Anaerobic Digestion in California Dairies: Electricty Generation or Biomethane Upgrading

Abstract

California is worldwide one of the major Green House Gas emitter due to a large use of fossil fuels in power generation and transportation. The dairy sector can play an important role in reducing these pollutants through the installation of anaerobic digesters and the production of biogas. This study has analyzed the two productive options, biomethane upgrading and on-site electricity generation that a dairy farmer can consider after installing an anaerobic digestion system. The two options have been applied to five California dairy farms with diverse productive, geographical and size conditions in order to identify the best applicable technology for the sector. Both the options have been proved in three modified scenarios in order to identify under which conditions each can achieve the best economical results. Biogas yield efficiency and reduction in capital costs appeared binding conditions in both cases even though electricity generation seemed more solid on average even with lower yields. Biomethane upgrading resulted the preferable path for large size farms or for associations of farmers intentioned to adhere and produce biomethane jointly. Electricity generation instead can guarantee better payback periods to small family-size farms due to lower investment costs. Last the study shows the necessity of dedicate policies to support both options in order to allow the development of the technologies in this sector.