A Production Scenario for Cellulosic Ethanol from Corn Stover. Developed by the National Laboratories

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1 A Production Scenario for Cellulosic Ethanol from Corn Stover Developed by the National Laboratories

2 4 Cellulosic Ethanol Production The 30 x 30 vision is grounded in the availability of biomass resources and the efficiency with which these resources can be converted to transportation fuels. Aligning these components to create a path forward to replacing 30% of 2004 motor gasoline by 2030 will require, among all else, process and technology flexibility. The feedstock resource addressed in the billion-ton study (Biomass as Feedstock 2005) validates the feasibility of achieving the 30 x 30 vision, provided R&D efforts overcome technical barriers to the development of advanced biomass conversion technologies. The feedstock resource base, however, includes a variety of regionally specific biomass materials with a range of chemical and physical properties. Figure 5-1 shows the existing and future distribution of the feedstock resources described in the billion-ton study. High Yield Growth With Energy Crops High Yield Growth Without Energy Crops Existing & Unexploited Resources Forest Resources Total Grains & Manure Sub-Total Ag Residues (non Energy Crops) Perennial (Energy) Crops Million Tons Annually Figure 4-1. Distribution of feedstock resources This implies that the conversion technologies of future integrated biorefineries will be a function of available feedstock resources. For this reason, cellulosic ethanol production technology must be sufficiently diverse to optimize the conversion of multiple biomass resources to fuel. In this section, two conversion technologies that can potentially process the projected feedstock resources are considered (Figure 5-2). Both of these routes have several variations, but the main difference is in the primary catalysis system /22/06

3 Transformation through Intermediates (sugars) Biochemical conversion Reduction to to building blocks (CO, H 2 ) ) Thermochemical conversion Figure 4-2. Primary conversion routes for cellulosic biomass Biochemical conversion uses biocatalysts (such as enzymes and microbial cells), heat, and chemicals to convert biomass first to an intermediate sugar stream and then to ethanol and coproducts such as heat, power, and chemicals. Thermochemical conversion reduces biomass to a fundamental chemical building block, syngas (CO, H 2 ), that can be converted into ethanol and other products through fuel synthesis processes. Pyrolysis is an alternative thermochemical conversion technology that yields an intermediate bio-oil product that can be upgraded to fuel with heat and chemical catalysts. For this discussion, forest residues from small-wood forest thinnings or residues such as hog fuel from the forest products industry are considered primarily for thermochemical conversion because of their anticipated higher lignin content. Agricultural residues, in contrast, are considered primarily for biochemical conversion technologies. These resources are expected to have a more uniform distribution of chemical composition because they are derived from cultivated crops that could be genetically engineered or selected for properties more amenable to biochemical conversion technologies (such as low recalcitrance or high cellulose or xylan content). This philosophy also holds for the development of energy crops. Biomass grown specifically for transportation fuel production can be engineered or selected to have the most desirable chemical and physical properties for a conversion technology. In addition, increasing the biomass resource base that can be biochemically converted to fuels provides an additional resource: lignin-rich fermentation residues that can be used for combined heat and power production or converted to biofuel in advanced, integrated biochemical-thermochemical biorefineries /22/06

4 The 30 x 30 vision of developing 60 billion gallons of ethanol capacity by 2030 highlights the need for optimization of all aspects of biofuels production, including: Conversion technology-specific feedstock resources Feedstock production, storage, and distribution Biochemical conversion technologies Thermochemical conversion technologies. As technology develops, existing conversion routes will mature and others will be developed, including some with the ability to reduce the energy expenditure of the overall biomass-toethanol process. Although specific scenarios are considered in this section, it is clearly the responsibility of the developing bioenergy industry to use opportunistic resources with specific conversion technologies to produce selected products (such as fuels, chemicals, materials, and power) that meet their strategic business goals /22/06

5 References Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply (April 2005). DOE/GO DOE/USDA /22/06

6 4.1 Feedstocks The emerging biorefining industry is dependent on a large and sustainable supply of biomass resources provided at an effective cost and quality. The joint U.S. Department of Energy and U.S. Department of Agriculture billion ton study 1 found that the biomass feedstock resource potential in the United States is more than sufficient for the 30 X 30 goal. About 368 million dry tons of sustainably removable biomass could be produced on forestlands and about 998 million dry tons (including agriculture residues and new perennial crops) could come from agricultural lands (Fig. 5-4). This full resource potential could be available roughly around mid-21st century. Forest resources 368 Agricultural resources 621 Perennial energy crops Million dry tons per year Figure 4-4. Agriculture and forest lands could produce 1.3 billion tons of biomass for conversion to ethanol, power, and products. The forestlands projection includes 52 million dry tons of fuelwood harvested from forests, 145 million dry tons of residues from wood processing and pulp and paper mills, 47 million dry tons of urban wood residues including construction and demolition debris, 64 million dry tons of residues from logging and site clearing operations, and 60 million dry tons of biomass from fuel treatment operations to reduce fire hazards. Agricultural lands in the United States could produce nearly 1 billion dry tons of biomass annually, while continuing to meet food, feed, fiber and export demands. This projection includes 428 million dry tons of primary crop residues and 377 million dry tons of perennial energy crops. The remainder of biomass from agricultural lands includes grains used for biofuels, secondary processing residues, and some post-consumer wastes. Feedstock Accessibility The joint DOE/USDA billion ton study 2 establishes the resource base and future potential for a large-scale biorefinery industry. The ethanol price target of $1.07/gallon by 2012 is based on a total biomass feedstock cost of $35/dry ton. This 2012 feedstock cost target can be subdivided into at $10/dry ton grower payment (stumpage fee for forest resources) to cover the biomass value and $25/dry ton for the feedstock supply system costs, which include harvest and collection, storage, preprocessing, and transportation and handling. It is estimated that from the 1.3 billion ton potential, as much as 130 million tons could be accessed for a grower payment at or near $10/dry ton. Therefore, technology advancements that reduce feedstock supply system 1 Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply: A Joint Study Sponsored by U.S.DOE and U.S.D.A. April Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply: A Joint Study Sponsored by U.S.DOE and U.S.D.A. April

7 costs to $25/dry ton for each of the major agricultural and forestry feedstock resource types will result in a 2012 biomass resource sufficiently large to establish both biochemical and thermochemical biorefining capacity in every region of the United States (Fig. 5-5). Figure 4-5. Accessible agriculture and forest resource with biorefinery capacity potential in As the industry expands from grain ethanol to include cellulosic ethanol, it is expected that agriculture crop residues and forest logging residue resources will be the first to develop for biorefining purposes. Energy crops will develop and become integrated into the agricultural cropping systems as the biorefining industry matures and creates a demand for those resources. The increase in energy crop production will likely occur as land managers (i.e., farmers, plantation foresters, etc.) use these additional cropping options provided by a biomass energy market to maximize the productive capacity and economic returns of the land they manage. Collaborations with USDA and regional partners will become critical in developing sustainable biomass production and crop rotation strategies for both existing and new biomass resources. The expanding utilization of lignocellulosic biomass resources will create a demand for feedstocks, which will result in biorefineries paying more to access larger tonnages of more expensive resources (i.e., resources requiring >$10/dry ton grower payment). By paying more for the feedstock (e.g., value in the field or on the stump), larger tonnages of biomass can be accessed. However, that feedstock tonnage demand will always be limited by the price the biorefining industry can actually pay and remain competitive in the ethanol fuel market. Initially, government policies/programs as outlined in section 3 will be the means to access higher value feedstocks. As technologies advance up to and beyond the 2030 time frame, these technology advancements will reduce biomass processing costs, which will provide increased purchasing power for biorefineries to access higher value biomass feedstocks. This combination of policy and technology advancement will develop a U.S. biomass resource large enough to support the 30 X 30 goal (Fig. 5-6). The trend of improving supply and conversion technologies 2

8 to purchase higher value feedstocks is well established in other processing and refining industries 3. Figure 5-6. Accessible agriculture and forest resource with biorefinery capacity potential to produce 60 billion gallons of ethanol in Feedstocks R&D Pathway to achieve the $35 per dry ton 2012 ethanol cost target of $1.07 / gallon The feedstock R&D encompasses all of the unit operations necessary to move biomass feedstocks from the land resource to the conversion process of the biorefinery (Fig. 5-7) 4. A general description of the overall feedstock R&D pathway, the state-of-technology, and the R&D and technology needs to achieve and validate the $35/dry ton cost target for the major feedstock types (i.e., dry herbaceous, wet herbaceous, and woody) is discussed in this section. Biomass production is the beginning of the feedstock supply chain and involves producing feedstocks to the point of harvest. Production addresses many important factors such as feedstock types, land use, policy, and agronomic practices that drive biomass yield and directly affect the harvest and collection operations. Harvest and collection encompasses all operations associated with getting the biomass from its source to the storage or queuing location. In addition to obvious operations such as cutting (e.g., combining, swathing, logging etc.) and hauling, these operations often include some form of densification such as baling, bundling or chipping to facilitate handling and storage of the biomass. Storage and queuing are essential operations in the feedstock supply system since it is the method used to deal with seasonal harvest times, variable yields and delivery schedules. The primary objective of a storage system is the lowest cost method (including cost incurred from 3 Stoppert, J Industrial Bio-Products: Where Performance Comes Naturally. BIO World Congress Meeting. Orlando, FL. April, Roadmap for agricultural biomass feedstock supply in the United States. U.S. Department of Energy. November

