Environmental and economic evaluation of energy recovery from agricultural and forestry residues

Abstract

Four conversion methods and five residues are examined in this report, which describes six model systems: hydrolysis of corn residues, pyrolysis of corn residues, combustion of cotton-ginning residues, pyrolysis of wheat residues, fermentation of molasses, and combustion of pulp and papermill wastes. Estimates of material and energy flows for those systems are given per 10/sup 12/ Btu of recovered energy. Regional effects are incorporated by addressing the regionalized production of the residues. A national scope cannot be provided for every residue considered because of the biological and physical constraints of crop production. Thus, regionalization of the model systems to the primary production region for the crop from which the residue is obtained has been undertaken. The associated environmental consequences of residue utilization are then assessed for the production region. In addition, the environmental impacts of operating the model systems are examined by quantifying the residuals generated and the land, water, and material requirements per 10/sup 12/ Btu of energy generated. On the basis of estimates found in the literature, capital, operating, and maintenance cost estimates are given for the model systems. These data are also computed on the basis of 10/sup 12/ Btu of energy recovered. The cost, residual, material, land, and water data were then organized into a format acceptable for input into the SEAS data management program. The study indicates that the most serious environmental impacts arise from residue removal rather than from conversion.