Dry anaerobic digestion of differently sorted organic municipal solid waste: a full scale experience

This paper presents a comparison of dry anaerobic digestion reactors fed with differently sorted municipal organic solid wastes. One reactor was fed with source sorted organic wastes and a second reactor was fed with mixed organic wastes consisting of grey wastes, mechanically selected municipal solid wastes and sludge. The two reactors utilised the same process (Valorga) and operational conditions at full scale. The results of the study emphasise the influence of the kind of treated material on the process performances, especially in terms of biogas and methane production, thus, energy reclamation. The reactor treating the source sorted organic waste and the reactor treating the mixed organic wastes generated some 200m3 and 60m3 of biogas per ton of waste treated, respectively, while the specific methane production was some 0.40 and 0.13m3CH4/kgTVS, respectively. The mass balance and the final fate of the digested material from the two reactors were also clearly different. As for the costs, these were some 29 e per ton of treated waste (50% for personnel) and 53 e/ton for disposing of the rejected materials. Incomes were some 100 e/ton (on average) and an other 15 e/ton came from green certificates. The initial investment was 16 million Euros.