9 losses) of holding the biomass material in a stable unaltered form (i.e., neither quality improvements nor reductions) until it is called for by the biorefinery. Prior to conversion, the feedstock must be preprocessed to physically transform it into the format required by the biorefinery. Preprocessing can be as simple as grinding and formatting the biomass for increased bulk density or improved conversion efficiency, or as complex as improving feedstock quality through fractionation, tissue separation, and blending. Transportation generally consists of moving the biomass from the storage location to the biorefinery via truck, rail, barge, pipeline, etc. The type of system used will directly affect how the feedstock is handled and fed into the conversion process. Transporting and handling the feedstock is highly dependent on the format and bulk density of the material, making them tightly coupled to each other and all other operations in the feedstock supply chain. Biomass Production Agricultural Resources Forest Resources Handling Harvest and Collection Storage Preprocessing Transportation and Queuing at the Biorefinery Equipment Capacity Equipment Capacity Material Bulk Density Compositional Impacts Compositional Impacts Handling efficiencies Pretreatment Impacts Pretreatment Impacts Handling compaction Material Bulk Properties Shrinkage Compositional Impacts Truck Capacity Pretreatment Impacts Loading compaction Soluble Sugar Capture Loading efficiencies Feedstock Interface Boundary Biomass Conversion: Biochemical Thermochemical Figure 4-7. Feedstock supply schematic for $35/dry ton feedstock. Significant advances have already been made in transforming the feedstock supply system from the traditional technologies used in the smaller distributed livestock, forage and wood products industries, to an assembly system specifically designed for the biorefinery industry, however much remains to be done in this area. Feedstock infrastructure development is difficult in that the equipment, methods and logistics vary not only among resource types (e.g., agricultural residues vs. forest residues) but also among different geographic regions (e.g., dry agricultural residues in the west vs. wet agricultural residues in the mid-west and northeast, or logging residues vs. urban wood residues). Consequently, the feedstock supply infrastructure must be developed for each specific class of biomass resource. These classes, categorized according to both feedstock type and geographic location consist of the following: Dry herbaceous (model feedstocks: stover, straw and switchgrass): Dry herbaceous feedstocks have been the model feedstock for work done to date on developing the feedstock infrastructure. Consequently, the dry herbaceous feedstock supply infrastructure is well developed and significant progress has been made towards achieving the $35/dry ton cost target. Wet herbaceous (model feedstocks: stover and switchgrass): The utilization of wet herbaceous feedstocks is currently limited by a host of infrastructure barriers. As a result, wet feedstock costs are still well beyond the $35/dry ton cost target. Since wet herbaceous feedstocks represent a significant portion of the overall feedstock resources, 4

10 overcoming these barriers provides the greatest potential to achieve the projected tonnage targets. Woody (logging residues): The use of logging residues for energy has been underway in Europe and the U.S. for nearly 30 years. As a result, the logging residue supply system is quite mature with available systems and methods already developed to support this industry 5, 6. Since near-term woody feedstock availability will consist largely of logging residues, the infrastructure for this feedstock can be readily adapted and validated against resource environment, resource policy, and other regional factors. Energy Crops (switchgrass): With the exception of production practices, herbaceous and woody energy crops can be accommodated by either a dry, wet, or woody feedstock supply system depending on the specific type and geographic region. Thus, energy crop supply system needs mirror those of the dry and wet herbaceous and woody systems. The R&D needs for developing and validating the feedstock supply infrastructures for the major feedstock types is shown in Table 5-1. This plan shows the technology advancements and key milestones for each element of the feedstocks R&D pathway that must occur to develop the dry, wet and woody supply systems capable of achieving the $35/dry ton cost target at the tonnages represented in Figure 5-1 above. The specific research that must be conducted to fulfill this plan is described below, with a more detailed description of the R&D plan given in Appendix D. 5 Wood chips production, handling and transport. Food and Agricultural Organization of the United Nations (FAO), Rome, Italy, Developing technology for large-scale production of forest chips. Wood Energy Technology Programme Tekes, the national Technology agency, Helsinki, Finland, April

11 Table 4-1. Technical research milestones and validation targets that form the basis for feedstock cost reductions and increased available tonnages Production Production is a critical component of the feedstock supply system, and it is a key research area for ensuring an adequate and sustainable feedstock supply. Through USDA and Regional Partnership collaborations, a number of regionally based validated assessments of feedstock resource types and potentials, agronomy, crop/resource type alternatives, rotations, etc. will be accomplished. Key milestones that must be accomplished in this area are shown in Table 5-1, and the specific research that must be conducted to address these production issues include: Assess the cost and availability of the feedstock resource on a local basis to define production costs of the feedstock (e.g., grower payments) and identify the regional tonnages available within each feedstock type or classification at or under the feedstock threshold costs. Identify and validate sustainable agronomic practices specific to feedstock types and regional variables to ensure sustainable production of the feedstock resource. 6

12 Investigate crop production improvements (increase yields, decrease yield variability, and consistent quality) through genetic modifications. Develop perennial crop program that includes matching varieties to specific site conditions, establishing optimum agronomic practices and developing a seed production program Harvest and Collection The Feedstock R&D plan depicted in Table 5-1 shows harvest and collection advances in three key areas: 1) selective harvest [including forest thinning operations], 2) single-pass or minimum impact harvest, and 3) harvest and collection efficiencies. The primary drivers for improved harvest system technologies are to reduce costs and to access larger tonnages of biomass through increasing producer participation. For example, improved harvest technologies that comply with soil quality concerns of no-till farming, such as soil carbon sequestration, soil nutrient/water retention, erosion control, and soil compaction, will become increasingly important for enticing grower participation and accessing the agricultural residues from these lands. Performance metrics for these new harvest and collection systems include: 1) efficiency [i.e., operational costs as influenced by materials, supplies, labor, logistical issues, material losses, etc.], 2) equipment capacity [i.e., element of efficiency, but includes technologies to reduce capital and improve throughput of specific equipment or sets of equipment]), and 3) quality [i.e., defines product specifications, value, and functional end-product yield of the biomass passing through the supply system, and is intrinsically linked to capacity and efficiency]. Without these improvements, the accessible biomass tonnage remains restricted due to limited or niche producer participation. Specific research that needs to be accomplished in this area is as follows: Develop innovative harvest and collection methods for all resource types to eliminate or reduce unit operations and agronomic/operational impact associated with the harvest and collection operation. Understand, quantify and validate harvesting-specific quality related to compositional impacts, pretreatment impacts, contaminant reductions, and bulk handling improvements. Develop and test innovative equipment specific to the recovery of wood residues for each resource class and conditions where existing equipment is too costly and inefficient Preprocessing Significant advances in dry herbaceous preprocessing have been made in the transition from a bale-based system to a bulk feedstock system, but as indicated in the Feedstock R&D plan shown in Table 5-1, additional advances are yet needed in three key areas: 1) preprocessing equipment capacity, 2) feedstock bulk density and 3) feedstock quality. Equipment capacity and bulk density directly affect feedstock cost and are thus important technical parameters to be addressed along with the interrelated effect on feedstock rheological properties. Furthermore, a key component of the feedstock R&D is to extend preprocessing beyond feedstock size reduction (e.g., grinding) to include value-added operations that improve feedstock quality to the biorefinery. These operations involve fractionation and separation of higher value feedstock components. Without these value-added operations to offset high feedstock costs, a large percentage of feedstock resources will not be available at the $35/dry ton cost target. Specific research that needs to be accomplished in this area is as follows: 7

13 Develop the preprocessing requirements for each feedstock type. This includes identifying the biorefinery feedstock requirements (e.g., particle size, fractionation), preprocessing logistics, as well as the storage, transportation and handling requirements. Understand the relationship between biomass structure and composition for assessing quality upgrade potential and for developing the equipment and methods of achieving the quality upgrades. Understand and control biomass tissue deconstruction in preprocessing and the relationship of grinder configuration, tissue fractions, tissue moisture and grinder capacity, in order to optimize grinder configuration for fractionation, capacity and efficiency. Increase bulk densities by coupling the understanding of biomass deconstruction and biomass rheological properties, along with innovative bulk compaction methods. Understand and control feedstock rheological properties resulting from preprocessing operations to provide a product that minimizes handling problems associated with transportation, handling and queuing operations Storage As illustrated in the Feedstock R&D plan presented in Table 5-1, feedstock shrinkage (dry matter loss) is the main consideration for feedstock storage. The shrinkage risks and the necessary mitigation strategies vary widely from region to region. DOE OBP s core R&D program has demonstrated that annual dry matter loss can be as low as 0.85%, but in wetter regions dry matter loss may exceed 25%. To achieve the 2012 cost and supply targets, dry matter losses are targeted to be less than 5% for all feedstock types. Specific research that needs to be accomplished to achieve this is as follows: Assess storage options and the effects on dry matter losses, compositional changes, and functional biomass changes specific to resource type and regional variables. Baseline the costs of storage systems at scales from 0.8 M tons per year to 10 M tons per year to identify key cost and infrastructure issues and develop paths to minimize industrial-scale storage costs. Understand soluble sugar and carbohydrate loss, and evaluate the feasibility of preventing and/or reclaiming those soluble sugars and carbohydrates from the feedstock during storage Transportation and Handling Transportation is a significant cost that can be a barrier to the utilization of certain feedstock resources. These operations can account for nearly 50% of the capital investment for the feedstock assembly system. Since these operations add no value to the feedstock, they represent significant costs that must be reduced to achieve the $35/dry ton cost target. The Feedstock R&D plan presented in Table 5-1 shows that feedstock bulk density is the key technical parameter that will be addressed to decrease transportation costs. As such, methods for increasing bulk density beyond those resulting from preprocessing are a focus of the feedstock R&D. In addition, since bulk handling is so affected by the feedstock rheological properties, this too is an area of focus. Specific research that needs to be accomplished to reduce transportation costs is as follows: Understand the feedstock physical and rheological properties (including bulk density) as they relate to handling systems for optimizing handling and transportation efficiencies. 8

