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RESEARCH PRODUCT

Review of the impact of biogas digestates on the microbiological quality of agricultural soils

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The global production of biogas has increased threefold during the last decade to partly replace fossil fuels, yet biogas production by anaerobic digestion generates substantial amounts of by-products named digestates. These biogas digestates can be recycled in soils to fertilize crops and to sequester carbon. However, the impact of digestates on the soil biological is actually poorly known. Here we reviewed the impact of digestates published in 56 articles reporting 23 microbial parameters. Half of the articles show neutral effects of biogas digestates and 7% showed negative effects. 25% of the articles show more stimulation of biogas digestates for the soil microbial quality, compared to other organic fertilizers; whereas 17% of the articles show less stimulation. Beyond these general results, our study pointed the lack of long-term and field experiments, including a large range of agro-pedological contexts. Some questions, such as the effect of feedstock type or the vulnerability of specific soil types, remain unsolved and need more intense research effort.