LAND APPLICATION OF SLUDGE GENERATED BY THE ANAEROBIC FERMENTATION OF BIOMASS TO METHANE

Although energy prices have remained relatively stable, or even declined, over the past several years, the problem of long-term reliance on finite fossil fuel reserves has not changed. Methane from the anaerobic digestion of biomass may offer at least a partial solution to this problem. Digester sludge generated from this process will have to be disposed of, most likely by land application. Nutrient concentrations in sludge normally increase during digestion, enhancing its value as a potential fertilizer. Mineralization kinetics will determine the conversion rate of organic nutrient forms in sludge to plant-available, inorganic forms. Ideally, sludge nutrient release would be synchronous with plant demand and would not create significant concentrations of residual soluble nutrients, which might result in environmental degradation. Excessive loading rates of methane generator sludge are of concern primarily because of potential nitrate (NO3-) contamination of groundwater. The purpose of this review of the literature and research summary is to emphasize potential problems and benefits associated with land application of this waste.