S1041: The Science and Engineering for a Biobased Industry and Economy

(Multistate Research Project)

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A. Use of increased renewable resources will require deliberate development of technologies for efficient use of resources due to three converging issues: (1) decrease in productive agricultural land areas under urbanization pressures; (2) clearing of land areas using unsustainable methods; and (3) increasing world population with an increased standard of living including a clean environment. One billion hectares of land will be cleared by 2050, resulting in the release of three Gt/year of greenhouse gases (Tilman et al., 2011). Global population will reach nine billion by 2050, resulting in increases in global food demand from 2005 to 2050 (Tilman et al., 2011). Breadth of these intersecting problems are so vast that constructive solutions can be designed and implemented only through collaborations crossing traditional disciplinary boundaries.

The objectives of this project are to address research relating directly to SAAESD Goal 1 F (biobased products) and H (processing agricultural coproducts); research will influence Goal 5 B (rural community development and revitalizing rural economies) indirectly. Because renewable energy systems occupy large land expanses, they are typically not located in urban areas, promoting economic development of rural US communities. Transitioning from sequestered-carbon sources such as oil, natural gas and coal, to more renewable energy systems requires research and development work. Without this productive research, the technical capacity to switch from a sequestered-carbon economy to a diverse bioresource-based economy will be severely hampered with unanswered questions, undeveloped technologies, and under-delivered capacity in production and utilization of bioresources. Research proposed herein is designed to help address these limitations as conducted by professional scientists and engineers either directly with or strongly associated with the Land Grant University system.

This project is written at a time when US natural gas has increased in productivity and decreased in costs. The natural gas production was 22.1 trillion cubic feet in the first nine months of 2012 compared to 21.0 for the same period in 2011. Although, natural gas may be considered the energy panacea for the next decade, natural gas combustion is a net emitter of greenhouse gases. Natural gas can certainly play a major role in assisting in the transition from sequestered-carbon based energy systems to renewable ones. However, due to continual increases in atmospheric carbon dioxide concentrations economically viable renewable energy systems must be developed and implemented. The Land Grant University system can partner with important policy-setting agencies including United States Departments of Agriculture (USDA), Energy (US DOE), Defense (US DOD), and the National Science Foundation (NSF) for doing the research that will allow us to meet our renewable energy production goals.

B. How S-1041 enabled new renewable energy industries.

Increasing the breath of renewable energy production systems includes the production of power and second-generation liquid biofuels, including biomass-derived power generation. Researchers in the S-1041 Multistate project are advancing this goal through research into most facets of bioenergy production systems, as detailed below.

B.1. Feedstock

Efficient feedstock supply chains are needed at commercial scale to enable the successful deployment of biobased systems. Progress was made in securing an abundant, economical supply of biomass feedstock delivered with predictable specifications that meet conversion needs. Biological feedstocks from across the US, ranging from the warm, humid southeast to dry, cool northern latitudes, representing various Land Grant University partners, were evaluated for yield, composition, and other characteristics. Feedstocks include switchgrass, giant miscanthus, energy cane and sweet sorghum with dry matter yields of 36-41 Mg/ha, 30 Mg/ha, 83 Mg/ha and 12-22 Mg/ha, respectively (West and Kincer (2011); Heaton et al. (2008); Heaton et al. (2010); Bischoff et al. (2008); Aita et al. (2011); and, Singh et al. (2012)). Camelina and other oilseed crops were evaluated as potential feedstock for biodiesel and aviation fuels, and included camelina cultivar development for higher yield and improved oil content/profile and camelina cropping system development. The yield potential of existing Conservation Reserve Program (CRP) were evaluated for different climate and geographic regions with an aim to increase yield, sustainable production, and less impact to environment and wildlife habitat.

The impact of soil type and fertility treatment on productivity and composition of switchgrass, tall fescue and reed canarygrass determined that composition was greatly affected by species and treatment, with fewer differences due to soil type. Prediction of biomass composition was improved using Fourier transform near-infrared (FT-NIR) spectroscopy coupled with multivariate analysis. A generalized, single broad-based predictive model for multiple types of biomass feedstock was developed using cornstover and switchgrass to predict concentrations of glucan, xylan, galactan, arabinan, mannan, lignin, and ash. Both cross-validation and independent validation supported a single FT-NIR model for both species, and results indicated the method's potential for wheat straw (Liu et al. 2010).

