Agriculture-based renewable energy can take several forms, including biofuels such as corn-based ethanol or soy-based biodiesel, wind-driven turbines located on farmland or in rural areas, anaerobic digesters that convert animal waste into methane and electric power, or biomass harvested for burning as a processing fuel or to generate heat as part of an industrial activity. Since the late 1970s, U.S. policymakers at both the federal and state levels have adopted a variety of incentives, regulations, and programs to encourage the production and use of agriculture-based renewable energy (mostly biofuels). In particular, the two most widely used biofuels—ethanol produced primarily from corn starch and biodiesel produced primarily from soybean oil—have received significant federal support in the form of tax incentives, loans and grants, and regulatory programs. By early 2008, just prior to the 2008 farm bill (the Food, Conservation, and Energy Act of 2008; P.L. 110-246 ), total direct federal biofuels subsidies were estimated at nearly $5.5 billion per year. By 2010, federal biofuels subsidies surpassed $7 billion. Motivations cited for these legislative initiatives included energy security concerns, reduction of greenhouse gas emissions, and raising domestic demand for U.S.-produced farm products. This report focuses both on those policies contained in the 2008 farm bill—and as extended by §701 of the American Taxpayer Relief Act of 2012 (ATRA; P.L. 112-240 )—that support agriculture-based renewable energy, especially biofuels, and on the outlook for bioenergy programs in the next farm bill. The introductory sections of this report briefly describe how USDA bioenergy policies evolved and how they fit into the larger context of U.S. biofuels policy. Then, each of the bioenergy provisions of the 2008 farm bill are defined in terms of their function, goals, administration, funding, and implementation status. Finally, a section reviews the outlook for bioenergy programs in the next farm bill, as well as the major emerging issues related to U.S. Department of Agriculture (USDA) energy programs. Two tables at the end of this report present data on 2008 farm bill energy provision funding—the budgetary authority ( Table 1 ), and the funding authority with the actual funding available for FY2008 through FY2012 ( Table 2 ). A third table ( Table 3 ) presents proposed bioenergy program funding for FY2014-FY2018 under farm bill legislation of the 113 th Congress—the Senate-passed S. 954 and the House-passed H.R. 2642 . CRS side-by-side comparison of energy-related provisions are available for: farm bill legislation of the 113 th Congress with current law, in CRS Report R43076, The 2013 Farm Bill: A Comparison of the Senate-Passed (S. 954) and House-Passed (H.R. 2642, H.R. 3102) Bills with Current Law ; the 2008 farm bill with those of the 2002 farm bill (the Farm Security and Rural Investment Act of 2002; P.L. 107-171 ), in CRS Report RL34130, Renewable Energy Programs in the 2008 Farm Bill ; and the 2008 farm bill with those of the 2007 energy bill (the Energy Independence and Security Act of 2007, P.L. 110-140 ), in CRS Report RL34239, Biofuels Provisions in the 2007 Energy Bill and the 2008 Farm Bill: A Side-by-Side Comparison . Renewable energy production plays a key role not just in agricultural policy, but also in energy, tax, and environmental policy. As a result, many of the federal programs that support renewable energy production in general, and agriculture-based energy production in particular, are outside the purview of USDA and have origins outside of omnibus farm bill legislation. For example, the three principal federal biofuels policies of the past decade were all established outside of farm bills as follows. The Renewable Fuel Standard (RFS) mandates an increasing volume of biofuels use and has its origins in the Energy Policy Act of 2005 ( P.L. 109-58 ). The RFS was expanded in the Energy Independence and Security Act of 2007 (EISA; P.L. 110-140 ) and divided into four distinct, but nested categories—biodiesel, cellulosic, advanced, and total—each with its own mandated volume. The volumetric ethanol excise tax credit (VEETC), originally established in the American Jobs Creation Act of 2004 ( P.L. 108-357 ), provided a tax credit that varied in value over the years, but was last at $0.45 per gallon of pure ethanol blended with gasoline when it expired on December 31, 2011. The ethanol import tariff (a most-favored-nation duty of $0.54 per gallon) was intended to offset the blending tax credit and was originally established by the Omnibus Reconciliation Act of 1980 ( P.L. 96-499 ). The ethanol import tariff also expired on