14 Understand feedstock rheological properties in bulk storage to predict and minimize adverse feedstock physical changes that may affect plant processing. Evaluate innovative transportation and handling methods Validation and Demonstration As the dry, wet and woody supply system technologies are developed and improved and the milestones shown in Table 5-1 are achieved, the supply systems will be validated to demonstrate that the resources represented in Figure 5-1 can be supplied at the $35/dry ton cost target. This validation will be accomplished in an integrated pilot-scale facility that includes the supply system equipment and unit operations necessary to demonstrate the capacities, bulk densities, rheological properties, composition and quality that contribute to the $35/dry ton feedstock cost for dry, wet, and woody feedstock systems. The R&D plan is supported by single point sensitivity analysis used to relate the cost impacts of different technical and market parameters on the $35 feedstock cost target (see appendix C for risk assessment methodology description). The sensitivity of each unit operation identified in the Feedstock Roadmap 7 for all feedstock types is shown in Figure 5-8. This sensitivity analysis represents delivered feedstock cost ranges where the mean value is based on the 2012 market target of $35/dry ton. The high-end cost ranges, shown in red, represent worst case conditions and operational parameters based on the current state-of-technology. In the cases of storage preprocessing and transportation and handling, the high-end costs are directly attributed to the moisture content of the biomass at the time each unit operation is applied. For example, the wet storage unit operation is shown to increase the delivered feedstock cost by 55% due to 30% dry matter and function yield losses during storage and transportation. Likewise, preprocessing costs increase by 45% due to reduced capacities in grinding wet biomass and transportation and handling costs increase by 19% due to non-productive water weight. Further, the 17% increase in harvest and collection costs comes from reduced machine efficiencies as a result of additional biomass throughput. Finally, the increase in production costs (grower payment) stem from conditions not easily controlled or mitigated by technology such as weather, grower business practices and harvesting preferences, competing biomass markets, and transportation laws and road limits. The cost ranges shown in blue identify the potential to reduce the delivered cost of biomass feedstocks through advances in feedstock infrastructure technologies. Feedstock quality improvements account for the 15% and 17% cost reductions in storage and harvest and collection, respectively. Storage quality improvements involve exploiting the potential to capture some of the lost sugar yield, resulting from in-storage degradation. The potential cost decrease in the harvest and collection operation is a result of harvest efficiency gains (singlepass, greater capacity) and selectively harvesting (separating) the higher sugar content component of the biomass residues from the lower sugar content components. These two separated streams allow for a more uniform biomass feedstock, in terms of composition, which for the higher sugar content stream produces more ethanol per ton of biomass and for the lower sugar content stream requires a less sever pretreatment process. The cost reduction in preprocessing and transportation and handling, 22% and 4% respectively, are a result of 7 Roadmap for agricultural biomass feedstock supply in the United States. U.S. Department of Energy. November

15 improved equipment efficiencies and bulk material properties. The potential to achieve these improvements have been shown on reduced scales to be reasonable through laboratory and field testing results, vender specifications and equipment performance guidelines, and integrated feedstock assembly models. A more detailed sensitivity analysis for the technical parameters that impact individual unit operations is discussed in Appendix D. Storage Cost (-15% to +55%) Preprocessing Cost (-22% to +45%) Harvest & Collection Cost (-17% to +17%) Transportation & Handling Cost (-4% to +19%) Production - Grower Payment (8 to 15 $/dt) Unit Operations Fuel Cost (0.57 to 4.28 $/gal) Average Labor Cost (6.04 to $/hr) Variable Costs ($8) ($6) ($4) ($2) $0 $2 $4 $6 $8 $10 $12 $14 $16 $18 $20 Change in Delivered Feedstock Cost ($ per dry ton) Figure 4-8. Sensitivity analysis of each unit operation in the feedstock assembly and the associated variable costs for all feedstock types. 10

16 521biochem_62606_final.doc 4.2 Conversion Technologies Biochemical Process Technology Target for 2012 Introduction/Background Basically, biochemical conversion of lignocellulosic biomass to ethanol can be described as the fermentation of sugars liberated from the feedstock. Challenges are to most efficiently convert biomass to sugars (saccharify) and ferment these impure sugars to ethanol with a robust microorganism. Even with these challenges this conversion process shows great promise for cost-effective production of ethanol at high yields with minimal environmental impact. There are two primary routes to saccharify the feedstock to fermentable sugars, 1) acid hydrolysis, either concentrated or multiple stages of dilute and 2) pretreatment followed by enzymatic hydrolysis. In the 1980s, the DOE evaluated (Wright, 1987) the long-term potential of each process. Of these, enzymatic hydrolysis technology was shown to have the lowest ultimate costs and highest yields. While at the time acid hydrolysis technology had been further developed and appeared less expensive, a comparison of progress and future potential suggested that enzymes offered greater opportunities for ethanol cost reduction in the long run (Sheehan 2001). Acid hydrolysis technologies are certainly feasible and with the proper niche situations are being pursued to commercialization. Enzyme hydrolysis requires pretreatment to generate an intermediate material that can be effectively digested by enzymes. For example, dilute acid pretreatment of corn stover followed by enzymatic hydrolysis can achieve over 90% conversion of cellulose (Jechura, 2005) to glucose compared to around 50% for acid hydrolysis technologies (Zerbe and Baker, 1987). Various pretreatment methods have been suggested; most use heat coupled with a chemical catalyst such as acid, base or other solvent. Recent advances suggest that accessory enzyme systems such as hemicellulases could lead to low severity and low cost pretreatment processes in the future. The biochemical conversion route utilizing dilute acid as the pretreatment was selected here because it has strong potential and is one of the most well studied of the options available. To understand how much development is still required the DOE tracks the research stateof-technology (SOT) of the biochemical conversion process by extrapolating current-year laboratory results to a conceptual process design and cost estimate. The design and cost estimates are based on engineering company consultations and ASPEN modeling (Aden 2002) (ASPEN Plus TM, Releases , Aspen Technology, Inc., Cambridge, MA). The SOT includes only ethanol and excess electricity sales (no co-product credits) and does not include any proprietary company-specific enhancements over the baseline conversion technology demonstrated at the DOE s core biomass research program. Figure 5-x shows the SOT advances from 2001 to 2005 and looks into the future using R&D targets in the same model to understand what is required to achieve the technical target in Much of the cost reduction from 2001 through 2005 were due to the DOE 1

17 521biochem_62606_final.doc industry partnerships to reduce the cost of enzymes (Harris, et al., 2006, Mitchinson, 2006). As can be seen from the figure the 2012 target was accelerated by the DOE to accommodate the President s Advanced Energy Initiative to a value of $1.07/gallon of ethanol. The research outlined here addresses that more aggressive target. $6.00 Minimum Ethanol Selling Price ($/gal) $5.00 $4.00 $3.00 $2.00 Conversion Feedstock Pre-initiative Targets President's Biofuels Initiative $1.00 $0.00 Integrated with Thermochemical Processing Figure -x Research State-of-Technology for Biochemical Conversion Process Description The biochemical conversion process selected for this scenario uses co-current dilute acid pretreatment, enzymatic saccharification and fermentation to convert lignocellulosic feedstocks to ethanol. The process also includes the necessary ancillary supporting operations such as feedstock interface (handling and storage), product recovery, wastewater treatment (not shown), residue processing (lignin combustion), and product storage, see Figure 5-y. 2

18 521biochem_62606_final.doc Figure 4-y. Process schematic for biochemical conversion The feedstock, initially corn stover (composed of stalks, leaves, cobs, and husks) and later other agricultural residues and energy crops, is delivered to the feed-handling area for storage and size reduction. From there, the biomass is conveyed to pretreatment and conditioning. In this area, the biomass is treated with a dilute sulfuric acid catalyst at a high temperature for a short time, which hydrolyzes the hemicellulose to a mixture of sugars (xylose, arabinose, galactose, mannose and a small amount of glucose) and other compounds. In addition, the pretreatment step makes the remaining biomass more accessible for enzyme saccharification later in the process. A conditioning process is required to remove by-products from the pretreatment process that are toxic to the fermenting organism. Hybrid saccharification and co-fermentation (HSF) is carried out by first saccharifying the pretreated material (now primarily cellulose) with cellulase enzymes to form glucose at conditions optimal to the saccharification. This requires a couple of days, after which the mixture of sugars and any unreacted cellulose is transferred to the fermenter. An inoculum of fermenting microorganism is added and fermentation of all sugars to ethanol is carried out while continuing to utilize the enzymes for further glucose production from any remaining biomass, now at conditions optimal to the fermentation. After a few days of fermentation and continued saccharification nearly all of sugars will have been converted to ethanol. The resulting beer (low concentration ethanol) is sent to product recovery. Product recovery involves distilling the beer to separate the ethanol from the water and residual solids. A mixture of nearly azeotropic water and ethanol is purified to pure ethanol using vapor-phase molecular sieves. Solids from the distillation bottoms are separated and sent to the boiler (residue processing). Concentration of the distillation bottoms liquid is performed by evaporation using waste heat. The evaporated condensate is returned to the process, and the concentrated syrup is sent to the burner. 3