Innovative methods for biomass physical property measurement were developed. For example, 3D laser scanner images were analyzed using image processing software. Physical property determination using 3D scanning and image analysis determination methodology was an accurate, non-invasive, and highly repeatable (CV <0.3%) alternative. A sieveless particle size distribution analysis method using computer vision was developed.

Bulk density, a major logistics factor in handling biomass, is a strong function of the size and shape of the particle and particle density. Mean loose-filled bulk densities were 67.5±18.4 kg/m3 for switchgrass, 36.1±8.6 kg/m3 for wheat straw, and 52.1±10.8 kg/m3 for corn stover (Chevanan et al. 2011). Pressure and volume relationship of chopped biomass during compression with application of normal pressure was observed to fit well for Walker model and Kawakita and Ludde model. Parameters of the Walker model correlated with compressibility at a Pearson correlation coefficient greater than 0.9.

Densification of biomass feedstocks was applied to switchgrass and woody biomass subjected to fast pyrolysis, and woody biomass fractionated into lignin, cellulose and hemicelluloses streams. Densified switchgrass, wheat straw, giant miscanthus, elephant grass, cotton gin trash, and softwood forest trimmings, were produced through pelleting and briquetting with resultant heating values ranging from 17,908 to 18,839 kJ/kg. Biomass specifications, energy, and costs for feedstock densification were identified particularly for pellets, cubes, or grinds. Minimum-pressure densification was investigated due to recognition of high cost and in-efficient pressure application associated with the pelleting process. Specific energy for minimum-pressure densification ranged from 0.25 to 2 kJ/kg, which was significantly less than energy to produce pellets. Integrated biomass pretreatment (AFEX) and densification process, namely billet compaction, of corn stover, switchgrass and prairie cordgrass indicated that pretreated billets hold together well without use of added binders.

Flowability of chopped switchgrass, wheat straw, and corn stover at pre-consolidation pressures of 3.80 kPa and 5.02 kPa indicated Mohr-Coulomb failure. Results of measured angle of internal friction and cohesive strength indicated that typical chopped biomasses cannot be handled by gravity alone. Unconfined yield strength and major consolidation strength used for characterization of bulk flow materials and design of hopper dimensions were 3.4 and 10.4 kPa for chopped switchgrass; 2.3 and 9.6 kPa for chopped wheat straw and 4.2 and 11.8 kPa for chopped corn stover (Chevanan et al. 2009). These results are useful for development of efficient handling, storage, and transportation systems for biomass in biorefineries.

Although, great strides were made in terms of better predicting biomass crop yields and quality on selected areas, there still remains knowledge gaps in terms of: 1) expected yields of these energy crops throughout US available land; 2) spatial and temporal variations in yield and supply due to climate and soil conditions; 3) harvesting and handling of these low bulk density materials; and, 4) identifying target physical properties important at the interface of processing and conversion.

B.2 Conversion

B.2.1. Thermochemical

Cellulosic biomass conversion to industrial chemicals and fuels is performed via thermochemical, biochemical or a combination of these platforms. Unfortunately there is no clear technology winner and both conversion platforms have tradeoffs. The thermochemical platform is robust in terms of feedstock processing, but somewhat complicated in terms of the resulting product portfolio (Sharara et al. 2012). Thermochemical conversion includes gasification, pyrolysis or a combination of these technologies. The effects of furnace temperature, steam to biomass ratio and equivalence ratio on gas composition, carbon conversion efficiency and energy conversion efficiency of the product gas were investigated with temperatures of 650, 750 and 850 °C, steam to biomass ratios of 0, 7.30 and 14.29 and equivalence ratios of 0.07, 0.15 and 0.29. Gasification temperature was determined to be the most influential factor in terms of hydrogen and methane contents, carbon conversion and energy efficiencies. A steam to biomass ratio of 7.30 resulted in maximum carbon conversion and energy efficiencies. Effect of initial biomass composition on gas compounds product composition and furnace temperature profile was modeled; predicted flow rate of hydrogen was similar, but the predicted flow rate of methane was lower (Kumar et al. 2008; Kumar et al. 2009). Gasification studies were reported for wood chips and agricultural residues (Gautam et al. 2011a), for pelletized biomass (Gautam et al. 2011b) and for coal/biomass mixtures (Brar et al. 2012).

