Conversion of Waste Biomass into Useful Products

Abstract

Waste biomass includes municipal solid waste (MSW), municipal sewage sludge (SS), industrial biosludge, manure, and agricultural residues. When treated with lime, biomass is highly digestible by a mixed culture of acid-forming microorganisms. Lime treatment doubles the ruminant digestibility of agricultural residues; thus, it may be used to upgrade their feed value. Alternatively, lime-treated biomass can be fed to an industrial-scale mixed-acid fermentation where acetic, propionic, and butyric acids are produced. To control the pH, these acids are neutralized with calcium carbonate. The resulting calcium salts can be used to reduce sulfur emissions from industrial furnaces by directly spraying salt solutions into the combustor. Alternatively, the calcium salts may be thermally converted to ketones -such as acetone, methyl ethyl ketone, and diethyl ketone -which are useful industrial solvents. Further, these ketones may be hydrogenated to alcohols -such as propanol, butanol, and pentanol -which may be used as industrial solvents or motor fuel. Alternatively, the calcium salts may be acidified to recover the acids. In recognition of the potential environmental benefits of this technology, it has been awarded the 1996 Presidential Green Chemistry Challenge Award.