Urban biowaste valorization by coupling anaerobic digestion and single cell protein production

Resource efficient and novel practices to produce proteinaceous food and feed sources can partially alleviate the protein scarcity problem. The conversion of low-value waste streams into single cell protein (SCP) seems a potent solution. This study evaluated the possibility of urban biowaste valorization through coupling anaerobic digestion and SCP production, and feeding a methanotroph mixed-culture with raw and upgraded biogas. In respect to nitrogen supply, the mixed-culture could grow well providing nutrients by direct addition of pasteurized centrifuged-filtered digestate or by adding electrochemically extracted ammonium from the digestate. The SCP yield on methane varied from 0.59 to 0.76 g cell dry weight (CDW)/g CH₄. A high yield on methane (0.87 g CDW/g CH₄) proved that biogas is a good substitute for natural gas for scaled-up microbial protein production. In addition, the produced SCP was rich in essential amino acids, marking the produced biomass comparable with other protein sources.