1. USE OF CELLULOSIC BIOMASS TO PRODUCE BIOFUELS
The President, in his State of the Union address (January 31, 2006), outlined his Advanced Biofuels Initiative which seeks to break our national dependence on imported oil by accelerating the development of domestic, renewable alternatives to petroleum-based transportation fuels. The President announced his Biofuels Initiative, an effort to develop cost competitive cellulosic biofuels as transportation fuels by 2012. In order to reach the President’s goal, the Office of the Biomass Program has set an internal R&D goal of reaching an ethanol cost of $1.07 (based on 2002 dollars) per gallon from cellulosic feedstocks (agricultural residues such as stalks and straws, forest-based resources, and dedicated energy crops such as switch grass and hybrid poplars) by 2012.
One important component of successfully achieving the goal is ensuring that cost competitive feedstocks for biofuels production are widely and sustainably available in sufficient quantity and at reasonable cost. Feedstock cost represents the largest single cost element in producing a gallon of ethanol. The Departments of Energy and Agriculture jointly released a “Billion Ton Study” in April 2005 that determined that the United States has the potential to sustainably generate about 1.3 billion dry tons of biomass feedstock annually. These potential resources are available primarily as agriculture and forest derived feedstocks, and are enough to produce biofuels needed to displace 30 percent of our current gasoline consumption. Research is needed on major biomass resources which could be supplied to biorefineries for conversion to biofuels and bioproducts. Biorefineries are processing facilities that extract carbohydrates, oils, lignin, and other materials from biomass, convert them into multiple products such as transportation fuels, power, and products. The biomass resources should be sustainably available in large quantities, at low cost, and of appropriate quality.
The other components of successfully achieving the goals are cost competitive conversion of biomass to fuels and other products by both biochemical and thermochemical conversion pathways.
The Office of Biomass Program investigates biochemical conversion pathways for the utilization of the cellulose and hemicellulose fractions of biomass to produce ethanol via pretreatment to breakdown the hemicellulose to fermentable 5 and 6-carbon sugars, enzymatic hydrolysis to break the cellulose portion of biomass down to glucose, and fermentation routes for C5 and C6 sugars to make ethanol. Current cost of cellulosic ethanol production is too high to compete in the market. New and improved technologies and resulting cost reductions are needed to make cellulosic biomass-based technologies more competitive.
The other area of interest of the Office of Biomass Program is thermochemical conversion pathways in which biochemical biorefinery residues, forest residues, agricultural residues, and future energy crops would be considered for conversion (e.g. by gasification, pyrolysis) into an intermediate, and synthesized into fuels and/or chemicals.
Grant applications are sought only in the following subtopics:
a. Handling and Preprocessing of Ensiled (Wet) Biomass—The emerging biorefining industry is dependent on having 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 identified a biomass resource potential of about 998 million tons (including agriculture residues and new perennial crops) that could come from agricultural lands1. While much of this agricultural biomass resource can be handled and managed with low moisture (less than 15%) forage system technologies, the greater portion of this tonnage will be produced in regions of the U.S. where climate and cropping practices will require these same agriculture biomass resources to be handled in high moisture systems (greater than 50% moisture). These high moisture biomass feedstock systems will require the biomass to be stored under wet, anaerobic conditions (ensiled)2.
Once the producer has harvested and stabilized the biomass in an ensiled storage system, the challenge is an effective high volume delivery system to take ensiled biomass from multiple on-farm storages to the biorefinery. The dry matter density of the biomass for cost-effective transportation, aerobic stability of the biomass throughout the entire handling and transport system to prevent carbohydrate loss, and delivered feedstock quality for efficient conversion to biofuels and products are key points that need to be addressed in these post-storage handling, preprocessing and transport systems3. Additionally, grant applications should demonstrate cost improvements that can be quantifiably evaluated in the context of a feedstock supply system cost target of $35/dry ton (based on 2002 dollars). Cost improvements could include, but are not limited to, efficiency improvements, credit for improved feedstock value, co-products, etc. Grant applications are sought to develop: 1) systems for biomass removal from multiple on-farm storage units, 2) biomass preprocessing to achieve biorefinery feedstock quality/format specifications and optimize dry matter density for transportation to a biorefinery, and 3) engineered systems for optimized transportation and handling of high moisture biomass. It is expected that projects awarded from this subtopic will lead to lower costs for high moisture biomass systems and higher quality biomass delivered to biorefineries, and that those systems will optimally interface with current agricultural and transportation infrastructures.
