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The aim of the study was to optimize methane fermentation of food waste products based on the composition of substrates mixture and technical parameters of anaerobic digestion to obtain the highest biogas and methane production. The study was conducted in the laboratory scale in the mesophilic (37°C) and thermophilic (55°C) conditions. Also the effects of the organic loading rates (OLRs) on the biogas productivity and composition were analysed. The highest biogas yield was obtained in mesophilic digestion of the substrates mixture containing 50% of meat, 40% dairy products, 10% fruit and vegetables. It amounted to 740.4 ± 19.9 cm3·g ODM−1 of biogas with 68.6 ± 1.8% of methane. Biogas potential in thermophilic digestion was from 2.1 to 2.8 times lower for analogical feedstock. It was caused by high concentration of volatile fatty acids (VFAs) in the reactor chamber. The ratio of VFAs to alkalinity was on the level from 0.5 ± 0.1 to 0.8 ± 0.1. In continuous experiments, the average biogas production rate was from 2646.9 ± 117.3 cm3·d−1 for OLR of 2 g ODM·dm−3·d−1 to 9893.4 ± 362.0 cm3·d−1 for OLR amounting to 8 g ODM·dm−3·d−1. Methane content in biogas was between 65.6 ± 2.5 and 65.5 ± 1.9%, respectively. It was confirmed that applying OLR above 6 g ODM·dm−3·d−1 causes inhibition of methane fermentation. • 740.36 ± 19.85 cm3·g ODM−1 was generated during mesophilic fermentation. • Biogas productivity in thermophilic process was from 2.1 to 2.8 times lower. • OLR above 6 gODM·dm−3·d−1 completely inhibited the process. [ABSTRACT FROM AUTHOR]

The study was aimed to compare the methane potential from the silage of Sida hermaphrodita mixed with cattle manure pretreated by microwave (MW) thermohydrolysis with liquid hot water (LHW) pretreatment. It was illustrated that both pretreatment methods significantly improved degradation of the lignocellulosic structure and improved the methane production. The maximum methane production of MW pretreated biomass was 590 NL/kg VS at 150 °C and 15 min with an improvement of 39.1% to an untreated sample. In turn, LHW treatment provided the maximum methane production of 575 NL/kg VS with the same pretreatment conditions. The net energy output significantly higher than calculated for the control sample was achieved only for MW pretreatment at 150 °C and 15–30 min. In other variants, pretreatment step needed higher energy input than the net energy gain from methane production. • Microwave and liquid hot water pretreatment methods were evaluated in this study. • Considerable increasing in biogas production with both methods was noted. • Microwave pretreatment reduced the pretreatment temperature and time. • The net energy output was unfavorable for most conditions tested. • Only for microwaves (150 °C, 15–30 min) a positive energy balance was obtained. [ABSTRACT FROM AUTHOR]