Biopower—the production of electricity from biomass feedstocks—contributes to the U.S. electricity portfolio and has done so for more than a century. Biopower comprised approximately 1.6% of total U.S. electricity generation in 2014. By comparison, electricity generated from fossil fuels and nuclear electric power comprised 87% of total U.S. electricity generation in the same year. When accounting solely for renewable energy sources, biopower constituted close to 12% of U.S. renewable electricity generation in 2014. As a renewable energy source, biopower has benefits and challenges. One of its primary benefits is that it can provide baseload or firm power. If an electric generation plant operates as a baseload plant, the plant can run continually except for maintenance and unexpected outages. In contrast, other renewable energy sources—such as wind and solar energy—are generated intermittently and require either a form of power storage, such as batteries, or another power source, such as natural gas turbines, to provide firm power. Additionally, biopower is not limited to a specific biomass feedstock and therefore is relatively flexible in terms of fuel suppliers. Challenges to biopower production involve infrastructure concerns, such as siting a biopower facility in close proximity to the biomass feedstock to reduce feedstock transportation costs. Moreover, it may be difficult to obtain a continuously available feedstock supply. Lastly, there is significant legislative and regulatory uncertainty surrounding incentives for biopower. Congress may view biopower with new interest, especially given recent developments announced by the Obama Administration and mounting discourse between environmental groups and certain biopower feedstock groups (e.g., the forestry industry). For instance, biopower is likely to play a role in the Administration's state-specific rate-based goals for carbon dioxide emissions from the power sector (i.e., the Clean Power Plan). Additionally, international demand for certain U.S. biomass feedstocks may be a part of any future legislative discussions (e.g., demand for wood pellets by European Union [EU] member countries to meet carbon goals using biopower). Congress may debate the future role for biopower in the U.S. electricity portfolio, and as such it may consider whether biopower requires new national policies or incentives to further encourage its use or if its use should be diminished. Congress also may explore biopower feedstock availability and accessibility, technological advancements, and new forms of economic support, along with other items such as environmental considerations. In considering congressional action to broaden or limit legislative authorities for biopower, an understanding of bioenergy, biopower, biomass feedstocks, federal incentives, and challenges to biopower production could be useful to policymakers. This report provides analyses on the aforementioned topics along with legislative issues. The report begins with general summaries about bioenergy and biopower—including potential benefits and challenges, feedstocks, and biopower technologies. The report then delves into federal support available for biopower, followed by legislative concerns. Bioenergy is renewable energy derived from biomass. It comes in three forms: biopower, biothermal, and biofuels. Essentially, biomass is used to produce electricity (biopower), heat (biothermal), and fuels (biofuel). Biomass also can be used to produce combined heat and power (CHP). Using bioenergy has several advantages and several challenges. One advantage to using bioenergy is its classification as a renewable energy source because it uses biomass feedstocks, which may be replenishable in a short time frame relative to fossil fuels. Bioenergy also has the potential to contribute to rural economic development and to reduce greenhouse gas (GHG) emissions. The carbon status of most bioenergy types has thus far been treated as neutral or as having a low impact, although this assumption has been questioned. Another benefit is the potential for the production of coproducts at bioenergy facilities, which may be of more value than the bioenergy being produced. Challenges to bioenergy production include limited biomass feedstock availability and, in some cases, limited access to the feedstock. Further, certain biomass feedstocks (e.g., corn stover) may have to be harvested in a way that the soil and water nutrient value they provide to the landscape is not diminished. Moreover, the feedstock condition and arrangement may make it difficult and costly to transport and process for energy generation. In some instances, biomass feedstock storage can be an issue, especially during periods of peak demand. Lastly, biomass feedstocks on average have a lower energy content than fossil-fuel feedstocks, often requiring more feedstock to match the energy potential of fossil fuels. Bioenergy is unique among renewable energy sources because it can come in three diverse forms. Each form, thus far, has received a different amount of attention. However, there are some aspects of all bioenergy forms that could be addressed