids profiling of the hydrolyzate was especially difficult. 

Obtaining a representative sample was problematic. The 

hydrolyzate contained a wide array of particle sizes, some 

larger than 1 mm, some smaller than 10 μm. Passing 

hydrolyzate through a 0.22-μm filter was nearly impossible. 

One syringe filter would allow approximately 200 μL 

to pass through the filter before it clogged. During this 

project, dissolved solids measurements was performed by 

centrifuging 15 ml of hydrolyzate, and then pouring the 

centrate into a solids weighing pan. Total solids testing was 

performed by using a cut off 10-mL transfer pipette, stirring 

the hydrolyzate with the transfer pipette, and sampling 

while the sample was being stirred. Typically, the difference 

between sample A and B was much larger than seen with 

other liquids tested this way.

Obtaining enough liquid for high-pressure liquid 

chromatography (HPLC) was challenging. A standard 

0.22-μm syringe filer would clog after a few drops, perhaps 

200 μL. Centrifuging the sample at 5100 rpm for 5 min did 

not improve the filterability of the centrate. To filter enough 

liquid for an HPLC vial, three to four syringe filters were 

required. We purchased filtering centrifuges. Typically, the 

15-mL sample yielded approximately 2 mL after 5 min of 

centrifuging at 5100 rpm. Because a syringe filter absorbs 

approximately 1 mL of liquid, we centrifuged the samples 

for 10 min to obtain enough liquid for the two HPLC 

vials—one vial for the acid column, which provides good 

data on substances like ethanol and isobutanol and one vial 

for the lead column, which provides good data on sugars 

such as glucose and mannose.

The amount of Novozymes Cellic CTec3 enzyme added is 

given in Table 9.1. In general, the VB1 tank was being filled 

continuously. Certain amounts were periodically transferred 

to the AF tanks. Therefore, exactly how much enzyme went 

into each batch prior to pasteurization is difficult to know. 

Unfortunately, the entire initial enzyme application was 

denatured during the heat-up. Only the amount actually 

added to the AF would have acted in the final complete 

saccharification.

9.4 Fermentation

After the completion of hydrolysis, the aerobic fermenters 

were sterilized and then dosed with 100 gal of nutrients. 

During fermentation run 4, comprising hydrolysis batches 

606, 607, and 608, the tanks were sterilized simultaneously, 

which took a total of 37 h of heating and cooling. During 

fermentation run 5, comprising hydrolysis batches 609, 610, 

and 611, the tanks were sterilized sequentially, which took 

34 h of heating and cooling. Runs 6 and 7 each took 40 h to 

complete sterilization (Table 9.2).

Following sterilization, the tanks were cooled to the 

fermentation temperature, and then a nutrient solution was 

pumped into the fermenters through a sterile filter.

After the first nutrient addition, a mixture of additives was 

added to the tanks by filter sterilizing through a 0.2-μm 

filter. The additives were combined in a sterile add bottle 

and pumped into the aerobic fermenters through a steam 

sterilized port.

Table 9.1—Amount of enzyme 

(CTec3) applied

Batch

Enzyme added (gal)

In AFa In VBb

Run 4 606 23.4 65.2

607 17.1 33.2

608 26.3 18.0

Run 5 609 15.1 60.0

610 11.7 0.9

611 9.4 18.2

Run 6 612 14.4 41.0

613 15.2 15.4

614 20.2 11.1

Run 7 615 17.5 56.0

616 20.5 18.8

617 16.7 3.3

Average 17.3 28.4

a

Amount added to aerobic fermenter after 

pasteurization.

b

Amount added continuously to VB tank for 

liquefaction; demarcation between batches is 

difficult, so overall average is more accurate.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

45

Table 9.2—Fermentation sterilization time

Run 4 Run 5 Run 6 Run 7

Batch 505 506 507 509 510 511 512 513 514 515 516 517

Heat time (h) 24 24 24 8 13 11 13 17 22 15 18 28

Cool time (h) 13 13 13 13 3 5 4 8 4 6 3 4

Total time (h) 37 37 37 21 16 16 17 25 26 21 21 32

Run total time (h) 37 34 40 40

During sterilization, the tanks were diluted as a result of 

the introduction of condensing steam into the tanks. The 

simultaneous sterilization strategy used in run 4 resulted 

in an additional 2,181 gal of condensate from steam. The 

sequential sterilization strategy used in runs 5, 6, and 7 

resulted in an additional 1,046 gal, 1,373 gal, and 1,629 gal 

of water from steam, respectively (Table 9.3).

After run 1, the standard inoculation procedure was to pump 

the yeast using a 4-Quat sanitized diaphragm pump. A 2-in. 

diaphragm pump was used in run 4, which resulted in the 

loss of many gallons of yeast cream. A 1-in. diaphragm 

pump and 1-in. hoses were used in run 5, which limited the 

loss during inoculation. The inoculation dosage in run 4 

was about 150 lb per tank. The dosage in runs 5 and 6 was 

reduced to approximately 100 lb per tank. For inoculation 

in run 7, sterile water was added to the yeast cream tote 

to facilitate mixing prior to pumping yeast cream for 

inoculation.

The fermentation plan for run 4 included running the 

broth through GIFT during fermentation. When the 

GIFT recirculation was engaged, the flow blocked nearly 

immediately in the beer flash preheater (ET-4701). A few 

attempts were made to clear the line but were unsuccessful. 

Removing isobutanol during fermentation became 

untenable, and a recovery step was added to the process. 

One batch in three tanks became three one-tank batches. The 

new batches were designated 505, 506, and 507 (but should 

have been 506, 507, and 508 to coincide with the hydrolysis 

batches). The fermentation scheme remained the same for 

follow-on batches.

Glucose consumption rates and isobutanol production 

rates were similar among all batches. The lag phase for 

run 4 fermentations was not very long; within the first 3 h, 

glucose consumption began to steadily increase (Fig. 9.5). 

During runs 5, 6, and 7 fermentations, however, there was a 

pronounced lag phase; 6 h into runs 5 and 6, glucose began 

to be consumed (Figs. 9.5, 9.6).

Table 9.3—Fermenter volume

Fermenter volume (gal)

Run 4 Run 5 Run 6 Run 7

End of hydrolysis 18,111 17,103 18,740 17,111

Start of fermentation 20,292 18,149 20,113 18,740

Difference 2,181 1,046 1,373 1,629

Glucose consumption and isobutanol production were slow 

in batch 514 of run 6, largely as a result of the low yeast 

population. At inoculation, average population in runs 4 and 

5 were 3 and 1.4 times higher than batch 514, respectively. 

The populations in the other batches of run 6, batches 512 

and 513, were also higher.

9.5 Fermentation Details

A run consisted of the following steps:

1. Sterilize each of the 3,000–6,000-gal aerobic fermenters.

2. Cool and fill each tank sequentially with partially 

liquefied slurry from the VB1 and YC1 tanks, where a 

small amount of enzyme had been added.

3. As each tank was filled, the partially liquefied slurry 

was pasteurized by heating to 190 °F. Volume and 

temperature profiles are provided in Figures 9.7–9.10.

4. After pasteurization (which also denatured the applied 

enzymes), the tank was cooled and a new dose of 

enzymes was added to complete saccharification. 

Saccharification yields are presented in Table 9.4 (with 

key times for the saccharification and fermentation runs 

given in Table 9.5).

5. Upon completion of saccharification, nutrients were 

added, and the tank was sterilized.

6. After cooling, the tanks were inoculated and fermentation 

started.

7. GIFT recovery of isobutanol was attempted during the 

fermentation in run 4, but plugging due to solids was too 

severe, so in the other runs GIFT was delayed until the 

fermentation was completed.

8. At the end of run 4, the fermenter was pasteurized after 

fermentation to kill the yeast and avoid any conversion of 

isobutanol to isobutyric acid.

9. After the completion of fermentation, GIFT was run until 

all isobutanol was recovered.

9.6 GIFT Operation

During run 4, a considerable amount of isobutyrate was 

produced between the end of fermentation and the end 

of isobutanol recovery (Fig. 9.11). We hypothesized that 

the yeast was consuming isobutanol and converting it to 
General Technical Report FPL–GTR–278

46

60

50

40

30

20

10

0

0 6 12 18 24 30

Time point

Gevo—HPLC (g/L) glucose 60

50

40

30

20

10

0

Run 4

Run 5

Batch ID 505 506 507 509 510 511

Figure 9.5—Run 4 (505, 506, 507) and run 5 (509, 510, 511) glucose consumption profiles.

Figure 9.6—Run 6 (512, 513, 514) and run 7 (515, 516, 517) glucose consumption profiles.

70

60

50

40

30

20

0

0 6 12 18 24 30

Time point

10

Gevo—HPLC (g/L) glucose 70

50

40

30

20

10

0

60

Run 6

Run 7

Batch ID 512 513 514 515 516 517
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

47

Figure 9.7—Run 4 saccharification and fermentation temperature and volume profiles.

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

0

100

200

300

400

500

600

700

800

3/13/2016

3/15/2016

3/17/2016

3/19/2016

3/21/2016

3/23/2016

3/25/2016

3/27/2016

3/29/2016

Fermenter volume (gallons)

Temperature (°F)

Temperature – Sacc 606 and Ferm 505

Temperature – Sacc 607 and Ferm 506

Temperature – Sacc 608 and Ferm 507

Volume – Sacc 606 and Ferm 505

Volume – Sacc 607 and Ferm 506

Volume – Sacc 608 and Ferm 507
General Technical Report FPL–GTR–278

48

Figure 9.8—Run 5 saccharification and fermentation temperature and volume profiles.

Fermenter volume (gallons)

Temperature (°F)

Temperature – Sacc 609 and Ferm 509

Temperature – Sacc 610 and Ferm 510

Temperature – Sacc 611 and Ferm 511

Volume – Sacc 609 and Ferm 509

Volume – Sacc 610 and Ferm 510

Volume – Sacc 611 and Ferm 511

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

0

100

200

300

400

500

600

700

800

3/27/2016

3/29/2016

3/31/2016

4/2/2016

4/4/2016

4/6/2016

4/8/2016

4/10/2016
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

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Figure 9.9—Run 6 saccharification and fermentation temperature and volume profiles.

Fermenter volume (gallons)

Temperature (°F)

Temperature – Sacc 612 and Ferm 512

Temperature – Sacc 613 and Ferm 513

Temperature – Sacc 614 and Ferm 514

Volume – Sacc 612 and Ferm 512

Volume – Sacc 613 and Ferm 513

Volume – Sacc 614 and Ferm 514

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

0

100

200

300

400

500

600

700

800

4/8/2016

4/10/2016

4/12/2016

4/14/2016

4/16/2016

4/18/2016

4/20/2016

4/22/2016

4/24/2016
General Technical Report FPL–GTR–278

50

Figure 9.10—Run 7 saccharification and fermentation temperature and volume profiles.

Fermenter volume (gallons)

Temperature (°F)

Temperature – Sacc 615 and Ferm 515

Temperature – Sacc 616 and Ferm 516

Temperature – Sacc 617 and Ferm 517

Volume – Sacc 615 and Ferm 515

Volume – Sacc 616 and Ferm 516

Volume – Sacc 617 and Ferm 517

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

0

100

200

300

400

500

600

700

800

5/3/2016

5/4/2016

5/5/2016

5/6/2016

5/7/2016

5/8/2016

5/9/2016

5/10/2016

Table 9.4—Campaign 2 saccharification yield (key times for the saccharification and fermentation 

runs are given in Table 9.5)

Batch 

Final 

glucose 

(g/L)

Total 

solids

(%)

Suspend 

solids

(%)

Tank 

volume 

(gal)

Total 

solids 

(lb)

Volume 

liquid 

(gal)

Total 

glucose 

(lb)

Theoretical 

glucose 

(lb)

Glucose 

yield 

(%)

Run 4 606 56.3 11.5 4.0 5,514 5,532 5,292 2,486 3,414 73

607 66.7 13.5 5.0 6,251 7,398 5,940 3,307 4,565 72

608 57.6 14.3 6.3 6,353 7,923 5,952 2,863 4,889 59

Run 5 609 57.4 12.9 5.0 5,561 6,266 5,286 2,531 3,867 65

610 52.4 11.6 4.9 5,636 5,726 5,362 2,345 3,534 66

611 49.8 9.6 5.7 5,907 4,975 5,567 2,314 3,070 75

Run 6 612 57.2 13.9 5.6 5,980 7,294 5,643 2,695 4,501 60

613 63.7 15.0 6.7 6,116 8,005 5,705 3,031 4,940 61

614 67.5 16.6 7.2 6,439 9,331 5,973 3,366 5,758 58

Run 7 615 78.0 16.2 6.2 6,016 8,523 5,643 3,675 5,260 70

616 82.4 16.6 5.8 6,152 8,929 5,792 3,982 5,510 72

617 63.8 13.5 4.9 6,031 7,107 5,737 3,054 4,386 70

Overall

C0310 59.4 13.8 5.6 71,957 87,008 67,893 35,650 53,693 66
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

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Figure 9.11—Run 4 (505, 506, 507) and run 5 (509, 510, 511) isobutyrate generation profiles.

Table 9.5—Key times for each saccharification and fermentation batch

Batch Tank Fill start Enzyme addition Inoculation Start of GIFT End of run

Run 3 C0310-605 H4 3/3/2016 8:00 3/7/2016 21:00 4/14/2016 0:00

Run 4 C0310-606 AF1 3/17/2016 9:00 3/18/2016 9:00 3/23/2016 0:00 3/23/2016 22:00 3/27/2016 6:00

C0310-607 AF2 3/18/2016 5:00 3/19/2016 5:00 3/23/2016 0:00 3/24/2016 1:00 3/27/2016 1:00

C0310-608 AF3 3/19/2016 4:00 3/20/2016 4:00 3/23/2016 0:00 3/23/2016 23:00 3/26/2016 20:00

Run 5 C0310-609 AF1 3/29/2016 16:00 3/31/2016 16:00 4/3/2016 12:00 4/4/2016 9:00 4/8/2016 15:00

C0310-610 AF2 3/30/2016 13:00 3/31/2016 13:00 4/3/2016 12:00 4/4/2016 8:00 4/8/2016 21:00

C0310-611 AF3 3/31/2016 10:00 4/1/2016 10:00 4/3/2016 12:00 4/4/2016 8:00 4/8/2016 23:00

Run 6 C0310-612 AF1 4/10/2016 11:00 4/11/2016 10:00 4/15/2016 13:00 4/16/2016 10:00 4/22/2016 1:00

C0310-613 AF2 4/11/2016 8:00 4/11/2016 23:00 4/15/2016 13:00 4/16/2016 14:00 4/22/2016 2:00

C0310-614 AF3 4/12/2016 5:00 4/12/2016 16:00 4/15/2016 13:00 4/16/2016 19:00 4/22/2016 3:00

Run 7 C0310-615 AF1 5/3/2016 18:00 5/4/2016 18:00 5/8/2016 5:00 5/9/2016 4:00 5/14/2016 0:00

C0310-616 AF2 5/4/2016 15:00 5/5/2016 5:00 5/8/2016 5:00 5/9/2016 8:00 5/14/2016 0:00

C0310-617 AF3 5/5/2016 0:00 5/5/2016 9:00 5/8/2016 5:00 5/9/16 11:00 5/14/2016 0:00

isobutyrate under carbon starvation conditions. Glucose 

was completely consumed after 24 h. Between the end of 

fermentation and the end of GIFT, an additional 2.54 g/L 

isobutyrate was produced, equivalent to a loss of 2.54 g/L 

isobutanol.

To limit the loss of isobutanol to isobutyrate, a 

pasteurization step was implemented in run 5 (Fig. 9.11). 

At the conclusion of fermentation, the temperature was 

increased in the fermenters to 160 °F to kill the yeast. 

Thermodynamics of the system limited how quickly the 

yeast could be killed. On average, heating the tank to 160 °F 

took 2 h. To prevent loss of isobutanol, the tank was sealed 

during heating and cooling.

0 6 12 18 24 30

Time point

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Gevo—HPLC (g/L) isobutyrate

Run 4

Batch ID 505 506 507 509 510 511

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Run 5

During run 4, recovery was about 44 h. During run 5, 

recovery was about 72 h. One of the biggest challenges 

in using GIFT for isobutanol recovery was limited flow 

through the GIFT reboiler. Flow steadily declined during 

run 4 from 350 to 100 gal/min. In the first 16 h of recovery 

for run 5, reboiler flow declined from 350 to 0 gal/min. 

Reboiler recirculation was stopped twice during run 5 

to flush the heat exchanger; however, the best flow rate 

of post-cleaning was approximately 200 gal/min. In the 

last 18 h of run 5, reboiler flow averaged 50 gal/min. The 

residual solids fibers from the unmilled Cosmo material 

were simply too large for this particular reboiler design.

Data for runs 6 and 7 are shown in Figure 9.12.
General Technical Report FPL–GTR–278

52

5

4

3

2

1

0

0 6 12 18 24 30

Time point

Gevo—HPLC (g/L) isobutyrate

5

4

3

2

1

0

Run 6

Run 7

Batch ID 512 513 514 515 516 517

Figure 9.12—Run 6 (512, 513, 514) and run 7 (515, 516, 517) isobutyrate generation profiles.

9.7 Post-Fermentation Processing

GIFT recovery successfully removed isobutanol from the 

fermentation broth, typically down to <1 g/L remaining in 

the fermenter. Condensation following the GIFT column 

results in two liquid phases. These are separated in a liquid/

liquid (L/L) separator. The heavy phase (about 90% water) 

is stripped of isobutanol in a steam stripper. The overheads 

of the stripper, when condensed, are again two phases and 

are recycled to the L/L separator. This process effectively 

recovers all the isobutanol from the heavy phase. The light 

phase (about 80% isobutanol) is usually recovered in a 

second stripper (generally called the “rectifier,” a legacy 

name from the ethanol process). The rectifier for isobutanol 

recovery in the ICM pilot plant is too large to easily run 

continuously, so it is operated in a batch mode after the 

GIFT column operation is completed. Dehydration of the 

isobutanol light phase in campaign 1 (November–December 

2015) was generally accomplished in the rectifier column 

(see totes 901, 902, and 903 in Table 9.6). Two of the totes 

(801 and 802) became contaminated with ethanol at the 

end of campaign 1 and could no longer be dehydrated with 

the simple distillation method. These two partial totes were 

2.7% and 3.7% ethanol. The light phase from campaign 

2 was all relatively low in ethanol (totes 905, 906, 907 in 

Table 9.6).

