Conversion of tomato, peach and honeydew solid waste into methane gas.

ABSTRACT METHANE production by anaerobic digestion of tomato, honeydew and peach solid wastes was in-vestigated. Results from a two-year laboratory investiga-tion and seasonal operation of a pilot plant size digester are presented. For 4L laboratory digesters operating at 35 °C the following loading rates and retention times were found to be optimal for tomato, honeydew and peach residues, respectively: 5, 3, and 1 kg VS/m^-d and 25, 20, and 15 d. Under these operating conditions 33 percent, 83 percent and 86 percent of the volatile solids were destroyed for tomato, honeydew and peach residues, respectively, and the corresponding gas productions, corrected to STP, were 0.43, 2.45, and 1.15 vol/digester vol/day. On a conversion efficiency basis these values relate to 0.14, 0.81 and 1.15 mVkg VS load-ed, respectively. Operation of the 22 m^ pilot plant generally confirmed the laboratory data for tomato solid waste.