Two-phase thermophilic anaerobic digestion process for biohythane production treating biowaste: preliminary results

摘要

This paper deals with the optimization of a two-phase anaerobic process treating biowaste fornhydrogen and methane production. Neither physical nor chemical pre-treatments were used tonoptimize the process. The work was carried out at pilot scale, using two CSTRs (200 and 380 Lnworking volume respectively) both maintained at thermophilic temperature (55 WC) and fed semicontinuouslynwith biowaste. The experiment was divided into three periods; during the first twonperiods the organic loading rate was maintained at 20 kg TVS/m3 d and the hydraulic retention timenwas changed from 6.6 to 3.3 days, while in the last period the digestate of the second reactor wasnrecirculated to the first reactor in order to buffer the system and control pH at levels around 5. ThenHRT was maintained at 3.3 days and the OLR was decreased at 16.5 kg TVS/m3 d. The best yield wasnobtained in the last period where a specific hydrogen production of 50.9 L/kg VSfed was reached, withna H2 content in biogas from the first reactor of 36%. The methanogenic stage after the hydrogennconversion reached a specific biogas production of 0.62 m3/kg VSfed and an overall organic removalnabove 70%, without any stability problem. The overall biogas production was some 1.5 m3 per daynwith a gas composition of 10% H2 and 50% CH4.