Influence of storage on methane yields of separated pig slurry solids

Biogas production from separated pig slurry solids is more profitable than using untreated raw slurry because there is a higher CH4 potential per unit fresh matter. However, logistics needs to be optimized. A stable storage without losing the high biogas potential could enable deliveries on demand. Self-heating and CH4 yields of aerobically and anaerobically stored pig slurry solids were analysed and compared. The aerobic storages had run times of 33 and 44 days. Anaerobic storage took 7, 23 and 35 weeks. Anaerobically stored solids show no self-heating and produce CH4 yields of up to 188 L kg−1 ODM. This is over twice as much as the aerobically stored solids produce and about the same CH4 yield produced by freshly separated solids. Additionally, a mass loss occurs under aerobic storage that reduces the methane yield of the original material too.