Forms of bioenergy include biopower, heat, and liquid and gas biofuels.  Biomass materials, after pre-processing into suitable forms for various conversion technologies, provide feedstock for a variety of bioenergy end products and end uses.  The majority of biomass for bioenergy feedstocks comes from three sources: forests, agriculture, and waste.  Non-forest conservation lands, such as grasslands and savannahs, and algaculture (cultivation of algae) are also potential sources of bioenergy feedstocks.  Regardless of source, however, biomass materials can be divided into two broad categories: woody and non-woody materials.  Although forest-based wood makes up the majority of biomass used in production of bioenergy in the U.S., agriculture-based biomass materials are likely to play a bigger role in the national energy portfolio over time. Agriculture-based biomass materials can be grown in production systems that are dedicated for bioenergy purposes, or as a secondary benefit from systems dedicated to plant production for other purposes.  Studies have concluded that approximately 90 tons of biomass can be produced annually in the U.S. for conversion into biofuel (liquid transportation fuel).  Primary co-products of bioenergy production are distillers grains, bagasse, glycerol, and biochar.  Primary by-products are fly ash and waste water, both of which are regulated materials.

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