19 521biochem_62606_final.doc Part of the evaporator condensate, along with other wastewater, is treated by anaerobic and aerobic digestion. The biogas (high in methane) from the anaerobic digestion is sent to the burner for energy recovery. The treated water is considered suitable to recycle and is returned to the process. The solids from distillation, the concentrated syrup from the evaporator, and biogas from anaerobic digestion are combusted in a fluidized bed combustor to produce steam for process heat. The majority of the steam demand is in the pretreatment reactor and distillation areas. Generally, the process co-generates electricity for use in the plant and as a by-product for sale to the grid. R&D Needs To Achieve 2012 Technical Target The R&D required in the future to meet the 2012 technical target is outlined in Table 5-x. It is important to note that technology advancement is not only done on the laboratory bench, but must be verified and optimized at larger and larger scale. By 2012 the technology, and subsequently the data for calculating costs, will be generated from an integrated pilot plant. Completion Year R&D Area Current Feedstock Interface Corn Stover Determine which feedstock types will be used in pioneer plants. Determine range of quality of each feedstock that will be used in pioneer plants. Complete pilot plant trials with multiple feedstocks. Determine response/ impact on process operations. Pretreatment 63% xylan yields and 13% sugar degradation in continuous reactor with > 30% solids Understand xylan in cell wall & how to hydrolyze to xylose at yields > 75% in laboratory 1) Make final decision on pretreatment process to accomplish 2012 target 2) Validate > 75% xylan yield & < 8% degradation in continuous reactor 1) Understand sugar degradation kinetics & how to reduce degradation to < 6% and 2) Test accessory enzymes' effect on reducing pretreatment costs, in lab equipment > 85% xylan yields and < 6% sugar degradation in continuous reactor with > 30% solids - Final process determination for pilot >90% xylan to xylose & < 5% xylan degradation in integrated pilot operation with > 30% solids Hydrolyzate Conditioning 13% sugar losses in overliming conditioning step Understand chemistry and impact on fermentation of hydrolyzate conditioning in lab equipment Reduce sugar losses in conditioning step to < 7% in laboratory equipment (ancilary enzymes is one option) Reduce sugar losses in conditioning step to < 2% in laboratory equipment Reduce sugar losses in conditioning step to < 1% in integrated pilot operation or eliminate need for conditioning Enzyme Production $0.32/gallon of Ethanol 1) Understand cellulase interactions at the plant cell wall Determine how cellulase 2) First computer model of enzymes move along key enzymes cellulose chains Conduct targeted substitutions of cellulase components to increase specificy activity Validate $0.10/gal EtOH cost Reduce cost of purchased Reduce cost of purchased of enzyme used in integrated enzyme to $0.16/gal EtOH enzyme to $0.10/gal EtOH pilot operation Enzymatic Saccharification and Fermentation > 85% Cellulose to EtOH, > 75% xylose to EtOH, 0% other sugars to EtOH in a total of 7 days in lab system with > 20% total solids > 85% Cellulose to EtOH, > 80% xylose to EtOH, > 40% other sugars to EtOH Understand lignin in a total of 7 days in redeposition and other continuous lab system with process effects on enzyme > 20% total solids kinetics > 85% Cellulose to EtOH, > 80% non-glucose sugar to EtOH in a total of 5 days in continuous lab system with > 20% total solids > 85% Cellulose to EtOH, > 85% Cellulose to EtOH, > > 85% non-glucose sugar 85% non-glucose sugar to to EtOH in a total of 3 days EtOH in a total of 3 days in in continuous lab system integrated pilot operation with with > 20% total solids > 20% total solids Integration/Modeling Research state-oftechnology utilizing current data and modeling shows a $2.26/gal ethanol selling price with total capital of $3.04/gal of annual installed capacity All analytical methods and equipment have been identified and work plan for implementation completed. 1) Integrated pilot is designed, all equipment has been ordered. 2) Process cost estimate updated with latest data and engineering consultations. Table 4-x Timeline of Key Activities to Accomplish 2012 Technical Target Integrated pilot system is complete, including all analytical methods, all individual units verified for safe operation Data from integrated pilot operation combined with process design & cost estimate validates a $1.07/gal ethanol selling price and capital cost of $1.85/gal of annual installed capacity for nth plant Accomplishing the 2012 goal requires additional technology advancement in key areas of the core dilute acid and enzymatic hydrolysis process 1 (Foust, et al, 2005). 1 The process described for this scenario burns the lignin residue for heat and power. It is assumed that this is existing technology so there are no near-term critical research needs for lignin combustion. However, better utilization of the lignin residue for additional value is something that is addressed in the section regarding research needs beyond

20 521biochem_62606_final.doc Feedstock Interface Feedstock Variation Feedstock Quality Enzyme Production Enzyme Cost HSF Pretreatment Hydrolyzate Conditioning Enzymatic Hydrolysis Fermentation Product Recovery Products Xylose Yield Xylose Degradation Solids Loading Reactor Costs Sugar Loses Glucose Yield Solids Loading (Titer) Ethanol - Yields from all sugars Concentration Rate Residue Processing By-products Figure 4-z. Process Flow Diagram Highlighting Major Research Barriers As illustrated in and Table 5-x and Figure 5-z most areas of the process have barriers to performance that need to be addressed by R&D in order to accomplish the technical target. Specific descriptions of the research and technology targets for each of the barrier areas follow. Feedstock/Process Interface R&D Needs Target Determine the sensitivity of the overall process to differences in the feedstock type and quality. Determine how to adjust and modify the process to accommodate these changes in feedstock. Research 1. Understand the range of feedstock types expected to be used in the initial pioneer plants. 2. Work with the feedstock suppliers and researchers to best understand and improve or make more suitable the of quality (physical and chemical characteristics) that might exist in each of these feedstocks 3. Determine the impacts on all downstream unit operations of these different feedstocks 4. Understand how to adjust the process to maintain optimal yields and productivities with varying feedstock quality or with different feedstocks Pretreatment and Hydrolyzate Conditioning R&D Needs Target While maintaining or increasing the solids loading of 30% increase the xylan to xylose conversion to 90% while reducing the xylan lost to degradation products to 5% in a continuous pilot scale reactor Research 1. Determine the location of the xylan in the plant cell wall and optimize pretreatments that selectively remove and hydrolyze it to xylose 2. Reduce sugar degradation to minimal levels by understanding the kinetic mechanisms that lead to the undesirable degradation products and then systematically blocking these pathways 5

21 521biochem_62606_final.doc 3. Make a down selection to one primary pretreatment technology to focus research Target Reduce the capital cost of pretreatment through the use of ancillary enzymes Research 1. Determine if other enzymes, such as xylanases, can be used to improve xylose yields, minimize formation of degradation products, reduce cost associated with the pretreatment process by reducing the required severity and potentially reduce the need for conditioning. Target Eliminate or greatly reduce the need for conditioning Research 1. Understand the role of hydrolyzate conditioning to eliminate sugar losses 2. Understand and control the degradation kinetics to minimize or eliminate the formation of inhibitory compounds Enzyme Production R&D Needs Target Reduce the purchased enzyme cost to $0.10/gallon of ethanol produced for a 90% conversion of cellulose to glucose within 3 days in a hybrid saccharification and fermentation system (HSF) Research 1. Understand cellulase interactions at the plant cell wall ultrastructural level to optimize hydrolysis processes and enzyme kinetics and, ultimately, cellulase use and cost. 2. Determine how cellulase enzymes move along the cellulose chain and the respective roles of the different enzyme sub-structures. 3. Conduct targeted substitutions of the enzyme s components to increase specific activity guided by molecular modeling of cellulase/substrate interactions. 4. Identify the enzyme production process and logistics that minimizes processing and transportation costs of enzyme products. Enzymatic Saccharification and Fermentation R&D Needs Target Develop a robust, commercially viable, biocatalyst (microorganism) capable of fermenting 85% of the hemicellulose sugars and 95% of the glucose to a concentration of at least 6% ethanol in 3 days in a combined hybrid saccharification and fermentation Research 1. Identify strain candidates that exhibit superior wildtype performance. 2. Utilize metabolomics, proteomics and other tools to understand metabolic bottlenecks in the carbon assimilation pathways limiting rates of pentose sugar uptake and the ability to withstand fermentation inhibitors such as organic acids, low ph, and increased temperature. 3. Extend omics studies to identify and understand secondary pathway limitations related to reaction cofactors and regulation of metabolism. 4. Increase pentose uptake rates by applying protein and metabolic engineering to increase sugar transporter efficiency, pentose specificity, and expression. 5. Improve strain robustness by manipulating cell membrane composition to reduce its permeability to organic acids and improve its temperature stability. 6

