The methanisation process, used to produce biogas, consists in the anaerobic digestion of organic matter (meaning it takes place in a low-oxygen environment). At the end of the process, some material remains untransformed: digestate.
That digestate arising from methanisation can be repurposed as renewable fertiliser for crops. It has less smell than the original farm effluent because of the transformation it has undergone.
It is possible to introduce phase separation for digestate, to obtain:
a solid phase with enriching qualities, due to its high proportion of organic matter and phosphating elements,
a liquid phase with fertilising properties for plants, because it is more nitrogen-rich.
The digestate originating from agricultural methanisation satisfies organic farming specifications under certain conditions when it comes from non-organic farms. The agricultural use of digestates from biomethane production is part of the regional circular economy.