Comparative performance between temperature-phased and conventional mesophilic two-phased processes in terms of anaerobically produced bioenergy form food waste

摘要

Comparative evaluation of bioenergy production from food waste was carried out with both a temperature-phased and a conventional mesophilic two-phased process at different organic loading rates (OLRs). No methane was detected in the temperature-phased thermophilic-acidogenic fermenter at all the OLRs tested. However, a significant amount of methane content was detected in the conventional two-phased mes-ophilic-acidogenic fermenter, with increments depending on the organic loading rate [from 17 percent at 3 g VS L~(-1) day~(-1) to 25 percent at 8 g VS L~(-1) day~(-1) (VS, volatile solid)]. Acetate and butyrate were the main volatile fatty acids (VFAs) in the temperature-phased thermophilic-acidogenic fermenter; conversely propi-onate was a major VFA in the conventional two-phased mes-ophiiic-acidogenic fermentSr. Through the chemical oxygen demand (COD) balance of both temperature-phased and conventional mesophilic two-phased processes, the fraction of the feed-COD converted to the hydrogen-COD in the thermophilic-acidogenic fermenter within the former process was estimated from 7.9 to 9.3 percent, with a peak at ORL of 6 g VS L~(-1) da~(-1), whereas it was quantified from 0.3 to 0.9 percent in the mesophilic-acidogenic fermenter within the latter one. Moreover, the fraction of the feed-COD converted to the methane-COD in the mesophilic-acidogenic fermenter within the conventional two-phased process ranged from 5.4 to 7.9 percent. On the other hand, conversion of the feed-COD to the methane-COD in the mes-ophilic-methanogenic fermenter of both temperature-phased and conventional mesophilic two-phased processes ranged from 66.2 to 72.3 percent and from 63.5 to 70.5 percent, respectively, with decrements related to the increase of organic loading rate.