Potential C storage through the recycling of organic residues: experimental evidence and potential efficiency at the french national scale
Résumé
The recycling of organic residues issued from animal breeding, urban and industrial activities may contribute to organic C storage in soils. Long-term field experiments have evidenced that organic C accumulation in soils is conditioned by the application rates and the characteristics of the applied organic residues. Increased soil organic C additionally enhances soil fertility and potential mineral fertilizer substitution. Most animal manures are already recycled in agriculture but the composting or the anaerobic digestion of urban organic residues such as biowastes or sewage sludge could produce additional C sources for soils. The potential of additional soil C storage at the French national scale through increasing the recycling of new organic resources and its cost, has been explored within the “4 per 1000” study (see Pellerin et al.). Approximately additional 25% of the arable crop surface could be amended. The average additional C storage calculated over 30 years ranged between +0.06 and 0.25 Mg C ha-1 yr-1 (i.e. between +1.1 and +4.5‰) for different tested hypothesis. This storing practice has one of the lowest cost among all tested. However, when considering climate change mitigation, it is important to calculate the global mass balance of greenhouse gas, including those emitted during the treatment process which has been calculated.
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