Troy Runge

Increasing the revenue from lignocellulosic biomass: Maximizing feedstock utilization

Replacing petroleum by biomass can be economically feasible by generating revenue from the three primary biomass constituents. The production of renewable chemicals and biofuels must be cost- and performance- competitive with petroleum-derived equivalents to be widely accepted by markets and society. We propose a biomass conversion strategy that maximizes the conversion of lignocellulosic biomass (up to 80% of the biomass to useful products) into high-value products that can be commercialized, providing the opportunity for successful translation to an economically viable commercial process. Our fractionation method preserves the value of all three primary components: (i) cellulose, which is converted into dissolving pulp for fibers and chemicals production; (ii) hemicellulose, which is converted into furfural (a building block chemical); and (iii) lignin, which is converted into carbon products (carbon foam, fibers, or battery anodes), together producing revenues of more than

Monolignol ferulate conjugates are naturally incorporated into plant lignins

500 per dry metric ton of biomass. Once de-risked, our technology can be extended to produce other renewable chemicals and biofuels.

Enabling integrated biorefineries through high-yield conversion of fractionated pentosans into furfural

Plants have convergently evolved to use monolignol ferulate conjugates to produce lignins containing chemically labile backbone esters. Angiosperms represent most of the terrestrial plants and are the primary research focus for the conversion of biomass to liquid fuels and coproducts. Lignin limits our access to fibers and represents a large fraction of the chemical energy stored in plant cell walls. Recently, the incorporation of monolignol ferulates into lignin polymers was accomplished via the engineering of an exotic transferase into commercially relevant poplar. We report that various angiosperm species might have convergently evolved to natively produce lignins that incorporate monolignol ferulate conjugates. We show that this activity may be accomplished by a BAHD feruloyl–coenzyme A monolignol transferase, OsFMT1 (AT5), in rice and its orthologs in other monocots.

Chemical preconversion: application of low-severity pretreatment chemistries for commoditization of lignocellulosic feedstock.

Dilute aqueous solutions of furfural were produced in high yield from biomass hydrolysates using an acid-catalyzed batch reactive distillation process that separated the vapor phase from the aqueous reactant medium. Hot water hydrolysates from hybrid poplar, miscanthus, switchgrass and corn stover were dehydrated using sulfuric acid. The vapor fraction from the reactor was condensed to produce furfural in excess of 85% of the theoretical yield based on total pentose. Using xylose as the model compound, and temperature and acid concentration as the variables, the process conditions were optimized by the construction of a three-level statistical model. Hot water hydrolysis of biomass provided with a cellulose-rich solid fraction which has potential for conversion into pulp or cellulosic ethanol, while the liquid fraction, rich in hemicellulose sugars, was converted into furfural. Fractionating the biomass allows for exploration of the concept of the integrated biorefinery where the hemicellulose sugars are not underutilized or encountered as potential inhibitors during microbial conversions of the solid stream, but are converted into furfural, a valuable chemical precursor. The availability of the cellulose fraction for further conversion into pulp or ethanol gives the current process a major advantage over the conventional batch process used in industry, where theoretical yields do not exceed 45–50% with the conspicuous absence of a usable cellulose stream.

Improving biomass combustion quality using a liquid hot water treatment

Securing biofuels project financing is challenging, in part because of risks in feedstock supply. Commoditization of the feedstock and decoupling its supply from the biorefinery will promote greater economies of scale, reduce feedstock supply risk and reduce the need for overdesign of biorefinery pretreatment technologies. We present benefits and detractions of applying low-severity chemical treatments or ‘chemical preconversion treatments’ to enable this approach through feedstock modification and densification early in the supply chain. General structural modifications to biomass that support cost-effective densification and transportation are presented, followed by available chemistries to achieve these modifications with minimal yield loss and the potential for harvesting value in local economies. A brief review of existing biomass pretreatment technologies for cellulolytic hydrolysis at biorefineries is presented, followed by a discussion toward economically applying the underlying chemistries at reduced severity in light of capital and operational limitations of small-scale feedstock depots.

Integrated biorefinery model based on production of furans using open-ended high yield processes

Background: Combusting or gasifying biomass with high ash can create operational issues, such as slagging and corrosion, as well as environmental issues, such as hazardous air emission, thus limiting the types of biomass that can be used in these conversions. Methodology: Exploration of a reduced severity liquid hot water treatment was performed on poplar wood, corn stover, switchgrass and Miscanthus to investigate the potential of this treatment to upgrade the biomass quality for combustion. Results: The results indicate that a significant reduction of ash occurs regardless of the treatment severity. Additionally, the treatment was able to increase the energy density up to 25% through increased heating values and pellet density. Conclusion: This treatment shows promise to improve the solid fuel quality of pelleted biomass.

Validation of lignocellulosic biomass carbohydrates determination via acid hydrolysis.

