Animal manure for biogas production - what happens to the soil?

Summary

Utilizing animal slurry to produce biogas may reduce fossil fuel usage and emissions of greenhouse gases. However, there is limited information on how the recycling of digested slurry as a fertilizer impacts soil fertility in the long run. This is of concern because organic matter in the slurry is converted to methane, which escapes the on-farm carbon cycle. In 2010, a study of this question was initiated on the organic research farm in Tingvoll, Norway. So far, a biogas plant has been built, producing anaerobically digested slurry to be compared with undigested slurry in perennial ley and arable crops. Effects on crop yields, soil fauna, microbial communities, soil structure, organic matter and nutrient concentrations are measured.