Photo credit: FREEPIK
Small-scale anaerobic digestion of residual flows (mainly at dairy farms) can help the farmer to fulfil the electricity needs of the farm and partly the heat demand through combustion of biogas in a combined heat and power unit. It has a local character and limited scale as compared to a larger digester. As a “waste stream” the resulting digestate can be used as a fertilizer. It can be used and spread in a similar way as classic manure but has environmental advantages. Under default practices animal production causes significant amounts of methane slipping from manure storage. By first putting manure in anaerobic digestion this methane slip is avoided and even captured into a renewable resource. This way the carbon footprint of (dairy) farms is reduced. Furthermore, during the AD process the nutrients from the animal manure are mineralized rendering them more plant available and thus increasing their nutrient use efficiency.