A downdraft gasifier was designed, fabricated and extensively tested using 11.6% dry basis switchgrass. Results consisted of the following: 1) specific air input rate, 542 kg/ h-m2 of combustion zone area: the average values for hot gas and cold gas efficiencies were 82 % and 72 %, respectively; the lowest heating value of gas was 1566 kcal/Nm3; CO, H2 and CO2 concentrations were 23 %, 12 % and 9 %, respectively; the corresponding average specific gasification rate was 663 m3 dry gas/h-m2 of combustion zone area; with specific air input rates of 647 kg/h-m2 of combustion zone area, CO2 concentration increased to 14 %, while the CO and H2 concentrations decreased to 19 and 10 %, respectively; and, anticipated establishment of high temperature swirling flows in annular section of pyrolysis and tar cracking section could not be achieved (Patil et al. 2011).

Wang et al. (2012) investigated the possibility of fermenting bio-oils sugars. New pyrolysis systems, including microwave assisted pyrolysis (MAP) and electromagnetic technologies for rapid pyrolysis, were developed and tested at the pilot scale and as mobile pyrolysis units. The mobile unit was 5 x 2.5 x 3.5 m with a processing capacity of 0.5 ton/hr (Wan et al. 2009a). Corn stover and aspen wood pellets were pyrolyzed using microwave heating with or without addition of catalysts (Moen et al. 2010). Medal oxides, salts, and acids, including K2Cr2O7, Al2O3, KAc, H3BO3, Na2HPO4, MgCl2, AlCl3, CoCl2, and ZnCl2, were pre-mixed with corn stover or aspen wood pellets prior to pyrolysis, which yielded three product fractions: 1) bio-oil; 2) syngas; and 3) charcoal. The addition of KAc, Al2O3, MgCl2, H3BO3, and Na2HPO4 were found to increase bio-oil yields. Increases in bio-oil yields were accompanied by changes in charcoal or syngas yields or both, suggesting that the catalysts used affected the fractional yields through different mechanisms. The catalysts could function as a microwave absorbent to speed up heating or could promote the so-called in situ upgrading of pryoltic vapors during MAP of biomass. Pyrolysis studies were conducted using corn stover (Capunitan and Capareda 2012), switchgrass (Iman and Capareda 2012), and sweetgum (Wang et al. 2012).

Catalytic-based processes were developed by S-1041 members (Street et al.
2012a; Street et al. 2012b; Street and Yu 2011). The upgrade, via catalysis, of synthesis gas to useable fuels was investigated (Yan et al. 2012a; Yan et al. 2012b). Specifically, catalysts may play an important role in solid-to-vapor conversion and reforming of vapors during microwave assisted pyrolysis (MAP) biomass processing. GC-MS analysis indicated that use of the catalysts significantly reduced the number of chemical species in the resulting bio-oils. Chloride salts suppressed most reactions during the pyrolysis. Adding 8 g MgCl2 per 100 g biomass resulted in bio-oils that contained more than 80% furfural, indicating that MgCl2 is effective in improving product selectivity of MAP processes. A number of biomass, including microalgae, corn stover, poultry litter, peanut, pinewood and switchgrass, was tested as MAP feedstocks (Du et al. 2011; Wan et al. 2010; Wan et al. 2009b). Microalgae-produced MAP bio-oils displayed better quality in terms of heating value, oxygen content, viscosity and density than those obtained from lignocellulosic biomass. Enhanced quality of microalgae bio-oils could be due to the higher concentration of hydrocarbons and lower concentration of oxygenated compounds. New Generation Fuels, a commercial entity, determined that microalgae bio-oils could readily be mixed with a commercial liquid fuel without any pretreatment, showing excellent fuel and combustion properties (Wan et al. 2010). Effect of catalyst loading and nature of support was examined on the gas shift reaction (Haryanto et al. 2011). The use of biomass was investigated in the Fischer-Tropsch reaction (Hu et al. 2012). Catalytic conversion of syngas to mixed alcohols over catalysts was studied (Lu et al. 2012).

Although, great advances were made in terms of designing pyrolysis, gasification and catalysts, there still remain knowledge gaps in terms of integration of these technologies to produce thermochemically-based economically viable energy systems.