Importantly, all the totes (Table 9.6) were out of 

specification with respect to acid number (as acetic acid, 

ASTM D1613). The specification is <70 ppm. It was 

deemed that the easiest way to remove this acid would be to 

return all the isobutanol to the fermenter and rerun through 

GIFT under different conditions.

ICM did not have the capability to measure acid number (as 

acetic acid, ASTM D1613) during the fermentation runs, 

and the acid number results obtained were from either MidWest Laboratory or Gevo (Table 9.7). The off-site analysis 

required many days to complete. ICM assured us that they 

had a reliable method on-site.

Putting the light phase back into the fermenter has 

limitations. Due to flammability issues, we were limited 

to a maximum isobutanol concentration of 50 g/L in the 

fermenter. This required that isobutanol be added to the 

fermenters multiple times because we had approximately 

1,700 gal of isobutanol and added only 6,000 gal of 

fermenter volume. Isobutanol had to be adding within the 

GIFT room because this was the only area electrically 

classified to allow high concentrations of isobutanol, such 

as was in the totes. Adding the isobutanol into the bottom 

of the GIFT column was difficult, and more than once the 

vacuum was upset in the column. Each time one of these 

upsets happened, multiple analyses were conducted of the 

GIFT overhead; each time, acid concentration was found to 

be only approximately 35 ppm, well within the specification 

of 70 ppm. It is unclear why initial analyses indicated that 

reprocessed isobutanol was out of specification, even though 

all on-site analyses indicated otherwise. The resulting 

isobutanol was crystal clear (Fig. 9.13).

After removing the acid (or most of it) from the isobutanol, 

the next step was to remove the water using the batch 
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

53

Table 9.6—Isobutanol material available after initial GIFT® recovery (analyses by Gevo)Tote

Total 

weight

(lb)

Specific 

gravity

Water

(%)

Acid 

no.

(ppm)

iBuOH

(%)

EtOH

(%)

1-PrOH

(%)

3M-1BuOH

(%)

2M-1BuOH

(%)

2PhEtOH

(%)

Unknown

(%)

Other

(%) Comments

901 599 0.8041 0.53 900 94.65 0.13 0.03 3.63 0.80 0.11 0.05 Dehydrated in Dec–Nov902 1,834 0.8050 0.52 5,800 96.62 0.04 0.02 1.72 0.29 0.13 0.27 0.06 Dehydrated in Dec–Nov903 2,087 0.8036 0.50 1,900 96.35 0.12 0.03 2.26 0.43 0.08 0.09 0.02 Dehydrated in Dec–Nov801 762 0.8436 16.55 19,200 76.20 2.69 0.70 0.76 0.15 0.23 1.03 0.77 Hi-EtOH partly 

dehydrated Dec

802 1,870 0.8402 17.44 4,900 76.86 3.73 0.34 0.27 0.06 0.04 0.37 0.75 Hi-EtOH partly 

dehydrated Dec

905 1,870 0.8366 16.07 1,200 79.13 0.76 0.09 1.74 0.30 0.02 0.30 0.34 Light phase Mar–April906 1,868 0.8376 16.46 1,500 79.98 0.60 0.22 1.78 0.27 0.02 0.03 0.50 Light phase Mar–April907 2,199 0.8370 16.48 400 80.07 0.50 0.22 1.78 0.27 0.02 0.03 0.60 Light phase Mar–April
General Technical Report FPL–GTR–278

54

Table 9.7—Light phase available after acid removal by GIFT® (analyses by Gevo)a

Tote

Gross 

weight

(lb)

Tare 

weight

(lb)

Net 

weight

(lb)

Water 

weight

(%)

iBuOH 

weight

(%)

EtOH 

weight

(%)

Acid 

no.

(ppm)

Density

(kg/L)

Estimated

iBuOH 

weight

(lb)

iBuOH 

volume

(gal)

C0310-820 2,790 573 2,217 16.03 81.25 0.26 71 0.827 1,806 262

C0310-821 2,843 578 2,265 16.99 79.88 0.31 97 0.830 1,824 264

C0310-822 2,846 582 2,264 14.86 81.50 0.49 120 0.827 1,870 271

C0310-823 2,867 565 2,302 16.85 79.88 0.47 102 0.830 1,857 269

C0310-824 2,873 578 2,295 14.93 82.98 0.40 88 0.826 1,894 275

C0310-825 2,244 576 1,668 14.52 82.62 1.32 189 0.824 1,383 201

C0310-827 2,384 576 1,808 13.16 83.64 0.32 65 82.5% 1,523 222

Total 12,156 1,764

a

Compositions and density were measured by Gevo. Data are from 160628 Gevo-GC13_NARA samples_160621.xls.

rectifier column. Unfortunately, this did not work. 

Apparently there was enough ethanol in this material 

(0.6–0.76%) to hold down the separation of water and 

isobutanol.

An alternative method of removing water from alcohol is 

by membrane separation. ICM had been discussing this 

possibility with Whitefox as a means to recover isobutanol 

from the two high ethanol totes from campaign 1. Now it 

would be necessary to process all the light phase through 

their process. A detailed daily historical summary of the 

ICM second campaign can be found in Appendix F.

9.8 Whitefox Dehydration of Isobutanol

Whitefox has a technology for removing water from 

alcohols using membrane systems. A vapor permeation 

Figure 9.13—Tote samples of completed material from ICM.

hollow fiber membrane (HFM) module was used by 

Whitefox to remove water from the isobutanol to the 

required specification (<1%). The tests were completed 

with a 92% recovery of isobutanol; an optimized membrane 

dehydration process is expected to deliver yields higher than 

99% (Table 9.8).

Two totes were analyzed for composition beyond water 

content to get an idea of what, if anything, changed during 

membrane dehydration. Table 9.9 shows that there were no 

changes other than the removal of the water.

The isobutanol was shipped from Whitefox to South 

Hampton Resources to conduct the final step, conversion of 

isobutanol to biojet fuel.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

55

Table 9.8—Material returned from 

Whitefox

Tote

Water concentration

(w%)

Liquid weight

(kg)

823 1.43 249

821 0.82 255

827 0.77 299

820 0.48 319

907 0.79 304

822 0.76 258

Total 1,683

Overall isobutanol yield 92%

Water content (wt%) 0.82%

Table 9.9—Comparison of isobutanol composition before and after 

membrane processing

iBuOH (%) Water (%) Acid no. (ppm)

Original tote Before After calca After actual Before After Before After

820 81.3 96.0 96.7 16.0 0.55 70.5 76

824 79.9 95.6 96.1 14.9 0.42 88.0 52

a

This is the concentration of isobutanol expected (calculated) if the water is removed.

10. Production of Biojet from 

Isobutanol

10.1 Overview

The production of biojet from isobutanol was done using 

technology that Gevo put together, and for which they built 

a demonstration process (Fig. 10.1) at South Hampton 

Resources (SHR) in Silsbee, Texas, USA (Fig. 10.2). SHR 

now owns and operates the process on a contract basis for 

Gevo.

The process consists of three main reactions: 

(1) dehydration of isobutanol to isobutylene, 

(2) oligomerization of isobutylene to branched C12 

and C16 olefins, and (3) hydrogenation of the olefins to 

paraffins. The process is shown in Figure 10.3. Usual 

operation of the process includes the production of C8 olefin 

or paraffin. This is a useful product for applications other 

than jet fuel. To maximize the amount of jet fuel produced, 

the C8 olefin was recycled to the oligomerization reaction 

rather than segregating it as a separate product.

Figure 10.1—Gevo-designed isobutanol to 

biojet process.

Figure 10.2—South Hampton 

Resources facility.
General Technical Report FPL–GTR–278

56

10.2 Isobutanol Preparation

Approximately 1,680 gal of purified isobutanol was 

received by SHR from Whitefox after removal of water. As 

noted earlier, all totes of isobutanol were tested for water 

and met the water specification of <1 %. Only two samples 

were analyzed for isobutanol after dewatering (Table 9.9). 

In one sample (tote 820), the acid number actually increased 

from 70.5 to 76 ppm, but in the other sample (tote 824), 

the acid number decreased from 88 to 52 ppm, a significant 

reduction. The results were inconclusive as to whether the 

membrane process reduced the acid aumber. Gevo installed 

a distillation at the beginning of the process at SHR (before 

the dehydration reactor) to purify isobutanol by removing 

heavy components that may result in gums (solvent washed 

gum is one of the isobutanol specification items) and salts 

of organic acids. A small amount of caustic was added to 

each isobutanol feed tote received by SHR to ensure that 

any organic acids contributing to the acid number were 

converted to salt. The amount of caustic added was 10% 

excess of the amount required to neutralize 150 ppm acid. 

Analysis of the isobutanol after distillation indicated acid 

number below the specification of <70 ppm (Fig. 10.4).

10.3 Process Operation

The process was started on August 29, 2016, by first 

building up some inventory of C8 olefin to ensure a smooth 

recycle. After a day of operating in this mode, the feed was 

shifted to NARA-produced isobutanol. For the next 10 

days, NARA isobutanol was fed, making a steady amount 

of jet fuel. No unexpected issues came up using the NARA 

isobutanol. There had been some concern that this feed 

contained a little more ethanol, which does not dehydrate 

to the olefin at the same rate as isobutanol and might make 

water removal more difficult. Figure 10.5 shows that 

water content in the oligomerization reactor ranged from 

approximately 30 to 100 ppm, which is about normal for the 

process.

Figure 10.3—Gevo isobutanol to biojet process at SHR.

Further, the product distributions were typical for this 

process and generally 80% to 90% C12, 8% to 10% C16, 

and ~1% C20 (Fig. 10.6).

Olefin content was initially very high. There is no 

specification on olefin content. The mass percentage of 

paraffin is reported in the Certificate of Analyses, but there 

is no specification on paraffin either. It is generally held 

that the product should be <2% olefin to make sure that 

other analyses are passed. Figure 10.6 shows that the initial 

olefin content was about 7%. This could have been due 

to an upset in the oligomerization system the week before 

the NARA project that might have sent sulfur through the 

system, reducing the capacity of the hydrogenation reactor. 

Operations supervisor at SHR raised the temperature of 

the feed to hydrogenation and that increased the reaction, 

bringing the product back down to a <2% value. A 

composite sample of the final product tank showed <2% 

(Table 10.1)

When the NARA isobutanol was exhausted, there was still 

a considerable amount of C8 olefin in the recycle tank. It 

was decided to just run this through the system. Laboratory 

experiments with pure C8 olefin at Gevo indicated that 

product was nearly all C16 at a low temperature of 

approximately 140 °F and a mixture of C12 and C16 at 

the normal operating temperature. There seemed to be no 

reaction. Nothing but C8 left the reactor. Figure 10.7 shows 

that C12 and C16 concentrations in the effluent of the 

oligomerization reactor dropped considerably.

The run was finished by running with Gevo isobutanol 

to flush out all o the NARA isobutanol. Approximately 

1,060 gal jet fuel were produced. Due to starting and 

stopping of NARA feed into a continuous process that 

already contained Gevo product (which Gevo needed to 

retain), it is estimated that between 25% and 30% of the 

final jet fuel is from Gevo isobutanol.

Impurities

iBuOH

purification

Water

removal

Oligomerization

Rxn

iBuOH

dehydration

Rxt

iBuOH

Water

Hydrogen

C8

removal

Lights

removal Hydrotreater Jet purification

Biojet
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

57

0

10

20

30

40

50

60

8/28/2016

8/30/2016

9/1/2016

9/3/2016

9/5/2016

9/7/2016

9/9/2016

9/11/2016

9/13/2016

9/15/2016

iBuOH acid number (ppm)

Figure 10.4—Acid concentration in isobutanol after distillation.

8/28/2016

8/30/2016

9/1/2016

9/3/2016

9/5/2016

9/7/2016

9/9/2016

9/11/2016

9/13/2016

9/15/2016

0

20

40

60

80

100

120

Isobutylene water concentration (ppm)

Figure 10.5—Water content of isobutylene feed to oligomerization reactor.
General Technical Report FPL–GTR–278

58

8/28/2016

8/30/2016

9/1/2016

9/3/2016

9/5/2016

9/7/2016

9/9/2016

9/11/2016

9/13/2016

9/15/2016

0

2

4

6

8

10

12

0

10

20

30

40

50

60

70

80

90

100

Weight % C8, C16, C20, olefin

% C12

% C12

% C8

% C16

% C20

% Olefin

Figure 10.6—Composition of biojet product while being produced.

Table 10.1—Final biojet 

composite analysis

Component Mass (%)

C4 0

C5–C7 0.01

C8 1.25

C9–C11 0.41

C12 87.05

C13–C15 1.15

C16 9.28

C17–C19 0.25

C20 0.55

C24 0.05

Olefin 1.93
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

59

8/28/2016

8/30/2016

9/1/2016

9/3/2016

9/5/2016

9/7/2016

9/9/2016

9/11/2016

9/13/2016

9/15/2016

0

1

2

3

4

5

6

7

8

9

10

0

10

20

30

40

50

60

70

80

90

Weight %, C8, C12

Weight %, C16, C20

% C8

% C12

% C16

% C20

Figure 10.7—Bottoms of oligomerization column.

A final product sample was sent to Inspectorate in 

Beaumont, Texas, USA, for an independent Certificate of 

Analysis confirming that the jet fuel produced conforms 

to the specifications of ASTM D7566 Annex 5 (Standard 

Specification for Aviation Turbine Fuel Containing 

Synthesized Hydrocarbons). The final fuel passed all tests 

and a Certificate of Analysis was issued (App. G).

10.4 Final Accounting

The jet fuel was loaded into three totes for transportation 

to Seattle to be used in a commercial flight by Alaskan 

Airlines. The actual commercial flight, flight number AS04 

from Seattle (SEA) to Washington, DC (DCA), took place 

on November 14, 2016.

Table 10.2 summarizes the total weight and volume of the 

jet fuel produced. The fuel was visually exceptionally clear, 

as shown in Figure 10.8.

11. Conclusions

11.1 NARA Outputs

As a result of this work, a little more than 1,000 gal of 

biojet fuel was produced utilizing softwood forest residue 

that was processed using the SPORL process and GEVO 

microorganism by NARA, with additional feedstocks 

provided by an industrial partner.

Table 10.2—Final biojet production 

weight and volume

Tote serial 

number

Net weight of fuel 

(lb)

Volumea

(gal)

244582 1,380 218.5

244601 2,540 402.2

244614 2,740 433.9

Total 6,660 1,054.6

a

Specific gravity = 0.7581.

Figure 10.8—Sample 

of final biojet.
General Technical Report FPL–GTR–278

60

A presentation of results was given at the 38th Symposium 

on Biotechnology for Fuels and Chemicals, held in 

Baltimore, Maryland, USA, April 25–28, 2016.

11.2 NARA Outcomes

This project constituted the first ever production and use of 

commercial jet fuel from softwood wood wastes from the 

U.S. Pacific Northwest.

Literature Cited

ASTM International. 2016. ASTM D7566-16b—Standard 

specification for aviation turbine fuel containing synthesized 

hydrocarbons. https://doi.org/10.1520/D7566-16B

Codner; J. 2015. NARA: Produce material by simulating 

conditions used at ZaeaChem and determine any process 

or material flow issues; Trial No: 2286, June 8–9, 2015. 

Springfield, OH: Andritz Springfield RD Center.

Gu, F.; Gilles, W.; Gleisner, R.; Zhu, J.Y. 2016. 

Fermentative high titer ethanol production from a Douglasfir forest residue without detoxification using SPORL: high 

SO2 loading at a low temperature. Industrial Biotechnology. 

12(3): 168–175.

Lan, T.Q.; Lou, H.; Zhu, J.Y. 2013. Enzymatic 

saccharification of lignocelluloses should be conducted at 

elevated pH 5.2 to 6.2. BioEnergy Research. 6(2): 476–485

Leu, S.-Y.; Gleisner, R.; Zhu, J.Y.; Sessions, J.; Marrs, G. 

2013. Robust enzymatic saccharification of a Douglas-fir 

forest harvest residue by SPORL. Biomass & Bioenergy. 

59: 393–401.

Lou, H.; Zhu, J.Y.; Lan, T.Q.; Lai, H.; Qiu, X. 2013. pHInduced lignin surface modification to reduce nonspecific 

cellulase binding and enhance enzymatic saccharification of 

lignocelluloses. ChemSusChem. 6(5): 919–927.

Wang, G.S.; Pan, X.J.; Zhu, J.Y.; Gleisner, R.L. 2015. 

Sulfite pretreatment for biorefining biomass. U.S. Patent 

No. 9,090,915 B2.

Zhang, C.; Houtman, C.J.; Zhu, J.Y. 2014. Using low 

temperature to balance enzymatic saccharification and furan 

formation in SPORL pretreatment of Douglas-fir. Process 

Biochemistry. 49: 466–473.

Zhou, H.; Zhu, J.Y.; Luo, X.; Leu, S-Y.; Wu, X.; Gleisner, 

R.; Dien, B.S; Negron, J. 2013. Bioconversion of beetlekilled lodgepole pine using SPORL: process scale-up 

design, lignin coproduct, and high solids fermentation 

without detoxification. Industrial & Engineering Chemistry 

Research. 52(45): 16057–16065.

Zhou, H.F.; Leu, S.-Y.; Zhu, J.Y.; Wu, X.; Gleisner, R.; 

Yang, D.; Qiu, X.; Horn, E. 2014. Comparisons of high titer 

ethanol production and lignosulfonate properties by SPORL 

pretreatment of lodgepole pine at two temperatures. RSC 

Advances. 4: 27030–27038.

Zhu, J.Y.; Pan, X. J.; Wang, G.S.; Gleisner, R. 2009. Sulfite 

pretreatment (SPORL) for robust enzymatic saccharification 

of spruce and red pine. Bioresource Technology. 100: 

2411–2418.

Zhu, W.; Zhu, J.Y.; Gleisner, R.; Pan, X.J. 2010. On energy 

consumption for size-reduction and yield from subsequent 

enzymatic hydrolysis of lodgepole pine. Bioresource 

Technology. 101: 2782–2792. 

