Estimating Farm Size Required to Economically Justify Anaerobic Digestion on Small Dairy Farms

The benefits of anaerobic digestion (AD) of dairy manure vary from economic (reduced power costs/income from excess electricity/heat), to environmental (reduced greenhouse gas emissions, better control over field application of digestate) to social (through reduced odor during storage and application). However to realize these benefits economically, is the true challenge of AD, and a part of the reason for the slow adoption rate in the US, particularly when compared to European countries such as Germany and Denmark. According to the EPA there are currently approximately 131 dairy farm based anaerobic digesters with cogeneration operating in the United States (AgSTAR, 2012). In Germany alone there are more than 3,000 on-farm biogas plants. In the US, the average herd size is 150 lactating cows, whereas in Germany it is 50. Clearly there must be a reason for why anaerobic digestion has not flourished in the US as it has in Europe.