Biomass feedstocks (BIOstocks) are living or recently living biological material which can be used as fuel or for industrial production. Most commonly, biomass refers to plant matter grown for use as biofuel, but also includes plant or animal matter used for production of fibers, chemicals, or heat. It is usually measured by dry weight.

For ease of discussion, BIOstocks are usually categorized as coming from Forestry, Agriculture, or Urban sources. According to the Department of Energy there are already vast quantities available in the U.S. include approximately:

• 1,200 million tons of forest residue
• 332 million tons of urban residue
• 596 million tons of agricultural energy crops, crops residue and biosolids and manure

BIOstocks are being recognizes as raw materials for new, clean technologies that produce heat, electricity, biofuels (including ethanol), charcoal, bioenergy gases, and safe chemicals. These products help to extend recycling while diverting biomass otherwise destined for polluting landfills.

Some of the conversion technologies (CTs) include sugar fermentation, enzymatic hydrolysis, catalytic conversion, anaerobic digestion, plasma arc, gasification, and pyrolysis.