Zhu, W.; Houtman, C.J.; Zhu, J.Y.; Gleisner, R.; Chen, KF. 

2012. Quantitative predictions of bioconversions of aspen 

by dilute acid and SPORL pretreatments using a unified 

combined hydrolysis factor (CHF). Process Biochemistry. 

45: 785–791.

Zhu, J.Y.; Chandra, M.S.; Gu., F.; Gleisner, R.; Reiner, R.; 

Sessions, J.; Marrs, G.; Gao., J.; Anderson, D. 2015. Using 

sulfite chemistry for robust bioconversion of Douglas-fir 

forest residue to bioethanol at high titer and lignosulfonate: 

A pilot-scale evaluation. Bioresource Technology. 179: 

390–397.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

61

Wednesday 8/19/2015 1:00 AM – 10:00 AM

• Ran consistently until needed to filter then shutdown due to problems in filtration system.

• T = 175 °C, P = 119–120 psig (about 4 psi over saturated steam pressure); expected ~15 psi over sat steam or 

130 psi.

• Feedrate ~7–7.8 BDT/day.

• Feed moisture ~28%.

• Feed moisture after pre-steaming bin ~27–28%.

• Material pre-refiner still “felt” hard, not mushy, material after refining looks fairly fine.

• Lighter in color than 35 or 45 min runs at Andritz.

• Produced ~3,500 lb pressed pulp (~40% solids).

• Conducted enzymatic hydrolysis resulting in about 40% yield to glucose.

• L:W ratio in chemical feed zone was extremely low (<2) due to under estimation of feed moisture out of 

steamer bin (estimated 50% moisture in chips was actually 27%).

• SO2 measured in vent condensate (after neutralization with NaOH) is about what we expected to make in the 

reactor.

• Measured SO2/HSO3 in blow tank and found none.

• Plan at restart

– Increase acid to increase delta P closer to 15 psi.

– Follow with increase of temperature to 180 °C and finally 185 °C.

– Increase liquid to initial feed chemical zone (lower conc H2SO4 and Mg(HSO3)2 feeds), target L:W in feed

 “zone” at 3 (before steam addition).

– Resulting also in increased overall L:W to ~5.

Thursday 8/20/2015 10:00 PM – 12:30 PM

• Looked like it was coming up, delta P was increasing to about 10 psi.

• Then discovered discharge blow-line was plugged—Shutdown.

• Observations

– If desired partial pressure of SO2 is about 15 psi in system that is 145 psi, then concentration of SO2 is ~10%.

– If we “sweep” ~1500 lb/h of steam through reactor without condensation, then we are removing 150 lb/h 

 of SO2.

– We only generate about 18 lb/h!

Friday 8/21/2015 5:00 AM – 10:00 AM

• Tom discovered that steam is superheated going into steam bin (corrected, but still some level of superheat).

• Discovered way to perhaps by by-pass steam from main digester body and feed just to discharger chamber.

• Work has been underway since about 10:30, not accomplished yet (problems with block valves).

• Tried to open the steam by-pass to the discharger chute, but found it was plugged — shutdown to clear.

• Current plan

– Took sample and are starting a hydrolysis test.

– Resolve steam by-pass issues — Done.

– Add acid to increase delta P — Done.

– Investigate adding water to feedstock — Done.

– Investigate addition of bisulfite to feedstock — Decided not to do.

– Increase T to 185 °C — Done.

Friday 8/21/2015 10:00 PM — Still Running

• Have been running pretty much smoothly since 10:00 PM last night.

• Minor shutdown (~1/2 h) when water addition to feed drag chain caused plug. Remedy was to better regulate 

water to flow only when biomass is flowing. This is a manual system, so we’ll see if they can keep-up with it.

• Minor upset (~1 h, about 8:00 AM) when acid tank went empty.

• Took filter press sample at 6:00 AM — Enzymatic hydrolysis results at 6 h are 7.67 vs Andritz 35 min 

Run: 6.31, Andritz 45 min Run: 8.71 (don’t worry about units they are relative).

• Feedstock moisture after steaming bin @ 1:00 PM was 44.6% (could still be higher).

Appendix A—Daily Historical Summary of the ZeaChem Run
General Technical Report FPL–GTR–278

62

• Temperature is 185 °C, pressure is about 158 psig or about 10 psi over pressure due to SO2, still lower than 

expected.

• Steam flow certainly appears to be 2/3 to 3/4 by-passing digester straight to discharger chute and blow line. 

There have been no issues with blow-line (so the amount of steam to that location must be sufficient). Also we 

are maintaining temperature in digester, so maybe enough steam is going there. Digester steam valve is nearly 

closed.

• Blow-tank pH is about 2.4 to 2.8.

• Current plan

– Investigate increasing water to feedstock — Look at getting 50–55% moisture in discharge of steamer bin

— Decided not to do this as amps on drag line are up and don’t want to trip out, also pump is maxed, also 

 L:W was increased due to increase in Mg(HSO3)2, see below.

– Review current acid and bisulfite concentrations and decide whether to increase, increased Mg(HSO3)2 by

 about 15%.

– Review inventory of Mg(HSO3)2 Inventory and use rate to determine probable shutdown Date/Time 

(we expect to run out before we get the new shipment) — will do a more detailed accounting today.

– Continue enzyme hydrolysis runs of each filter dump — continuing, results about the same.

– Investigate getting data for temperature in chemical mixing area of Inclined Screw (there is a probe and 

transmitter, just need range to interpret data in DCS) — Got data, temperature is holding steady at about 

248 °F (reasonable temperature for mixing chemicals).

– Investigate steam control valves to determine if we can deduce flow to each — Not done.

Sunday 8/23/2015 10:00 AM — Continues running smoothly since 10:00 PM Friday 8/21 (36 h)

• No known issues in last 24 h.

• Rates are steady as are T & P.

• Current plan

– Inventory feedstock fed — 20 BDT as of 12 NOON Sunday.

– Inventory filter cake produced —13 BDT as of 6 AM Monday.

– Identify if moisture has been run on each filter press drop and get done if not already — Remains about 44%.

– Determine general solids material balance — TBD.

– Photograph each filter press material since start-up for visual comparison — TBD.

– Continue hydrolysis testing for each filter pressing — Material is improving and is about equivalent with best 

45 min run at Andritz.

– Continue conditions as they are now.

– Inventory Mg(HSO3)2 — Should last until Thursday, new shipment is due on Thursday.

Monday 8/25/2015 9:00 AM

• Running smoothly since 10:00 PM Friday 8/21 until about 6:00 PM last night (with a short shutdown for rock 

plugged blow line), restart 6:00 AM today.

• Small pebbles plugged the blow line on Saturday night. They had to shut-down and clear them out, which took 

a few hours after which they returned to normal operation.

• Ran smoothly until about 7 PM Sunday when they had to shutdown till 2:00 AM Monday to refill the 

Mg(HSO3)2 tank.

• That was followed by an issue with the refiner and the boiler. They lost the back pressure regulator on the 

boiler and have to manually regulate the pressure. Refiner is down and probably needs a rebuild so it won’t be 

available for us on the remainder of the run.

• Restarted about 6:00 AM and seems to be running fine. We will see the first filter dump about 10–11:00 without 

the refiner.

• We also discovered that the unit was only feeding 6 BDT/day rather than 7, so the decision was made to 

increase the rate of biomass and ratio up the chemicals as well. This morning it doesn’t appear that they have 

changed the feed rate.

• Enzymatic hydrolysis results have improved and are on par with the 45 min Andritz–Springfield results with a 

yield of glucose of about 75%.

• Have produced about 13 BDT of product.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

63

• Current plan

– Understand if feed rate change is going to be made — Yes it was.

– Try to assess impact of no refiner — Appearance of the material was only slightly different. Rather than 

 being all small particles about 1/16 x 1/16 x 1/16 in. in size, there are a few strings mixed in, still about 

 1/16 x 1/16 in. but maybe up to 3/8–1/2 in. in length. I did not see any large pieces. Sorry I didn’t think to 

 take a photo before I left.

– Ship 2 pails of solids to Gevo — These have been received by Gevo.

– Determine general solids material balance — This is very difficult from the “batch” feed weights into the feed 

 bin and “batch” discharge of filter presses. Look like it is in the 50-55% range. I will try to work with Brian to 

 do a material balance on one blow tanks fill. For that they will keep close track of the feed in and the cake 

 out. He has done this on other runs and claims it gives him a good balance.

Wednesday 8/26/2015 11:00 AM

• Shutdown last night to repair boiler back-pressure regulator valve and discharger motor. They expect to restart 

by noon.

• Restarted about 6:00 AM Tuesday. Seems to have run fine without the refiner.

• Sent a sample to WSU about 1:00 PM for enzyme hydrolysis test. Initial (very preliminary results as this is 

a new lab and analytical) indicated the yield might be a little lower than it was, but this is early to make that 

conclusion.

• Back-pressure valve on boiler was replaced over night as was the discharger sweeper motor which was failing.

• 44 super sacks from NR03 have been loaded on the trailer to be transported to cold storage.

• Current plan

– Plan is to continue to run through Friday, which should complete the initial 40 tons feedstock — Boiler issues 

 caused down time thru the week.

– Shutdown for the weekend and restart on Monday to run remaining 20 tons — Plan is to shut down for the 

 weekend.

– See if we can do a “material balance” around a single blow tanks fill. This is standard for ZeaChem and 

should give us a better understanding of yield. — Brian was about to do this and we started experiencing 

 various issues with continuous operation.

Friday 8/28/2015 10:00 AM

• System experienced issues with the boiler through Wednesday and Thursday. Thursday 2:00 PM boiler 

was operating well and system was brought back-up and ran into the night until there were issues with the 

progressive cavity pump feeding the filter. That was repaired and system restarted this morning.

• We’ve received product solids analysis from WSU–Tricities.

• Current plan

– Plan is to shut down tonight for the weekend and restart on Monday morning — Shutdown on Friday, restart 

 delayed on Monday.

– Will clean out the blow tank to make sure there is no debris that might foul the pump again — Done.

– Fourth load of wood will be delivered from Lane on Tuesday — Was Delivered Monday.

– They had scheduled a boiler manuf rep to come out on Tuesday, but the boiler is running so well they 

 cancelled that.

– Still want to do a “material balance” around a single blow tanks fill. This is standard for ZeaChem and should

 give us a better understanding of yield. Need to have the system running smoothly to perform this.

– Review mass in/out of system and compositional data now on hand to get a better “feel” for probable 

yield — Done.

Monday 8/31/2015 6:00 PM

• System was shut down as scheduled last Friday night. Start-up was delayed on Monday waiting to replace the 

connector between the reactor and the blow-line. That was completed about 5:30 PM and the system is starting 

up.

• About 18 BDT of feedstock was received from Lane Products. This load consisted of about 8 BDT of material 

as we have received to date and some larger material. Pete feels this larger material would work without issue. 

I am trying to have them keep the material separate and only use the larger material if we need to.
General Technical Report FPL–GTR–278

64

• 29.5 BDT have been fed and 18.1 BDT of product has been bagged through the shutdown last Friday night 

(NR01: 2.6BDT, NR03: 10.1, NR04: 5.4).

• 88 supersacks have been delivered to the cold storage.

• Current plan

– Six samples of solids are being sent to FPL for tests similar to what they were doing on-site at Boardman the 

first week of the run — Shipped today for delivery at FPL tomorrow morning.

– Still want to do a “material balance” around a single blow tanks fill. This is standard for ZeaChem and should 

 give us a better understanding of yield. Need to have the system running smoothly to perform this.

– Concern continues regarding the rocks and stones that were cleaned out of the blow-tank pump, these can 

 possibly destroy the pump. Replacement of the pump is a long delivery time (might not impact us, but would 

 possibly impact their continued operation).

– What to do about the refiner is still being discussed. There may not be room to get at it with the current 

 operations on the pad (wood-chip pile and bags). Will continue to engage them in a discussion to determine 

 the fate of the unit for this run.

Tuesday 9/1/2015 8:00 PM — System puffed along all day without issue.

• ~34 BDT have been fed and ~22 BDT of product has been bagged.

• Mg(HSO3)2 tank was nearing empty at the end of the day (the end of the initial 12 totes).

• There will probably be some length of shutdown as the Mg(HSO3)2 tank is recharged.

• Current plan

– Sample of NR04 FP9 was sent to Weyerhaeuser (Johnway Gao), more will be sent as the week goes on.

– Samples of each filter pressing will be sent to FPL as the week goes on.

– Still want to do a “material balance” around a single blow tanks fill. This is standard for ZeaChem and 

should give us a better understanding of yield. Need to have the system running smoothly to perform this — 

 Test was completed today, result to be available TBD.

– No resolution on the refiner.

Wednesday 9/2/2015 5:00 PM — System puffed along all day without issue.

• ~39.5 BDT of chips have been fed.

• Mg(HSO3)2 tank was successfully replenished last night by feeding 2-Mg(HSO3)2 totes plus water measured 

in empty totes. This went faster and the concentration was right on. Before they had been adding water based on 

tank level, which is not very accurate. They will need to repeat this tonite and tomorrow nite and then mix the 

remainder on Friday and let it mix over the weekend.

• The 8 h material balance run was made today. We should see the data from this tomorrow.

• A new storage location was found for the remainder of the sacks. It is not refrigerated, but the hottest of 

temperatures might be over here. It will keep the bags out of the sun, wind and rain.

• Current plan

– One sample bag of each filter press in the last 24 hours was sent to FPL and to Weyerhaeuser. This sampling 

will continue until I leave on Saturday.

– They seem to be running just a little over 5 BDT/day. Therefore another 4–5 days of operation are needed to 

complete the 62 BDT. With 2 days left this week, and restarting on Tuesday after Labor Day, I project they 

will finish next Wednesday or Thursday.

– Repair of the refiner seems to be a moot point now.

– Plan is to fill 6, 5-gallon Jerri cans with liquid hydrolyzate, 5 for freezing and 1 for shipping as is. Four cans 

will be taken back to WSU next week and the others will be sent from here. — Cans have been filled and 5 

are in the freezer.

– Additional pails of solids will be sent to Gevo on Friday. — Material has been packaged and will be shipped 

on Friday.

Thursday 9/3/2015 5:00 PM — System puffed along all day without issue.

• ~45 BDT of chips have been fed, completion of 63 BDT might be late Wednesday 9/9/2015, another day if we 

run extra or have issues.

• Mg(HSO3)2 tank was replenished last night by feeding 2-Mg(HSO3)2 totes plus water measured in empty 

totes. Concentration was high ~ 8.1% rather than 7.5%.

• The 8 h material balance run was made yesterday. We should see the data from this Monday.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

65

• Mg(HSO3)2 is higher than expected, conference call was held and decision was made to reduce concentration 

by 15%.

• Current plan

– Reduce Mg(HSO3)2 concentration from target 7.5% to 6.6% concentration and monitor performance over 

tomorrow. A sample of filter cake will be sent to JY at 3:00 on Friday for Saturday delivery and analysis over 

the weekend. Based on those results we will restart on Monday with low concentration (good results) or back 

at the high concentration (bad results).

– The supply of Mg(HSO3)2 is running low, so reduction of use is necessary to insure we can run 63 or 

possibly more BDT.

Friday 9/4/2015 3:00 PM — System puffed along all day without issue until about 2:00. Plan was to shutdown 

tonight for the weekend anyway.

• ~50 BDT of chips have been fed, completion of 63 BDT might be early Thursday 9/10/2015, another day if we 

run extra feedstock or have issues.

• Mg(HSO3)2 tank was replenished last night by feeding 2-Mg(HSO3)2 totes plus water measured in empty 

totes. Concentration was lowered to ~6.3% so as to lower the use of Mg(HSO3)2. We’ve been running about 

1.5x what we originally intended, so a reduction should not interfere with the results.

• P & T were unaffected by the reduction of Mg(HSO3)2, indicating that the SO2 concentration was not 

impacted. The material looked the same as it has been (color and texture).

• Current plan

– Samples were sent to JY for analysis over the weekend. — Analysis completed.

– Start-up is not scheduled until Tuesday (taking the holiday weekend off). Based on the results of JY’s 

analysis we’ll either keep the Mg(HSO3)2 in the lowered condition or raise it back to where it was. — 

Analysis was the same as previous samples.

Tuesday 9/8/2015 7:00 PM — System is down for repairs.

• Repairs are still in progress for the blow tank agitator bearings and seal issues. The discharger was also being 

repaired. We should know more tomorrow about when we’ll start-up.

• Samples from NR05 with a 15% reduction in Mg(HSO3)2 were sent to JY and an enzymatic hydrolysis test 

performed. The results were the same as for all of the recent samples from ZeaChem. A decision was made to 

continue at the reduced Mg(HSO3)2 level.

• Contract was signed with Cascade warehouse who is just down the street from ZeaChem. They have lots of 

space (not refrigerated) so we’ll start sending our super sacks there probably tomorrow.

• Current plan

– Start-up when repairs are completed.

Wednesday 9/9/2015 7:00 PM — System is down for repairs.

• Repairs are still in progress for the blow tank agitator bearings and seal issues. Turns out they need to get a new 

shaft for the blow tank agitator, so that might not arrive till Monday. So start-up will be sometime after that.

• Super sacks are being taken to the warehouse, 3 or 4 loads today and the rest tomorrow.

• Current plan

– Start-up when repairs are completed. — Repairs completed Tuesday 9/15.

– I won’t plan to update you all, until I know more definitely the start-up date, so probably next Monday.

– This delay does not impact our schedule as we are not planning on starting at ICM until November 1.

Tuesday 9/15/2015 5:00 PM — System is being restarted.

• Repairs to blow tank agitator bearings and seal have been completed.

• Remaining 4 totes of Mg(HSO3)2 have been diluted with water in the feed tank.

• System is being restarted tonight.

• All super sacks on site have been taken to the Cascade warehouse down the road.

• Current plan

– Continue to run until Mg(HSO3)2 supply is exhausted.

– We will inventory where we are tomorrow to make sure we want to run all of Mg(HSO3)2 or not.
General Technical Report FPL–GTR–278

66

Wednesday 9/16/2015 11:00 PM — System is being restarted, again.

• They restarted last night and ran for about 2 h before finding that the Mg(HSO3)2 pump was not working. Took 

quite some time to figure out why the pump was not pumping. A check valve in the pump had cracked, not 

completely failed so it was leaking back and not going forward.

