Post-breeding waste from Zophobas morio for biogas and energy generation via anaerobic methane fermentation

•Waste from Zophobas morio farming has not so far been tested for biogas production.•Unseparated waste (M) as well as feces (F) and wheat bran (W) fractions were tested.•F waste had the highest biogas potential of 668 ml·g−1·VS while W had the lowest.•The average CH4 content was 51.9% (vol.).•Biogas potential of the feces was 3% higher than that obtained for the mixed waste. Zophobas morio is one of the most widely bred insect species in commercial farms around the world, however Z. morio post-breeding waste has never been tested for its biogas and biomethane potential. The unseparated waste (M) was sieved to separate it into fractions of feces (F) and remaining wheat bran (W) in order to investigate whether isolated feces can have higher biomethane potential. Mesophilic (37 °C ± 1 °C) anaerobic digestion was performed in glass bioreactors (2 l total volume) for 24 days. The substrate loading was 8 g of the air-dried sample and the inoculum-to-substrate total mass was 125:1. The physicochemical parameters of the wastes and sludges after fermentation were investigated. The biogas potential of the feces was only approximately 3% higher than other tested materials and reached 650 ml of biogas · g−1VS. The average methane concentration was 52% (vol.). The calculation of theoretical electric and heat energy recovery in a co-generation system reached (per 1 Mg of waste VS) 1.3–1.4 MWh and 1.4–1.5 MWh, respectively. Post-breeding waste from Z. morio can be successfully used for energy recovery in the form of biogas.