110-140 ), Congress mandated the use of a large and rapidly increasing volume of biofuels as part of the U.S. national transportation fuel base. In particular, the share of cellulosic biofuels is mandated to grow to 16 billion gallons by 2022—a daunting challenge considering that no commercial production existed as of mid-2010. However, substantial research has been done in recent years concerning the economics of production, harvest, and energy yield for various biomass sources under different processing technologies. This report attempts to summarize the current state of knowledge regarding potential biomass feedstocks, production and marketing constraints, processing technologies, and the economics of biomass from field to fuel under current and hypothetical policy circumstances. As such, it is intended to serve as a reference for policymakers interested in understanding the complexity underlying the development of a large-scale, biomass-based fuel system. Potential biomass feedstocks are numerous and widespread throughout the United States, and include agricultural residues from such crops as corn, wheat, rice, and sugarcane, perennial grasses such as switchgrass and Miscanthus , short-rotation woody crops such as poplar and willow, and forest residues removed directly from the forest or taken from mills after processing. Each type of biomass faces tradeoffs in terms of production, storage, and transportation. Dedicated energy and tree crops have large up-front establishment costs and may take several years to produce a commercial harvest, but can produce high yields with relatively low maintenance costs thereafter. Residues are nearly costless to produce, but confront difficult collection strategies and do not always produce uniform biomass for processing. Agricultural residues also face complicated trade-offs between soil nutrient loss and biomass yield, as well as questions about the optimal timing strategy for harvesting the main crop and the residue (either jointly or separately). Logging residues confront both a tradeoff with energy production at the plant (via burning) and a uniformity of quality issue for processing. Producer participation . A key aspect of biomass production will be understanding what economic incentives will encourage producer participation in growing and/or collecting biomass feedstocks. The biochemical conversion process is similar to the process currently used to produce ethanol from corn starch. Production costs . Petroleum infrastructure equivalency . The thermochemical conversion of biomass into synthetic fuels (or green hydrocarbons) produces liquid fuels that are essentially energy-equivalent to their petroleum counterparts, and fully adaptable for use in existing petroleum fuel infrastructure. The final section of the report (" Chapter 5: Economics and Policy of Cellulosic Biofuels ") discusses the current status of relevant biofuels policy and some of the potential future policy options related to cellulosic biofuels. Miscanthus is expected to yield well in the same locations where switchgrass yields well. The current language of the Energy Independence and Security Act of 2007 puts restrictions on the types of land from which residues can be collected for use as a cellulosic feedstock. The establishment, maintenance, harvest, storage, and transport of cellulosic feedstocks remain far from perfect and will need to be improved in order to reduce feedstock costs. The technology can also be used to convert biomass to liquid fuels. For practically any type of biomass, drying will be required. These synthetic petroleum products can be used by existing petroleum-based distribution and storage infrastructure and the current fleet of U.S. vehicles. Plants that have qualified for the program are from a variety of geographic locations and are using a variety of biomass feedstocks. The choice is crucial because the two methods lead to different results due to the lower energy content of ethanol—the energy from a gallon of ethanol (measured in Btu's) is only about 67% of the energy content of a gallon of gasoline.
In the Energy Independence and Security Act of 2007 (P.L. 110-140), Congress mandated the use of a large and rapidly increasing volume of biofuels as part of the U.S. national transportation fuel base. In particular, the share of cellulosic biofuels is mandated to grow to 16 billion gallons by 2022—a daunting challenge considering that no commercial production existed as of mid-2010. Cellulosic biofuels can be produced from almost any sort of biomass. As a result, a variety of biomass types that can be produced or collected under a range of geographic settings are potential feedstock sources. However, part of the mandate's challenge will be encouraging farmers to produce or collect non-traditional biomass materials that require multiple growing seasons to become established, and for which markets currently do not exist. Participation represents a substantial risk for producers, and even under the most optimistic conditions, U.S. agriculture will be challenged to produce the enormous volume of biomass needed to meet the biofuels mandate.
Potential biomass feedstocks are numerous and widespread throughout the United States, and include woody biomass, perennial grasses, and agricultural and forest residues. Each type of biomass faces tradeoffs in terms of production, storage, and transportation. Dedicated energy and tree crops have large up-front establishment costs and will likely take several years to produce a commercial harvest, but can produce high yields with relatively low maintenance costs thereafter. Residues are nearly costless to produce, but confront difficult collection strategies and do not always produce uniform biomass for processing. Agricultural residues face complicated trade-offs between soil nutrient loss and biomass yield, as well as questions about the optimal timing strategy for harvesting the main crop and residue (either jointly or separately). Logging residues confront a tradeoff with energy production at the plant (via burning).
None of the potential feedstocks (other than starch from corn) are economical to convert into biofuels under current commercial technology without substantial federal policy intervention. In addition to federal policy and the choice of feedstock, the processing technology used, the distribution infrastructure, and blending rates are expected to play major roles in the economic viability of cellulosic biofuels. Different processing technologies yield different biofuels in terms of energy content and usability, while also strongly influencing the economic viability of biofuels production. Ethanol produced under current biochemical processes yields only 67% of the energy of an equivalent volume of gasoline, and (due to its chemical properties) cannot use the same storage tanks, pipelines, and retail pumps as gasoline. In contrast, synthetic petroleum products (i.e., green hydrocarbons) obtained from biomass processed using more costly thermochemical technology yield an energy content nearly equal to petroleum fuels and can be used in existing fuel infrastructure. Currently ethanol is blended in most gasoline at about a 10% rate. If the rising usage mandate is to be met, the biofuels blending rate will necessarily have to increase, at which point the energy equivalence of a biofuel will likely influence the choice of processing technology, distribution infrastructure, and federal policy incentives.
Many uncertainties remain concerning biomass producer participation rates, the choice of biomass, and associated yields and costs of production, harvest, storage, and transportation, as well as contractual marketing arrangements, plant location, and conversion technology, among other issues. This report attempts to summarize the current state of knowledge regarding potential biomass feedstocks, production and marketing constraints, processing technologies, and the economics of biomass from field to fuel under current and hypothetical policy circumstances. As such, it is intended to serve as a reference for policymakers interested in understanding the complexity underlying the development of a large-scale, biomass-based fuel system.
An executive summary of the report is available in Chapter 1.