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DOE OSTI2022

Global distribution, formation and fate of mineral‐associated soil organic matter under a changing climate: A trait‐based perspective

Abstract Soil organic matter (SOM) is the largest actively cycling reservoir of terrestrial carbon (C), and the majority of SOM in Earth's mineral soils (~65%) is mineral‐associated organic matter (MAOM). Thus, the formation and fate of MAOM can exert substantial influence on the global C cycle. To predict future changes to Earth's climate, it is critical to mechanistically understand the processes by which MAOM is formed and decomposed, and to accurately represent this process‐based understanding in biogeochemical and Earth system models. In this review, we use a trait‐based framework to synthesize the interacting roles of plants, soil micro‐organisms, and the mineral matrix in regulating MAOM formation and decomposition. Our proposed framework differentiates between plant and microbial traits that influence total OM inputs to the soil (‘feedstock traits’) versus traits that influence the proportion of OM inputs that are ultimately incorporated into MAOM (‘MAOM formation traits’). We discuss how these feedstock and MAOM formation traits may be altered by warming, altered precipitation and elevated carbon dioxide. At a planetary scale, these feedstock and MAOM formation traits help shape the distribution of MAOM across Earth's biomes, and modulate biome‐specific responses of MAOM to climate change. We leverage a global synthesis of MAOM measurements to provide estimates of the total amount of MAOM‐C globally (~840–1540 Pg C; 34%–51% of total terrestrial organic C), and its distribution across Earth's biomes. We show that MAOM‐C concentration is highest in temperate forests and grasslands, and lowest in shrublands and savannas. Grasslands and croplands have the highest proportion of soil organic carbon (SOC) in the MAOM fraction (i.e. the MAOM‐C:SOC ratio), while boreal forests and tundra have the lowest MAOM‐C:SOC ratio. Drawing on our trait framework, we then review experimental data and posit the effects of climate change on MAOM pools in different biomes. We conclude by discussing how MAOM is integrated into soil C models, and how feedstock and MAOM formation traits may be included in these models. We also summarize the projected fate of MAOM under climate change scenarios (Representative Concentration Pathways 4.5 and 8.5) and discuss key model uncertainties. Read the free Plain Language Summary for this article on the Journal blog.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Engineering Innovations, Challenges, and Opportunities for Lignocellulosic Biorefineries: Leveraging Biobased Polymer Production

Alternative polymer feedstocks are highly desirable to address environmental, social, and security concerns associated with petrochemical-based materials. Lignocellulosic biomass (LCB) has emerged as one critical feedstock in this regard because it is an abundant and ubiquitous renewable resource. LCB can be deconstructed to generate valuable fuels, chemicals, and small molecules/oligomers that are amenable to modification and polymerization. However, the diversity of LCB complicates the evaluation of biorefinery concepts in areas including process scale-up, production outputs, plant economics, and life-cycle management. We discuss aspects of current LCB biorefinery research with a focus on the major process stages, including feedstock selection, fractionation/deconstruction, and characterization, along with product purification, functionalization, and polymerization to manufacture valuable macromolecular materials. We highlight opportunities to valorize underutilized and complex feedstocks, leverage advanced characterization techniques to predict and manage biorefinery outputs, and increase the fraction of biomass converted into valuable products.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Modeling the Moisture Content and Dry Matter Loss in Dynamic Woody Biomass Storage Piles with Variable Extraction

