Turning great ideas into viable solutions 

requires the ability to test theories under 

real world conditions. Few companies 

have the resources to build pilot-scale 

processing plants to test their ideas. The 

U.S. Department of Energy’s (DOE) 

National Renewable Energy Laboratory 

(NREL) helps by sharing its world-class 

equipment and expertise with industry 

and other research organizations through a 

variety of contractual arrangements.

At the NREL campus in Golden, 

Colo., researchers use state-of-the-art 

laboratories to develop and improve 

the technologies that convert biomass 

to fuels, chemicals, and materials. One 

of the most important tools available to 

biomass researchers is the Biochemical 

Pilot Plant housed in the Alternative Fuels 

User Facility (AFUF). In this facility, 

researchers test ideas for creating highvalue products from cellulosic biomass. 

They can test individual processing steps 

at the bench scale or they can test entire 

conversion processes at the “mini-pilot 

plant” scale (10- to 100-L vessel size) or at 

the pilot plant scale (one ton feedstock per 

day).

A model biochemical process for 

deriving usable products from biomass 

involves thermochemical pretreatment 

of the biomass, followed by enzymatic 

hydrolysis, fermentation, and product 

separation and recovery. The AFUF has 

equipment for performing all of these 

operations.

Pretreatment 

After it is mechanically milled, biomass 

is “pretreated”—a process that typically 

uses heat, pressure, and chemical catalysts 

such as acids to break down hemicellulose 

into its component sugars (hydrolysis) and 

make the cellulosic fraction accessible 

to enzymatic hydrolysis. NREL has 

historically focused on pretreatment 

processes that use dilute sulfuric acid; 

however, all of the pretreatment equipment 

can be used to explore alternative 

pretreatment chemistries. 

Pretreatment Equipment

Bench-scale (less than 10-L working 

volume) pretreatment equipment: 

•	Batch 4-L steam gun

•	Batch 1-L high solids stirred-tank

reactor.

Pilot-scale systems: 

•	Continuous one ton biomass per day

(dry basis) capacity vertical pressure 

reactor system 

•	Continuous 200 kg per day (dry basis)

capacity horizontal-screw pressure 

reactor system 

•	 130-L high solids steam-jacketed and

steam-injected batch mixed reactor.

Biomass Program

What Is a Biorefinery?

At a petroleum refinery, crude 

oil is processed into a variety 

of fuels and chemicals. DOE 

and NREL are leading efforts 

to develop a similar refinery 

model based on biomass. 

Biomass includes all plant 

and plant-derived material, 

but NREL research focuses 

particularly on cellulosic 

materials—the fibrous parts 

of plants, as opposed to the 

starch, sugar, and oil already 

used for food and fuel. 

The three primary components 

of biomass are cellulose, 

hemicellulose, and lignin. The 

challenge is to economically 

break down the cellulose 

and hemicellulose into their 

component sugars—one way 

to do this is through a process 

known as biochemical biomass 

conversion. In a biorefinery, 

the component sugars are then 

processed into ethanol or other 

fuels, chemicals, or materials. 

NREL’s Alternative Fuels User Facility is an 

integral part of the National Bioenergy Center, 

which leads national laboratory research and 

development for the Biomass Program. 

“I am pleased to note that 

some of the most promising 

recent breakthroughs and 

accomplishments in ethanol 

and biobased products 

are being developed by 

our Department’s National 

Renewable Energy Laboratory.”

Energy Secretary 

Samuel Bodman 

July 20, 2005

Modeling Tomorrow’s Biorefinery—the NREL 

Biochemical Pilot Plant

Dave Parsons, NREL PIX 04972
Enzymatic Hydrolysis 

After pretreatment, the residual solids are treated 

with enzymes to break down the cellulose 

to sugar—a process known as enzymatic 

hydrolysis. NREL researchers have determined 

that enzymatic hydrolysis of cellulose has the 

greatest potential to achieve cost-effective 

biomass conversion. 

Hydrolysis Equipment

NREL has a wide range of reactors for 

conducting experiments and assessing 

performance.

Fermentation 

After hydrolysis, the sugars obtained from 

pretreatment and enzymatic hydrolysis are 

fermented to ethanol or otherwise processed 

to desired products. NREL has developed an 

improved bacterium (Zymomonas mobilis) 

capable of cofermenting both glucose (the 

six-carbon sugar derived from cellulose) and 

xylose (the primary sugar from hemicellulose, 

which is a five-carbon sugar that is more

difficult to ferment). This patented strain

holds promise for reducing capital equipment 

costs and streamlining process operations in a 

cellulose-based ethanol production plant. For a 

biorefinery, however, it may prove advantageous

to ferment the sugar streams separately to 

produce different products. AFUF fermentation 

reactors can be used to test a variety of 

prospective aerobic or anaerobic bioprocesses in 

batch, fed-batch, or continuous operation.

Fermentation Equipment 

Pilot-scale systems available in the 

AFUF include: 

•	 A 20-L fermentor, two 160-L fermentors,

two 1,500-L fermentors, and four 9,000-L 

fermentors

•	 Numerous sterilizable support and feed vessels ranging in size from 100 to 9,000 L.

Product Separation and Recovery 

By fermenting sugars we produce ethanol or 

other products that must then be effectively 

recovered. Biorefineries will probably rely

on a variety of separation, purification, and

recovery technologies. AFUF’s fermentation and 

downstream separations and product recovery 

sections can also be operated for industrial 

partners who develop processes that start with 

sugars instead of raw biomass.

