Economics of GHG emissions mitigation via biogas production from Sorghum, maize and dairy farm manure digestion in the Po valley

摘要

The Greenhouse gas (GHG) emissions and economic feasibility of electricity production from the anaerobic digestion of different substrates are studied in this paper. Three realistic substrate options for the climatic and soil conditions of a modelled farm in the Po Valley in Italy are analysed: manure from a dairy farm, Sorghum and maize. A detailed cost analysis is performed with field data provided by farmers and suppliers and literature sources. The capital costs (CAPEX) and the operational costs (OPEX), disaggregated by their components, are presented. Investment payback time is then calculated for the different substrates and technologies, while taking into account the Italian government feed-in tariff scheme for biogas plants implemented in 2013. In the specific conditions assumed, electricity production via anaerobic digestion of manure and co-digestion of manure with at most 30% Sorghum (no till) provide both GHG savings (in comparison to the Italian electricity mix) and profit for economic operators. The anaerobic digestion of silage maize or Sorghum alone, instead, provides no (or very limited) GHG savings, and, with the current feed-in tariffs, generates economic losses. Both economic and environmental performance are improved by the following practices: cultivating Sorghum instead of maize; implementing no till agriculture; and installing gas-tight tanks for digestate storage. A tool allowing a customised calculation of the economic performances of biogas plants is provided.