Greenhouse gas emissions of electricity and biomethane produced using the Biogasdoneright system: four case studies from Italy

We reported previously on the Biogasdoneright system for on-farm biogas production. This innovative system employs sequential (year-round) cropping to produce both food and energy from agricultural biomass, primarily cellulosic materials. This paper uses a marginal analysis approach to estimate the life cycle greenhouse gas emissions (GHGs) of electricity and biomethane produced by four currently operating Italian biogas plants that process various agricultural feedstocks, residues, and by-products. The biogas is burned on-farm to generate electricity that is then exported to the grid. The marginal lifecycle GHGs of this farm-produced electricity range from -335 to 25 grams CO2 per kilowatt hour (kWh). By comparison, the marginal GHGs of electricity generated by fossil fuels in the European Union (EU) is 752 grams CO2 per kWh. The biogas might also be upgraded to produce pipeline-quality biomethane, a direct substitute for natural gas. The marginal lifecycle GHGs of biomethane potentially produced from the Biogasdoneright plants range from 10 to -36 grams CO2 per megajoule (MJ) while the corresponding figure for a conventional biogas plant is 27 grams CO2 per MJ. Natural gas in the EU produces 72 grams CO2 per MJ and marginal fossil fuel in the EU generates 115 grams CO2 per MJ. Negative GHG emissions arise largely from avoided emissions of agricultural effluents and residues. (c) 2017 Society of Chemical Industry and John Wiley & Sons, Ltd