• They had the parts so they were able to fix the pump.

• Restarting this evening.

• Current plan

– Continue to run until Mg(HSO3)2 supply is exhausted.

Friday 9/18/2015 5:00 PM — System ran into the night of Thursday, 8/17, when they experienced a valve 

positioner failure. Without mechanical help to fix, they shutdown. Plan was to shut down for the weekend 

anyway.

• The finer feedstock (Accepts) has been completely fed to the system. By the incoming truck weights, that is 

about 60 BDT.

• They started into the Overs pile. They will restart on Monday and Pete estimates that they will run out of 

Mg(HSO3)2 solution late Monday or early Tuesday.

• Current estimate is that the total feed will be about 68 BDT when complete.

• ZeaChem will be having visitors on the site on Monday and Tuesday so they need to hold off on any 

videotaping until Wednesday. Pete assured me that they will be running on Wednesday, so we’ll be able to tape 

material being loaded into the sacks (just not ours, but it all looks the same).

• Current plan

– Continue to run until Mg(HSO3)2 supply is exhausted. As of Monday night there is about 24 h of material 

left.

– We’ll inventory the warehouse when completed and get an exact accounting of the sacks and weights.

Monday 9/21/2015 5:00 PM — When they started up on Monday there was a problem with the discharger, some 

foreign material in it. They shutdown to clear it. About 2:00 PM PDT when I talked to Brian, they had just gotten 

going.

• Current plan

– Continue to run until Mg(HSO3)2 supply is exhausted.

– We’ll inventory the warehouse when completed and get an exact accounting of the sacks and weights.

Thursday 9/24/2015 2:00 PM —The run is completed.

• No data or accounting yet of feed amount and product super sacks.

• Current plan

– Obtain data, weights and inventory of filter press super sacks.

– Obtain samples of final filter pressings.

– On to St. Joseph.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

67

Table B.1—Polymer sugar composition in magnesium-bisulfitepretreated forestry residuals (Douglas-fir)

Composition (%, wt/wt)

Sample ID Arabinan Galactan Glucan Xylan Mannan Total

NR03 8E 9A <0.09 0.40 47.3 0.80 1.38 49.93

NR03 FP18C <0.09 0.30 49.6 1.04 1.69 52.63

NR04 FP10C <0.09 0.16 53.4 1.04 1.35 56.05

NR04 FP11C <0.09 0.21 52.1 1.01 1.43 54.75

NR04 FP12C <0.09 0.25 51.2 1.00 1.49 53.94

NR04 FP13C <0.09 0.23 53.0 0.96 1.47 55.66

NR04 FP14C <0.09 0.23 50.1 0.97 1.50 52.85

NR04 FP15C <0.09 0.25 49.8 1.00 1.53 52.58

NR04 FP16C <0.09 0.21 50.5 1.00 1.41 53.12

NR04 9D/10A <0.09 0.17 53.0 1.05 1.43 55.75

NR04 FP17C <0.09 0.30 48.8 1.07 1.68 51.85

NR04 FP19C <0.09 0.30 49.3 1.02 1.68 52.30

NR04 FP20C <0.09 0.24 50.8 0.94 1.45 53.43

NR04 FP21C <0.09 0.22 50.6 0.89 1.38 53.09

NR04 FP22C <0.09 0.23 51.0 0.96 1.44 53.63

NR04 FP23C <0.09 0.24 50.6 0.94 1.48 53.26

NR04 FP24C <0.09 0.22 50.2 0.94 1.38 52.82

NR04 FP25C <0.09 0.19 49.6 0.96 1.29 52.04

NR05 FP-1C <0.09 0.18 49.2 0.90 1.22 51.50

NR05 FP-2C <0.09 0.21 47.1 0.84 1.19 49.34

NR05 FP-3D <0.09 0.19 46.3 0.73 1.24 48.52

NR05 FP-04 <0.09 0.24 47.8 0.75 1.14 49.93

NR05 FP-05 <0.09 0.26 47.0 0.75 1.23 49.24

NR05 FP-7 <0.09 0.25 42.2 0.70 1.18 44.35

NR05 FP-8 <0.09 0.30 44.5 0.80 1.40 47.01

NR05 FP-9 <0.09 0.27 45.8 0.70 1.23 48.03

NR05 FP-10 <0.09 0.30 46.9 0.75 1.32 49.29

NR06 FP-1 <0.09 0.29 47.2 0.70 1.25 49.49

NR06 FP-2 <0.09 0.29 46.3 0.69 1.22 48.46

NR06 FP-3 <0.09 0.32 48.1 0.77 1.30 50.54

NR06 FP-4 <0.09 0.50 45.8 1.03 1.85 49.18

NR06 FP-5 <0.09 0.26 49.9 0.79 1.21 52.16

NR06 FP-6 <0.09 0.23 48.2 0.77 1.17 50.37

NR06 FP-7 <0.09 0.24 48.6 0.76 1.18 50.78

NR06 FP-8 <0.09 0.29 48.8 0.70 1.20 50.99

NR06 FP-9 <0.09 0.25 46.8 0.69 1.12 48.86

NR06 FP-10 <0.09 0.26 46.8 0.66 1.12 48.84

NR06 FP-11 <0.09 0.26 49.0 0.65 1.11 51.02

NR06 FP-12 <0.09 0.25 47.8 0.60 1.06 49.71

Appendix B—Chemical Analyses Performed at 

Weyerhaeuser for Magnesium-Bisulfite-Pretreated 

Douglas-fir Forest Residuals
General Technical Report FPL–GTR–278

68

Table B.2—Lignin and acid-soluble lignin in 

magnesium-bisulfite-pretreated forestry residuals 

(Douglas-fir)

Composition (%, wt/wt)

Sample ID Lignin Acid-soluble lignin Total lignin

NR03 8E 9A 32.0 0.28 32.3

NR04 FP 11C 27.6 0.38 28.0

NR04 FP 14C 28.2 0.35 28.6

NR04 9D/10A 27.5 0.35 27.9

NR04 FP-24C 29.7 0.30 30.0

NR05 FP-3D 32.0 0.26 32.2

NR05 FP-9 34.8 0.31 35.1

NR06 FP-1 33.7 0.31 34.0

NR06 FP-3 33.6 0.26 33.9

NR06 FP-7 32.8 0.26 33.1

NR06 FP-11 34.4 0.24 34.6

Table B.3—Extractives in 

magnesium-bisulfite-pretreated 

forestry residuals (Douglas-fir)

Sample ID Extractives (%, wt/wt)

NR03 8E 9A 12.5

NR04 FP 11C 9.4

NR04 FP 14C 10.0

NR04 9D/10A 8.5

NR04 FP-24C 9.9

NR05 FP-3D 10.0

NR05 FP-9 10.6

NR06 FP-1 11.4

NR06 FP-3 11.4

NR06 FP-7 NA

NR06 FP-11 10.5

Table B.4—Ash in magnesiumbisulfite-pretreated forestry 

residuals (Douglas-fir)

Sample ID Ash (%, wt/wt)

NR03 8E 9A 2.43

NR04 FP 11C 2.89

NR04 FP 14C 2.97

NR04 9D/10A 2.54

NR04 FP-24C 2.60

NR05 FP-3D 2.28

NR05 FP-9 2.23

NR06 FP-1 2.17

NR06 FP-3 2.13

NR06 FP-7 1.81

NR06 FP-11 2.02
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

69

Table B.5—Sulfur content in 

magnesium-bisulfite-pretreated 

forestry residuals (Douglas-fir)

Sample ID Sulfur (%, wt/wt)

NR03 8E 9A 1.45

NR04 FP 11C 1.76

NR04 FP 14C 1.98

NR04 9D/10A 1.73

NR04 FP-24C 1.57

NR05 FP-3D 1.35

NR05 FP-9 1.38

NR06 FP-1 1.40

NR06 FP-3 1.37

NR06 FP-7 1.25

NR06 FP-11 1.28

Table B.6—Total composition balance of magnesium-bisulfite-pretreated 

forestry residuals (Douglas-fir)

Composition (%, wt/wt)

Sample ID Total lignin Extractives Ash Sulfur Polymer sugar Total

NR03 8E 9A 32.3 12.5 2.43 1.45 49.93 98.6

NR04 FP 11C 28.0 9.4 2.89 1.76 54.75 96.8

NR04 FP 14C 28.6 10.0 2.97 1.98 52.85 96.3

NR04 9D/10A 27.9 8.5 2.54 1.73 55.75 96.4

NR04 FP-24C 30.0 9.9 2.60 1.57 52.82 96.9

NR05 FP-3D 32.2 10.0 2.28 1.35 48.52 94.4

NR05 FP-9 35.1 10.6 2.23 1.38 48.03 97.3

NR06 FP-1 34.0 11.4 2.17 1.40 49.49 98.5

NR06 FP-3 33.9 11.4 2.13 1.37 50.54 99.3

NR06 FP-11 34.6 10.5 2.02 1.28 51.02 99.5
General Technical Report FPL–GTR–278

70

Table B.7—Metal content in magnesium bisulfite pretreated forestry residuals (Douglas-fir)

Metal content (mg/kg, ovendried basis) by sample ID

Metal

NR03 

8E 9A

NR04 

FP11C

NR04 

FP14C

NR04 

9D/10A

NR04 

FP-24C

NR05 

FP-3D

NR05 

FP-9

NR05 

FP-1

NR06 

FP-3

NR06 

FP-7

NR06 

FP-11

Ag <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1

Al 225 320 270 280 250 240 250 180 190 150 170

As 0.1 0.1 0.2 0.1 0.1 0.1 <0.1 <0.1 <0.1 <0.1 <0.1

B 2 3 3 2 2 2 2 2 2 2 2

Ba 29.95 30.1 30.8 30.5 28.5 28.5 30.6 27.7 28.2 24.1 24.2

Be <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1

Bi <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

Ca 695 970 920 860 810 780 820 720 520 640 590

Cd <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1

Co 0.2 0.2 0.2 0.2 0.1 0.1 0.2 0.2 0.2 0.2 0.2

Cr 29.15 7.9 8.2 8.9 6.1 9.6 19.4 14.5 15.4 24.2 33

Cu 3.65 4.1 4 4.4 3.3 3.9 4.8 4.4 4.5 3.9 5.1

Fe 230 200 190 180 140 170 170 140 150 130 170

K 195 170 190 160 160 150 180 170 170 160 150

Li <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1

Mg 4,810 5,830 6,680 5,620 5,540 4,620 4,670 4,650 4,860 4,480 4,420

Mn 20.7 19 20.7 17.8 16.7 15.6 18.5 17 17.1 14.5 14.6

Mo 4.15 3.1 3.6 3.7 2.9 2.8 7.2 4.9 5.2 3.6 6.2

Na 50 40 40 40 40 30 40 40 40 40 40

Ni 8.35 20.5 15.6 14.2 13.2 15.4 15.3 11.7 11.3 9.8 23.4

P 30 30 30 20 20 20 20 20 20 20 20

Pb 0.3 21.6 0.3 0.2 0.2 0.2 0.2 0.2 0.2 0.1 0.1

Sb <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1

Se <0.1 0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1

Sn <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10

Sr 4.8 6.1 6 5.7 5.2 5.2 5.6 5.1 4 4.6 4.8

Tl <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1

V 0.4 1.5 1.6 1.4 1.6 1.3 0.8 0.7 0.5 0.4 0.2

Zn 3 3 4 3 2 2 3 2 2 2 2

Total 6,341.8 7,680.3 8,418.2 7,252.1 7,041.9 6,096.7 6,257.6 6,010.4 6,040.6 5,709.4 5,675.8
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

71

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

NR03 8E 9A

NRO3 FP18CNRO4 FP10CNRO4 FP11CNRO4 FP12CNRO4 FP13CNRO4 FP14CNRO4 FP15CNRO4 FP16C

NRO4 9D/10A

NRO4 FP17CNRO4 FP19CNRO4 FP20CNRO4 FP21CNRO4 FP22CNRO4 FP23CNRO4 FP24CNRO4 FP25C

NR05 FP-1CNR05 FP-2CNR05 FP-3D

NR05 FP-04NR05 FP-05

NRO5 FP-7NRO5 FP-8NRO5 FP-9

NRO5 FP-10

NRO6 FP-1NRO6 FP-2NRO6 FP-3NRO6 FP-4NRO6 FP-5NRO6 FP-6NRO6 FP-7NRO6 FP-8NRO6 FP-9

NRO6 FP-10NRO6 FP-11NRO6 FP-12

Sample ID

Galactan Xylan Mannan

Galactan, xylan, and mannan

(%, wt/wt on pretreated biomass)

9000

8000

7000

6000

5000

4000

Mg and total metal

(mg/kg pretreated biomass)

3000

2000

1000

0

NR03 8E 9A

NR04 FP11C

NR04 FP14C

NR04 9D/10A

NR04 FP-24C

NR05 FP-3D

NR05 FP-9

NR05 FP-1

NR06 FP-3

NR06 FP-7

NR06 FP-11

Mg Total metal

Sample ID

Figure B.1—Galactan, mannan, and xylan in pretreated forestry residuals (Douglas-fir).

Figure B.2—Magnesium and total metal (mg/kg) in magnesium bisulfite 

pretreated forestry residuals (Douglas-fir).
General Technical Report FPL–GTR–278

72

Appendix C—Stream Ladder

In an effort to determine how much wood would be required to produce 1,000 gal of biojet fuel, given the 

various processing steps and inherent inefficiencies in the multiple site tolling operation, a material balance was 

developed. A complete stream ladder with a breakdown of compositional flows was developed based on a known 

feed composition and anticipated yields. Yields for the SPORL pretreatment were derived from Zhu et al. (2015).

The detailed stream ladder was documented in multiple spreadsheets (150319 ICM Mat Balance.xls).

Table C.1—Material balance and yield calculations to 

determine how much wood would be required to produce 

1,000 gallons of biojet fuel

Process step Proposed yields Yield by step (%)

Feedstock 90

Starting feedstock 74 BDT

Feedstock to Rxt 66.60 BDT

Poly carb out of Rxt 4.3

Glucan 21.97 BDT

Mannan 0.48 BDT

Xylan 0.31 BDT

Poly carb ship to ICM 95

Glucan 20.87 BDT

Mannan 0.46 BDT

Xylan 0.29 BDT

After saccharification 77.2

Glucose 18.55 BDT

Mannose —

Xylose —

Feed to fermentation 90

Glucose 16.69 BDT

Arabinose —

Xylose —

iBuOH produced 5.63 BDT 82

iBuOH produced 1,700.9 gal

iBuOH/feed ratio 22.99 gal/BDT

iBuOH shipped to SHR 5.07 BDT 90

iBuOH after distillation 4.82 BDT 95

Jet produced and recovered 3.17 BDT 86

Jet produced and recovered 1,005.4 gal

Product/feed ratio 13.6 gal/BDT

Overall yield 21%
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

73

Monday 11/16/2015 6:35 PM

• ICM spent most of the morning doing some final preps on the solids feeding system. Turns out that the only 

way to practically feed the solids is to dump the bags on the floor and scoop up with a Bobcat into a feed 

hopper. This operation is working well and we’re trying to collect the printed sheets that we had on each sack as 

a form of inventory control.

• The solids are then augered into a small tank and mixed with hot water and pumped out. They have a capability 

to flow control the water and the solids are volumetrically metered in together. 

• Pumping of the 14+% solids seems to be going well now, we’ll see if they can keep it up overnight.

Tuesday 11/17/2015 7:57 PM

• Continued dumping supersacks, slurrying them up and pumping to hydrolysis tank and adjusting pH. 

Hydrolysis tank is now over 50% full.

• Charles and Kevin from WSU visited and completed the videotaping with great cooperation from ICM folks.

• We decided late in the day to transfer about 2,000 gal of slurry to a smaller tank, adjust final pH, T and add 

full enzyme. This 2,000 gal will on be complete on Friday and give us a good read on the rate and yield of 

saccharification and allow us to start the filter press to see how it will work. This will save time at the end of the 

full hydrolysis tank completion, we’ll know what filtering option we’re going to use.

• Also started adding enzyme to the large tank as it fills to get a jump start on that saccharification.

• Additional heat exchanger plates arrived and a team will show up tomorrow to install, greatly increasing the 

GIFT reboiler capacity. We plan to do a test of the GIFT system with isobutanol and water on Friday.

• Last of the sacks from Oregon arrive this morning.

Wednesday 11/18/2015 9:43 PM

• A small 2,000 gal tank was initiated with enzyme at about 1:00 AM this morning. Sugar concentration when 

sampled this morning was about 30 g/L, on track with lab runs at this time.

• Tomorrow this tank will be used to test filtration when completed late tomorrow.

• The expansion HX plates for the GIFT reboiler were received yesterday and installed today.

• GIFT is being pressure tested. We expect to add the isobutanol tomorrow or Friday to test the capacity.

• The first large saccharification tank was filled today and is currently being pH adjusted and will have enzyme 

added tonight.

• The second large saccharification tank is now filling. The scheme of dumping sacks and scooping into a small 

slurry tank and pumping over to the saccharification is working, but it is slower than had been expected (by 

ICM, not by me). There has been some minor plugging, but they have been generally able to continue.

• Schedule is about a day behind, but the first fermentation is expected to be completed before Thanksgiving.

• At 13% solids in the saccharification reactor is lower than anticipated. To make up for this, more ZeaChem 

material will be co-hydrolyzed with the third saccharification with Cosmo material. This is not expected to 

increase our cost.

Thursday 11/19/2015 6:53 PM

• A small 2,000 gal tank was initiated with enzyme at about 1:00 AM this morning. Sugar concentration when 

sampled this morning was about 30 g/L, on track with lab runs at this time.

• Tomorrow this tank will be used to test filtration when completed late tomorrow.

• The expansion HX plates for the GIFT reboiler were received yesterday and installed today.

• GIFT is being pressure tested. We expect to add the isobutanol tomorrow or Friday to test the capacity.

• The first large saccharification tank was filled today and is currently being pH adjusted and will have enzyme 

added tonight.

• The second large saccharification tank is now filling. The scheme of dumping sacks and scooping into a small 

slurry tank and pumping over to the saccharification is working, but it is slower than had been expected (by 

ICM, not by me). There has been some minor plugging, but they have been generally able to continue.

