Cal. Public Resources Code § 40106

(a) “Biomass conversion” means the production of heat, fuels, or electricity by the controlled combustion of, or the use of other noncombustion thermal conversion technologies on, the following materials, when separated from other solid waste: (1) Agricultural crop residues. (2) Bark, lawn, yard, and garden clippings. (3) Leaves, silvicultural residue, and tree and brush pruning. (4) Wood, wood chips, and wood waste. (5) Nonrecyclable pulp or nonrecyclable paper materials. (b) “Biomass conversion” does not include the controlled combustion of recyclable pulp or recyclable paper materials, or materials that contain sewage sludge, industrial sludge, medical waste, hazardous waste, or either high-level or low-level radioactive waste. (c) For purposes of this section, “nonrecyclable pulp or nonrecyclable paper materials” means either of the following, as determined by the department: (1) Paper products or fibrous materials that cannot be technically, feasibly, or legally recycled because of the manner in which the product or material has been manufactured, treated, coated, or constructed. (2) Paper products or fibrous materials that have become soiled or contaminated and as a result cannot be technically, feasibly, or legally recycled.