Energy recovery from biowaste: influence of hydraulic retention time on biogas production in dry-anaerobic digestion

DESTEC Department of Energy, Systems, Territory and Construction Engineering, 56122 Pisa, Italy

^* Corresponding author: isabella.pecorini@unipi.it

Abstract

The hydraulic retention time (HRT) is a key parameter in dry-anaerobic digestion to set during the reactor configuration in order to achieve the optimal biogas production. For this reason, the study compared the results of two experimental tests operating with an HRT of 23 and 14 days. During the tests, the feedstock was organic fraction of municipal solid waste with a solid content of 33% and the digester was a pilot-scale plug-flow reactor operating in thermophilic condition. The highest specific biogas production of 311.91 Nl_biogas kg^-1 d^-1 was achieved when the HRT was set to 23 days. On the contrary, the highest methane production rate of 1.43 Nl_CH4 l^-1 d^-1 was achieved for an HRT of 14 days. In addition, the volatile solids removal (49.15% on average) and the energy content o(4.8 MJ kg^-1 on average) were higher for HRT 23 days than for HRT14 days. The results indicated that in dry-anaerobic digestion of organic fraction of municipal solid waste, 23 days is a suitable HRT for energy recovery.