22 521biochem_62606_final.doc 6. Use a combination of metabolic engineering, mutagenesis and/or long term culture adaptation strains on actual pretreatment hydrolyzate, to achieve the target fermentation performance. 7. Perform parametric analysis of such factors as lignin redeposition and the detrimental effects this can have on enzyme kinetics to minimize these effects. using structural and surface analysis tools. Target Develop an HSF process capable of saccharifying 90% of the cellulose to glucose and fermenting 85% of the hemicellulose sugars and 95% of the glucose to ethanol in 3 days while maintaining solids concentration necessary for ethanol concentration target above Research 1. Use information on the enzyme capabilities and fermenting strain s performance to develop and test strategies for efficiently integrating enzymatic hydrolysis with biomass sugar fermentation to maximize cellulose hydrolysis and sugar fermentation rates and yields. Quantify the impact of enzyme loading, strain inoculation time and inoculum charge on batch process performance. 2. Utilize reactor designs and operational schemes that will maximize the solids loading and conversion of cellulose and other sugars to ethanol. Integration/Process Engineering R&D Needs Target Optimize the key unit operations, pretreatment, hybrid saccharification and fermentation, product recovery and residue processing (separations only) in an integrated pilot plant with appropriate recycles. Obtain data necessary to update the conceptual the process design and cost estimate necessary to validate the 2012 technical target. Research 1. Set-up all appropriate unit operations in a safe integrated system capable of continuous operations, 24 hours per day, 7 days per week with data gathering capabilities. 2. Develop appropriate analytical methods and equipment to monitor the process and collect appropriate data. 3. Test the integrated process and optimize conditions to maximize performance. 4. Use appropriate data from the operating pilot plant to complete a conceptual full scale process design and cost estimate to validate the 2012 technical target. Reaching the 2012 technical target for biomass conversion as outlined in Table 5-x and in the above description calls for a very specific set of research targets. Missing anyone of these would mean that the 2012 target is not met. There could be other combinations of research results that would still result in the meeting the 2012 technical target of $1.07 ethanol selling price. Also, there will be more sensitivity (higher benefit if exceeded or bigger detriment if not met) to some research activities than others. A set of ethanol selling prices were calculated using variations of research targets to help understand the impact of missing or exceeding the targets. These variations (exceeding or falling short) are based on the judgment of researchers in the field, e.g., what is the range of possible 7

23 521biochem_62606_final.doc outcomes to the research? In some cases the low end value is what has been accomplished, highlighting for example, what if we can t do any better? Figure 5-zz illustrates the impact in calculated selling price due to the range of possible research results and other parameters. These are only the targets which exhibit a sensitivity range greater than $0.10/gal (see Appendix C for additional sensitivities). This illustrates that 1) some targets will have a significant impact on the final out come and 2) if some targets are exceeded and others missed that the final target selling price of $1.07/gallon can still be achieved.. Plant Size (10,000:2,000:1,000 dry tonnes/day)* Electricity Co-product Value ($0.06:$0.04:$0.00 per kwh) Feedstock Cost ($10:$30:$53 per dry ton) Cellulose Content (50%:37.4%:20%) Xylan Content (30%:21.1%:10%) Lignin Content (11%:18%25%) Xylan to Xylose Yield (95%:90%:63%) Cellulase Cost ($0.03:$0.10:$0.32/gal ethanol) Cellulose to Glucose Yield (95%:90%:80%) Solids Loading in Saccharification (25%:20%:15%) Nutrients for Ethanol Production (none:1x:4x) Total Project Investment (0.9x:1x:1.25x) ($0.40) ($0.30) ($0.20) ($0.10) $0.00 $0.10 $0.20 $0.30 $0.40 Reduced Ethanol Selling Price Increased Ethanol Selling Price *Values represent the Reduced Price impact parameter: Target Parameter: Increased Price impact parameter Figure 5-zz Research Outcomes and other Variables with Potentially High Impact on 2012 Technical Target Reference: Sheehan, J. Annual Bioethanol Outlook: FY01, NREL report submitted to DOE. May, Internal NREL/DOE report. ( Harris, P., S. Teter, J. Cherry, The path to commercialization: Planting the enzymes for biomass business, presentation at US DOE Biomass Program Pretreatment Core R&D Interium Stage Gate Review, Golden CO, June 9-10, 2006 ( Mitchinson, C., Genencor s Perspective, presentation at US DOE Biomass Program Pretreatment Core R&D Interium Stage Gate Review, Golden CO, June 9-10, 2006, ( Wright, J., Fuel Ethanol Technology Evaluation in Biofuels and Municipal Waste Technology Research Program Summary FY 1986, pp , DOE Report DOE/CH/1093-6, NTIS Report DE , Solar Energy Research Institute, July,

24 521biochem_62606_final.doc Jechura, J., Sugar Platform Post Enzyme-Subcontract Case, NREL Technical Memo, National Bioenergy Center, 10/11/2005 Zerbe, J. and A. Baker, Investigation of Fundamentals of Two-stage Dilute Sulfuric Acid Hydrolysis of Wood in Klass, Donald, ed. Energy from biomass and wastes X. Chicago: Institute of Gas Technology; pp ,

25 4.2.2 Thermochemical Process Technology Target for 2012 Background/Introduction Thermochemical conversion technology options include both gasification and pyrolysis to enable the developing lignocellulosic biorefineries and maximize the biomass resource utilization for production of biofuels. Moving forward, the role of thermochemical conversion is to provide a technology option for improving the economic viability of the developing bioenergy industry by converting the faction of the biomass resources that are not amenable to biochemical conversion technologies into liquid transportation fuels. The thermochemical route to ethanol is synergistic with the biochemical conversion route described in the previous section. A thermochemical process can more easily convert low-carbohydrate or non-fermentable biomass materials such as forest and wood residues to alcohol fuels, which adds technology robustness to efforts to achieve the 30 x 30 goal. This section describes the R&D needed to achieve the market target production price in 2012 for a stand-alone biomass gasification-mixed alcohol process. Advanced technology scenarios rely on considerable yield enhancements achieved by combining the two conversion technologies into an integrated biorefinery that implements thermochemical conversion of lignin-rich bioconversion residues into biofuel thus maximizing the liquid fuel yield per delivered ton of biomass. Section describes this advanced technology scenario. Biomass gasification can effectively convert a heterogeneous supply of biomass feedstock into a consistent gaseous intermediate that can be reliably converted to liquid fuels. The biomass gasification product gas ( synthesis gas or simply syngas ) has a low to medium energy content (depending on the gasifying agent) and consists mainly of CO, H 2, CO 2, H 2 O, N 2, and hydrocarbons. Minor components of the syngas include tars, sulfur and nitrogen oxides, alkali metals, and particulates. These minor components of the syngas potentially threaten the successful application of downstream syngas conversion steps. Commercially available and near-commercial syngas conversion processes were evaluated on technological, environmental, and economic bases in a recent report by Spath and Dayton (2003). This report provides the basis for identifying promising, cost-effective fuel synthesis technologies that maximize the impact of biomass gasification for transforming biomass resources into clean, affordable, and domestically produced biofuels. For the purpose of this 30x30 Scenario report, the pre-commercial mixed alcohols synthesis process implementing an alkali promoted MoS 2 catalyst, a variant of Fischer-Tropsch synthesis, was selected as the conversion technology of choice because high yields of ethanol are possible with targeted R&D technology advancements. The sulfided Mo catalyst is also tolerant of low levels of sulfur gases that are common catalyst poisons. Conceptual designs and techno-economic models were developed for a stand alone biomass gasification process with thermochemical ethanol production via mixed alcohols synthesis to determine how overcoming associated technical barriers contribute to reductions in finished ethanol costs (Aden and Spath, 2005). The proposed mixed alcohol process does not produce ethanol with 100% selectivity. Production of higher normal alcohols (e.g., n-propanol, n-butanol, and n-pentanol) is unavoidable. Fortunately, these by-product higher alcohols have value as commodity chemicals and fuel additives. Projecting the 2004 market volume and market price for each higher alcohol in 2012, assuming a 3%/year growth rate, implies that the n-propanol and n-pentanol markets will saturate as the number of thermochemical plants approaches 10, however, the n-butanol remains profitable (Bizzari, et al., 2002). Therefore, two thermochemical 6/26/06

26 ethanol scenarios were considered: (1) separating the higher alcohols from the mixed alcohol product and selling them at a percentage of their chemical market value and, (2) selling the unseparated mixed alcohol stream as fuel at a lower value. Economics are provided for both scenarios; however only the case with the higher alcohol by-product credits achieves the $1.07/gallon market target. The value of the higher alcohols provides the initial economic benefits that will accelerate the deployment of these thermochemical technologies by making the first plants economically competitive. The current case design defines today s R&D state of technology, particularly with regard to removal/conversion of tars and literature data for mixed alcohol synthesis catalyst performance. The schedule for meeting specific research goals for improved tar reforming and mixed alcohol synthesis catalyst performance is accelerated by the President s Biofuels Initiative to achieve $1.07/gal thermochemical ethanol by The conceptual process design and ethanol production cost estimate quantify the benefits of meeting the R&D goals for tar reforming and improved mixed alcohol catalyst performance as shown in Figure.1. Minimum Ethanol Selling Price ($ per gallon) $2.50 $2.00 $1.50 $1.00 $0.50 State of Technology Estimates Forest Resources 56 gal/ton Conversion Feedstock Previous DOE Cost Targets President's Initiative Costs in 2002 Dollars Forest & Agricultural Resources 67 gal/ton $ Figure -1. Research state-of-technology assessments for thermochemical ethanol production to reach the $1.07/gallon market target Process Description Figure 5.2 shows a block process flow diagram of the $1.07/gallon market target thermochemical process and the major technical barriers that need to be addressed to accomplish the target case. The feedstock interface addresses the main biomass fuel properties that impact the long-term technical and economic success of a thermochemical conversion process: moisture content, fixed carbon and volatiles content, impurity (S, N, Cl) concentrations, and ash content. High moisture and ash contents reduce the usable fraction of delivered biomass fuels proportionally. Therefore, maximum system efficiencies are possible with dry, low ash biomass fuels. 6/26/06

