Biomass comes from recently living material and its wastes, not from every substance that can be burned.
The six main source groups differ in moisture, contamination, transport cost and conversion options, so the feedstock should be evaluated before the technology.
1. Wood and forestry residues
Firewood, chips, pellets, bark, sawdust and forest-management residues are widely used for heat, industrial energy and power generation. Pulp and paper mills also use black liquor, a liquid byproduct containing wood-derived material.
Sustainable sourcing, moisture content, ash and transport distance strongly affect performance. Whole-tree harvesting and genuine mill residues should not be treated as environmentally identical.
2. Agricultural crops and crop residues
Corn, sugar cane, oilseeds and other crops can become ethanol, renewable diesel or other biofuels. Straw, corn stover, husks, shells and processing residues can provide heat, power or feedstock for conversion.
Dedicated energy crops such as switchgrass and short-rotation willow may grow on suitable land, but land use, water, fertilizer and competing uses must be included in the assessment.
3. Food and industrial organic waste
Food scraps, fats, oils, grease and byproducts from food and beverage processing can be digested to produce biogas. Dry material may suit combustion or thermochemical conversion if its composition is controlled.
Separating contaminants at the source is critical. Packaging, grit and chemicals can damage equipment or make digestate and ash harder to use.
4. Animal manure
Manure from livestock operations can feed an anaerobic digester, where microorganisms produce methane-rich biogas and digestate. The gas can supply heat, combined heat and power or renewable natural gas after upgrading.
A dependable manure supply helps, but a digester still needs appropriate scale, temperature control, maintenance, gas treatment and a nutrient-management plan.
5. Wastewater and sewage solids
Wastewater treatment plants can digest biosolids and use the resulting biogas in boilers or generators. Some facilities clean it further for pipeline injection or vehicle fuel.
Gas quality, siloxanes, hydrogen sulfide and moisture require careful treatment to protect engines and meet emissions or pipeline specifications.
6. Biogenic municipal waste and landfill gas
Paper, food, yard trimmings, wood and other biogenic parts of municipal solid waste can provide energy. Landfills also generate methane as organic material decomposes without oxygen.
Municipal waste often contains fossil-derived plastics and other non-biomass material. Counting all waste as renewable biomass overstates the renewable share and ignores contamination and air-emissions concerns.
What is not biomass?
Coal, petroleum, fossil natural gas and most conventional plastics are not biomass because their carbon is fossil-derived. Rubber may be natural or synthetic, so its origin matters.
Algae can be biomass. So can the renewable portion of mixed waste, but only when that fraction is identified and the conversion process meets applicable environmental rules.
How to choose a biomass feedstock
Compare annual quantity, seasonal reliability, moisture, energy content, particle size, ash, contaminants, storage, transport and competing uses. Then match the material to combustion, digestion, fermentation, gasification or another proven conversion route.
Bottom line: the strongest biomass projects start with a consistent local feedstock and a valuable energy use. A broad claim that material is renewable is not enough.
Sources: U.S. Energy Information Administration biomass overview, EPA anaerobic digestion guidance and EPA landfill-gas overview.