• Schedule is about a day behind, but the first fermentation is expected to be completed before Thanksgiving.

Appendix D—Daily Historical Summary of the 

ICM First Campaign—0290
General Technical Report FPL–GTR–278

74

• At 13% solids in the saccharification reactor is lower than anticipated. To make up for this, more ZeaChem 

material will be co-hydrolyzed with the third saccharification with Cosmo material. This is not expected to 

increase our cost.

Friday 11/20/2015 8:30 PM

• First 33,000 gal enzyme saccharification batch will be completed tomorrow by morning. This morning after 

36 h of saccharification the conversion had reached about 85%. This is very good for that point in the reaction. 

This batch is all ZeaChem best material.

• Second 33,000 gal tank finished filling last night. It will be T and pH adjusted and the enzyme added tonight. 

This batch is all ZeaChem best material.

• Third saccharification tank will finish accepting the last of the ZeaChem and the Cosmo material. This batch is 

a combination of the last of the ZeaChem best material, the ZeaChem NR01 material and the Cosmo.

• Feeding the Cosmo solids to the top of the saccharification tank was attempted with one box, but was deemed 

too dangerous for the operator. An alternative approach of dumping Cosmo solids into an open tote located 

on the floor next to the large tank, adding a random amount of water and using a diaphragm pump to pump it 

directly into the large tank. This is working and will be finished tonight.

• GIFT system was tested out re: vacuum pressure and recirculating water. Testing with iBuOH will happen 

tomorrow.

• The filter press trial was analyzed today and the rate was slow but reasonable. The sugar recovery was close 

to being not acceptable. The rotary drum filter will be tested in the morning as the first 33,000 gal batch is 

completed.

• We continue to examine and optimize the schedule with Gevo. We are trying to balance the duration of filtration 

with the optimum schedule for fermentation and sugar storage.

• When sugar storage is necessary, ICM experience suggests that storing concentrated (150 g/L) cold (40 °F) will 

be best.

Saturday 11/21/2015 10:02 PM

• Started filtering first 33,000 gal enzyme saccharification batch through rotary drum filter. Apparently it is going 

well, but overnight will tell for sure.

• Evaporation of the filtered material was started late today. Sugars will be stored in clean ethanol fermenters 

until the aerobic fermenters are emptied after GIFT testing.

• Enzyme was added to the second 33,000 gal tank finished filling last night.

• Third saccharification tank has completed filling and is waiting for pH to stabilize before enzyme is added. It 

is about 26,000 gal and about 12.5% solids. It contains a mix of ZeaChem good material, NR01 and Cosmo 

solids. A total of about 15,000 lb of Cosmo wet solids were added.

• No contamination has been detected in any of the saccharification tanks.

• Final flow meter was replaced in GIFT system and it appears ready to go. It was decided to wait until Monday 

to test GIFT system with iBuOH when Jon Licklider is available.

Sunday 11/22/2015 7:11 PM

• Filtering of first 33,000 gal enzyme saccharification batch through rotary drum filter continues to be slow. We 

will be meeting with engineers Jon and Jesse and lead operator Kelly tomorrow to improve the filter operation. 

None of these guys was in today.

• Filtration remains the main issue and is currently delaying the schedule.

• Evaporation of the filtered material seems to be going well. Sugars are being stored cold (40 °F) in clean 

ethanol fermenters until the aerobic fermenters are emptied after GIFT testing.

• Second 33,000 gal saccharification batch has been underway for a little over 24 h. We will report on yield 

progress tomorrow.

• Third saccharification batch is about 26,000 gal and is made up of 57% “good” ZeaChem solids (NR03, 04, 05, 

06), 16% NR01 ZeaChem material and 27% Cosmo solids. Enzyme was added this afternoon and is reacting. 

I will report on its progress tomorrow.

• No contamination has been detected in any of the saccharification tanks.

• GIFT system is ready to go. It will be tested with isobutanol from Gevo tomorrow.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

75

0.35

0.30

0.25

Vol. rate (g/L-h)

0.20

0.15

0.10

0.05

0.00

0 1 2

Time (h)

Inst. lactate rate

Ave. lactate rate

3 4 5 6

Monday 11/23/2015 10:02 PM

• After two days of rotary drum filter with an average rate of 2 gal/min we have gone back to filter pressing. 

Filter press is averaging 10 gal/min over the last 10 h. Filtering at this rate will enable fermentations to begin 

back to back starting Monday 11/30/2015.

• The first saccharification batch has some contamination.

• This morning’s HPLC analysis from the first enzyme hydrolysis tank showed increasing levels of lactic acid 

indicating the presence of bacterial contamination in the tank. It is suspected that material returned from the 

rotary drum filter to the hydrolysis tank (during recoating with DE) contributed to introducing bacteria into 

the tank. When the lactate level was observed Monday morning, ICM took steps to mitigate the situation by 

increasing the dosage of virginiamycin and introduced erythromycin and penicillin, increased the temperature 

from 122 °F to eventually 150 °F, and stopped adjusting pH allowing it to drop naturally.

• Since these steps were taken, the rate of lactate production has slowed. ICM staff will continue to monitor the 

glucose and lactate in the tank.

• Kent and Andrew from Gevo are both in St. Joseph. Contamination prevention and control is Kent’s specialty.

• See graph below.

• The second saccharification batch is essentially complete (it has been going for 67 h; it is not contaminated). It 

will be held at a higher (pasteurization) temperature and has had antibiotic added all to ward off contamination 

until it can be filtered and evaporated. It will be continued to be monitored for hints of contamination.

• The third saccharification batch is still going (it has been 34 h since enzyme was added); it was at 45 g/L

glucose this afternoon.

• GIFT testing began this morning at 10. We injected about 500 gal of isobutanol into the system. During GIFT 

startup the vacuum pump became problematic and GIFT was shut down. During start up, the vacuum pump seal 

water began to leak (it had been working fine as it is used for the evaporator also). The testing was stopped to 

repair the pump. Repair parts are on order and should arrive about 1200 tomorrow.
General Technical Report FPL–GTR–278

76

Tuesday 11/24/2015 9:31 PM

• The first saccharification batch contamination appears to be under control, the rate of lactic acid formation has 

dropped to zero.

• Filtration through the filter press is continuing for the first saccharification batch. Average rate is about 

6–7 gal/min, including the whole cycle.

• Adding DE as a precoat to the filter press did not help, nor did adding DE to the hydrolyzate before filtering.

• The second saccharification batch has completed reacting. The temperature was raised to pasteurization 

temperature to ward off contamination as the batch waits to be filtered.

• The third saccharification batch is essentially complete (it has been 58 h since enzyme was added); it was at 

62 g/L glucose this afternoon.

• We will test a centrifuge tomorrow. This method could possibly operate at 20–25 gal/min and recover 80% of 

the sugar. The solids would be re-slurried and returned to an empty reactor to be filtered through the filter press 

(or possibly Fournier Press) to recover the remainder of the sugar. If the centrifuge proves out to be useful this 

could be started as soon as Saturday after the first saccharification batch is emptied through the filter press so 

that it can be used to receive the solids from the second and third batches as they are processed through the 

centrifuge.

• Parts to repair the vacuum pump in GIFT will not be received until Friday. GIFT testing to be done Sunday 

afternoon or Monday.

• First fermentation should be able to start Monday or Tuesday, depending on timing and success of GIFT testing.

Thursday 11/26/2015 9:08 AM (Thanksgiving Day)

• Filtering, evaporation and contamination battling continue on through Thanksgiving.

• Adding more DE to the slurry before going to the filter press has improve the filtration rate significantly (the 

first attempt didn’t add enough and so it looked like this scheme wouldn’t help, but with more addition it has 

helped). We are now at a rate of close to 10 gal/min.

• Filtration of the first saccharification batch is just about complete ~4,000 gal to go.

• The sesond saccharification batch has not shown any signs of contamination and is being held hot waiting to be 

filtered.

• The third saccharification batch was declared complete yesterday morning and the temperature was raised 

160 °F to ward off contamination. There still appears to be contamination. Final concentration of sugar was 

lower than reported yesterday, more like 48 g/L, which is about 70% yield for that batch.

• Concentrated sugars are being held in EF1. Kent detected contamination in that tank yesterday and because we 

couldn’t cool it fast enough (intent was to cool to 40 °F and store) it was decided to keep it hot. It is now 

160 °F. There is 6700 gal of 150 g/L sugar there.

• With the improved filtration performance, we have put off testing the centrifuge as we probably won’t need it.

• Parts to repair the vacuum pump in GIFT will not be received until Friday. GIFT testing to be done Sunday 

afternoon or Monday.

• First fermentation should be able to start Monday or Tuesday, depending on timing and success of GIFT testing.

Friday 11/27/2015 11:23 PM

• Filtering, evaporation continue. Contamination seems to be under control for now.

• Filtration rate appears to have leveled out at about 7.5 gal/min, ~70 h for the whole saccharification batch.

• The second saccharification batch is currently being filtered.

• The third saccharification batch is holding at 140 °F after an extended time at 160 °F to pasteurize, 

contamination seems to be stopped.

• Concentrated sugars are being held in EF1. This is also at 140 °F.

• Parts to repair the vacuum pump in GIFT should arrive about noon today. GIFT testing will be done Sunday 

afternoon most likely.

• First fermentation should be able to start Monday or Tuesday, depending on timing and success of GIFT testing.

Saturday 11/28/2015 9:19 PM

• Filtering of 602 (second saccharification batch) seemed to go at a record pace, completing 24,000 gal in 24 h. 

However, the amount of concentrated sugar collected in the storage tank waiting to feed fermentation seemed to 

be a little short.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

77

• Filtration was stopped while various aspects could be sorted out, like sugar analysis of tanks and what was 

being lost in filtration.

• Jeremy and Rick calculate that we have enough sugar for 1,500 gal of isobutanol (this would be just 1,000 jet 

fuel). I have yet to verify.

• The third saccharification batch is holding at 140 °F after an extended time at 160 °F to pasteurize, 

contamination seems to be stopped.

• Concentrated sugars are being held in EF1. This is also at 140 °F.

• Vacuum pump in GIFT has been repaired successfully. GIFT testing will be done Sunday afternoon most likely.

• First fermentation should be able to start Monday or Tuesday, depending on timing and success of GIFT testing.

• No shift reports today.

• I will verify where I think we are with respect to amount of sugar, and predicted amounts of isobutanol and jet 

fuel as soon as I arrive in St. Joseph tomorrow.

Sunday 11/29/2015 10:01 PM

• Filtering of 602 (second saccharification batch) is complete.

• After switching back to the rotary drum filter, they are running at a rate of about 10+ gal/min. It is unclear what 

is different from the original attempt on the rotary drum, which only got about 3 gal/min. Sugar recovery should 

certainly be much better as there is positive washing.

• The third saccharification batch is bring filtered.

• EF1 is now full of concentrated sugar and a second tank is being filled.

• GIFT testing was started tonight. The desired pressure of 0.6 psia was reached in the vacuum condenser, but we 

could not get that in the GIFT column due to a leak somewhere. They will be tracking down leaks tonight. We 

expect that to be successful.

• First fermentation should be able to start Tuesday or Wednesday as it will take at least 24 h after the GIFT test 

is completed.

• There are no shift reports today.

• I will verify where I think we are with respect to amount of sugar, and predicted amounts of isobutanol and jet 

fuel tomorrow.

Monday 11/30/2015 10:03 PM

• Filtering of 603 (third saccharification batch) is about 25% complete going through the rotary drum filter at a 

good pace. The first and second saccharification batches have completed filtering and evaporating.

• An inventory of glucose shows 25,500 lb of glucose “in the bank”, i.e., filtered, evaporated and stored at 

pasteurization temperature. Another 10,000 lb of glucose is either in the process of filtering and evaporating 

or still in the third saccharification tank. This is enough sugar to make about 1,080 gal of biojet, assuming 

conservative yields in fermentation and conversion to biojet. In addition, there is some amount of mannose and 

galactose, probably about 5% additional fermentable sugars.

• The GIFT was successfully started up. After some difficulty in finding the last leak in the G-Column the 

pressure was reached in the barometric condenser and just a little higher pressure in the G-Column is holding. 

The system was run for about 8 h and was shutdown until morning so that the key people could complete the 

start-up and testing.

• First fermentation should be able to start Wednesday or Thursday as it will take at least 24 h after the GIFT test 

is completed.

• Andrew compiled all of the data thus far from the three hydrolysis batches as well as the concentrated/filtered 

sugar storage tanks. This required opening each PDF file, copy-pasting the date & time of injection, method 

name, and any analytical results into a tab for each tank, e.g. T601, T397, etc. Tank names are not the same as 

the DCS codes. There are several different “methods” labeled on the HPLC printouts that needed to be sorted 

out

• There was no filtering, everything was imported. If an analyte was reported on multiple methods, I copied it all 

in. This can explain some of the saw-toothed charts.

Wednesday 12/2/2015 5:53 AM

• Filtering of 603 (third saccharification batch) is about 50% complete going through the rotary drum filter. The 

first and second saccharification batches have completed filtering and evaporating.
General Technical Report FPL–GTR–278

78

• The GIFT was successfully started up. Testing through the day yesterday confirmed the operation of the system. 

A range of feed iBuOH compositions and reboiler heat was tested as well as completely purifying iBuOH to 

<1% water. All systems are ready to go. A relatively easy restart after 4.5 years of abandonment.

• GIFT was shut down about 7:00 PM last night and the fermenters are being prepared for fermentation. Filling 

and sterilization will continue through today.

• First fermentation will start early tomorrow morning.

Wednesday 12/2/2015 8:37 PM

• Filtering of 603 (third saccharification batch) continues, there are about 5,000 gal remaining. No additional 

contamination has been detected in 603 or the sugar storage tanks.

• The fermenters were steam sterilized as was the GIFT loop today.

• Sugar and a portion of the nutrients were being added tonight. The tanks of sugar and nutrient will be sterilized 

(heating to 121 °C and holding) in place tonight.

• After cooling the fermenter to operating temperature the remaining nutrients will be added through sterile 

filters.

• Inoculum will be added tomorrow morning and we’ll be off to the races with the first fermentation. The first 

fermentation is expected to be completed in 48 h.

• Recirculation through GIFT will occur immediately. Heat and vacuum being added to GIFT once isobutanol 

reaches a threshold value and isobutanol will begin.

• Once 603 has completed filtering and evaporating, there is a tank of additional low concentration sugars 

(evaporator carry-over) that will be re-evaporated and the sugars recovered to supplement the second 

fermentation.

Friday 12/4/2015 11:28 AM

• We have started making isobutanol! After a much longer time to cool and pH adjust we were ready to add yeast 

last night about 2:00 AM and the pump we had chosen would not pump the yeast. The yeast had settled after 

setting in the tote for several weeks and without a sterile way of mixing we planned to use a blender pump that 

could be sterilized to recirculate the tote, thus mixing it up. Well, the yeast was so thick on the bottom (kind 

of a light colored peanut butter). They then switched to a large diaphragm pump (these pumps had saved us 

twice already in saccharification), sanitized it with chemicals (it’s plastic and can’t take steam) and Andrew 

and company were able to get the yeast in about 4:30 AM (I had left at 3:00 AM). By early morning we were 

detecting isobutanol and the GIFT was started about 10:30 AM.

• Filtering of 603 (third saccharification batch) is complete. There is still some evaporation continuing to finish 

up some rinse water that has sugar. We’ll take an accounting of remaining sugar this afternoon.

• This first fermentation is expected to be completed in 48 h, by Sunday morning.

Saturday 12/5/2015 6:40 PM

• We are making isobutanol. The fermentation is very slow, it appears that there was not any growth. At the same 

time we have struggled to keep the GIFT at a reasonable pressure, so removal of isobutanol is slow and the 

concentration appears to be drifting up, but our analytical is multiple hours behind. We will probably need to 

increase the reboiler temperature to try and get the isobutanol out and see what happens to the cells. The amount 

of lactic acid has not changed, but the levels of glycerol and isobutyric acid are slowly increasing.

• We have two tanks of sugars in waiting, 8,500 gal @ 162 g/L and 1,000 gal @ 54 g/L.

• At the current glucose consumption rate the fermentation will be another 24 h.

Monday 12/7/2015 9:10 PM

• We are nearly complete with the first fermentation. The fermentation was much slower than expected, there 

are multiple reasons for this, few if any are related to the NARA technologies, but are more the result of 

compromises that we had to make at ICM.

• One of the biggest issues has been the inability to get the same vacuum level in GIFT during fermentation that 

we had seen in testing. Even the slightest increase in pressure makes isobutanol recovery from the fermentation 

difficult.

• On the positive side, we have not seen any contamination during the long fermentation, see the nice charts 

below that Andrew prepared. The yield of isobutanol is still being determined as we finish processing the 

streams through distillation.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

79

• We expect the fermentation to finish tomorrow. At that point we will investigate the GIFT to determine if the 

vacuum can be improved (ICM exhausted all efforts of fixing it that were possible while we kept it operating). 

Hopefully without trying to support a fermentation and diagnose the problem we’ll be able to fix the vacuum. 

We also need to improve the cool-down time after sterilization to shorten the time the sugar and media are 

exposed to high temperature.

• After fixing GIFT and cleaning the system the remaining sugars will be loaded, sterilized and we’ll start the 

second fermentation.

HPLC Sugar Concentrations 140

120

100

80

Sugar (g/L)

60

40

20

0

0 8 16 24 32 40 48

Elapsed fermentation time (h)

56 64 72 80 88

Glucose

Xylose

Arabinose

Lab average glucose

Contaminating By-Products Concentrations

Acetate, lactate, ethanol (g/L)

18

16

14

12

10

8

6

4

2

0

–2 6 14 22 30 38 46 54 62 70 78 86

Elapsed fermentation time (h)

Acetic acid

Lactate

Ethanol
General Technical Report FPL–GTR–278

80

Saturday 12/12/2015 10:07 AM

• The first fermentation, B501, completed on Wed 12/9/2015. It was shut down due to contamination with little

sugars remaining. We are still trying to determine if we can recover those sugars as a “feed” into the second

batch, B502. It is currently in tank EF1, 10,100 gal, of unknown quality.

• The B501 broth was processed to remove iBuOH to <0.7 g/L.

• During that final processing, the iBuOH product was contaminated with fermentation broth because of several

separate UPEs.