The urgent need to mitigate climate change has spurred significant interest in renewable energy sources. This paper explores the storage and processing of woody biomass for biofuel production, considering the dynamic nature of biomass piles in real-world scenarios. A model has been developed to analyze moisture content changes and dry matter loss in woody biomass stored in piles prior to processing, taking into account varying extraction methods and environmental conditions. Case studies that examine the effects of different unpiling methods (FIFO, LIFO, and homogeneous) on moisture content and dry matter loss under various feedstock arrival rates and weather conditions are presented. Results indicate that unpiling methods significantly impact moisture content, with LIFO typically resulting in higher moisture content due to the utilization of fresher feedstock. Dry matter loss increases with pile size and time, emphasizing the importance of accurate modeling for assessing carbon emissions and feedstock quality. Furthermore, the model highlights the importance of process loading order and extraction methods in biomass storage, suggesting potential cost benefits associated with decreased moisture content. The difference between different extraction methods could vary the moisture content in the feedstock reaching the biofuel process by as much as 37.6%, however dry matter loss varies minimally for realistic pile changes. Overall, this research contributes to a better understanding of biomass storage dynamics and informs sustainable biofuel production practices.

Niska, Janel↗
DOE OSTI2013

Comparison of sugar content for ionic liquid pretreated Douglas-fir woodchips and forestry residues

The development of affordable woody biomass feedstocks represents a significant opportunity in the development of cellulosic biofuels. Primary woodchips produced by forest mills are considered an ideal feedstock, but the prices they command on the market are currently too expensive for biorefineries. In comparison, forestry residues represent a potential low-cost input but are considered a more challenging feedstock for sugar production due to complexities in composition and potential contamination arising from soil that may be present. We compare the sugar yields, changes in composition in Douglas-fir woodchips and forestry residues after pretreatment using ionic liquids and enzymatic saccharification in order to determine if this approach can efficiently liberate fermentable sugars. : These samples were either mechanically milled through a 2 mm mesh or pretreated as received with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate [C 2 mim][OAc] at 120°C and 160°C. IL pretreatment of Douglas-fir woodchips and forestry residues resulted in approximately 71-92% glucose yields after enzymatic saccharification. X-ray diffraction (XRD) showed that the pretreated cellulose was less crystalline after IL pretreatment as compared to untreated control samples. Two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR) revealed changes in lignin and hemicellulose structure and composition as a function of pretreatment. Mass balances of sugar and lignin streams for both the Douglas-fir woodchips and forestry residues throughout the pretreatment and enzymatic saccharification processes are presented. While the highest sugar yields were observed with the Douglas-fir woodchips, reasonably high sugar yields were obtained from forestry residues after ionic liquid pretreatment. Structural changes to lignin, cellulose and hemicellulose in the woodchips and forestry residues of Douglas-fir after [C 2 mim][OAc] pretreatment are analyzed by XRD and 2D-NMR, and indicate that significant changes occurred. Irrespective of the particle sizes used in this study, ionic liquid pretreatment successfully allowed high glucose yields after enzymatic saccharification. These results indicate that forestry residues may be a more viable feedstock than previously thought for the production of biofuels.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

High-throughput prediction of eucalypt lignin syringyl/guaiacyl content using multivariate analysis: A comparison between mid-infrared, near-infrared, and Raman spectroscopies for model development

Background: In order to rapidly and efficiently screen potential biofuel feedstock candidates for quintessential traits, robust high-throughput analytical techniques must be developed and honed. The traditional methods of measuring lignin syringyl/guaiacyl (S/G) ratio can be laborious, involve hazardous reagents, and/or be destructive. Vibrational spectroscopy can furnish high-throughput instrumentation without the limitations of the traditional techniques. Spectral data from mid-infrared, near-infrared, and Raman spectroscopies was combined with S/G ratios, obtained using pyrolysis molecular beam mass spectrometry, from 245 different eucalypt and Acacia trees across 17 species. Iterations of spectral processing allowed the assembly of robust predictive models using partial least squares (PLS). Results: The PLS models were rigorously evaluated using three different randomly generated calibration and validation sets for each spectral processing approach. Root mean standard errors of prediction for validation sets were lowest for models comprised of Raman (0.13 to 0.16) and mid-infrared (0.13 to 0.15) spectral data, while near-infrared spectroscopy led to more erroneous predictions (0.18 to 0.21). Correlation coefficients (r) for the validation sets followed a similar pattern: Raman (0.89 to 0.91), mid-infrared (0.87 to 0.91), and near-infrared (0.79 to 0.82). These statistics signify that Raman and mid-infrared spectroscopy led to the most accurate predictions of S/G ratio in a diverse consortium of feedstocks. Conclusion: Eucalypts present an attractive option for biofuel and biochemical production. Given the assortment of over 900 different species of Eucalyptus and Corymbia , in addition to various species of Acacia , it is necessary to isolate those possessing ideal biofuel traits. This research has demonstrated the validity of vibrational spectroscopy to efficiently partition different potential biofuel feedstocks according to lignin S/G ratio, significantly reducing experiment and analysis time and expense while providing non-destructive, accurate, global, predictive models encompassing a diverse array of feedstocks.

