Environmentally Sustainable Biogas? The Key Role of Manure Co-Digestion with Energy Crops

Abstract

Abstract:We analysed the environmental impacts of three biogas systems based on dairy manure, sorghum and maize. The geographical scope of the analysis is the Po valley, in Italy. The anaerobic digestion of manure guarantees high GHG (Green House Gases) savings thanks to the avoided emissions from the traditional storage and management of raw manure as organic fertiliser. GHG emissions for maize and sorghum-based systems, on the other hand, are similar to those of the Italian electricity mix. In crop-based systems, the plants with open-tank storage of digestate emit 50% more GHG than those with gas-tight tanks. In all the environmental impact categories analysed (acidification, particulate matter emissions, and eutrophication), energy crops based systems have much higher impacts than the Italian electricity mix. Maize-based systems cause higher impacts than sorghum, due to more intensive cultivation. Manure-based pathways have always lower impacts than the energy crops based pathways, however, all biogas systems cause much higher impacts than the current Italian electricity mix. We conclude that manure digestion OPEN ACCESSEnergies 2015, 8 5235 is the most efficient way to reduce GHG emissions; although there are trade-offs with other local environmental impacts. Biogas production from crops; although not providing environmental benefits per se; may be regarded as an option to facilitate the deployment of manure digestion.

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

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Spent mushroom compost (SMC) as a source for biogas production in Iran

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Szarvasi-1 and its Potential to Become a Substitute for Maize Which is Grown for the Purposes of Biogas Plants in the Czech Republic

“…Farm animal excrement, side products of crop production, and energy crops are especially common. Species originating the input material (e.g., maize, grass, or manure) have turned out to be the decisive factors determining the impacts of a biogas unit on the environment [5,6]. Plant biomass represents more than 50% of all biogas substrates.…”