The Presence of Inhibitors in Rotten Tropical Fruits for Biogas Production

Rotten fruit is regarded as a cheap biomass for biogas production that can be used as energy source. Generally, anaerobic digestion was seen as an ideal way to treat biomass waste. In this paper, rotten orange, mangosteen, pineapple, banana, and rambutan which was separated into its fragments were chosen as feedstock for biogas production. In addition, the presence of inhibitors in fruits is a main challenge on convertion of fruit waste into biogas. The ratio methane yield was used to evaluate the process performance of biogas production. For the biogas production, orange, mangosteen, pineapple, banana, and rambutan as well as starch (as reference) were run in triplicate using a glass batch digester under mesophilic conditions (35°C). The concentration ratio between volatile solid (VS) of substrate and inoculum was 0.15:0.60 g VS. During the time period of 60 days, measurements of methane and carbon dioxide production were taken. The highest biogas production of investigated fruits was achieved by seed of rotten orange which was 0.566 Nm 3/ kg VS methane yield. The highest initial methane production rate was obtained from pulp of fresh pineapple and pulp of rotten mangosteen, which was 0.067 Nm3/ kg VS/ day. Among the fruit fragments, peel of orange, mangosteen, and rotten rambutan indicated an inhibitory effect on anaerobic digestion