09 BIOMASS FUELS↗
DOE OSTI2018

Rheological properties of corn stover slurries during fermentation by Clostridium thermocellum

Background: Milling during fermentation, termed cotreatment, has recently been proposed as an alternative to thermochemical pretreatment as a means to increase the accessibility of lignocellulosic biomass to biological attack. A central premise of this approach is that partial solubilization of biomass changes the slurry’s physical properties such that milling becomes more impactful and more feasible. A key uncertainty is the energy required to mill partially fermented biomass. To inform both of these issues, we report rheological characterization of small-particle, corn stover slurries undergoing fermentation by Clostridium thermocellum . Results: Fermented and unfermented corn stover slurries were found to be shear-thinning and well described by a power law model with an exponent of 0.10. Plastic viscosity of a slurry, initially at 16 wt.% insoluble solids, decreased as a result of fermentation by a factor of 2000, with the frst eightfold reduction occurring in the frst 10% of carbohydrate conversion. Large amplitude oscillatory shear experiments revealed only minor changes to the slurry’s rheological fngerprint as a result of fermentation, with the notable change being a reduction in the critical strain amplitude needed for the onset of nonlinearity. All slurries were found to be elastoviscoplastic, with the elastic/viscous crossover at roughly 100% strain amplitude. Conclusions: Whereas prior biomass rheology studies have involved pretreated feedstocks and solubilization mediated by fungal cellulase, we report results for feedstocks with no pretreatment other than autoclaving and for solubilization mediated by C. thermocellum . As observed in prior studies, C. thermocellum fermentation results in a dramatic decrease in viscosity. The magnitude of this decrease, however, is much larger starting with unpretreated feedstock than previously reported for pretreated feedstocks. LAOS measurements provide a detailed picture of the rheological fngerprint of the material. Viscosity measurements confrm the hypothesis that the physical character of corn stover slurries changes dramatically during fermentation by C. thermocellum , and indicate that the energy expended on overcoming slurry viscosity will be far less for partially fermented corn stover than for unfermented corn stover.

09 BIOMASS FUELS↗
DOE OSTI2025

Structural features of xylan dictate reactivity and functionalization potential for bio-based materials

Plant-based materials have the potential to replace some petroleum-based products, offering compostability and biodegradability as critical advantages. Xylan-rich biomass sources are gaining recognition due to their abundance and underutilization in current industrial applications. Research of potential xylan applications has been complicated by the complex and heterogeneous structure that varies for different xylan feedstocks. Acylation is a broadly used reaction in functionalization of polysaccharides at an industrial scale. However, the efficiency of this reaction varies with the xylan source. To optimize xylan valorization, a systematic understanding of structure–reactivity relationships is essential. This study explores, characterizes, and compares various xylan feedstocks in the acylation process. Xylan feedstocks were analyzed for their chemical composition, degree of polymerization, branching, solubility, and presence of impurities. These features were correlated with xylan glycotypes’ reactivity toward functionalization with succinic anhydride in an optimized DMSO/KOH condition, achieving carboxyl contents of up to 1.46. We used principal component analysis and hierarchical clustering to identify key structural features of xylan that promote its reactivity. Our findings reveal that xylans with higher xylose content and lower degrees of branching exhibit enhanced reactivity, achieving higher carboxyl content and yields. Structural analyses confirmed successful modification, and light scattering analyses showed dramatic changes in the solution properties. Succinylation improves the solubility and film-forming properties of native xylans. This study shows key structure–reactivity relationships in xylan succinylation, establishing that low branching, high xylose content, and reduced lignin impurity enhance chemical functionalization. The results offer a framework for selecting optimal biomass feedstocks and support future efforts in genetic and synthetic biology to design plants with tunable xylan architectures. These findings advance the hemicellulose valorization for applications in coatings and packaging.