Questions - contact Sam Tagore (sam.tagore@hq.doe.gov)
Subtopic a References:
1. “Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply,” U.S. DOE/ U.S. Department of Agriculture, April 2005. (Full text available at: http://bioenergy.ornl.gov. Click on title under “News and Events” in center of page.)
2. Berger, L. L. and Bolsen, K. K., “Silage for Dairy Farms: Growing, Harvesting, Storing and Feeding,” Proceedings of the Natural Resource, Agriculture, and Engineering Service (NRAES) Conference, Camp Hill, PA, January 23-25, 2006; NRAES, 2006. (ISBN-10: 1-933395-06-0) (News release and ordering information available at: http://www.nraes.org/publications/nraes181.html)
3. “Roadmap for Agricultural Biomass Feedstock Supply in the United States,” U.S. DOE Office of Energy Efficiency and Renewable Energy, November 2003. (Full text available at: http://www.inl.gov/bioenergy/docs/biomass_roadmap2003.pdf)
b. Densification/Granulation of Dry Biomass—Biomass from agricultural crops will be available to a biorefinery in a dry (moisture content less than 15%) or wet form. Biomass material can be densified into square or round bales for storage and transportation. The attainable bulk density for most grasses, straw, and stover using the existing baling equipment is about 10 pounds per cubic foot. This bulk density does not max out the allowable pay load of the transport equipment. Baled biomass is difficult to handle and store safely.
Most animal feeds are pelletized to increase their bulk density to roughly 30-40 pounds per cubic foot. Dense pellets can be handled and stored as bulk granules using conventional equipment and existing infrastructure for grain handling. Pelletized materials are less prone to spoilage and combustion than loose or baled biomass. Grinding and mixing operations reduce variability in physical and chemical characteristics. The composition of pelletized material can be rationed to specific ingredients (fiber content, lignin, etc) to maximize conversion efficiencies. This enhances the quality and increases the value of biomass to biorefinery.
The existing pelletization requires drying, grinding and conditioning process in order to produce durable pellets. Mechanically formed pellets are easy to handle and can be transported efficiently. Unfortunately the numerous processes involved in producing pellets are energy and power intensive and require expensive capital equipment. Many biomass materials especially those from grasses, straw and stover do not form durable pellets without an additional binder that would add to the cost of pellets.
Grant applications are sought to overcome one or several of the technical barriers against producing economical biomass pellets. New technologies are sought to reduce the moisture content of biomass in the field - for example, using solar energy or natural drying processes. The biomass can also be modified through physical and chemical modifications to make it easier to be pelletized. There are also opportunities to reduce power requirement of pelletizing equipment through designing new pelletization equipment.
Grant applications are also sought to address
any of the processes that would lead to producing biomass pellets economically.
The biomass of interest to be pelletized at this time is corn stover, cereal
straws, and switchgrass. Other crop residues or grasses may be considered if
they are of regional economic significance. The application should clearly show
and quantify how a proposed research and technology development will lead to
cost reductions in pelletization of biomass. The proposal should also address
any improvements in the quality of biomass as a result of pelletization
processes. Additionally, proposed technologies should demonstrate cost
improvements that can be quantifiably evaluated in the context of a feedstock
supply system cost target of $35/dry ton (based on 2002 dollars).
