Optimal energy use of agricultural crop residues preserving soil organic carbon stocks in Europe

Abstract

The European Union has committed itself to ambitious targets of Renewable Energy and bioenergy is expected to play a major role, increasing its contribution to Gross Final Energy Consumption from 2458PJ in 2005 to 4605PJ by 2020.Agricultural crop residues are considered a reliable resource for energy uses but important concerns still exist on the potential depletion of Soil Organic Carbon (SOC) stocks that may partially offset the environmental suitability and convenience of their large-scale exploitation.This paper provides an estimate of available agricultural residues and related potential energy production obtainable without impacting the EU SOC stock showing how SOC content preservation imposes the application of different collection rates for agricultural residues across the EU, depending on factors such as climate, soil type, current farming practices and pre-existing cultivation history.The results suggest that a potential amount of residues of 146,000kt/year of dry matter leading to a potential gross energy production of about 2300PJ/year could be obtained in EU-2711Excluding Croatia. without impacting the current SOC stocks. Agricultural residues are then theoretically able to provide a substantial contribution to renewable energy targets in several EU-27 countries as well as accommodating competitive uses and SOC preservation. Nevertheless, the spatial pattern of results also clearly indicates regions and countries where residues exploitation should be handled with care and current practices on residues collection are risky in term of SOC content.The estimate provided builds on results from previous studies (e.g., Scarlat et al. Waste Manage 2010;30:1889–1897, Monforti et al. Renewable Sustainable Energy Rev 2013;19:666–677) and on the analysis of future scenarios of SOC content obtained from an innovative pan-EU modelling platform (Lugato et al. Global Change Biol 2014;20:313–326. doi:10.1111/gcb.12292. Such an integrated approach, making use of soil, climate and energy transformation modelling, is unique and constitutes a substantial applied value for assessing the sustainability of crop residues use.