Acylation↗
DOE OSTI2023

Chapter 6: Recycling Plastic Waste to Produce Chemicals - A Techno-Economic Analysis and Life-Cycle Assessment

This study presents the results of a preliminary assessment on the technology, economics, and sustainability of using waste plastics as a feedstock to produce low molecular weight olefins via pyrolysis and gasification pathways. We also studied the formation of formaldehyde - an important polymer precursor - via the gasification of waste plastics. Process pathways for recovery of ethylene and propylene and production of formaldehyde from a simulated mixed plastic waste were constructed based on literature data. They included direct and indirect pathways based on either gasification or pyrolysis as the primary conversion step. Results of these studies have shown that significant economic challenges exist of producing olefins via pyrolysis and gasification, with the latter pathway especially difficult. Base costs of pyrolysis naphtha from waste plastics are higher when compared to the same material produced from fossil feedstocks. Base olefin costs for one direct route are two times higher than comparable costs from steam cracking of fossil naphtha. These costs are driven primarily by feedstock costs; some pyrolysis scenarios become more economically feasible when very low feedstock costs are used. Similarly, for gasification, the cost of methanol - the central intermediate - was found to be noticeable higher when produced by gasification of waste plastics compared to current selling prices, which negatively impacts all pathways that go through methanol as the central intermediate. Life-cycle assessment indicates that the production of pyrolysis naphtha from plastics is a carbon intensive operation; no major advantages were found in terms of greenhouse gas emissions for any of the pathways producing C2 and C3 olefins. The results of this study can serve as the baseline for future comparison to other plastic waste valorization processes.

BIOMASS FUELS,ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2026

Data for Greenhouse Gas Accounting Procedures in Low Carbon Fuel Policies Overlook the Spatial Variability of Miscanthus-Derived Sustainable Aviation Fuel

Low carbon fuel policies such as the U.S. Renewable Fuel Standard (RFS), Canada Clean Fuel Regulations (CFR), and California Low Carbon Fuel Standard (LCFS) as well as the 45Z tax credit are intended to reduce greenhouse gas (GHG) emissions from transportation. Cellulosic feedstocks, optimized biorefineries, and favorable farming locations can significantly reduce biofuel carbon intensity (CI). Despite advances in field-to-fuel GHG monitoring and flexibility in resource allocation within biorefineries (e.g., governing net electricity production), rigid CI accounting procedures in current policies may limit CI responsiveness across candidate sites and processing facilities. This work examines a hypothetical biomass-to-sustainable aviation fuel (SAF) pathway using miscanthus and alcohol-to-jet (i) to demonstrate how GHG accounting requirements drive estimates of biofuel CIs and (ii) to explore potential CI and financial implications of scenario-specific life cycle assessment (LCA). Results demonstrate that GHG accounting using the CFR/LCFS can reasonably account for distinct levels of net electricity production by a biorefinery, but only the CFR yields similar CI sensitivity to spatially explicit factors (feedstock CI, grid electricity CI) as scenario-specific LCA: most GHG accounting frameworks do not capture CI variation across candidate sites in the United States. Ultimately, this work demonstrates the importance of LCA methodological specifications in low carbon fuel policies and tax credits.