• ICM reprocessed the product and was able to recover several hundred gallons of iBuOH.

• We are in the process of analyzing this ‘product’ now to determine composition and best path forward.

• We are also further estimating and measuring gallons of product made in the first batch. This is not an easy

task, as there is product in several totes, pipes, and tanks. We may not know total gallons until the end of the

campaign and all equipment is drained.

• The second fermentation batch, B502, started on Friday 12/11/2015 at 10:00 AM Central time.

• Despite holding the concentrated hydrolyzate/sugars again for >250 h at >140 °F, contamination of the sugars

with lactic and acetic acids, and likely contamination by other thermochemical products that act as inhibitors,

the yeast is performing well.

• We had lower initial sugar concentration in B502 because we a) did not start with as much sugar mass as B501

and b) added some dilution water to dilute out the inhibitor concentrations that built up during the sugar hold.

This seems to have worked.

• I’ll share a couple charts below to show comparison between B501 and B502 (first and second batches)

(Supplemental Material D.1).

• Attached are also recent shift reports from ICM that contain additional details (Supplemental Material D.2).

Sunday 12/13/2015 7:46 AM

• Bob arrived safely at ICM yesterday and Joe departed.

• Bob and I babysat B502 (second fermentation) until about 8:00 PM last night.

• By 10:00 PM, glucose was exhausted <1 g/L, galactose <1g/L and mannose was still being consumed, but

<2.5 g/L.

• Therefore, we instructed ICM to raise the temp on GIFT and begin the iBuOH recovery phase.

• This batch went considerably better than the first. Rates were ~2-fold higher, there was no 12 h lag at the

beginning, and the fermentation consumed all C6 sugars in <38 h.

• We used the same yeast and same amount as the first batch, but added ~9,000 gal dilution water to the

~9,000 gal sugar to reduce the high concentrations of inhibitors that had been created during the crazy long

1.5 week sugar hold at 140 °F.

• iBuOH recovery will continue today. We have now two totes of iBuOH product that are being analyzed.

Tuesday 12/15/2015 2:20 PM

• Fermentation 2 completed late Saturday night. Since Sunday has been spent recovering iBuOH from the

fermentation broth and processing through distillation.

• As of yesterday we had 627 gal of iBuOH in product totes with another 100–150 gal in the process. The plant is

stripping all of the fermentation broth (stripper is independent of GIFT) to wring out the last little bit of iBuOH.

• We have sent samples to Gevo and an outside laboratory for analysis. The physical appearance of some of the

material is poor. Water analysis at ICM shows the product meeting the <1% and ranging about 0.5%. A mass

spec analysis at Gevo of an initial sample showed some lignin degradation compounds, likely caused during

various upsets in the GIFT operation. Composition in the standard Gevo gas chromatograph analysis showed

~96% iBuOH with several percent of pentanol and very little ethanol, all as we would expect. We have no

analysis on the acid content, that is being done at the outside lab.

• The lignin derivative and poor color (indicating possible other unknown compounds) will probably require that

the material be redistilled. Redistillation will remove the acid if it is present as well.

• This is well short of the amount necessary to produce 1,000 gal of biojet.

• We are in the process of analyzing the run, identifying where everything went and what our next options are.

• On a positive note we made about 44,000 lb of sugar, enough for >2,000 gal of iBuOH, we just didn’t get it to

the fermenter.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

81

• Saccharification yields for tanks 1 & 2 were 77.6% and 78.7%, respectively, this is very good. The third tank, 

which was a mix of good ZeaChem material, poor ZeaChem material and Cosmo material, had a yield of 

66.2%, also very good.

• Filtration of the solids after saccharification was the primary cause of our problems. This aggravated 

contamination issues and caused a long heat history for the sugars causing other losses and problems. Filtration 

of saccharification solids is not a step envisioned in the commercial process.
General Technical Report FPL–GTR–278

82

Appendix E—Composition of Cosmo Rejects and Fermentation 

Residuals

Table E.1—Polymer sugar composition in Cosmo rejects

Composition (%, wt/wt)

Sample ID Arabinan Galactan Glucan Xylan Mannan Total

Cosmo rejects <0.09 <0.09 55.0 0.60 2.00 57.60

Cosmo rejects truck 4 <0.09 <0.09 55.9 0.60 2.04 58.54

Cosmo rejects truck 5 <0.09 <0.09 56.3 0.75 2.05 59.10

Cosmo rejects truck 6 <0.09 <0.09 55.4 0.72 2.00 58.12

Last Cosmo rejects <0.01 0.05 57.8 0.63 1.99 60.47

Table E.2—Lignin in Cosmo rejects

Composition (%, wt/wt)

Sample ID Lignin Acid-soluble lignin Total lignin

Cosmo rejects 29.4 0.57 29.97

Cosmo rejects truck 4 29.7 0.56 30.26

Cosmo rejects truck 5 29.2 0.51 29.71

Cosmo rejects truck 6 28.7 0.54 29.24

Table E.3—Solids, extractives, ash, and sulfur in Cosmo 

rejects

Composition (%, wt/wt)

Sample ID Solids Extractives Ash Sulfur

Cosmo rejects NA 5.23 1.02 1.11

Cosmo rejects truck 4 36.4 5.71 1.05 1.25

Cosmo rejects truck 5 38.9 5.93 1.07 1.19

Cosmo rejects truck 6 39.5 5.47 1.11 1.21
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

83

Table E.4—Metal content in Cosmo rejects

Metal content (mg/kg, ovendried basis) by sample ID

Metal Cosmo rejects

Cosmo rejects 

truck 4

Cosmo rejects 

truck 5

Cosmo rejects 

truck 6

Ag <0.2 <0.1 <0.1 <0.1

Al 22.5 14 16 23

As <0.2 <0.1 <0.1 <0.1

B <2 <1 <1 <1

Ba 1.1 1.2 1.3 1.5

Be <0.2 <0.1 <0.1 <0.1

Bi <2 <1 <1 <1

Ca 485 360 360 490

Cd <0.2 <0.1 <0.1 <0.1

Co <0.2 <0.1 <0.1 <0.1

Cr 0.85 0.5 0.8 0.8

Cu 3.3 4 3.8 3.7

Fe 585 67 50 64

K 40 130 80 90

Li <0.2 <0.1 <0.1 <0.1

Mg 3,165 3,410 3,350 3,250

Mn 55 60.4 48.9 47.6

Mo 0.5 0.3 0.1 0.1

Na 30 50 20 40

Ni 3.05 0.3 0.3 0.3

P <20 20 20 20

Pb <0.2 0.1 <0.1 <0.1

Sb <0.2 <0.1 <0.1 <0.1

Se <0.2 <0.1 <0.1 <0.1

Sn <20 <10 <10 <10

Sr 2.15 2.1 1.8 2.4

Tl <0.2 <0.1 <0.1 <0.1

V <0.2 <0.1 <0.1 0.2

Zn 3 3 1 2

Total 4,396.5 4,122.9 3,954.0 4,035.6

Table E.5—Polymer sugar composition in fermentation residuals 

of Cosmo rejects

Composition (%, wt/wt)

Sample ID Arabinan Galactan Glucan Xylan Mannan Total

C310 515 9999 <0.01 0.05 19.1 0.20 1.35 20.70

C310 516 9999 <0.01 0.06 20.2 0.21 1.40 21.87

C310 517 9999 <0.01 0.05 21.7 0.22 1.33 23.30

Table E.6—Lignin in fermentation residuals of 

Cosmo rejects

Composition (%, wt/wt)

Sample ID Klason lignin Acid-soluble lignin Total

C310 515 9999 58.3 3.6 61.9

C310 517 9999 57.5 3.3 60.8
General Technical Report FPL–GTR–278

84

Table E.7—Total solid, ash, and sulfur 

in fermentation residuals of Cosmo 

rejectsa

Composition (%, wt/wt)

Sample ID Total solid Ash Sulfur

C310 515 9999 8.41 11.4 1.66

C310 517 9999 8.44 10.9 1.60 a

Extractives were not analyzed in the fermentation 

residual samples.

Table E.8—Metal content in fermentation 

residuals of Cosmo rejects

Metal content (mg/kg, ovendried basis) 

by sample ID

Metal C310 515 9999 C310 517 9999

Ag <0.1 <0.1

Al 30 30

As <0.1 <0.1

B 2 2

Ba 2.9 2.8

Be <0.1 <0.1

Bi <1 <1

Ca 1,420 1,380

Cd <0.1 <0.1

Co <0.1 <0.1

Cr 1.8 1.9

Cu 4.8 4.6

Fe 180 180

K 86,600 85,200

Li 0.3 0.4

Mg 5,700 5,570

Mn 85 80

Mo 0.8 0.8

Na 15,600 15,100

Ni 1.6 1.7

P 3,200 3,030

Pb 0.2 0.2

Sb <0.1 <0.1

Se <0.2 <0.2

Sn <10 <10

Sr 7.2 6.8

Tl <0.1 <0.1

V 0.1 <0.1

Zn 30 20

Total 112,867 110,611
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

85

Appendix F—Daily Historical Summary of the ICM Second 

Campaign—0310

Thursday, March 3, 2016

• Loading of the first hydrolysis tank began today, current volume is about 18%.

• The material was being fed at a rate of about 650 lb/h, which will take a little over the budgeted 4 days to load, 

if the rate isn’t increased (they should be able to increase the rate).

• As received Cosmo material is being hammer milled in the feedstock tent and then loaded into tote boxes and 

shuttled to the biomass building next to the hydrolysis tank. The tote is held over a “slurrying bin” (a liquid tote 

with the top cut out) and the solids are scrapped thru a hole in the bottom of the tote (hole is about 12 x 12 in. 

max) and they are not pushing it into the hole from the top, but trying to scrape it out through the hole from the 

bottom (very awkward). I suggested that they need to safely get on top of the tote to push it through. Not sure 

they will do that. They could also use a dumping tote, but were afraid it would all dump into the “slurry bin” too 

fast. I’ll check in the morning to see if they have improved any and put more pressure on them if they haven’t.

• The hammer mill bag house was giving them some plugging issues. They decided to go directly from the mill 

to the floor and not use the blower, that seems to be working much better, but maybe milling a little less.

• Need to monitor the solids level in the tank, they seemed to be adding a little too much water (more than I think 

might be needed) and therefore are probably low in total solids. We’ll check that in the morning.

Friday, March 4, 2016

• Loading of the first hydrolysis tank continued today, at about 50% after about 30 h. We are still ahead of 

schedule.

• 10 gal of CTec added last night another 50 gal today, viscosity seems to be less. ~4 g/L of glucose on an 

analysis a little after noon. Don’t expect much glucose (good) from initial viscosity reduction.

• Added 2 bags of lactrol (antibiotic) as a preventive measure.

• Recycling slurry from the hydrolysis tank to mix with the added solids with the intent to increase the solids 

concentration. Temperature has gone down to 140 °F and they are recirculation through HX, but that is only 

heated with hot water making for a slow heat up. Will check in morning for temperature and composition 

(glucose and contamination). Maybe steam sparging will be needed to get temp up.

• No reliable solids analysis yet.

• Milling went well. They were milling material from truck 3, so they have plenty for this tank load.

• Wet weight of solids received in first three trucks is 136,920 lb with fourth truck total should be 183,320 at a 

conservative moisture content of 45% that gives us 15% more than we planned for. With the viscosity reduction 

due to initial CTec addition we will try and get more solids in (and hopefully more iBuOH).

• Fourth truck load was picked up at Cosmo yesterday and is expected to arrive here over the weekend.

Saturday, March 5, 2016

• Loading of the first hydrolysis tank continued today, IR solids at 11% and pH 5.4, continuing to use recycled 

slurry to mix with added solids (thus continuing to increase solids).

• Continued milling throughout the day.

• Added two bags of Lactrol, “hint” of lactic acid, pH probe not working, monitoring by grab sample. Analysis 

from hour 60 (which is either 8:00 PM today according to the run clock or 6:00 PM per the HPLC time) shows 

0.7 g/L lactic acid. Glucose is up to 13 g/L.

• Slurry being recycled appears reasonably “thin” and it is coming from the bottom of the tank. Rick says there 

is no movement in the bottom sight glass, but that there is a little higher. I’m not sure that is critical at this early 

stage.

• Added another 40 gal of CTec today (total expected quantity is about 350 gal of CTEC).

• As of 3:00 PM there was still 6–8 ft of head space to fill in the tank and they have not been adding any 

additional water today, so there is still flexibility there to get us to our ultimate solids volume.

Sunday, March 6, 2016

• Received fourth and final truck load of pulp rejects last night.

• Composition this morning was about the same as last night, a little higher in lactic acid, up to about 1.3 g/L 

from 0.7 g/L last night. There is enough lactrol in the vessel to take care of the contamination, but the bacteria 
General Technical Report FPL–GTR–278

86

might be in some of the solids that might not be mixing at the bottom edges of the tank (Andrew is not 

concerned about this increase).

• Solids by oven test were 11% this morning, but level was only about 60% and below the top agitator blade. 

Water was added to get to the top agitator (~74% now) and solids went down as expected. Hopefully mixing 

is as good as it can be. Jesse thought it would be possible to increase the power to the agitator, but that would 

take DCS programming (we’re at 100% on DCS, but amps are not excessive). Jon can probably do this in the 

morning.

• The material seems “thin” enough and pumps well. The only indication that there might not be perfect mixing 

is there appears to be no movement past a sight glass near the bottom of the tank. However, this sight glass is at 

the same height and within a few feet of the pump suction and the pump is pumping well and from that pump is 

where the solids samples are taken. They’ve added a second pump (large diaphragm) to recirc to the top of the 

tank (I don’t think the flow is really high enough to make much difference, but it shouldn’t hurt).

• Milling is going well. They will be done with it tomorrow if they continue. There is more than enough milled 

for the first tank full.

• About 100 gal of CTec has been added to this point (350 gal is what is planned for the whole tank). Temperature 

in the tank is around 67 °C out of the HX and probably >60 °C in the tank.

• Will assess where we are re: schedule, solids addition, possible contamination and next step tomorrow morning. 

We could decide that it is time to get to optimal T and add the rest of the enzyme or continue to add solids.

Monday, March 7, 2016

• This morning after examining the volume change due to solids addition it was estimated that we probably 

had enough solids in the tank, even though the solids measurement was only 11.5% and 26,000 total gallons 

(target is 13% and 32,000 gal), we stopped adding solids. It is anticipated that there is a ring of solids around 

the bottom. Further, due to the high temperature of the system, most enzyme that had been added (about 100 

gal or 1/3 of the full dose) was probably denatured. Viscosity did not appear to be going down and the solids 

obviously present in the bottom sight glasses of the tank were not moving.

• We were behind schedule this morning, as temperature and pH would need to be adjusted before enzyme could 

be added, another reason to move on.

• To cool the tank about 3,500 gal of 45 °F water was added (this was superior to the method they had anticipated 

using to cool the tank).

• Then we found that they had overshot the pH, which was at about 6.5, too high to add enzyme.

• They had no procedure to add acid, so after spending too much time discussing how to add the acid we added a 

calculated dose that brought the pH down to about 6. (There were also problems with the pH meter in the tank 

and we finally moved it to the recirculation line.)

• With the pH and temperature finally adjusted (pH is still a little high at 6, but we expect it to drift down as 

saccharification starts), temperature is about 55–58 °C, also a little high, but still reasonable.

• About 250 gal of enzyme was added at about 10:00 tonight.

• It is expected that as the saccharification proceeds, the solids in the bottom will be broken-up and solubilized 

(like what happens in a shake flask).

• About half of the remaining feedstock has been milled, they might finish that tonight, if they don’t have other 

issues.

• Given the delays today, we are currently about 12 h behind schedule. With the impact of the Lifeline fumigation 

happening on Wednesday, we will be about 24 h behind and it looks like we will inoculate early on Friday 

morning.

Wednesday, March 9, 2016

Good News

• After adding enzyme on Monday night saccharification got underway, the glucose shot up to 18 g/L, the solids 

at the bottom of the tank were freed up and the tank was fully mixing.

• Experimented with adding solids using an insulation blower showed very good promise, but a more industrial 

version would be needed to sustain an operation.

Bad News

• Saccharification broke up the solids in the tank and must have freed up a pocket of KOH, spiking the pH up 

over 7. Took most of the night to recover the pH.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

87

0

2

4

6

8

10

12

14

16

18

20

3/3/16 12:00 AM

3/4/16 12:00 AM

3/5/16 12:00 AM

3/6/16 12:00 AM

3/7/16 12:00 AM

3/8/16 12:00 AM

3/9/16 12:00 AM

3/10/16

12:00 AM

Analyte (g/L)

Glucose

Lactic acid

EtOH

Glycerol

Acetic acid

Isobutyrate

NARA-ICM/Cosmo Batch #1 Hydrolysis (T605)

• Everyone with experiences in enzymatic sacc at ICM thought that while high pH would reduce the activity of 

the enzymes, that they would return to normal when the pH was recovered.

• Saccharification did not return and lactic acid production picked up significantly. A second antibiotic was added 

to no avail.

• Once all of the solids were mobilized the concentration of solids did not increase. Result is that we are about 

30% short of our targeted solids in the tank.

Next Steps

• Added additional enzyme to a sample from the large tank and saccharification began again, confirming that the 

enzymes in the large tank were probably irreversibly destroyed by the high pH.

• A chlorine based disinfectant Fermasure was added to try to stop the contamination. This has been used by ICM 

extensively and is usually more effective than antibiotics.

• Add another dose of enzyme to the tank.

• Continue to assess the value of continuing this tank.

Thursday, March 11, 2016

• The Fermasure did not stop or really even slow down the lactic acid production.

• Glucose production took off after addition of additional 5% CTec3.

• Combining the glucose and lactic acid results in a 70% saccharification in 12–20 h. That is above expectations.

• Other than trying to heat the tank, we know of no way to control the contamination and then that might not 

work either. Given that we were short of our target solids and with all of the sugar lost to lactic acid, it is really 

not good use of our limited supply of expensive yeast to attempt to ferment this batch.

• We (with the approval of Mike) have decided to scrap this batch.

• We have already started developing plans for another run. A key criterion is to learn from this run and make 

significant procedural changes to try and avoid the contamination (or reduce it to a tolerable amount).