B.2. 2 Biochemical

As opposed to thermochemical processing, biochemical processing does not require temperatures in the realm of 500 °C. On the other hand, this processing platform is based on the saccharification of sugars that make up the plant cell wall into high quality sugar streams that will then be converted to biobased fuels or chemicals. To produce fuels using biochemical processing technologies, feedstock must be reduced in size, pretreated, hydrolyzed with enzymes and fermented (Lynd et al. 2008). Specific pretreatment methods attack different components of the cell wall, with ammonia and lime treatments resulting in the disruption of lignin, while water and dilute acid causing hemicellulose solubilization (Kumar and Wyman 2008a). The efficacies of pretreatments are rated according to their production of reactive fiber, utility of the hemicellulose fraction and limitation of the extent to which the pretreated material inhibits enzymatic hydrolysis and growth of the fermentation microorganism. Pretreatment can lead to the generation of inhibitory products such as lignin derivatives and xylose degradation products, such as furfural and formic acid (Du et al. 2010).

Members of S-1041 are actively involved in pretreatment research. Examples of work are found below. Lime pretreatment with loadings in the range of 0.02 to 0.2 g/ g of dry biomass were investigated; maximum sugar recovery from Bermuda costal grass was obtained with a loading of to 0.1 g/g of dry biomass at 100 °C for 15 min (Wang and Cheng 2011). Combinations of lime, 0.05 g/ g of dry biomass, and sodium hydroxide, 0.05 g/ g of dry biomass, place on corn stover for 6 h at 21 °C yielded 77% theoretical sugar recovery (Zhang et al. 2011). Using sweetgum wood, 1% sulfuric acid at 160 °C for 60 min in non-stirred batch reactors, yielded 82 and 86%, respectively, of theoretically available xylose and glucose (Djioleu et al. 2012). Dilute acid pretreatment processing parameters can be adjusted such that biomass can be fractionated into hexose-rich and pentose-rich streams (Zhang and Runge 2012). In addition to traditional pretreatments, processing methods, such as solid-state treatments, offer interesting options in terms of saccharification. Maceration of corncobs with rot fungus, such as Ceriporiopsis subvermispora, for 35 days at 28 °C enabled the recovery of 75 % and 40 % of theoretical glucose and xylose yields, respectively (Cui et al. 2012).

Although pretreatment is critical, this processing step unfortunately can lead to the production of inhibitory compounds that restrain the enzymatic saccharification of the carbohydrate polymers. The enzymatic saccharification step is obstructed mainly by three groups of compounds: lignin derivatives that cause non-productive binding of the saccharification cocktail (Berlin et al. 2006); xylose-derived compounds inhibiting the enzyme cocktail (Cantarella et al. 2004); and, oligomers and phenolic-derived compounds deactivating the enzymes over time (Kumar and Wyman 2008a; Berlin et al. 2006 and Ximenes et al. 2011). To lessen the effect of these inhibitory compounds and minimize the amount of enzymes used, the inhibitors must be removed by separation methods, for example, washing the pretreated biomass with successive volumes of water (Hodge et al. 2008). Members of S-1041 are actively involved in determining exactly which inhibitory compounds, produced during pretreatment, need to be minimized. By knowing exactly which compounds are the bad actors, pretreatment processing parameters can be adjusted such that their concentration can be minimized, alleviating colossal pretreated biomass water washes (Frederick et al. 2012).

Pretreatments open tightly woven biomass plant cell walls, increasing internal surface areas. With more available surface area, enzymes have access to carbohydrate polymers, hydrolyzing hemicellulose into the five-carbon xylose and cellulose into the six-carbon glucose. The hydrolysis of the treated cellulose is performed with an enzymatic cocktail composed of xylanase, ²-glucosidase, endo-cellulase and exo-cellulase. These enzymes hydrolyze hemicellulose, cellobiose as well as the middle and extremities of the cellulose polymer, respectively. It is critical to digest the plant cell wall monosacharides with the least amount of cellulase and xylanase enzymes; these biocatalysts account for the most costly component of the biochemical process and, if not used sparingly, could forfeit the economic viability of the biorefinery. Members of S-1041 are involved in enzymatic hydrolysis research. Bioreactors, such as deep-bed solid-state reactors, are developed to optimize xylanase, ²-glucosidase, endo-cellulase and exo-cellulase production (Brijwani et al. 2011). Adding adjuvants to enzymatic cocktails increases their activity. As an example, adding 2.5 g casein, the milk protein, per g of glucan allowed for a two fold reduction in enzyme loading, from 50 FPU to 25 FPU, significantly reducing enzyme costs (Eckard et al. 2012).