Miscanthus↗
DOE OSTI2026

Data for Multisite Field Evaluation of Oil Accumulation and Agronomic Performance in Grain and Sweet Sorghums Engineered for Lipid Hyperaccumulation

Oil sorghum (OS) has been developed by engineering grain (TX430) and sweet (Ramada) genetic backgrounds to accumulate triacylglycerols (TAG) in vegetative tissues as an energy-dense feedstock for sustainable aviation fuel (SAF) and other biofuels. This study evaluated two TX430 OS lines (TxHO-2, TxHO-3) and two Ramada OS lines (RmHO-1, RmHO-2) alongside wild-type (WT) lines in NE and IL over 2 years (2023–2024) to quantify genotype × environment effects on agronomic performance and TAG accumulation. Across four environments, TX430 OS lines showed average TAG concentrations of 15.0 g kg−1 in leaves and 12.8 g kg−1 in stems, approximately 19-fold higher than WT. Ramada OS lines accumulated 26.1 g kg−1 in leaves and 12.3 g kg−1 in stems, approximately 25-fold and 13-fold increases over WT, respectively. OS lines in TX430 exhibited an 18% reduction in biomass (8.4 vs. 9.9 Mg ha−1 for WT), while Ramada OS lines had similar WT biomass (18.3 vs. 19.9 Mg ha−1 for WT). Among TX430 OS lines, TxHO-2 achieved the highest TAG yield (190 kg ha−1), while RmHO-1 led the Ramada lines (335 kg ha−1) due to higher biomass and similar TAG concentration. Enhanced TAG accumulation increased N, P, and K removal in TX430 lines but not in Ramada lines. Structural carbohydrate and ash concentration were unaffected. Overall, results confirm vegetative lipid accumulation as a viable strategy for high-biomass sorghum, supporting its potential as a dual-purpose feedstock for SAF. Future work should focus on minimizing biomass yield penalties and improving nutrient use efficiency in oil sorghum systems.

Agronomy↗
DOE OSTI2018

Demonstration of a Pilot-Scale Plant for Biomass Torrefaction and Briquetting

Abstract. A semi-mobile torrefaction and densification pilot plant was constructed in order to determine ideal operating conditions and evaluate briquette quality and throughput rate using forest residuals as the input feedstock. Experiments were conducted at various conditions with feedstock moisture content ranging from 4% to 25% (wet basis), reactor residence times of 10 and 20 min, and final product temperatures between 214°C and 324°C. Optimal operating conditions, evaluated based on throughput rate, specific electricity demand, torrefied briquette grindability, briquette volumetric energy density, and briquette durability, were identified to occur with a short residence time (10 min), low feedstock moisture content (<11% wet basis), and high final product temperature between 267°C and 275°C. These conditions were able to process 510 to 680 kg h -1 (wet basis) feedstock with a dry mass yield of 79% to 84% to produce torrefied biomass with a higher heating value of 21.2 to 23.0 MJ kg -1 (dry basis) compared to 19.6 MJ kg -1 for the original biomass. Torrefied briquettes produced at these conditions had a neatly stacked packing density of 990 kg m -3 and a volumetric energy density of 21,800 MJ m -3 . Their specific grinding energy was an average 37% of the energy required to grind a raw biomass briquette. These torrefied briquettes were more durable (94% DU) than raw briquettes (85% DU) directly following production, but were less durable after undergoing temperature and humidity fluctuations associated with long distance transportation (74% DU for torrefied and 84% DU for raw biomass briquettes). Results from this pilot plant are promising for commercial scale production of high quality torrefied briquettes and should lead to additional research and development of a torrefaction system optimized for a higher throughput rate at these conditions. Keywords: Biomass, Biomass conversion technology, Bioenergy, Briquetting, Densification, Forest residuals, Pyrolysis, Torrefaction.