December 31, 2011. In addition to the RFS, VEETC, and import tariff, several other tax credits that originated outside of farm bills were available for biodiesel production as well as for small producers (less than 60 million gallons per year per plant) of ethanol and biodiesel. A substantial number of federal programs also support renewable energy sources other than biofuels. In addition to federal programs, many states offer additional support to biofuels producers, blenders, and consumers. An awareness of the non-USDA federal programs is important for appreciating the role envisioned for the energy title of the 2008 farm bill, which is designed to provide incentives for the research and development of new agriculture-based renewable fuels, especially second-generation biofuels (based on non-food crop biomass such as cellulose and algae), and to expand their distribution and use. The 2002 farm bill (Farm Security and Rural Investment Act of 2002, P.L. 107-171 ) was the first omnibus farm bill to explicitly include an energy title (Title IX). The energy title authorized grants, loans, and loan guarantees to foster research on agriculture-based renewable energy, to share development risk and to promote the adoption of renewable energy systems. Since enactment of the 2002 farm bill, interest in renewable energy has grown rapidly, due in large part to a strong rise in domestic and international petroleum prices and a dramatic acceleration in domestic biofuels production (primarily corn-based ethanol). Annual U.S. ethanol production has expanded rapidly since 2001, rising from under 2 billion gallons to nearly 14 billion gallons in 2011. Similarly, corn use for ethanol has grown from a 7% share of the U.S. corn crop in 2001, to an estimated 41% share of the 2011 corn crop. In 2007 (during the 2008 farm bill debate), about 23% of the U.S. corn crop was used for ethanol and projections had ethanol's corn-use share rising rapidly, sparking concerns about unintended consequences of the policy-driven expansion of U.S. corn ethanol production. Dedicating an increasing share of the U.S. corn harvest to ethanol production evoked fears of higher prices for all grains and oilseeds that compete for the same land, higher livestock feed costs, higher food costs, and lower U.S. agricultural exports. In addition, several environmental concerns emerged regarding the expansion of corn production onto non-traditional lands, including native grass and prairie land. As a result of these concerns, policymakers sought to refocus biofuels policy initiatives in the 2008 farm bill (the Food, Conservation, and Energy Act of 2008, P.L. 110-246 ) in favor of non-corn feedstock, especially cellulosic-based feedstock. Renewable energy policy in the 2008 farm bill became law six months after the enactment of the Energy Independence and Security Act of 2007 (EISA, P.L. 110-140 ). A key component of EISA was a significant expansion of the renewable fuels standard (RFS), which mandates the increasing use of "advanced biofuels" (i.e., non-corn starch biofuels), whose minimum use must grow from zero in 2008 to 21 million gallons by 2022. The energy provisions of the 2008 farm bill were intended to reinforce EISA's program goals via a further refocusing of federal incentives toward non-corn sources of renewable energy. Key biofuels-related provisions in the enacted 2008 farm bill include expansion of the existing bio-based marketing program to encourage federal procurement of bio-based products (§9002); expansion of the federal bio-products certification program (§9002); additional support for biorefinery development (§9003); grants and loan guarantees for advanced biofuels (especially cellulosic) production (§9005); an education program to promote the use and understanding of biodiesel (§9006); support for rural energy efficiency and self-sufficiency and biofuels marketing infrastructure (§9007); reauthorization of biofuels research programs (§9008) within USDA and the Department of Energy (DOE); a new program to incentivize the production, harvesting, storage, and transportation of cellulosic ethanol feedstock (§9011); reauthorization of Sun Grant Initiative programs that coordinate research on advanced biofuels at land-grant universities and federally funded laboratories (§7526); establishment of a new cellulosic ethanol production tax credit (§15321); reduction of the blender tax credit for corn-based ethanol (§15331); studies of the market and environmental impacts of increased biofuels use (§15322); and continuation of the duty on imported ethanol (§15333). In general, two types of funding are authorized by Congress in a farm bill—mandatory and discretionary.