Influence of temperature on the anaerobic stabilization of organic solid residues

Abstract

This study was aimed at determining the effect of temperature on the stabilization of organic solid waste conjugated with sewage sludge in anaerobic batch reactors (ABR), and to estimate the efficiency of the process in producing biogas and methane. The substrate contained 36.2 g L-1 of total solids comprising residues from fruits and vegetables enriched with anaerobic sludge from sanitary sewage (4:1, w/w). The reactors were of 1.15 L capacity and were operated at 25.5, 40 and 50°C (ABR1, ABR2 and ABR3, respectively) for 160 days. The efficiencies of transformation of total volatile solids in ABR1, ABR2 and ABR3 were, respectively, 43.2, 34.2 and 32%, and the transformation of chemical oxygen demand showed a similar tendency with efficiencies of 39.5, 33.6 and 16.6%, respectively. The mean volumes of biogas accumulated by ABR1, ABR2 and ABR3 were 28.85, 21.24 and 20.54 L, respectively, while the respective mean volumes of methane were 9.04, 7.11 and 1.11 L. The results demonstrate that the activity of methane-producing microorganisms was inhibited at higher process temperatures. It is concluded that anaerobic digestion at ambient temperature represents an economical and environmentally viable strategy for the disposal of municipal solid wastes.

Key words: Plant residues, anaerobic digestion, biofuel, methane