Agriculture↗
DOE OSTI2016

A Slag Management Toolset for Determining Optimal Coal Gasification Temperatures

Abstract Gasifier operation is an intricate process because of the complex relationship between slag chemistry and temperature, limitations of feedstock materials, and operational preference. High gasification temperatures increase refractory degradation, while low gasification temperatures can lead to slag buildup on the gasifier sidewall or exit, either of which are problematic during operation. Maximizing refractory service life and gasifier performance require finding an optimized operating temperature range which is a function of the coal slag chemistry and viscosity. Gasifier operators typically use a slag’s viscosity-temperature relationship and/or ash-fusion fluid temperature to determine the gasification temperature range. NETL has built a slag management toolset to determine the optimal temperature range for gasification of a carbon feedstock. This toolset is based on a viscosity database containing experimental data, and a number of models used to predict slag viscosity as a function of composition and temperature. Gasifier users typically have no scientific basis for selecting an operational temperature range for gasification, instead using experience to select operational conditions. The use of the toolset presented in this paper provides a basis for estimating or modifying carbon feedstock slags generated from ash impurities in carbon feedstock.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

First Harvest Timing and Nitrogen Application Rate Effects on Chemical Composition and Ethanol Yield of Switchgrass

Switchgrass ( Panicum virgatum L.) chemical composition dynamics must be evaluated if dual‐purpose use as both forage and feedstock is to be considered. This 2‐year study, conducted at the Brown Loam Branch Experiment Station, Raymond, MS, quantified first harvest timing (HT) and nitrogen (N) rate effects on forage nutritive value, feedstock chemical composition, and ethanol yield of both primary and aftermath harvests of ‘Alamo’ switchgrass. Treatments were factorial combinations of six HT (monthly intervals from May to October) and four N application rates (0, 35.7, 71.2, and 107.1 lb/acre) in a randomized complete block design. Aftermath was harvested in November. In both years, first harvest acid detergent fiber (ADF), neutral detergent fiber (NDF), lignin, cellulose, and hemicellulose concentrations of aboveground biomass, stems, and leaves increased with HT from May to October while aftermath harvest concentrations decreased with shorter regrowth after the first harvest. Stems had greater concentrations than leaf. Crude protein (CP) and in vitro dry matter digestibility (IVDMD) decreased with plant maturity and were greatest in the leaf component. Concentrations of major sugars increased with maturity and were greatest in the most mature stand in the aftermath. Ethanol yield was greatest in the least mature stands; however, ethanol production increased with maturity, largely because of greater biomass harvested. Nitrogen rate had no effect on forage nutritive value or feedstock composition in either the primary or aftermath harvests. These results provide information that can guide potential utilization of switchgrass as forage in early season and harvesting for biofuel feedstock at the end of the season.