Questions - contact Sam Tagore (sam.tagore@hq.doe.gov)
Subtopic b References:
1. Tabil, L. and Sokhansanj S., “Process Conditions Affecting the Physical Quality of Alfalfa Pellets,” Applied Engineering in Agriculture, 12(3): 345-350, 1996. (ISSN: 0883-8542) (Ordering information available at: http://www.asabe.org/pubs/PubCat02/periodicals.html)
2. Mani, S., et al., “Economics of Producing Fuel Pellets from Biomass,” Applied Engineering in Agriculture, 22(3): 421-426, 2006. (ISSN: 0883-8542) (Abstract and ordering information available at: http://asae.frymulti.com/abstract.asp?aid=20447&t=1)
c. Fermentation/Biochemical Conversion—Grant applications are sought for innovative technologies for fermentation of the sugar portions of lignocellulosic biomass to fuels and chemicals.
Robust strains that ferment sugars at high rates with minimum byproduct formation must be developed for commercial scale1. The ability to develop robust, industrially useful fermentation strains to meet performance and cost metrics listed below will require the acquisition of substantial knowledge regarding the fundamental factors that limit efficient sugar bioconversion in hydrolysate. A collective knowledge on strain improvement including deeper understanding of strain physiology, metabolic engineering options, hydrolysate toxicity as well as process considerations are required.
In the case of lignocellulosic biomass to ethanol, applicants must address the following metrics. The organism must be able to be produced at low cost via on-site production with hydrolysate sugars and minimal nutrients or supplied at low cost (pennies per gallon ethanol) as in the corn ethanol industry. Inhibitors in hydrolysate such as acetic acid can severely inhibit the cell growth, so overcoming such growth inhibition is critical.
Working in a solids environment presents special challenges for an organism. To meet the $1.07 target, the organism must be able to ferment hydrolysate with a minimum total solids content of 20% (with 11-15% total sugars), with minimal nutrient supplement and hydrolysate conditioning. A tolerance to at least 5% ethanol, preferably to 8-10% (w/w) is needed to achieve higher ethanol titer2.
Improving the xylose to ethanol process yield (currently 25-50%) to 85% is essential to meet the $1.07 target. The xylose fermentation rate needs to be enhanced 3 to 10 fold to approach the glucose fermentation rate. Reducing the toxic effect of inhibitors on pentose fermentation by either improving microbial resistance to the hydrolysate or minimizing toxic levels during pretreatment and subsequent process treatment must also be achieved. Improved microbial resistance can be achieved by traditional adaptation or a more rational approach using advanced biological tools available now. It would be beneficial to understand the toxic mechanisms not only to help develop superior strains but also to provide guidance in pretreatment process.
The investigator must use slurries that are consistent with what is being produced at the lab and pilot scales at the National Renewable Energy Laboratory (NREL).
Questions - contact Sam Tagore (sam.tagore@hq.doe.gov)
Subtopic c Reference:
1. Aden et al., “Lignocellulosic Biomass to Ethanol Process Design and Economics Utilizing Co-Current Dilute Acid Prehydrolysis and Enzymatic Hydrolysis for Corn Stover,” Design Report, U.S. DOE National Renewable Energy Laboratory, June 2002. (Full text available at: http://www.nrel.gov/docs/fy02osti/32438.pdf)
2. “Biochemical Process Technology Target for 2012,” Section 4.2.1 of 30x30: A Scenario for Supplying 30% of 2004 Motor Gasoline with Ethanol by 2030, U.S. DOE Office of Energy Efficiency and Renewable Energy, 2006. (Full text available at: http://30x30workshop.biomass.govtools.us/. On menu under photos, click on “Supporting Documents”. Scroll down to green heading “Agricultural Residues”, and click on “30x30 Lab Scenario (Section 4)”. Scroll down to title, above, at Section 4.2.1.
d. Distributed Biomass Pyrolysis and Bio-oil Upgrading/Thermochemical Conversion—Grant applications are sought to improve the quality and energy density of biomass-based pyrolysis oil (bio-oil). The R&D needs are a fast pyrolysis process, to produce a liquid fuel oil with a high energy density per unit volume; and a ganged upgrading process that allows the final product oil to be used directly as a fuel or chemical or as refinery feedstocks for renewable fuels and specialty chemicals.