Separation and Recovery Equipment

Pilot-scale systems include systems for 

distillation/evaporation:

•	 10-m tall by 0.5-m diameter sieve tray

distillation column

•	Continuous forced recirculation evaporator for

concentrating or evaporative operations.

Pilot-scale systems for centrifugation include:

•	 Small solid bowl high-speed centrifuge

(17,000 G) for cell recovery

•	 Sterilizable continuous 100-L per hour

capacity high performance decanter (5,000 G)

•	Continuous 1,200-L per hour capacity

decanting centrifuge (3,000 G)

•	 A semi-automatic basket centrifuge (900 G)

with automatic feed and discharge capability.

Pilot-scale systems for filtration include:

•	 Semi-continuous pressure belt filter

•	Continuous ultrafiltration/reverse osmosis

system.

Pilot-scale systems for purification include:

•	 A continuous ion exchange/chromatography

moving bed system.

9,000-L 

fermentation tanks in 

the Biochemical Pilot 

Plant. 

Warren Gretz, NREL PIX 01008
Available tools include: 

•	 A range of spectrometers (infrared, visible,

ultraviolet), automated extraction units, and 

high performance liquid chromatographs 

equipped with a variety of columns and 

detector systems. 

•	 “Rapid analysis” methods that use

multivariate techniques to extract 

compositional information directly from 

complex sample spectra. Such methods

enable accurate and low-cost determination of 

multiple components in solid, liquid, and even 

slurry samples, and are being developed to 

speed process development and to enable online compositional analysis during processing 

operations. 

•	 A sophisticated data acquisition and control

system that permits effective real-time process 

control and monitoring during any mode of 

operation (batch, fed-batch, or continuous). 

•	 Dedicated mass spectrometers that permit

on-line monitoring of fermentor exhaust gas 

compositions.

Process Integration 

Creating cost-effective industrial processes

involves integrating the different bioconversion 

processing steps. NREL researchers are adept 

at integrating bioconversion processes and 

using the AFUF’s systems to test prospective 

processes as they would be used in production. 

NREL researchers also have extensive 

experience supporting specific industrial partner

research and development activities aimed 

at commercializing the next generation of 

bioconversion and bio-processing technologies.

Compositional Analysis and Process 

Monitoring 

NREL researchers are well versed in biomass 

compositional analysis and process monitoring, 

and can reliably assess mass and element 

balance closures across discrete process steps. 

NREL analytical chemists have expertise in 

developing, applying, and refining analytical

methods to determine the composition of a 

wide range of biomass feedstocks and process 

intermediates. Components monitored include

polymeric and monomeric sugars, lignin, organic 

acids, protein, sugar degradation products, 

extractives, ash, and moisture. 

This evaporation system concentrates sugar-rich 

streams or removes volatile compounds.

Researchers use this continuous ion exchange/

chromatography system for product recovery and 

purification. 

Mike Linenberger, NREL PIX 14976

Dan Schell, NREL PIX 12629
For more information contact:

EERE Information Center

1-877-EERE-INF

(1-877-337-3463)

www.eere.energy.gov

A Strong Energy Portfolio for a Strong America

Energy efficiency and clean, renewable energy will mean a stronger economy, 

a cleaner environment, and greater energy independence for America. 

Working with a wide array of state, community, industry, and university 

partners, the U.S. Department of Energy’s Office of Energy Efficiency and 

Renewable Energy invests in a diverse portfolio of energy technologies.

Produced for the U.S. Department of Energy 

by the National Renewable Energy Laboratory, 

a DOE national laboratory

DOE/GO-102008-2403, March 2008

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Creating an Integrated Biorefinery 

Research Facility

The AFUF has much of the equipment required

to pilot biomass-to-ethanol processes. It 

does not, however, contain all the necessary 

equipment, nor is it large enough, to fully test 

integrated biorefinery operations. In 2009, DOE

will add extensive processing, separations, and 

materials handling equipment that will allow us 

to test fully integrated biorefining processes and

research alternative concepts and technologies. 

For example, DOE plans to install frontend processing trains for testing different 

pretreatment chemistries. It also plans to add 

equipment to prepare residues from biochemical 

conversion for subsequent thermochemical 

conversion. 

The expanded facility will provide a pilot-scale

plant that is both large enough and flexible

enough to accelerate biorefining process

development and deployment. As different 

research activities are developed and tested, 

researchers and industrial partners will be 

able to add or remove equipment, operate 

multiple process trains, and reconfigure biomass

conversion processes. Expanded analytical 

laboratory facilities will support biochemical 

process research and development and will 

allow us to more efficiently and accurately

analyze samples throughout the process. 

For More Information

For more information about NREL’s AFUF, 

including inquiries about using the Biochemical 

Pilot Plant facilities, contact John Ashworth 

(303-384-6858, john_ashworth@nrel.gov),

or visit our Web site at www.nrel.gov/biomass.

With this pressurized filter press system, researchers 

can separate liquid hydrolyzate from the remaining 

solids at high temperature using NREL’s patented 

hot-wash process. 

Automated basket centrifuge and pump separate sugarrich liquors from pretreated biomass slurries.

Nick Nagle, NREL PIX 11550

Mike Linenberger, NREL PIX 14926