27 Biomass gasification is a complex thermochemical process that begins with the thermal decomposition of a lignocellulosic fuel followed by partial oxidation of the fuel with a gasifying agent, usually air, oxygen, or steam to yield a raw syngas. The raw gas composition and quality are dependent on a wide range of factors including feedstock composition, type of gasification reactor, gasification agents, stoichiometry, temperature, pressure, and the presence or lack of catalysts. Gas cleanup is a general term for removing the unwanted impurities from biomass gasification product gas and generally involves an integrated, multi-step approach that depends on the end use of the product gas. This entails removing or eliminating tars, acid gas removal, ammonia scrubbing, alkali metal capture, and particulate removal. Gas conditioning refers to final modifications to the gas composition that makes it suitable for use in a fuel synthesis process. Typical gas conditioning steps include sulfur polishing to remove trace levels of remaining H 2 S and water-gas shift to adjust the final H 2 /CO ratio for optimized fuel synthesis. Comprehensive cleanup and conditioning of the raw biomass gasification product gas yields a clean syngas comprised of essentially CO + H 2, in a given ratio, that can converted to a mixed alcohol product. Separation of ethanol from this product yields a methanol-rich stream that can be recycled with unconverted syngas to improve process yield. The higher alcohol-rich stream yields by-product chemical alcohols. The fuel synthesis step is exothermic so heat recovery is essential to maximize process efficiency. Size Reduction Storage & Handling De-watering Drying Feedstock Interface Products Ethanol Gasification Partial Oxidation Pressurized Oxygen Indirect/Steam Technical Feasibility of Syngas Quality Gas Cleanup & Conditioning Particulate removal Catalytic Reforming Tars Benzene Light Hydrocarbons Methane S, N, Cl mitigation CO 2 removal H 2 /CO adjustment Heat Fuel Synthesis & Power Separations Recycle Selectivity By-products Methanol n-propanol n-butanol n-pentanol Figure 5-2. Process flow diagram with research barriers for thermochemical ethanol production at $1.07/gallon R&D Needs To Achieve the 2012 Technical Target for Thermochemical Ethanol Essential R&D activities from 2007 through 2011 to overcome identified technical barrier areas to meet the established 2012 technical target for thermochemical ethanol production are outlined in Table 5.Y. These R&D activities include fundamental kinetic measurements, micro-activity catalyst testing, bench-scale thermochemical conversion studies, pilot-scale validation of tar 6/26/06

28 reforming catalyst performance, and pilot-scale demonstration of integrated biomass gasification mixed alcohol synthesis. Process data collected in the integrated pilot-scale testing will provide the basis for process optimization and cost estimates that will guide deployment of the technology. Table 5.Y Timeline of Key R&D Activities to Accomplish 2012 Thermochemical Ethanol Technical Target R&D Area Current Feedstock/ Process Interface Gasification Studies Cleanup and Conditioning Catalytic Fuels Synthesis Integration / Demonstration $30/dry ton wood chips 50% moisture dried to 12% tpd plant Low pressure Indirect - 78% syngas yield with 15% CH 4 Tar Reformer Efficiency 20% CH 4; 70% benzene; 95% heavy tars 79% CH 4 conversion in separate SMR 2000 psia; 38.5% single pass CO conversion; 80% selectivity to mixed alcohols; 56 gal/dry ton EtOH Research state-oftechnology - $2.02/gal minimum EtOH selling price (higher alcohols sold at 85% of market value) at $2.71/gal installed capital costs. Continue bench-scale kinetic thermochemical conversion studies Initial design for continuous, regenerating tar reforming reactor based on pilot-scale deactivation results Validate syngas quality for mixed OH synthesis from corn stover and wood gasification Tar Reformer Efficiency 50% CH 4; 90% benzene; 97% heavy tars 79% CH 4 conversion in separate SMR Improved hydrocarbon conversion efficiency yields- $1.72/gal minimum EtOH selling price (higher alcohols sold at 85% of market value) at $2.69/gal installed capital costs. Develop correlations for syngas quality in pilot-scale gasification studies with a variety of feedstocks forest & biorefinery residues Targeted effort to develop improved mixed alcohol catalysts higher single pass conversion efficiencies and greater selectivity to EtOH Tar Reformer Efficiency 80% CH 4; 99% benzene; 99.9% heavy tars; eliminate SMR Pilot-scale demonstration of regenerating fluidizable tar reforming catalyst to eliminate SMR $30/dry ton biorefinery residues based on $45/dry ton corn stover. 50% moisture dried to 12% tpd plant 1000 psia; 50% single pass CO conversion; 90% selectivity to mixed alcohols; 67 gal/dry ton EtOH Demonstrate mixed alcohol yields via indirect gasification of lignin-rich biorefinery residues at pilot-scale 6/26/06

29 Feedstock/Process Interface Feedstock handling, processing, and feeding specifically related to the thermochemical conversion process will need to be addressed. Because the 30 x 30 scenario envisions mixed alcohol conversion for low-grade or non-fermentable feedstocks, refinements in dry biomass feeder systems for use with gasification will be required to meet cost targets. These refinements should reduce upfront feed processing requirements to yield biomass feedstocks at $30/ton at less than 20% moisture delivered to the thermochemical process. Additional challenges will be associated with feeding the delivered biomass into developing pressurized biomass gasification systems. In all cases, demonstrating biomass feed systems beyond the pilot-scale will be necessary but this is not a significant component of the proposed research portfolio. Gasification Studies R&D Needs The thermochemical mixed alcohol synthesis conversion route is envisioned initially for forest thinnings and other predominately low carbohydrate feedstocks and residues. Hence, gasification studies will need to be performed to determine how feedstock composition affects syngas composition and quality and syngas efficiency. The gasifier technology chosen for the basis of this analysis is the Battelle Columbus Laboratory indirectly heated gasifier. Other gasifier technologies are under development (Appendix F) that could prove more promising. These technologies will need to be tracked to ascertain their applicability to the mixed alcohol synthesis process. Cleanup and Conditioning R&D Needs Techno-economic analysis (Aden and Spath, 2005) has shown that achieving the research goals for cleanup and conditioning of biomass-derived syngas to remove chemical contaminants such as tar, ammonia, chlorine, sulfur, alkali metals, and particulates has the greatest impact on reducing the cost of mixed alcohol synthesis. To date, gas cleanup and conditioning technologies and systems are unproven in integrated biorefinery applications. The goal of this research is to eliminate the tar removal and disposal via water quench, which is problematic both from efficiency and waste disposal perspectives, and develop a consolidated tar and light hydrocarbon reforming case. The current lab-scale demonstration results and target conversions for various impurities measured in biomass-derived syngas are listed in Table 5.2 for the year 2005 current state of technology case and the year 2012 goal case. The goal case conversions were selected to yield an economically viable clean syngas that is suitable for use in a catalytic fuel synthesis process without further hydrocarbon conversion steps. The research target will be met when tar and light hydrocarbons are sufficiently converted to additional syngas, technically validating the elimination of an additional steam methane reforming unit operation to separately reform methane and other light hydrocarbons. Specific research to generate the required chemical and engineering data to design and successfully demonstrate a regenerating tar reforming reactor for long-term, reliable gas cleanup and conditioning includes: Performing tar deactivation/regeneration cycle tests to determine activity profiles to maintain the required long-term tar reforming catalyst activity 6/26/06

30 Performing fundamental catalyst studies to determine deactivation kinetics and mechanisms by probing catalyst surfaces to uncover molecular-level details Determining optimized catalyst formulations and materials at the pilot scale to demonstrate catalyst performance and lifetimes as a function of process conditions and feedstock Although consolidated tar and light hydrocarbon reforming tests performed with Ni-based catalysts have demonstrated the technical feasibility of this gas cleanup and conditioning strategy, alternative catalyst formulations can be developed to optimize reforming catalyst activity and lifetime in addition to expanded functionality. Specific further improvements that could be realized in catalyst functionality are: Further process intensification is possible by designing catalysts with higher tolerances for sulfur and chlorine poisons. Further reductions in gas cleanup costs could be realized by lowering or eliminating the sulfur and chlorine removal cost prior to reforming. Optimizing the water gas shift activity of reforming catalysts could reduce or eliminate the need for an additional downstream shift reactor. Catalytic Fuels (Mixed Alcohol) Synthesis R&D Needs The commercial success of mixed alcohol synthesis has been limited by poor selectivity and low product yields. Single-pass yields are on the order of 10% syngas conversion (38.5% CO conversion) to alcohols, with methanol typically being the most abundant alcohol produced (Wender 1996; Herman 2000). For mixed alcohol synthesis to become an economical commercial process, there is a need for improved catalysts that increase the productivity and selectivity to higher alcohols (Fierro 1993). Improvements in mixed alcohol synthesis catalysts could potentially increase alcohol yields and selectivity of ethanol production from clean syngas and improve the overall economics of the process through better heat integration and control and fewer syngas recycling loops. Specific research targets to achieve the $1.07/gallon 2012 market target case are: Develop improved mixed alcohol catalysts that will increase the single-pass CO conversion from 38.5% to 50% and potentially higher and improve the CO selectivity to alcohols from 80% to 90%. Develop improved mixed alcohol catalysts with higher activity that will require a lower operating pressure (1,000 psia compared with 2,000 psia) to significantly lower process operating costs. This combination of lower syngas pressure for alcohol synthesis and less unconverted syngas to recompress and recycle has the added benefit of lowering the energy requirement for the improved synthesis loop. Alternative mixed alcohol synthesis reactors and catalysts should be explored. Greatly improved temperature control of the exothermic synthesis reaction has been demonstrated to significantly improve yields and product selectivity. Precise temperature control 6/26/06