• We are working through the costs to continue, this is a key point. We must see that we can produce the 

isobutanol needed to meet our goal, and do it with the funds available.
General Technical Report FPL–GTR–278

88

0

5

10

15

20

25

30

3/3/16 12:00 AM

3/4/16 12:00 AM

3/5/16 12:00 AM

3/6/16 12:00 AM

3/7/16 12:00 AM

3/8/16 12:00 AM

3/9/16 12:00 AM

3/10/16

12:00 AM

Analyte (g/L)

Glucose

Lactic acid

EtOH

Glycerol

Acetic acid

Isobutyrate Additional CTec3 added

Fermasure added

NARA-ICM/Cosmo Batch #1 Hydrolysis (T605)

Friday, March 11, 2016 AM

• ICM (Jeremy) came up with a new scheme that should allow us to more easily load the system and sterilize the 

material.

• The idea is to pump a slurry of about 2% to a screw press immediately above a small tank capable of high 

viscosity mixing. Along with the pressed cake, water to dilute to 13% solids, KOH to adjust pH and a low dose 

of enzyme will be continuously added.

• With about a 3–5 h residence time in that tank the material will liquefy. It is next pumped through the 

ICM pretreatment reactor to sterilize and then directly to the aerobic fermenter where it will be cooled to 

saccharification temperature and the remainder of the enzyme added. When saccharification is complete, the 

fermenter will be sterilized and prepared for fermentation.

• On Thursday they tested the filter press, liquefaction rates at low enzyme loading and last night they were to 

test pumping the 2% solution.

• Today we will review costs, amount spent and a detailed estimate of conducting this scheme, if the tests are all 

satisfactory and the costs are reasonable, we will begin on Monday morning.

Friday, March 11, 2016 PM

• Some successful testing was completed last night and today.

• Filtering of a low concentration slurry of feedstock was successfully tested tin the Fornier screwpress.

• Pumping the low solids slurry from the feedstocks tent to the area of the hydrolysis reactor was successful. 

Liquefaction of 13% solids was easily accomplished with low level of enzymes.

• Setting up equipment modifications will be completed on Monday and start-up on Tuesday.

Monday, March 14, 2016

• Parts of the new processing scheme were tested, high flow rate of dilute solids were successfully run through 

the Fornier press.

• The press was relocated to the top of the “viscosity break tank” high mixing tank to be used for liquefaction.

• Pumping system was set up in the feedstocks tent.
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• A flow test on the GIFT was conducted with hydrolyzate from the failed batch, the first valve encountered 

plugged quickly. While the particles are generally small, many are oblong, maybe 1/16 by 1/4 in., but there are 

also bits of rubber in the solids (perhaps from conveyor belts at Cosmo). Additional schemes and testing are 

being explored to overcome this problem.

Wednesday, March 16, 2016 AM

• Started the new system last night. Slurry feed to Fornier press worked reasonably well. Every so often the solids 

concentration in the slurry being pumped over from the feedstocks tent would drop off and cause the filter 

press to “blow through”. This means that the filterpress stops working and the dilute slurry runs through. The 

operators were watching pretty close, so they were able to make adjustments and get the filter cake back. A little 

extra water would go into the tank, but the solids were generally coming out of the filter press at 23%, so there 

was a need to add water.

• The solids “metered feeder” is not so reliable, and there is no positive control of water to the dilute slurry 

(I’ll check on that this morning and see what can be done to fix).

• The operators did not get the enzyme loaded last night due to a miscommunication, so the material in the 

“viscosity break tank” (our liquefaction tank) was extremely high, but it was still pumpable with the diaphragm 

pump and was generally mixing, but solids were accumulating at the bottom. Enzyme was added this morning, 

10 gal to a mix of 2,500 gal of 12.5% slurry. That is 3.7%, I think too much, glucose level is already 20 g/L.

• They are working on getting pretreatment ready to start to sterilize the slurry and start filling the first aerobic 

fermenter to finish the enzymatic saccharification.

Wednesday, March 16, 2016 PM

• ICM felt that they needed 5,000 gal inventory of liquefied material before attempting to start-up the 

pretreatment reactor (this will act as the HTST sterilizer) for the liquefied material. Unfortunately, this means a 

minimum of an additional 8 h that the first 2,500 gal will have to sit before sterilization. Also this is the first I 

heard of this requirement.

• The amount of enzyme initially added to the liquefaction tank was 10 gal (4.8% wt enz/wt biomass). An 

additional 10 gal was added to 2,500 gal of 13% solids, another 4%. Seems too high for liquefaction. Plan for 

tonight is to continuously add 3.1% wt enz/wt biomass.

• ICM spent all day shift not being able to run the liquefaction system. Seems they overflowed the slurry tank 

and that not only destroyed some feedstock, but took multiple hours to clean up before the liquefaction system 

could be restarted.

• Analysis of liquefaction tank at 10:00 AM was about 20 g/L (seems high for simple liquefaction), no 

contamination. At 3:00 PM glucose production had slowed and was 23 g/L. Lactic was at 0.2 g/L, I’m not 

sure if that is an indication of anything or not. So as of 5:00 PM they still wanted to make the extra 3,000 gal. 

Pretreatment hopefully starts tonight.

• As soon as pretreatment starts it will begin filling the aerobic fermenter for hydrolysis.

• Tomorrow will be a big day to see if the liquefaction and pretreatment (sterilization, HTST) can work 

continuously and fill the aerobic fermenters.

Thursday, March 17, 2016

High Level

• The Cosmo reject material is being liquefied and saccharified! Glucose levels are 30–35 g/L—just not yet in the 

tank where we planned hydrolysis (aerobic fermenter 1, AF1). Those sugar levels were measured this morning 

in the viscosity break tank and “surge tank” as I describe below and in the attached process flow sketch.

• Lactic acid increased from last night to this morning—from 0.2 g/L to about 1.8 g/L as of 8:00 AM today. This 

level may still be OK. I don’t have more recent data yet. But ICM injected steam into the surge tank earlier 

today to try to stop the contaminants.

• There have been a few issues with plugging from larger feedstock particles and chunks of rubber (>1 in.) in the 

Cosmo feedstock. Bob’s looking into the origin of the rubber. Current hypothesis is conveyor belts at Cosmo. 

I checked the tires on the ICM skid-loader in the feedstock tent, too, but that’s not a probable match.

• New plan is to get the partially saccharified material from its current location in several tanks into the AF1 tank, 

pasteurize at 180–190 °F, adjust to hydrolysis pH and temperature as quickly as possible, and add more CTec3 

to finish liberating sugar.
General Technical Report FPL–GTR–278

90

• The first fermentation will not begin until next Monday, 3/21/2016. I will provide continued tech support by 

phone and PC for the fermentation (Dad duty calls with my 6-year old starting this Sunday).

0

5

10

15

20

25

30

35

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

3/16/16 4:48

3/16/16 9:36

3/16/16

14:24

3/16/16

19:12

3/17/16 0:00

3/17/16 4:48

3/17/16 9:36

3/17/16

14:24

3/17/16

19:12

3/18/16 0:00

Analyte concentration (g/L)

Glucose (g/L)

Xylose

Lactic acid

Glycerol

Acetic acid

Isobutyrate

Ethanol

Glucose

Mannose

Viscosity Break Tank (VB1) HPLC Data

Details

• The solids in the viscosity break tank are currently not pumpable. Rick indicated it was at ~14%, but they’re not 

mixing well and keep plugging the lines out of that tank. This is despite adding a 0.1 g CTec3 per g glucan dose 

of enzyme to that tank. I don’t know the temperature or pH of the tank...perhaps that’s the issue. The Fournier 

press also expels “bricks” of solids that ICM hypothesized might settle to the bottom of the tank. Here’s a 

photo.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

91

• Rick also said that larger chunks of feedstock and bits of rubber in the feedstock are plugging the pretreatment 

reactor. The pretreatment reactor was intended to sterilize the feedstock at 300 °F for 10 min before hydrolysis. 

ICM now wants to bypass the pretreatment reactor. We agreed this could work, because Rick also has a plan to 

pasteurize in the aerobic fermenter. Again, I’m concerned that the “sugar dinner bell” rang with the first drop of 

enzyme was added yesterday or earlier...and the clock is ticking.

• A surge tank called YC1 was added in line after the viscosity break tank. See attached XLS for a process flow 

sketch. ICM made that decision sometime yesterday after Bob left because of struggling to keep the viscosity 

break tank flowing.

• Rick said they want to keep going from viscosity break tank (about 140 °F) into the surge tank to enable longer 

residence time to enhance liquefaction. The surge tank, aka tank YC1, is about 160 °F because they added 

steam directly injected, but Rick needs to laser this to know the actual temp because there is no control or gauge 

on it.

• Right now, ICM is planning to add hot water to the viscosity break tank to thin that out to become mixable and 

pumpable again. Then they will start the flow back to the surge tank.

• Rick thinks that there is now ~4,000 gal of partly saccharified material in the surge tank and about 1,000 gal in 

the aerobic fermenter 1. Goal would be to push that all over to AF1 as soon as possible (not sure when) and top 

it off to get hydrolysis really started with more enzyme.

• Rick also wants to keep AF1 hot at 180 °F or higher (by adding 210 °F water to the jacket and coils of that 

vessel) to fend off contamination prior to cooling, pH adjustment, then adding enzyme and starting the 

hydrolysis.

• Once hydrolysis reaches the estimated glucose concentration of 50 g/L or greater, hydrolysis would be 

considered complete (per expected hydrolysis yield and solids).

• Fermentation nutrients would be added, the entire vessel(s) SIPed, cooled, pH adjusted, then inoculated with 

Gevo yeast.

Friday, March 18, 2016

• Today was a good day at ICM.

– Most of the feedstock for this batch (B606 hydrolysis, B505 fermentation) has been slurried and is pumping 

or hydrolyzing somewhere in the system.

– ICM is continuing to feed the slurry tank (VB1) until level is ~2,200 gal, targeting 15% TS, currently 

~1,500 gal in VB1. Should finish tonight.

– The surge tank, YCT1, has 3,400 gal of product ready for transfer to AE3.

– I have attached a process block flow sketch that I labeled (pardon the quality).

• AF1 is hydrolyzing!

– A dose of CTec3 was added to the tank at about 1:00 PM today after the tank was pasteurized at 190 °F.

– As of 6:00 PM tonight, pH = 5.13, 37 g/L glucose (sugar column), 1.2 g/L lactic, 0.75 g/L acetic, 1.4 g/L 

furfural (organic acid column).
General Technical Report FPL–GTR–278

92

• AF2 is full and being pasteurized to 190 °F.

– Heating now and at 170 °F on the way up to 190 °F.

– Will be held for 1 h at 190 °F (long pasteurization).

– ICM thought it would be at hydrolysis temp and have enzyme dosed sometime overnight.

• AF3 is now empty and will be cleaned and sterilized.

– AF3 is the third and final fermenter that will pull double duty as a hydrolysis tank then fermenter.

– Tank is empty and spray balls are being installed for CIP.

– After CIP, empty SIP will take place.

– After SIP, 5,500 gal of media from VB1/YCT1 will be transferred and pasteurized for 1 h.

• PROJECTIONS (these are my own estimates)

– All three AFs should be in hydrolysis mode by the time I leave here at 11:00 AM-ish Saturday.

– Hydrolysis should be complete in each tank by Sunday evening (AF3 might take until Monday AM).

– Once hydrolysis is complete, all three AFs (aerobic fermenters) will have fermentation nutrients added and 

will be steam sterilized prior to inoculation.

– Then fermentation should be inoculated sometime on Monday.

Saturday, March 19, 2016

• So far, so good today at ICM. I am headed back to sunny CO this afternoon, so this will be my final report. 

Bob will take the baton back tomorrow.

• Aerobic1 is hydrolyzing and is at close to 24 h of hydrolysis (enzyme added 3/18/2016 1:00 PM).

• Aerobic2 is hydrolyzing and is at close to 12 h of hydrolysis (enzyme added 3/18/2016 8:00 PM)? Need to 

verify time.

• Aerobic3 was still being SIPed in preparation to receive the last 5,500 gal of “pre-hydrolyzed” feedstock.

• AF3 will then be pasteurized, enzyme added when cooled and at pH, and enzyme added to start hydrolysis.

• GIFT testing was completed yesterday and went OK.

• While CIPing the GIFT unit, the valve between the GCOL and the CO2 scalper plugged (likely with feedstock). 

ICM is working to unplug this, then will finish CIPing and do SIP on the GIFT loop. Note: the test material 

used was NOT fully hydrolyzed. So it may be a worst-case scenario.

• Rick reported that there was a pH upset in the first slurry tank, VB1—and about 2,000 gal of feedstock destined 

for AF3 tank was overdosed with KOH to a pH of about 10. ICM is working to neutralize this before pumping 

into AF3. I’m told it’s “kinda thick”.

• Because all of the feedstock received a higher dose of CTec3 in the liquefaction process than planned (0.1 g 

enzyme/g glucan), the hydrolysis in each of the AF tanks is expected to take 24 h or less. ICM will monitor the 

hydrolysis reactions, but fermentation nutrient addition and SIP will not occur until the last tank filled (AF3) 

finished hydrolysis.

• Attached is the most updated data I have for the five tanks in the process (Supplemental Material F.1).

• Solids analysis has also been taken and is drying in the oven. Data are pending.

• Awaiting additional data from HPLC and solids analysis as hydrolysis continues.

Sunday, March 20, 2016

• All three aerobic fermenters have been loaded from the liquefaction system (consisting of viscosity brake tank 

and yeast conditioning tank). Enzyme was added to the third tank last night.

• The sugar concentrations in the three tanks are 59, 69, 58 g/L and lactic acid levels of ~0, ~0, 2.4 g/L. Our 

target concentrations of sugar was about 48 g/L, so we have exceeded that.

• Sterilization of the tanks has been started and with inoculation expect tomorrow afternoon.
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0

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50

60

70

0.0

0.5

1.0

1.5

2.0

2.5

3/18/16 0:00

3/18/16 6:00

3/18/16

12:00

3/18/16

18:00

3/19/16 0:00

3/19/16 6:00

3/19/16

12:00

3/19/16

18:00

3/20/16 0:00

3/20/16 6:00

3/20/16

12:00

3/20/16

18:00

3/21/16 0:00

Analyte concentration (g/L)

Glucose (g/L)

Xylose

Lactic acid

Glycerol

Acetic acid

Isobutyrate

Ethanol

Glucose

Mannose

Aerobic Fermenter 1 (AF1) HPLC Data

Glucose (g/L)

Xylose

Lactic acid

Glycerol

Acetic acid

Isobutyrate

Ethanol

Glucose

Mannose

Aerobic Fermenter 2 (AF2) HPLC Data

0

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30

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50

60

70

80

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3/19/16 0:00

3/19/16 6:00

3/19/16

12:00

3/19/16

18:00

3/20/16 0:00

3/20/16 6:00

3/20/16

12:00

3/20/16

18:00

3/21/16 0:00

Analyte concentration (g/L)
General Technical Report FPL–GTR–278

94

Glucose (g/L)

Xylose

Lactic acid

Glycerol

Acetic acid

Isobutyrate

Ethanol

Glucose

Mannose

Aerobic Fermenter 3 (AF3) HPLC Data

0

10

20

30

40

50

60

70

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

3/19/16 0:00

3/19/16 6:00

3/19/16

12:00

3/19/16

18:00

3/20/16 0:00

3/20/16 6:00

3/20/16

12:00

3/20/16

18:00

3/21/16 0:00

Analyte concentration (g/L)

Tuesday, March 22, 2016

• SIP was completed on three aerobic fermenters with nutrients added.

• pH dropped with the introduction of nutrient.

• They have had trouble with adjusting pH, took considerable time, by 10:00 AM the next step was to try to run 

GIFT and then inoculate.

• There were issues with sterility of the GIFT loop and they SIPed the GIFT independently of the fermenters.

• Attempted to flow through GIFT and plugged around pre-heater.

• Plan is to inoculate without GIFT, continue to clean-out plug.

• I am concerned that they have a clear plan to vent the tanks. Operation without GIFT will be without vacuum 

and venting through the scalper. Jon Licklider needs to be consulted as to how this is to be operated, Rick was 

unclear. It is how they would normally operate fermentation when not making iBuOH.

Wednesday, March 23, 2016 AM

• All three fermenters were inoculated at 11:40 PM last night and are fermenting.

• All tanks seem to be running about the same (they are now independent because we are not running through 

GIFT).

• We will look at options for recovery of iBuOH when the batch is completed, we will not try to use GIFT while 

the fermentation is underway. We will not exceed a level of iBuOH that would be toxic.

Wednesday, March 23, 2016 PM

• Fermentation continues, see charts below as of about noon today.

• Some of the level in the tanks had to be emptied because they were too full, (lost about 4%).

• As of 1:00 PM the amount of iBuOH produced was about 160 gal if the rest of the sugars are consumed at the 

yield so far there would be another 122 gal produced for a total of 280 gal. Our goal per fermentation was 

285 gal, so at this point we are on target.

• They are having difficulty with the pH probes, they appear to be in the heavier solids, which are suspected of 

being at the bottom of the tank.

• There is concern as to how the recovery will go once the fermentation is complete.

• Below are graphs of the sugar consumption and iBuOH production through 1 or 2 PM, 0 time is midnight.

• Fermentation could be completed by early tomorrow.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

95

Glucose (g/L)

Glucose (g/L)

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16

Elapsed fermentation time (h)

Tank 505

Tank 506

Tank 507

Friday, March 25, 2016

• Fermentation was declared complete as of yesterday morning, see graph below.

• Given the volume of liquid in the fermenters, the final composition and discounting a little for a volume of 

solids in the fermenter, the total amount of iBuOH produced is about 275–280 gal, very close to our target of 

285 gal.

• They installed a dip-pipe into the fermenter and slowed the agitator to 20% in a hope to pull liquid out with 

minimal solids to feed GIFT.

• GIFT was started last night.

Isobutanol and Glucose vs. Time

Glucose Isobutanol

Time

60

50

40

30

20

10

15

10

–5 0 5 10 15 20 25 30 35

5

0

0

505

506

507

Batch ID
General Technical Report FPL–GTR–278

96

Tuesday, March 29, 2016

• GIFT recovery of the fermenters was completed late Saturday.

• The fermenters were successfully washed out, the solids did not cause an issue. In addition, the GIFT system 

(reboiler & GCOL) were also flushed of solids with no issues.