Biomass pyrolysis is the thermal depolymerization of biomass at modest temperatures in the absence of additional oxygen. The slate of products from biomass pyrolysis depends on the process temperature, pressure, and residence time. Charcoal yields of up to 35 % can be achieved for slow pyrolysis at low temperature, high pressure, and long residence time. Fast pyrolysis is used to optimize the liquid products in an oil known as pyrolysis oil, bio-crude or bio-oil. High heating rates and short residence times enable rapid biomass pyrolysis with minimal vapor cracking; this maximizes liquid product yields with up to 80% efficiency. Pyrolysis oils are multi-component mixtures rich in oxygenated materials that, in general, retain the overall elemental composition of the biomass feed. Oil from flash pyrolysis is usually a dark brown, free-flowing liquid with a distinctive smoky odor. Oil from slow pyrolysis is more like a tar. In addition, pyrolysis oils can be separated because of differences in the chemical nature of the constituents. For example, excess water can preferentially separate components that are soluble in water (the “aqueous fraction”) and those that are not (the “pyrolytic lignin”).
Pyrolysis oils have been used for heat and power generation, usually requiring only minor modifications to existing equipment. Pyrolysis oil has been successfully used as boiler fuel and has also showed promise in stationary diesel engine and gas turbine applications. Upgrading pyrolysis oil to a liquid transportation fuel poses technical challenges, but recently separation and upgrading of the pyrolytic lignin using traditional petroleum refinery unit operations has shown technical and economic promise for producing precursors to renewable fuels and specialty chemicals.
Pyrolysis oil production in a petroleum refinery may be problematic because of economic issues of transport and storage of biomass on site. Transportation costs have historically been a major barrier for biomass upgrading, becoming “very significant after 20 miles, and usually prohibitive beyond 100 or 200 miles.” A more promising option may be the distributed production of pyrolysis oil at distributed locations, followed by transportation of pyrolysis oil to a central processing facility.
Grant applications are sought to determine the technical and economic feasibility of distributed production of pyrolysis oil. Two classes of systems need to be considered, modular skid mounted systems (remote, off-grid locations) and permanent facilities. This project should not include construction of facilities, but may include production of pyrolysis oil to obtain material and energy balance information, and oil properties. A successful Phase 1 project may lead to a Phase 2 prototype demonstration project.
The application should address:
1) Identification and characterization of feedstocks
2) Characterization of pyrolysis oil
3) Preliminary process flow diagram, material and energy balances, and equipment lay-out
4) Proposed feed preparation, drying and utilities systems. For off-grid applications a discussion of electricity generation facilities will be required.
5) Preliminary equipment lists and costs and
6) Preliminary
environmental evaluation (air, water, solids)
Questions - contact Sam Tagore (sam.tagore@hq.doe.gov)
Subtopic d References:
1. Czernik, S. and Bridgwater, A. V., “Overview of Applications of Biomass Fast Pyrolysis Oil,” Energy & Fuels, 18(2): 590-598, February 2004. (Abstracts and purchasing information available at: http://pubs.acs.org/cgi-bin/abstract.cgi/enfuem/2004/18/i02/abs/ef034067u.html. To purchase article, see menu at top of page.)
2. Oasmaa, A. and Czernik, S., “Fuel Oil Quality of Biomass Pyrolysis Oils - State of the Art for the End User,” Energy & Fuels, 13(4): 914-921, April 1999. (Abstracts and purchasing information available at: http://pubs.acs.org/cgi-bin/abstract.cgi/enfuem/1999/13/i04/abs/ef980272b.html. To purchase article, see menu at top of page.)
3. Solantausta, Y., et al., “Assessment of Liquefaction and Pyrolysis Systems,” Biomass & Bioenergy, 2(1-6): 279-297, 1992. (ISSN: 0961-9534) (Abstract and ordering information available at: http://www.sciencedirect.com/. Search by document title.)
4. Solantausta, Y., et al., “Feasibility of Power Production with Pyrolysis and Gasification Systems,” Biomass & Bioenergy, 9(1-5): 257-269, 1995. (ISSN: 0961-9534) (Abstract and ordering information available at: http://www.sciencedirect.com/. Search by document title.)
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