31 reactor designs need to be developed for the mixed alcohol synthesis reaction to improve the yields and the economics of the process. Integration/Demonstration As is the case for any sophisticated conversion process, combining the individual unit operations into a complete, integrated systematic process is a significant challenge. Individual pilot-scale operations to demonstrate the required performance of the unit operations as well as complete integrated pilot development runs will be required to demonstrate the $1.07/gallon technology. A specific challenge will be to continue to demonstrate process intensification and higher yields at pilot scale to reduce capital costs. Achieving the technical target for the accelerated path to thermochemical ethanol requires meeting the specific research targets as outlined above. Missing or delaying any of these targets forfeits the 2012 target and jeopardizes the deployment of technologies in time to meet the 30x30 goal. The cost implications of missing, hitting or exceeding a target or set of targets are easily determined with process uncertainty analysis. The figure below (Figure 5.Z) depicts the results of a single-point uncertainty analysis, based around the 2012 thermochemical ethanol technology. The uncertainties in the figure show the range of ethanol costs around the $1.07 target. Various key parameters expected to have the greatest impact on the $1.07/gallon cost targets were identified and categorized in terms of Financial, Market, or Process uncertainties. This is not an exhaustive list of all items of uncertainty that could be analyzed but rather those thought a priori to have the greatest affect. The market and financial uncertainties examined here are the essentially the same as that explored for the biochemical process. The analysis shows that the affect of certain process variables is less than expected; for example, the relatively small impact of reforming catalyst lifetime. Combinations of sensitivity analysis can provide several ways to achieve the same $1.07/gallon cost target, which reduces the overall risk of the process. Quantifying the relative cost savings for process improvements allows work to be directed to the most cost effective R&D to achieve the 2012 technical target for thermochemical ethanol production. 6/26/06

32 Plant Size (10,000 to 600 dry tonnes/day) By-Product Values (100% Market to Residual Fuel Value) Catalyst Lifetime (10 to 1 yr) Tar Reformer Benzene Conversion (99.9% to 90%) Tar Reformer Methane Conversion (95% to 50%) Gasifier Temperature (1665 F to 1535 F) Moisture Content (15% to 70%) Fixed Composition - Fixed:Volatile C Feedstock C:H:O (Lignin to Ag Residue) Feedstock Quality - Ash (0% to 12%) Feedstock Cost ($10 to $53 per dry ton) Loan vs. Equity Financing (100% 7.5% to 100% Equity) Contingency (0% to 17%) Average Installation Factors (1.5 to 2.5) Total Project Investment (-10% to +25%) $0.50 $0.75 $1.00 $1.25 $1.50 $1.75 MESP ($ per gallon Ethanol) Figure -3. Thermochemical process sensitivity analysis References Aden, A., Spath,. P.L. (2005) Milestone Completion Report The Potential of Thermochemical Ethanol Via Mixed Alcohols Production. September Bizzari, S.N.; Gubler, R.; Kishi, A. (2002). Oxo Chemicals. Chemical Economics Handbook, SRI International, Menlo Park, CA. Report number Fierro, J. L. G. (1993). "Catalysis in C1 chemistry: future and prospect." Catalysis Letters 22(1-2): Herman, R. G. (2000). "Advances in catalytic synthesis and utilization of higher alcohols." Catalysis Today 55(3): Wender, I. (1996). "Reactions of synthesis gas." Fuel Processing Technology 48(3): Spath, P.L. and Dayton, D. C. Preliminary Screening -- Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas. 160 pp.; NREL Report No. TP /26/06

33 523advancedstate_62306_final.doc Long Term Technology Target Requirement for 30 x 30 Market Goal The intermediate technology target (ethanol selling price of $1.07/gallon in 2012) will enable the start of a viable industry converting lignocellulosic biomass to ethanol. Ethanol from lignocellulosic feedstocks will join that produced from starch feedstocks to displace imported petroleum and provide a sustainable, renewable resource to meet our nation s transportation needs. However, the market analysis reported earlier in this report (see Section 3) indicates that the market goal of displacing 30% of 2004 gasoline demands with ethanol by 2030 will require additional advancements in technology with continued reduction in feedstock supply system and processing costs. Future R&D efforts will be focused on four complimentary approaches to achieve the 30x30 goal. Taken independently, these approaches will not result in technology improvements that will easily meet the 30x30 target. However, collectively they combine revolutionary scientific breakthrough technologies with evolutionary process development to meet and exceed the 30x30 target for displacing non-renewable transportation fuels. Some cost reduction will be achieved by continuous process improvement to optimize technology developed in Construction and operation of full-scale biorefineries will highlight unit operations that require additional optimization and provide operational experience necessary to fully optimize the process and maximize cost reductions. This continued operating experience and engineering data accumulation will enable the design of larger scale biorefineries which will further reduce the biofuels production costs by leveraging economies of scale. These are the evolutionary cost reductions. More dramatic cost reductions will be required from scientific breakthroughs to reach the reduced conversion cost (technology) target for 2030 (see Section 3 to understand the impact of this cost reduction on the market penetration). Earlier sections of this report have described how technology will be developed for feedstock supply systems and two independent conversion options, biochemical and thermochemical, to accomplish the 2012 technology target. In the future, advancements will be made in all three areas and there will be opportunities for cost savings by integrating the two technologies and through larger facilities. The four areas of future technology advancement that will be described here to accomplish the 2030 technology target are: 1) Development of Advanced Large Tonnage Feedstock Supply Systems 2) Utilization of Systems Biology to Improve the Biochemical Processing 3) Utilization of Selective Thermal Transformation to Improve Thermochemical Processing 4) Technology Integration, Economies of Scale and Evolutionary Process Optimization 1

34 523advancedstate_62306_final.doc Advanced Large Tonnage Feedstock Supply Systems By 2012, functional feedstock supply systems for all the major types of biomass resources will have been demonstrated, and feedstock R&D needs will shift to increasing the accessible biomass tonnage sufficient to produce 60 billion gallons of ethanol per year. As the biorefining industry expands, process improvements will drive biorefinery capacities up. The longer-term feedstock supply R&D challenge is to develop technologies to ensure that supply systems will not limit achievable biorefinery size or consume biorefinery profits that can be used to purchase higher value feedstocks (Fig. 5-2-A). By increasing the purchase price for feedstock up to about $50 per ton, all of the required feedstock needed to produce the 60 billion gallons of ethanol can be accessed (see appendix C). Then by adding the estimated feedstock supply system costs, that gives a final feedstock cost estimate of about $70. Notice that the linear cost increases do not produce linear tonnage estimates, so the $70 represents a maximum feedstock cost for only the largest tonnage levels. Biomass Threshold Cost ($/dry ton) $80 $75 $70 $65 $60 $55 $50 $45 $40 $35 $30 $25 $20 $15 $10 $5 $35.00 $10.00 Wet Agricultural Residues Dry Agricultural Residues Wet Energy Crops Dry Energy Crops Woody Private Resources Other Woody Public Resources National Forest Resources Feedstock Cost (delivered) Feedstock Value (payment) $44.04 $20.29 $53.08 $30.58 $62.12 $40.87 Feedstock Supply System Costs Supply versus Grower Payment $71.15 $51.15 $ Figure 5-2-A: Advanced feedstock supply system technologies maintain supply system cost so that all increases in feedstock cost can go toward purchasing higher value feedstock (i.e., grower payment) 1,300 1,200 1,100 1, Million Dry Tons Available at Threshold Cost Value-add Feedstock Preprocessing An advanced feedstock supply system will be needed to collect the large tonnages of feedstocks required to supply large-scale biorefineries. An efficient interface between producers and the commodity biomass system is important for large-scale feedstock supply technology development. Production, harvesting and collection systems will be will be widely varied based on the biomass resources and local practices. Primary research needs include storage, preprocessing and transportation systems that are suited to these varied systems. The development of value-add feedstock preprocessing and blending technologies will provide flexibility in the biomass feedstock supply system and allow suppliers to 1) reformat/condition different feedstocks into a common format and 2

