Anaerobic digestion of the liquid fraction of dairy manure in pilot plant for biogas production: Residual methane yield of digestate

摘要

The performance of the only dairy manure biogas plant in Cantabria (Northern coast of Spain) was evaluated in terms of liquid-solid separation and anaerobic digestion of the liquid fraction. Screened liquid fraction was satisfactorily treated in a CSTR digester at HRTs from 20 to 10 days with organic loading rates ranging from 2.0 to 4.5 kg VS/(m~3 d). Stable biogas productions from 0.66 to 1.47 m~3/(m~3 d) were achieved. Four anaerobic effluents collected from the digester at different HRTs were analyzed to measure their residual methane potentials, which ranged from 12.7 to 102.4 L/g VS. These methane potentials were highly influenced by the feed quality and HRT of the previous CSTR anaerobic digestion process. Bio-methanization of the screened liquid fraction of dairy manure from intensive farming has the potential to provide up to 2% of total electrical power in the region of Cantabria.