OPTIMAL WORKING TEMPERATURE OF BIO-H2 AND BIO-CH4 FROM PSICHROPHILIC vs. THERMOPHILIC REGIME

摘要

Effect of temperatures ranging from 16 °C to 50 °C on fermentative hydrogen production by mixed cultures was investigated in a stirred batch reactor with 2 liter of working volume, using as inoculum the anaerobic sewage sludge pretreated with HCl at pH=3 for 24 h in order to avoid methanogenesis step during fermentation. Test at 35 °C was conducted to convert VFAs produced at the end of the 1st acidogenic step into bioCH4 by adding an untreated anaerobic sewage sludge as inoculum in order to evaluate the total energy produced as bioH2+bioCH4. An estimation of the bioCH4 at different temperatures was carried out thanks to a smoothing function extrapolated by literature from 35 °C to 16 °C. Results of batch tests at different temperatures (from 16 to 50 °C) for only the first acidogenic step show that the biggest quantity (10 L H2/ Lreactor) of H2 and the maximum H2 production rate (1.5 L H2 l-1day1) were obtained at 35 °C even if it is feasible to produce H2 also at extreme temperature (16 °C and 50 °C). In particular we obtained that hydrogen production increases with increasing temperature from 16 °C to 35 °C and it decreased with further increasing temperatures from 40 °C to 50 °C. The two-step H2+CH4 process significantly increases the total energy production thanks to an energetic valorization of the produced liquid metabolites (VFAs).