Seepaul, Ramdeo↗
DOE OSTI2011

Fiscalini Farms Biomass Energy Project

In this final report describes and documents research that was conducted by the Ecological Engineering Research Program (EERP) at the University of the Pacific (Stockton, CA) under subcontract to Fiscalini Farms LP for work under the Assistance Agreement DE-EE0001895 'Measurement and Evaluation of a Dairy Anaerobic Digestion/Power Generation System' from the United States Department of Energy, National Energy Technology Laboratory. Fiscalini Farms is operating a 710 kW biomass-energy power plant that uses bio-methane, generated from plant biomass, cheese whey, and cattle manure via mesophilic anaerobic digestion, to produce electricity using an internal combustion engine. The primary objectives of the project were to document baseline conditions for the anaerobic digester and the combined heat and power (CHP) system used for the dairy-based biomass-energy production. The baseline condition of the plant was evaluated in the context of regulatory and economic constraints. In this final report, the operation of the plant between start-up in 2009 and operation in 2010 are documented and an interpretation of the technical data is provided. An economic analysis of the biomass energy system was previously completed (Appendix A) and the results from that study are discussed briefly in this report. Results from the start-up and first year of operation indicate that mesophilic anaerobic digestion of agricultural biomass, combined with an internal combustion engine, is a reliable source of alternative electrical production. A major advantage of biomass energy facilities located on dairy farms appears to be their inherent stability and ability to produce a consistent, 24 hour supply of electricity. However, technical analysis indicated that the Fiscalini Farms system was operating below capacity and that economic sustainability would be improved by increasing loading of feedstocks to the digester. Additional operational modifications, such as increased utilization of waste heat and better documentation of potential of carbon credits, would also improve the economic outlook. Analysis of baseline operational conditions indicated that a reduction in methane emissions and other greenhouse gas savings resulted from implementation of the project. The project results indicate that using anaerobic digestion to produce bio-methane from agricultural biomass is a promising source of electricity, but that significant challenges need to be addressed before dairy-based biomass energy production can be fully integrated into an alternative energy economy. The biomass energy facility was found to be operating undercapacity. Economic analysis indicated a positive economic sustainability, even at the reduced power production levels demonstrated during the baseline period. However, increasing methane generation capacity (via the importation of biomass codigestate) will be critical for increasing electricity output and improving the long-term economic sustainability of the operation. Dairy-based biomass energy plants are operating under strict environmental regulations applicable to both power-production and confined animal facilities and novel approached are being applied to maintain minimal environmental impacts. The use of selective catalytic reduction (SCR) for nitrous oxide control and a biological hydrogen sulfide control system were tested at this facility. Results from this study suggest that biomass energy systems can be compliant with reasonable scientifically based air and water pollution control regulations. The most significant challenge for the development of biomass energy as a viable component of power production on a regional scale is likely to be the availability of energy-rich organic feedstocks. Additionally, there needs to be further development of regional expertise in digester and power plant operations. At the Fiscalini facility, power production was limited by the availability of biomass for methane generation, not the designed system capacity. During the baseline study period, feedstocks included manure, sudan grass silage, and refused-feed. The ability of the dairy to produce silage in excess of on-site feed requirements limited power production. The availability of biomass energy crops and alternative feedstocks, such as agricultural and food wastes, will be a major determinant to the economic and environmental sustainability of biomass based electricity production.

03 NATURAL GAS↗
DOE OSTI2014

NREL 2012 Achievement of Ethanol Cost Targets: Biochemical Ethanol Fermentation via Dilute-Acid Pretreatment and Enzymatic Hydrolysis of Corn Stover

For the DOE Bioenergy Technologies Office, the annual State of Technology (SOT) assessment is an essential activity for quantifying the benefits of biochemical platform research. This assessment has historically allowed the impact of research progress achieved through targeted Bioenergy Technologies Office funding to be quantified in terms of economic improvements within the context of a fully integrated cellulosic ethanol production process. As such, progress toward the ultimate 2012 goal of demonstrating cost-competitive cellulosic ethanol technology can be tracked. With an assumed feedstock cost for corn stover of $\$$58.50/ton this target has historically been set at $\$$1.41/gal ethanol for conversion costs only (exclusive of feedstock) and $\$$2.15/gal total production cost (inclusive of feedstock) or minimum ethanol selling price (MESP). This year, fully integrated cellulosic ethanol production data generated by National Renewable Energy Laboratory (NREL) researchers in their Integrated Biorefinery Research Facility (IBRF) successfully demonstrated performance commensurate with both the FY 2012 SOT MESP target of $\$$2.15/gal (2007$\$$, $\$$58.50/ton feedstock cost) and the conversion target of $\$$1.41/gal through core research and process improvements in pretreatment, enzymatic hydrolysis, and fermentation.

09 BIOMASS FUELS↗
DOE OSTI2013

Center for Renewable Energy Science and Technology

The CREST research team conducted research that optimized catalysts used for the conversion of southwestern lignite into synthetic crude oil that can be shipped to nearby Texas refineries and power plants for development of transportation fuels and power generation. Research was also undertaken to convert any potential by-products of this process such as CO2 to useful chemicals and gases which could be recycled and used as feedstock to the synthetic fuel process. These CO2 conversion processes used light energy to drive the endogonic reduction reactions involved. The project was divided into two tasks: A CO2 Conversion Task, and a Catalyst Optimization Task. The CO2 Conversion task was aimed at developing molecular and solid state catalysts for the thermal, electro- and photocatalytic reduction of CO2 to reduced products such as simple feedstock compounds (e.g. CO, H2, CHOOH, CH2O, CH3OH and CH4). For example, the research team recycled CO that was developed from this Task and used it as a feedstock for the production of synthetic crude in the Catalyst Optimization Task. In the Catalyst Optimization Task, the research team conducted bench-scale experiments with the goal of reducing overall catalyst cost in support of several synthetic crude processes that had earlier been developed. This was accomplished by increasing the catalyst reactivity thus reducing required concentrations or by using less expensive metals. In this task the team performed parametric experiments in small scale batch reactors in an effort to improve catalyst reactivity and to lower cost. They also investigated catalyst robustness by testing lignite feedstocks that vary in moisture, h, and volatile content.

