External organic matters for climate mitigation and soil health (EOM4SOIL) : report for stakeholders and policy makers

Many activities generate organic wastes, including housing and urban activities (e.g. biowastes, sewage sludges and green wastes), industries and agriculture (e.g. manures). Such organic matters have been defined as external organic matters (EOM) since not directly issued from the soils where they are applied or transformed during a treatment before their application on soils (anaerobic digestion for example). The recycling of EOM on soils, with or without pre-processing, is strongly encouraged by the Europe Union as part of a Circular Economy. Recycling on soils is however only possible, if application (i) is beneficiary for soils (carbon storage, increased biological activities…) and/or crop production (substitution of fertilizers…); (ii) does not generate environmental impacts through excess contaminant upload, nutrient losses (nitrate leaching for example) or gas emission (N2O, NH3…). Transformation process before application and EOM application management (dose, period of application, fertilized crop…) could help enhancing the EOM associated benefits while decreasing the trade-off. The general objective of the EOM4SOIL project was to propose best management practices of EOM treatment and application for climate change mitigation and soil health improvement, for representative farming systems of arable crops in Europe and considering the diversity of pedoclimatic conditions. More specific objectives were: (i) to assess multiple effects of EOM applications including contaminants; (ii) to evaluate the C balance between C storage and greenhouse gas (GHG) emission including during treatments; (iii) to recommend innovative pre-processing to improve C budget and soil health; (iv) to define best management practices from scenarios of use based on multicriteria simulation tools. The document presents the main conclusions of the project.