From laboratory to farm-scale psychrophilic anaerobic co-digestion of cheese whey and cattle manure

Abstract

This paper aims to prove the feasibility of cheese whey (CW) and cattle manure (CM) anaerobic co-digestion, from biomethane potential (BMP) laboratory assays to monitoring a farm-scale digester under psychrophilic conditions, and the impact on surrounding communities. The results show that while CW mono-digestion at 15 °C suffers inhibition, the CW:CM blend (70:30 volatile solids -VS- basis) is favorable at a similar temperature generating 0.24 m3 CH4/kg VS (35 °C yield: 0.60 m3 CH4/kg VS). A farm-scale digester (8 m3) installed in a rural school operated at 17.7 °C reached 0.42 m3CH4/kg VS, 0.31 m3 CH4/m3digester d with an organic loading rate of 0.61 kg VS/m3digester d (CW:DM 54:46). Even with CW's high volatile fatty acids (VFA) load, the digester did not show metabolic activities inhibition: VFA consumption was around 96.45 ± 2.25 %. In the rural school, biogas generation replaced the wood utilization and reduced propane consumption by 33 %. Despite these results, there are issues around psychrophilic BMP test to be reviewed, and user's misperceptions of biogas technology to overcome.