Billo, Richard↗
DOE OSTI2014

Development and Deployment of a Short Rotation Woody Crops Harvesting System Based on a Case New Holland Forage Harvester and SRC Woody Crop Header

Biomass for biofuels, bioproducts and bioenergy can be sourced from forests, agricultural crops, various residue streams, and dedicated woody or herbaceous crops. Short rotation woody crops (SRWC), like willow and hybrid poplar, are perennial cropping systems that produce a number of environmental and economic development benefits in addition to being a renewable source of biomass that can be produced on marginal land. Both hybrid poplar and willow have several characteristics that make them an ideal feedstock for biofuels, bioproducts, and bioenergy; these include high yields that can be obtained in three to four years, ease of cultivar propagation from dormant cuttings, a broad underutilized genetic base, ease of breeding, ability to resprout after multiple harvests, and feedstock composition similar to other sources of woody biomass. Despite the range of benefits associated with SRWC systems, their deployment has been restricted by high costs, low market acceptance associated with inconsistent chip quality (see below for further explanation), and misperceptions about other feedstock characteristics (see below for further explanation). Harvesting of SRWC is the largest single cost factor (~1/3 of the final delivered cost) in the feedstock supply system. Harvesting is also the second largest input of primary fossil energy in the system after commercial N fertilizer, accounting for about one third of the input. Therefore, improving the efficiency of the harvesting system has the potential to reduce both cost and environmental impact. At the start of this project, we projected that improving the overall efficiency of the harvesting system by 25% would reduce the delivered cost of SRWC by approximately $0.50/MMBtu (or about $7.50/dry ton). This goal was exceeded over the duration of this project, as noted below.

09 BIOMASS FUELS↗
DOE OSTI2015

Supply Chain Sustainability Analysis of Fast Pyrolysis and Hydrotreating Bio-Oil to Produce Hydrocarbon Fuels

The Department of Energy’s (DOE) Bioenergy Technology Office (BETO) aims at developing and deploying technologies to transform renewable biomass resources into commercially viable, high-performance biofuels, bioproducts and biopower through public and private partnerships. BETO and its national laboratory teams conduct in-depth techno-economic assessments (TEA) of technologies to produce biofuels. These assessments evaluate feedstock production, logistics of transporting the feedstock, and conversion of the feedstock to biofuel. There are two general types of TEAs. A design case is a TEA that outlines a target case for a particular biofuel pathway. It enables preliminary identification of data gaps and research and development needs, and provides goals and targets against which technology progress is assessed. On the other hand, a state of technology (SOT) analysis assesses progress within and across relevant technology areas based on actual experimental results relative to technical targets and cost goals from design cases, and includes technical, economic, and environmental criteria as available. In addition to the TEA process, BETO also performs a supply chain sustainability analysis (SCSA). The SCSA takes the life-cycle analysis approach that BETO has been supporting for more than 17 years. It enables BETO to identify energy consumption or environmental issues that may be associated with biofuel production. Approaches to mitigate these issues can then be developed. Additionally, the SCSA allows for comparison of energy and environmental impacts across biofuel pathways in BETO’s research and development portfolio. This report describes the SCSA of the fast pyrolysis of two woody feedstocks, pine and forest residue, to renewable gasoline and diesel.

09 BIOMASS FUELS↗