Automated Biomass Pretreatment Analysis using 

Accelerated Solvent Extractor

Operated by the All

Introduction:

The ability to screen feedstocks for their relative structural recalcitrance is an important tool in the development of 

advanced cellulosic biofuels. Methods are needed which can be reproducibly repeated across a variety of laboratories so 

that comparisons between data sets can be meaningful. While such methods have been developed for enzymatic 

Saccharification and fermentation (ref), no similar standard method has emerged for evaluating a feedstock’s response to 

pretreatment (the process by which the biomass structure is altered to aid in the enzymatic Saccharification of the 

bi ) O h thi h t d l d i th i t f t t t t i th b h l Whil

Why use the ASE 35

•Fully automated system, casequentially•Can do solid liquid separatconsuming step•Acid resistant construction 

Noah D. Weiss, Christopher Scarlata, Nicholas J. Nagle, National Renewable Energy Laboratory, National Bioenergy Center. 1617 Cole Blvd, Golden, Colorado. Contact: Noah.Weiss@nrel.gov

biomass). One reason why this has not developed is the variety of pretreatment reactors in use on the bench scale. While 

some reactors have been applied in a variety of labs, (Parr reactors, modified sand bath and tube apparatus’, etc.) these 

reactors require significant operator knowledge and have not conclusively proven to provide similar results under similar 

conditions. As well, they lack the capacity to effectively screen a large amount of feedstocks. It is desirable to develop a 

standard pretreatment platform which is easy to use, automated, can provide reproducible results, and relies on 

commercially available and multifunctional equipment. In this study, we present data showing the use of an Automated 

Solvent Extractor (ASE 350, Dionex corp.) to conduct dilute acid pretreatments of corn stover. We evaluate the ability of 

the equipment to effectively pretreat the corn stover and its ability to provide meaningful information for feedstock analysis.

•Acid resistant construction

acid pretreatment•Capable of handling high t•Commercially available sysmethods possible•Equipment has other labor•Sample size large enough 

Drawbacks

•Slow heat up time for high •Limited reaction temperatu

N t bl t h l t 

Research Goals: •Not able to change solvent

reactions

•Determine whether biomass can be effectively pretreated in ASE 350. •Determine whether the ASE350 can perform consistently in desired ranges•Identify an operating range which can provide sufficient xylan hydrolysis for comparing feedstocks while minimizing degradation products

Experiments•Full factorial design to determine the impacts of reaction time (2-6 minutes), reacacid concentration (0.3-1% w/w), and solvent flush volume (50-100% reactor volu•Central composite surface response design to determine region with ~80% total furfural production. factors: reaction time (5-17 minutes), Reaction temperature (1concentration (0.7-1.3% w/w)•Verification study to determine reproducibility and sensitivity around one possible 

60%80%

100%

an recovered 99% of xylose recovered with 170ml, ~5 cell volumes

A: Time

B: TempC: Acid %D: Flush volume

Positive Effects Negative Effects 

n hydrolyzed 5.26 7.02

B

C

comparing feedstocks along with coordinate points to asses sensitivity. •Equipment shakedown to determine adequate operating conditions such as flush 

0%

20%40%

60%

0 50 100 150 200 250 300

mass of solvent through sample cell, g

% hydrolyzed xyla

Figure 1: Fraction of hydrolyzed xylose recovered in successive washes. ASE has the ability to wash 

t-Value of total xyla

Rank

0.001.753.51

Bonferroni Limit 3.48368

t-Value Limit 2.13145

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

BC A

Figure 2: Pareto chart showing the main effects on total xylan hydrolysis in the ASE350 St d d ti i bl h

Design points0.340

0.02 0.11 0.19 0.20.3

an Degraded to Furfural 40% 50% 60% 70% 80% 90%

tal Initial Xylan 

Monomeric xylose yieldTotal xylose yieldFurfural produced

pretreated biomass and effectively recover xylan hydrolyzed during pretreatment. 

ASE350. Standard reaction variables show a 

normal effect on xylan hydrolysis as opposed to equipment operating parameters.

Design points0.8442490.244067

0.56 

0.66 

0.77 

0.87 

Total Xylan 

Actual FactorA: acid Conc. = 1.30 %

Xyla

Reaction 

Figure 4: Furfural fraction of initial xexcessive amounttemperatures and lower acid concenneeds to be run at 

0%

10%20%30%

160° C, 1.25% H2SO4, 5 min 175° C, 1% H2SO4, 11 min

Pretreatment Conditions

% Tot

Figure 5: Xylan yields for two selected replicated conditions, n=5. The ASE shows good reproducibility between samples and run days. 

Conclusions•ASE 350 is capable of pretreating biomass and achieving high levels of xylan hydrolysis. The system was easy to use and exhibited good reproducibility •The ASE 350 shows similar pretreatment Methods and Equipment

Equipment and materials: The ASE 350 (figure 1) was purchased from Dionex corpoDionium® cells, which are manufactured to be resistant to corrosion by dilute acid. Suand was diluted to a working solution of either 1% (w/w) or 2% (w/w). Corn stover was stover was Pioneer variety 33A14, (from the Kramer farm, Wray, CO) harvested in 200either a 6mm round rejection screen. The material was then sieved using a 20 mesh sused for the analysis. The composition has previously been reported in the literature (2Standard Pretreatment methods: Between 11 and 13 grams of air dried corn stover cell using a packing rod. The cell was brought on the carousel into the oven which was temperature. Room temperature acid solution was pumped into the cell and allowed to 

W d th l t d hi h i t i d t t 

Actual FactorC: Reaction Time = 11.0 min

0.7 

0.8 

1.0 

1.1 

1.3 160

168

175

183

190

0.45 

Acid Concentration, % Temperature, C 

Figure 3: Surface response model for total xylan hydrolysis. ASE 350 is capable of a range of xylan yields and can effectively remove ~87% of total xylan. Better xylan yields were seen at lower temperatures due to xylose degradation (figure 4). 

The ASE 350 shows similar pretreatment

trends to other bench scale reactor systems.•Large amounts of degradation were observed at higher severities, suggesting the need to operate at lower severities. This may be due to the long heat up times•The system needs to be evaluated 

further to determine the optimal operating pressure. 

We used the solvent saver pressure mode, which maintained a constant pre

cell was then held at static temperature and pressure for the desired reaction time, and collection vial. The cell was flushed with one reactor volume of the acid solution and thseconds. The samples were then flushed in the cells with four reactor volumes of DI whydrolyzed sugars in the cell, quench the hydrolysis reaction and bring down the tempeAnalytical Methods: All analytical methods used followed standard NREL Laboratory be accessed at http://www1.eere.energy.gov/biomass/analytical_procedures.html 

further to determine the optimal operating

conditions for feedstock comparisons. An evaluation of different feedstocks is also necessary. 

Acknowledgements 

We would like to thank Courtney Payne, Jeff Wolfe, and David Templeton for their help on this project. This project was funded by the

U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy, Office of the Biomass Program. NREL/PO‐510‐45787

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Ren

Sustainable Energy, LLC. Presented at the 31st Symposium on Biotechnology for Fuels and Chemica