The biodetoxification pathway for the reduction of the fermentation inhibitor furfural was utilized to produce furfuryl alcohol using both a commercial Bakers’ yeast and six other native strains, selected for their high tolerance towards the inhibitory effects of furfural. This study explores the potential of the microbial method as an environmentally-benign alternative to the conventional catalytic hydrogenation process for producing furfuryl alcohol used extensively in industry. The microbial method for furfuryl alcohol production provides the benefit of a homogeneous biochemical conversion, devoid of chemical catalysis, in conjunction with other carbohydrate-based processes (e.g. production of ethanol). Results showed that the yields of furfuryl alcohol using the laboratory yeast strains exceeded 90% of the theoretical yield at a furfural concentration of 25 g l−1, which are comparable to yields obtained using the catalytic process. Furfuryl alcohol yields progressively declined as the furfural concentration was increased up to 65 g l−1, where the yields averaged over 37%. Piecing together novel high-yield conversion processes for furfural and furfuryl alcohol, an integrated biorefinery model based on the production of furans has been envisioned. Such a facility bypasses the need for high pressure hydrogenation using copper chromite catalysts and hydrogen and azeotropic distillation of furfural to produce dilute streams of both notable platform chemicals.

Combined sodium hydroxide and ammonium hydroxide pretreatment of post-biogas digestion dairy manure fiber for cost effective cellulosic bioethanol production

This work studied the two-step acid hydrolysis for determining carbohydrates in lignocellulosic biomass. Estimation of sugar loss based on acid hydrolyzed sugar standards or analysis of sugar derivatives was investigated. Four model substrates (starch, holocellulose, filter paper and cotton) and three levels of acid/material ratios (7.8, 10.3 and 15.4, v/w) were studied to demonstrate the range of test artifacts. The method for carbohydrates estimation based on acid hydrolyzed sugar standards having the most satisfactory carbohydrate recovery and relative standard deviation. Raw material and the acid/material ratio both had significant effect on carbohydrate hydrolysis, suggesting the acid to have impacts beyond a catalyst in the hydrolysis. Following optimal procedures, we were able to reach a carbohydrate recovery of 96% with a relative standard deviation less than 3%. The carbohydrates recovery lower than 100% was likely due to the incomplete hydrolysis of substrates, which was supported by scanning electron microscope (SEM) images.

Potential for Electrified Vehicles to Contribute to U.S. Petroleum and Climate Goals and Implications for Advanced Biofuels

BackgroundThe current higher manufacturing cost of biofuels production from lignocellulosics hinders the commercial process development. Although many approaches for reducing the manufacturing cost of cellulosic biofuels may be considered, the use of less expensive feedstocks may represent the largest impact. In the present study, we investigated the use of a low cost feedstock: post-biogas digestion dairy manure fiber. We used an innovative pretreatment procedure that combines dilute sodium hydroxide with supplementary aqueous ammonia, with the goal of releasing fermentable sugar for ethanol fermentation.ResultsPost-biogas digestion manure fiber were found to contain 41.1% total carbohydrates, 29.4% lignin, 13.7% ash, and 11.7% extractives on dry basis. Chemical treatment were applied using varying amounts of NaOH and NH3 (2-10% loadings of each alkali on dry solids) at mild conditions of 100°C for 5 min, which led to a reduction in lignin of 16-40%. Increasing treatment severity conditions to 121°C for 60 min improved delignification to 17-67%, but also solubilized significant amounts of the carbohydrates. A modified severity parameter model was used to determine the delignification efficiency of manure fiber during alkaline pretreatment. The linear model well predicted the experimental values of fiber delignification for all pretreatment methods (R2 > 0.94). Enzymatic digestion of the treated fibers attained 15-50% saccharification for the low severity treatment, whereas the high severity treatment achieved up to 2-fold higher saccharification. Pretreatment with NaOH alone at a variety of concentrations and temperatures provide low delignification levels of only 5 − 21% and low saccharification yields of 3 − 8%, whereas pretreatment with the combination of NaOH and NH3 improved delignification levels and saccharification yields 2–3.5 higher than pretreatment with NH3 alone. Additionally, the combined NaOH and NH3 pretreatment led to noticeable changes in fiber morphology as determined by SEM and CrI measurements.ConclusionsWe show that combined alkaline treatment by NaOH and NH3 improves the delignification and enzymatic digestibility of anaerobically digested manure fibers. Although pretreatment leads to acceptable saccharification for this low-cost feedstock, the high chemical consumption costs of the process likely will require recovery and reuse of the treatment chemicals, prior to this process being economically feasibility.

Integrated two-stage chemically processing of rice straw cellulose to butyl levulinate

To examine the national fuel and emissions impacts from increasingly electrified light-duty transportation, we reconstructed the vehicle technology portfolios from two national vehicle studies. Using these vehicle portfolios, we normalized assumptions and examined sensitivity around the rates of electrified vehicle penetration, travel demand growth, and electricity decarbonization. We further examined the impact of substituting low-carbon advanced cellulosic biofuels in place of petroleum. Twenty-seven scenarios were benchmarked against a 50% petroleum-reduction target and an 80% GHG-reduction target. We found that with high rates of electrification (40% of miles traveled) the petroleum-reduction benchmark could be satisfied, even with high travel demand growth. The same highly electrified scenarios, however, could not satisfy 80% GHG-reduction targets, even assuming 80% decarbonized electricity and no growth in travel demand. Regardless of precise consumer vehicle preferences, emissions are a function of the total reliance on electricity versus liquid fuels and the corresponding greenhouse gas intensities of both. We found that at a relatively high rate of electrification (40% of miles and 26% by fuel), an 80% GHG reduction could only be achieved with significant quantities of low-carbon liquid fuel in cases with low or moderate travel demand growth.