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The development of bio-economy in agriculture can notably be envisaged with the recycling of residual organic matter (ROM) and the development of anaerobic digestion, which contribute to closing biogeochemical cycles and producing renewable energy. Although the effects of ROM recycling in agriculture (saving mineral fertilisers, soil fertility, etc.) have been effectively studied under experimental conditions, as has the environmental balance of anaerobic digestion and the recycling of ROM, the implementation methods used by farmers and their real effects are less well known.

Indeed, the development of anaerobic digestion may lead to changes in cropping systems to ensure the supply of the anaerobic digester. On the other hand, the reasoning behind the fertilisation strategies of farmers that use ROM is not necessarily well known, and the fertiliser savings actually achieved remain theoretical. These potential "deviations from theory" may influence the mitigation (C storage, emissions avoided due to fertiliser substitutions...) and adaptation capacities of agriculture to climate change (sensitivity of biomass production systems for anaerobic digestion to summer droughts, improvement of water properties with the increase of soil organic matter).

The objective of the thesis will thus be to study the changes in cropping systems induced by the implementation of ROM recycling or an anaerobic digestion system by farmers, and then to assess the effects on their capacity to adapt to and mitigate climate change. To do so, the thesis will rely on the analysis of existing spatialised databases, agricultural surveys and modelling. Finally, the thesis will highlight possible areas of concern in order to maximise the benefits of ROM recycling and anaerobic digestion.