Reliance on fossil fuels will eventually decrease by increasing fuel efficiency standards, transitioning whenever possible to electric vehicles and manufacturing biofuels. Production of 36 billion gallons of renewable fuels by 2022 will remain in the Energy Security and Independence Act (ESIA). Second generation fuels, such as cellulosic ethanol, will eventually gain traction, as the price of oil gradually increases. Iowa will soon be the home of POET and DuPont cellulosic ethanol plants, while ABENGOA has chosen to locate in Kansas; each of these manufacturing plants will be using corn residue as feedstock. Although, great strides were made in terms of pretreatment and enzymatic hydrolysis, there still remain knowledge gaps in terms of integration of these technologies to produce second-generation production systems that are economically viable energy systems.

Great progress has made over the last five years in creating viable feedstock supply chains, deciphering between important and trivial pre and post harvest parameters, integrating thermochemical energy production systems, and designing fermentable sugar streams, there still remain knowledge gaps in understanding the environmental impact of these systems such that their carbon footprint is minimized.

C. Funding landscape: Challenges and Opportunities for the next five years

Although oil prices have stabilized over the last few years, the impetus for development of environmentally sustainable and economically viable sources of bioenergy and bioproducts is driven by the need to reduce the environmental impact of the energy industry, and US dependence on fossil fuels. The Energy Independence and Security Act of 2007 has set high standards for the production of energy from biomass. Of the 36 billion gallon per year mandated by this act, corn to ethanol contribution is limited to close to 15 billion gallons per year, with the remaining 21 billion gallons to be produced from cellulosic and other feedstocks. Subsequent studies indicate that the biomass required for production of this advanced biofuel is available, though the lack of commercial scale conversion facilities raises concern over our ability to achieve this goal. To address this need for development that is becoming more urgent by the year, agencies continue to provide broad-based funding in all aspects of bioenergy production. The most significant sources include United States Department of Agricultures National Institute of Food and Agriculture (USDA NIFA), the United States Department of Energy (US DOE), the Department of Transportation Sun Grant, and the National Science Foundation (NSF).

The National Institute for Food and Agriculture (NIFA) under the USDA manages the Sustainable Bioenergy Challenge program that has been supporting research and educational initiatives through annual funding competitions since 2009. Research funding has been approximately $10 million annually in 2011 and 2012 (USDA, 2011). USDA and DOE have also partnered to provide the Biomass Research and Development Initiative (BRDI), which provide funds to multi-institution, interdisciplinary teams working in feedstock development, biofuels, and biobased products development. These grants have been awarded nearly annually since 2003 (USDA 2012). The USDA / US DOE partnership has also existed in the Genomics Science Program that fund has supported approximately ten projects annually since 2006 in the Plant Feedstock Genomics for Bioenergy (DOE - USDA 2012). USDA also supports National Centers, such as the National Center for Agricultural Utilization Research, that have groups devoted to bioenergy research. Moreover, USDA has developed its Energy Research Education and Extension Strategic Plan which contains four goals: 1) Sustainable agriculture and natural resource-based energy production; 2) Sustainable bioeconomies for rural communities; 3) Efficient use of energy and energy conservation; and 4) Work force development for the bioeconomy. The four goals are in line and complementary to the mission of the Energy Efficiency and Renewable Energy of DOE. To attain their four goals, the USDA is aligning itself with the Land Grant Universities.

NSF has also provided two major programs designed to advance research and development in the biomass and bioenergy space. The Sustainable Bioenergy Pathways program was developed to support innovative and interdisciplinary research in basic sciences that support systems approaches to sustainable bioenergy solutions (NSF 2012a). And the Energy for Sustainability Program in the Division of Chemical, Bioengineering, Environmental, and Transport Systems is awarding nearly $10 million in research grants for fundamental and applied research in electricity and transportation fuels, with specific interest in biomass conversion and biofuels (NSF 2012b).

In 2009, the American Reinvestment and Recovery Act also provided significant investment in the biofuels industry with $800 million for biofuel research, development, and demonstration projects (Recovery Act 2009).
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