Autor/autori: Lacour S., Descombes G, Podevin P.,Chinese T.,Alkadee D. (Franta)

Abstract: The fossil fuel resources are decreasing and many research's are looking for alternative fuels to comply with transportation need while reducing the environmental impact of this sector. Inside the transport activity sector, off road vehicle and machine used for agriculture needs a small, but vital energy amount of around 2 MToe in France and the anaerobic digestion of rural wastes could roughly cover machine needs. This paper aims to study environmental and energetic interest of this short power supply path. An ideal biogas production system is built up from average characteristic of current rural biogas plant in France. Pollutant emission and energy demand and production are assessed for various way of producing methane for dual fuel engine. Life Cycle Assessment (LCA) is used to look for the environmental impact of the dual fuelled agricultural machines and a comparison with other biofuel's LCA is made. Results show the great impact of biogas on "ecotoxicity" and "respiratory diseases" of the biogas: these are mainly related to electricity production and improvement can be reached with some care about methane losses and local electricity production. For human health, HAP measurements could improve the assessment and avoid inconsistency between different models used in LCA. Then, the impact on the climate change and energy depletion is discussed: therefore, different methods are used to build the energetic and carbon balance of the biogas production system. Then, from this comparison, we discussed about the choice of energy for agricultural machines: biogas energy cost could be reduced by using agricultural machines with high substitution rate instead diesel.

Keywords: methanation, Life cycle assessment, biogas fuelled tractors, carbon balance, dual fuel engine.