VAAFM - Anaerobic Digestion Technology

Vermont Agency of Agriculture

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Anaerobic Digestion Technology - Overview

Anaerobic digesters transform the volatile organic compounds in manure, forages (corn silage, haylage, etc.) and other digestible materials (whey, food wastes, etc.) into “biogas.” Anaerobic digesters are basically sealed tanks that hold hot manure in the absence of oxygen and cultivate growth of bacteria. The bacteria first break down materials into acids, and then a different group of bacteria break down the acids to produce biogas. Biogas is typically 60% methane (CH4) and is either piped to a generator to create electricity and heat or to a boiler to produce just heat. The electricity can be used on the farm and/or be sold to a power company. Besides heat and electricity, biodigestion produces several valuable co-products. The solids left over after digestion can be used as animal bedding and/or soil amendments. The remaining liquid can be used as a soil amendment. Because the digester effluent has far less odor, you can spread on days and in areas that have been problematic, and with the increased solubility of the nitrogen and phosphorus, you have more control over soil nutrient management. Anaerobic digesters also significantly reduce pathogens, and can be integrated into a farm’s overall manure management system. Manure Digester Technology Biogas Engine/Generator Technology Forage Crop Digesters