• About 300 gal of “light phase” was recovered. This translates to about 240 gal of iBuOH. In addition, there is 

still some hold-up in the system as it was started after being cleaned out. Our target was 275 gal of iBuOH from 

one fermentation, so this should be about right.

• The distillation of light phase to iBuOH is a batch operation and will be started later.

• A fifth load of pulp rejects was received from Cosmo on Friday.

• The system was sterilized last night and solids addition should be starting today.

Wednesday, March 20, 2016

• Monday started out with considerable difficulty pumping the dilute slurry across from the feedstock tent to the 

screw press & viscosity break tank. They are not milling the Cosmo material, to save labor.

• In the afternoon they changed the slurry pump and that corrected their pumping issues. System is pumping well 

over to the tank to add enzyme (viscosity break tank).

• As of about 4:00 PM (CDT) they had about 5,000 gal in the two tanks being used for initial saccharification and 

liquefaction (viscosity break tank and yeast conditioning tank).

• Liquefaction showed 10 g/L glucose and 0 g/L lactic acid (i.e., no contamination).

• They will start transferring to one of the sterilized aerobic fermenters overnight.

• They are on target to complete hydrolysis and begin the second fermentation on Sunday.

Friday, April 1, 2016

• Operations at ICM continue to be OK!

• Solids additions for liquefaction run #2 was completed yesterday and all three fermenter tanks are now full, 

have been pasteurized to 190 °F and have had enzyme added.

• Fermenter 1 is now at 58 g/L glucose, 1.9 g/L lactic. It has been about 32 h since enzyme was added (target is 

about 50 g/L).

• Fermenter 2 is now at 53 g/L glucose, 1.8 g/L lactic. It has been about 28 h since enzyme was added.

• Fermenter 3 is now at 37 g/L glucose, 1.3 g/L lactic. It has been about 12 h since enzyme was added.

• Plan is to continue fermenter 1 in hydrolysis mode until about 6:00 PM today and then start SIP, followed by 

fermenter 2 a few hours after that.

• Fermenter 3 will be allowed to continue hydrolyzing until sometime tomorrow, targeting 55+ g/L sugar in that 

tank as well before SIP is started. SIP takes about 24–30 h.

• As each fermenter is finished with SIP it will be held at fermentation temperature (it is sterilized) until all three 

tanks have been SIPed.

• It is expected that inoculation will take place on Sunday.

Sunday, April 3, 2016

• Hydrolysis was completed in all fermentation tanks.

• All tanks were sterilized followed by sterile addition of the urea, lactrol and vitamins.

• Yeast was added about 11:00 AM CDT Sunday.

• Andrew expects the fermentation to be complete in about 30 h, which would be late Monday.

Monday, April 4, 2016

• Round 2 fermentation was completed this morning.

• All tanks were then closed (to prevent loss of iBuOH and heated to 160 °F to kill the yeast.

• Once cooled again, the GIFT will be started.

• The yield was as expected by Andrew at about 0.23 to 0.26 g iBuOH/g glucose.

• The following graph shows the progress of enzymatic saccharification that occurred over the weekend. 

Sugar doesn’t start at zero because of sugars liberated during liquefaction.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

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0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80

Glucose (g/L)

Elapsed hydrolysis time (h)

Beta Campaign—Hydrolysis in Aerobic Fermenters

H609 H610 H611

Tuesday, April 5, 2016

• Fermentation was finished Monday morning and was then pasteurized at 160 °F to kill the yeast and prevent the 

yeast from possibly consuming isobutanol and or making more isobutyric acid.

• GIFT was started Monday night, there were issues with foaming in the fermenters and GIFT column. Theory is 

that perhaps the yeast was lysed during the pasteurization and the protein was causing the foaming.

• Antifoam was added as well as the reboiler appeared to be plugging, reducing the flow through it (high flow 

through the reboiler is key to being able to get heat into the GIFT to effect the iBuOH stripping).

• The reboiler was flushed out and eventually the foaming subsided (it probably took some time to distribute the 

antifoam throughout the system).

• As of this evening the GIFT was running with good flow and heat input through the reboiler.

• Fermentation start time (0 on charts) was at 12:00 Noon on Sunday (4/3/2016) and was complete at 20 h, 

pasteurization was from 20–30 h and GIFT recovery has been since then. 

Wednesday, April 6, 2016

• GIFT continued to go well overnight and until late afternoon. The iBuOH level was <3 g/L when the system 

foamed over into the GIFT condenser, contaminating the iBuOH in the system.

• Material in the downstream equipment was returned to the fermenters to be separated a second time.

• There was about 205 gal of light phase that had been taken out of the system and put in temporary tote storage; 

this was not contaminated.

• It is expected that it will take through the night to finish the iBuOH recovery.

• As soon as stripping of this batch through GIFT is completed the tanks will be emptied, cleaned and the next 

run started.

• We will reexamine the goals for the third run tomorrow.

Sunday, April 10, 2016

• The GIFT recovery of iBuOH from the second fermentation was completed on Friday.

• Tanks were cleaned out Saturday and the next enzymatic hydrolysis was started at 10:00 AM this morning.

• The first tank was filled at 6:00 PM this evening and was showing 27 g/L glucose and <0.1 g/L lactic.

• The other two of three tanks will fill in series as before.
General Technical Report FPL–GTR–278

98

Tuesday, April 12, 2016

• One side of the Fournier press is a view window and it popped off—had to be re-seated over the weekend. The 

Fournier press is used to dewater the solids going into the liquefaction tank (initial enzymatic hydrolysis).

• Shutdown of the EtOH plant for annual maintenance will occur on 4/25/2016. This will force pilot plant to shut 

down by midnight on 4/24/2016. So NARA work will either need to be finished before this—or pause.

• Rick thinks that B611–613 will start fermentation on Thursday 4/14/2016 and the next fermentation will 

start Friday 4/22/2016 or 4/23/2016 Sat. So this will be tight. May need to delay fourth fermentation till after 

shutown.

• 38,000 lb of feedstock remaining as of the start of this batch—might not be enough for two batches, including 

the current one, so we’re considering getting another load.

• GIFT reboiler HX was very clogged at the end of running on the last fermentation. ICM will try flushing out 

(which has worked to a reasonable extent after the last fermentation and once during this last GIFT run). An 

alternative would be to hire an outside firm to dismantle and clean (~$6–8K).

• Second fermenter started filling at 6:00 AM yesterday and should have been finished yesterday afternoon. Tank 

3 is probably filled as well by now. Will update the status of the hydrolysis tanks this afternoon.

Wednesday, April 13, 2016

• All fermentation tanks have been filled and are being enzymatically saccharified.

• Sugar concentrations as of about 9:00 AM today are AF-1 57 g/L, AF-2 62 g/L, AF-3 59 g/L. AF-1 has been at 

this stage for 48 h and AF-3 about 24 h.

• Plan is to start SIP (sterilization) of AF-1 this afternoon, followed by the other two.

• Fermentation inoculation will either be late Thursday or early Friday.

• We have decided that we will wait until after the ICM Plant shutdown (4/25/2016 to 5/1/2016) before doing 

run 4. This takes the pressure off trying to get finished with 3 and complete fermentation and GIFT 4 by 

4/24/2016.

• We will get one more load from Cosmo as the amount of solids remaining would either be extremely close or 

probably short of what we would like to run in the last run.

• They are still working on flushing out the GIFT reboiler in anticipation of completing this fermentation about 

Saturday or Sunday.

Friday, April 15, 2016

• All three fermentation tanks were finished with enzymatic saccharification yesterday. See the graph below to 

see the progress of sugar production. Sugar levels this time (56, 64, 66 g/L) were better than the previous run, 

which were 57, 53, 51 g/L. So here’s hoping for a little more iBuOH.

• All tanks were steam sterilized overnight and inoculated with the Gevo yeast at 1:00 PM today. It is expected 

that the fermentation will be completed in about 24–30 h, or tomorrow afternoon.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

99

Saturday, April 16, 2016

• Fermentation to isobutanol is progressing well in run 3 and after 18 h the glucose is down to 10.4, 19.1 and 

27 g/L in the three tanks. See the charts below from Andrew regarding formation progress.

Glucose

0

10

20

30

40

50

60

70

0 5 10 15 20 25 30 35 40 45

g/L

Elapsed fermentation time (h)

512

513

514

GEVO LAB

Sunday, April 17, 2016

• All three tanks were heated to kill the yeast and GIFT was started late last night.

• Recovery of isobutanol via GIFT has been taking about 36 to 48 h, so still a couple more days to complete the 

iBuOH recovery.

• There is not enough time to complete the fourth and final fermentation before the ICM plant shutdown a week 

from Monday, so it will be delayed and start two weeks from tomorrow, 5/2/2016.

Hydrolysis B612–B613–B614 Cosmo Reject Fibers

NARA @ ICM

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80

Glucose (g/L)

Elapsed hydrolysis time (h)

B612 (AF1) hydrolysis start:

4/10/2016 11:00:00 AM

B613 (AF2) hydrolysis start:

4/11/2016 6:00:00 AM

B614 (AF3) hydrolysis start:

4/11/2016 11:00:00 PM
General Technical Report FPL–GTR–278

100

Lactate

Elapsed fermentation time (h)

509

510

511

LAB

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 10 20 30 40 50 60

g/L

Isobutyrate

Elapsed fermentation time (h)

509

510

511

LAB

g/L

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 10 20 30 40 50 60

Tuesday, April 19, 2016

• The GIFT operation ran well for about 30+ h until yesterday afternoon. See chart below from ICM regarding 

the concentration coming out of the GIFT. The chart is through about 8:00 AM yesterday.

• The concentration into the GIFT is not taken at a representative location. They remove the liquid from the 

fermenters through a dip-pipe to avoid solids and the sample is not taken from that line so disregard.

• The plan was to run with no agitation and avoid the solids for as long as possible, then agitate and mix in 

iBuOH that might be at the bottom. That was done yesterday at about 2:00 PM, which created a foaming event 

and plugging of the reboiler.

• The downstream system was contaminated (not the product tote, which has about 130 gal of light phase in it) 

with material from the fermenters, so it was sent back to the fermenters and the system cleaned. The reboiler 

was flushed out as well. Shouldn’t have been much iBuOH actually lost.

• System was brought back and the reboiler is running at about 250 gal/min (max is probably 350 gal/min). 

For some reason the lactic acid is increasing, there is no glucose for it to consume, so it isn’t clear what is 

happening. No one suspects that it is consuming iBuOH, so the decision is to just continue.

• There is at least another day’s worth of recovery left.
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

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Thursday, April 21, 2016

• Recovery of isobutanol from run 3 is just about complete. It is taking a while because of the solids and the fact 

that they had one of the agitators off to keep solids out and then when they turned it on, the iBuOH went back 

up high. The low concentrations take the longest time to get the iBuOH out because you’re boiling mostly 

water.

• Run should be completed tonight.

• ICM Biofuels production plant is down next week, so we can’t start another run. That will wait until May 2.

• I’ll be in Europe for the next run, so I’ll ask someone else to send out some updates.

• Another load of solids will be picked up and delivered from Cosmo next week, in time for the last run.

• After completion of the runs, two steps of purification will be performed on all material:

• First, removal of acid, this is done by putting the iBuOH back in a fermenter and running thru GIFT at hi pH, 

which holds all the acids as nonvolatile salts.

• Second, removal of water from light phase, batch distillation in the “rectifier” will accomplish this.

Wednesday, May 4, 2016

• The load of Cosmos material arrived. Rick noted that the % solids are 42% and higher than the last loads, which 

were in the 38% range. The material has a lighter appearance, probably due to the higher solids. No foreign 

matter has been detected in the Cosmos material so far.

• Filling of the fermenters started late Monday. AF1 is full at this time with an IR solids of 17%. The oven dried 

measurements will be completed this afternoon. There is only a trace of lactic acid detected. AF2 should be 

filled today.

• The solids in the fermenter are higher than the last runs due to operating the Fournier press at higher pressure. 

The operating staff is running the press at the fine line between a wet solids discharge and a discharge that is too 

dry to easily sink into the slurry.

• There was some concern at ICM that the glucose levels may be too high using a higher solids loading in 

enzymatic hydrolysis. It was felt that 17% solids was a good target. It was discussed that 17% solids was one 

of the original targets so this should not be an issue. If after enzymatic hydrolysis is complete, the slurry could 

always be diluted to lower the glucose levels.

• There was discussion on yeast viability. Andrew indicated the yeast typically have a shelf life of 10–12 weeks 

and since it was delivered in early March, it should be fine. ICM’s plan is to dilute the remaining yeast with 

sterile water so the level is above the tote mixer and then mix for ~1 h. The yeast will then be evenly distributed 

between the three fermenters.

• Fermentation is expected to start Sunday, May 8.

Friday, May 6, 2016

• AF1 hydrolysis is complete with 76 g/L glucose.

• AF2 hydrolysis is almost complete with 79 g/L glucose although it has not quite plateaued.

• AF3 hydrolysis still needs 12 h to finish and is at 59 g/L.

• There is concern that this is too much glucose. The worry is that using the previous yield of 0.28 g isobutanol/g 

glucose, the excess glucose could lead to ethanol production during the GIFT separation.

• The concentration of glucose will drop during SIP, but it is not known if the dilution will get into the 65 g/L 

glucose range. It will be close as it is estimated that ~500 gal of steam will condense in the fermentation tanks 

during SIP and there is only about 500 gal volume left in the tanks.

• ICM could drop some of the hydrolysis slurry before SIP, add sterile water and then SIP. This option would 

present the lowest chance of contamination in fermentation, since the transfers would occur before SIP. 

However, there is the risk of possibly ending up low on glucose.

• After much calculation and discussion, Andrew suggested that the option of SIP the slurry, measure the glucose 

and then dump slurry only if necessary was most prudent. It was felt that since flow would be out, and since 

ICM has been able to keep contamination issues under control, this option should give minimal risk. Rick was 

going to discuss with his team, gather any other concerns and verify this option is possible after SIP. He will 

contact Andrew directly to confirm today.

• If system configurations allow, AF3 may receive SIP first when its glucose level reaches ~70 g/L, stopping any 

further glucose production and thus avoid the need for dilution other than SIP.

• Inoculation is still expected to occur Saturday, May 7.
General Technical Report FPL–GTR–278

102

Lactic Acid (85%) and 3 More vs. Time

Isobutyrate

5

4

3

2

1

0

Ethanol

0.5

0.4

0.3

0.2

0.1

0

Lactic acid (85%)

4.50

3.75

2.25

3.00

1.50

0.75

0.00

Acetic acid

1.0

0.8

0.4

0.6

0.2

0.0

515

516

517

Batch ID

0 6 12

Time

18 24

Saturday, May 7, 2016

• At current heating pace we will get to 250 °F in AF3 at about 4:00 PM. If we can cool as fast as we did with 

AF2, tanks will be at ferm temps around 7:00 PM. We will inoculate about an hour later after we add urea and 

pH adjust to 5.1.

• AF1 60 g/L glucose after SIP.

• AF2 67 g/L glucose after SIP.

• AF3 65 g/L glucose before SIP.

Monday, May 9, 2016

Tuesday, May 10, 2016

• Fermentation is complete in all vessels. There are only traces of glucose and no further increases in any 

contaminants.

• After pasteurization, the pH in the broth was raised to 8 to minimize any acid carryover during GIFT. 

Additional dilution water was also added to aid in GIFT recirculation. Additional broth samples were taken as a 

basis for monitoring the separation.

• The GIFT system is being started this morning. Agitation will be used in AF2 & AF3. AF1 agitation will be 

started later in the GIFT separation.

• The latest DCS and LIMS data were uploaded to the FTP site.

• Re-GIFTing of the isobutanol inventory is expected to start May 18 followed by rectification on the May 19 

and 20.
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Wednesday, May 11, 2016

• GIFT was started yesterday and the current isobutanol level is down to 4 g/L. Based on the previous runs, it is 

expected to take an additional 24–36 h to finish.

• AF2 and AF3 are being continuously agitated. AF1 was briefly agitated this morning to release any trapped 

isobutanol. With only intermittent agitation in AF1, ICM has not had any plugging problems in the GIFT 

system thus far.

• Lactic acid is slowly increasing in the broth. The source is not known as there are only traces of glucose and 

0.5 g/L xylose left and the broth was pasteurized at the end of fermentation. It is not anticipated to be a 

problem.

• The pH of the broth had dropped to 7.5 by this morning. It will be brought back up to 8 for the remainder of 

GIFT.

• After GIFT is complete, the fermenters will be cleaned and AF3 filled with water waiting for the start of 

re-GIFTing the isobutanol inventory (May 18).

• ICM is working on the logistics and paperwork for sending the two high-ethanol totes to Whitefox in Canada 

for processing.

• Andrew will try to get ICM the full list of ASTM required tests to be conducted on the isobutanol after the 

inventory is reprocessed next week. It will be determined if ICM can conduct the tests themselves or if GEVO 

(or others) need to complete the tests.

Thursday, May 19, 2016 AM

• Re-GIFTing is going OK. The over-optimistic predictions of yours truly were squelched by the inability of the 

LL separator to handle the high flow of iBuOH, so it’s running per the “ICM way”, slower than expected. A 

method of adding the iBuOH to the system was worked out, it was not simple because the totes are flammable 

and must be kept in the electrically classified area when open and the fermenter is in the standard electrical 

area (which is ok once the iBuOH is diluted). Once this procedure for adding was worked out (took most of the 

morning) it seemed to purr along.

• Great progress was made till late into the night shift, when things slowed.

• Four totes have been filled with acid on-spec light phase. There are still two totes waiting to be added (maybe 

1/3 of the total). They should complete the low ethanol totes today. Or at least they should be in the “draw 

down” mode (pulling the last iBuOH out after all totes have been added) by that.

• Acid spec is 70 ppm, all analyses that I’ve seen have been 30–50 ppm.

Thursday, May 19, 2016 PM

• All totes (hi acid, lo EtOH) have been fed into the GIFT with about 2/3 of the product having been recovered in 

totes and the rest still in the process as of this afternoon, yet to be recovered.
General Technical Report FPL–GTR–278

104

Appendix G—Final Fuel Certificate of Analysis
Production of 1,000 Gallons of Certified Biojet Fuel through Biochemical Conversion of Softwood Forest Residues

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