35 523advancedstate_62306_final.doc quality, 2) fractionate secondary co-products for local markets, and 3) produce blended large-scale commodity biomass. The development of value-add preprocessing will help create a market specification for the feedstock (transition biomass into a large-scale commodity) and ensure that feedstocks from varied sources can supply a large-scale biorefinery without process upset. Advanced Feedstock Transportation and Handling Systems Advanced feedstock supply systems will also rely heavily on the development of new transportation methods and technologies that take advantage of the value-add preprocessing and merchandising of the raw feedstock material. Truck transportation systems may not be economically possible because of the large transport distances, traffic congestion, or community opposition. Rail transport reduces the frequency of loads, but is often more expensive than truck because of infrastructure constraints. Advanced transportation systems will likely incorporate technologies that not only provide infrastructure and operational cost savings but also incorporate in-transit value-add processes. Systems Biology to Achieve the 2030 Technology Target Systems biology research will result in improvements to the feedstock to maximize the recoverable liquid fuel per acre of land as well as the drastic simplification of the conversion process. These improvements have the potential to reduce the cost of converting lignocellulosic biomass to ethanol by 28 to 44% for 2000 tpd plants and as much as 70 to 80% for 10,000 tpd operations (Jechura, 2006) (not including the cost of feedstock) over the 2012 technology target. These kinds of additional cost reductions are typical of conversion technologies. The oil industry, corn industry and others have seen the processing costs be dramatically reduced over time until feedstock is clearly the predominate cost. By utilizing systems biology it is envisioned that the overall conversion process can be simplified, thus reducing capital and operating costs (see Figure 5-2-A). Biochemical Conversion 2012 Technology Target Biochemical Conversion 2030 Technology Target Figure 5-2-B: Process Simplification through Systems Biology Research 3

36 523advancedstate_62306_final.doc The advanced technology to be developed will combine several unit operations into one as well as improve the pretreatment operation. Enzyme production and fermentation will be combined in a single organism. With enzyme being produced simultaneously during saccharification and fermentation processes, the three previous process operations are combined into one. More robust microorganisms will eliminate the need for hydrolyzate conditioning. These technology improvements will lower the total installed capital cost for a 2000 dry ton/day facility from $1.85 (for the 2012 technical target) to $1.51 per installed annual gallon of ethanol capacity (Wallace, 2006). This capital cost can be further reduced to $0.93 per gallon (Wallace, 2006) of installed capacity with a 10,000 t/day facility. R&D Requirements for Biochemical Technology Advancement Translational Science concepts will be adapted to make these advancements a reality. This approach is familiar to the biomedical industry and describes the integration of basic research (fundamental biological science) with industrial application of technology (bioengineering). Regardless of the technical topic, fundamental science must be guided by applied objectives to ensure success. To meet the 2030 technical target, a significant base of new fundamental science must be completed. Part of the plan to accomplish all of this in the timeframe available is to coordinate the research activities of DOE s Energy Efficiency and Renewable Energy (EERE) office and the DOE Office of Science (SC). SC has developed an extensive Roadmap (Thomassen and Johnson, 2006) for their systems biology research approach to this endeavor. This roadmap will guide their efforts and is crucial to the success of this goal. The following description and Table 5-2A describe the research required to accomplish the 2030 technical target for biochemical conversion. Fundamental Biological Science In general, a full and detailed integration of science and engineering research will lead to the most efficient process development plan. Fundamental R&D in biomass conversion must be targeted to needed process improvements based on identified technical barrier areas. An integrated fundamental and applied research program in biochemical conversion required to meet the 30 x 30 objectives must include advancements in three topical areas of biomass conversion to fuels: Feedstock Engineering. Genomics and agronomic strategies to maximize the yield and quality of developing energy crops. Design and manipulate plant cell wall composition and structure to maximize yield of fermentable sugars. Cell Wall Saccharification. Glycosyl hydrolase structure/function as it applies to plant cell wall deconstruction. Develop improved (engineered) enzymes for advanced biological conversion technologies and integrate with pretreatment chemistries. Strain Development. Systems biology and biochemistry applied to strain improvement for improved conversion of sugars released during biomass deconstruction to ethanol and products. Focus on strains that will produce the 4

37 523advancedstate_62306_final.doc saccharifying enzymes as well as ferment the resulting sugars to ethanol. These consolidated processing strategies offer the greatest potential for process simplification and reduced costs. The detailed R&D strategies for each of these areas are presented in Appendix G. Bio-Engineering Research The objective will often be to acquire new understanding in broad based aspects of applied process engineering research, such as the support of experimental consortia (e.g., the multi-university project, Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI)) that propose to develop improved biomass pretreatment processes, and feedstock qualification work to build new data bases for those considering new feedstock options for process design. The application of commercial enzyme preparation components to various pretreated biomass samples, within and beyond the scope of established consortia, is also a function of the 30 x 30-impacting engineering research. This work will extend the comparative pretreatment analysis to multiple feedstocks (corn stover, switchgrass, and hybrid poplars) and additional pretreatment process impacts (identification of hydrolyzate conditioning requirements for different pretreatments, for example). The applied research program required to meet the 30x 30 objectives will include advancements in process application knowledge at primarily two levels of focus: the first will address key process related engineering research that converts new understanding from fundamental research to the biorefinery context; and the second will use process related engineering information to make recommendations to industry regarding selection of process parameters, equipment, or operating conditions. Process Unit Operation Engineering This work targets the interface between fundamental science and process scale integration engineering. The objective will be to acquire new understanding in broad based aspects of applied process engineering research, potentially through experimental consortia, such as CAFI, that are working to develop improved biomass pretreatment processes, and feedstock qualification work to build new data bases to enable new feedstock options for process design. 5

38 523advancedstate_62306_final.doc Completion Year R&D Area Current Feedstock Engineering Cell Wall Saccharification Strain Development Engineering Research E1 cellulase expressed at 2% in Arabidopsis - Aspen demonstrated with 15% increase in cellulose Develop and apply Systems Biology methods (high Cell walls have been studied throughput and computational from a synthesis perspective, not simulation) leading to enhanced deconstruction. Current enzyme understanding of the basic hydrolysis at $0.32/gallon of science questions in biomass ethanol produced conversion Limited hydrolyzate sugar conversion. Identify best pretreatment technology for use with single step biological processing in the lab Cellulase expression in feedstocks demonstrated at economically viable level Demonstrate > 5x improved cellulase activities based on a more complete understanding of cell wall deconstruction Organism available for single step processing that compares with commercial fermentative organisms and enzymes in lab fermentors Operate a pilot scale pretreatment for single step biological processing with multiple feedstocks Table 5-2A Timeline of Key Activities to Accomplish 2030 Biochemical Technical Target Selective Thermal Transformation to Achieve the 2030 Technology Target Achieving the 2012 technology target for biomass gasification-mixed alcohol synthesis defines specific improvements in catalytic tar and light hydrocarbon reforming to increase conversion efficiencies and reduce capital costs of syngas cleanup and conditioning. To further improve the thermochemical conversion to meet the 2030 technical target two complimentary approaches, similar in nature to the translational science described for biochemical conversion, will be taken. These are; 1) pursue scientific achievements to improve yields and efficiencies and maximize process integration opportunities in existing thermochemical processes (engineering approach) and 2) utilize a rigorous research program to investigate fundamental biomass thermochemical conversion for enabling the discovery of alternative processes that will help erase the lines between gasification and pyrolysis as separate technology options (scientific approach). Energy crops demonstrated in cultivation with 25% increase in carbohydrate Demonstrate feedstocks with modified cell walls and new enzymes that easily digest and high yielding in fermentatble sugars Commercially available organism for single step processing that produces ethanol yields and productivities compariable with existing individual organisms Combine best pretreatment and organism for single step biological processing into an integrated pilot plant 6

39 523advancedstate_62306_final.doc R&D efforts toward the 2030 technology target for thermochemical technology will focus on the front end of processes while the downstream unit operations continue to be optimized. Significant improvements in the catalytic gasification will be made increasing carbon conversion efficiencies to syngas and decreasing tar formation. Internally within the gasifier, this concept converts 50% of the methane produced during biomass gasification to CO and H 2 (the syngas components required for downstream conversion to ethanol). Throughput of the gasifier also increases by 25%. This improved technology will reduce the thermochemical conversion cost by 38% (Jechura, 2006) over the 2012 technology target. (Spath 2006) Process consolidation by further integration of processes will continue to lower capital and operating costs to meet the technology targets. The block flow diagram in Figure 5-1 illustrates the research and development required to advance thermochemical conversion technology and meet the 2030 technology target. Figure 5-1. Selective thermochemical processing Feed Pretreatment and Transformation Selective Thermochemical Processing Product Separation and Process Integration Chemical Fractionation Thermochemical pretreatment Catalytic modification (hetero/homogeneous) Acid/base Solid acid catalytst Transition metals organometallics Biomass deconstruction De-polymerization Thermochemical/catalytic/chemical transformation with high yields and controllable selectivity R&D Requirements for Selective Thermal Processing The following description and Table 5-2B describe the research that must be completed to accomplish the 2030 technical target for thermochemical conversion. Catalytic Gasification and Pyrolysis Since the beginnings of coal gasification, catalysts have been sought to improve carbon conversion to products and increase gasification rates while minimizing temperature to increase process efficiency. Alkali metals have long demonstrated catalytic activity in steam gasification of solid fuels and metal-based catalysts, particularly Ni-based materials, are active and effective for hydrocarbon reforming. 7