in tandem. For example, as biomass is the foundation of any form of bioenergy, the initial stages of the bioenergy pathway—feedstock production, harvest, and transport—all bear the same environmental and sustainability concerns. Although some stakeholders may voice their concerns more strongly for one bioenergy form than for another, often the concerns are transferable to other bioenergy forms (e.g., the impact of land use change on biofuel production). Congress, the executive branch, and others have tended to focus on one bioenergy form at a time, at the exclusion of others. For instance, in the last decade, legislative, research, and industrial attention have focused more on biofuels (e.g., corn-based ethanol) than on other bioenergy forms. Such focus may occur due to the regulatory requirements necessary for the bioenergy end use as opposed to the bioenergy supply. One issue for Congress is that bioenergy can cross multiple committee jurisdictional boundaries, possibly making it harder to reach a consensus on a more comprehensive approach to bioenergy. Biopower was the third-largest renewable energy source for electricity generation in 2014, after conventional hydroelectric power and wind. The top five states to contribute the largest amounts of net electricity generation from biomass year-to-date through December 2014 were California, Florida, Georgia, Virginia, and Maine. The Energy Information Administration (EIA) projects that electricity generation from biomass will grow through 2030 by an average of 3.1% annually, led by co-firing at existing coal plants through 2030, and that after 2030 new dedicated biomass power plants will account for most of the growth in biopower. Woody biomass is the primary biomass feedstock used for biopower. In 2014, roughly two-thirds of biopower generation used wood and wood-derived fuels as its biomass feedstock. The remaining one-third came from municipal solid wastes from biogenic sources, landfill gas, and agricultural byproducts, among others. EIA reports that biomass consumed as combustible fuel for electricity generation in 2014 was 723 trillion British thermal units (btu)—430 trillion btu from wood and wood-derived fuels, and 293 trillion btu from other biomass feedstocks. Like other power sources, biopower has its advantages and disadvantages. The intensity of those advantages and disadvantages varies based on the scenario under consideration. The sections below discuss some of these potential benefits and challenges. Biopower can be a firm source of power for baseload power production . Baseload power is the minimum amount of electric power delivered or required over a given period of time at a steady rate. Baseload plants produce electricity at a constant rate and generally run continuously throughout the day. With sufficient feedstock supplies, among other things, a biopower plant can provide firm power for baseload needs. It is one of the few renewable energy sources that can provide consistent power. Biopower originates from a feedstock—renewable biomass—that can be replenished in a short time frame relative to fossil fuels and may offer certain environmental benefits. Renewable biomass , or simply biomass , is organic matter that can be converted into energy. Biomass can come from food crops, dedicated energy crops, crop residues, trees, forestry residue, and reusable feedstocks that once were considered wastes (e.g., animal manure). Currently, woody biomass and wood wastes are the principal biomass feedstocks used for biopower generation. However, biopower generation is not limited to a specific feedstock and therefore is relatively flexible in terms of supply. Thus, each region of the country can pursue biomass feedstocks that are native, cost-effective, and readily available to generate biopower (e.g., food waste in urban areas). The amount of biopower that can be produced depends on the availability and cost of biomass feedstocks, both of which fluctuate given various conditions. Some biomass feedstock can be available at substantially lower costs than fossil fuels and integrated relatively easily into a bioenergy production process (e.g., yard waste). However, other biomass feedstocks have higher logistical and transaction costs associated with their removal and transport (e.g., forestry residues). An overarching concern is maintaining an environmentally and economically sustainable biomass feedstock supply. Collecting or harvesting biomass without regard to replenishment, or in an otherwise unsustainable manner, may lead to the deterioration of certain natural resources, such as soil erosion or the depletion of forested land. Thus far, biomass used for biopower is not subject to the same constraints as biomass used for liquid transportation fuels under federal statute. Additionally, feedstock diversity is a formidable challenge to biopower growth, because cultivation, harvest, storage, and transport vary according to the feedstock type and conventional agriculture is based on mass production of one crop. Another challenge is determining the amount of available feedstock due to market fluctuations and weather variability.