Valorisation of the selectively collected organic fractions of municipal solid waste in anaerobic digestion

Biogas productivity (BP) with kinetics and microbial structure during methane fermentation and co-fermentation of food (FW) and green waste (GW) was investigated. Biogas potential tests (GP21) were performed with FW:GW 0:100, FW:GW 30:70, FW:GW 50:50, FW:GW 70:30 and FW:GW 100:0. Although all the substrates had similarly high contents of organic matter (88.4 +/- 2.2-93.1 +/- 2.3% TS), they differed in characteristics and composition. Biogas production and methane content were lowest with GW alone (518.9 +/- 14 L/kg VS; 58.6 +/- 0.2% CH4); these values were highest with FW alone (733.9 +/- 14 L/kg VS; 65.2% CH4). When the share of FW in the mixtures was increased, content of fibrous materials decreased, BP increased. The kinetic coefficients of biogas production and of organic matter content loss during fermentation of GW alone were lowest (0.27 +/- 0.01 d(-1), 0.36 +/- 0.02 d(-1)), they increased as the share of FW in the mixtures was increased, up to 0.57 +/- 0.02 d(-1) and 0.68 +/- 0.02 d(-1) with FW alone. Methanosarcinaceae made up the largest share of the Archaea (6.1-13.2%) that were present. The abundance of Methanosaeta ranged from 2.4% to 7.8%. The most numerous core group was Cytophagaceae, comprising about 13-17% of all identified sequences. Bacteroides and Spirochaeta predominated in all digestates and positively correlated with the content of fibrous materials in the feedstock. Bacteroidetes abundance increased if the effectiveness of organic matter loss diminished.