Biochemical Methane Potential of Agro Wastes

The focus of our work is on anaerobic digestion of locally available agro wastes like coconut oil cake, cashew apple waste, and grass from lawn cuttings. The most productive agro waste, in terms of methane yield, was coconut oil cake and grass. The results showed that the initial volatile solids concentration significantly affected the biogas production. The methane yield from coconut oil cake was found to be 383？ml CH4/g？VS and 277？ml？CH4/g？VS added at 4 and 4.5？g？VS/l. In case of grass the biogas production increased with increasing VS concentrations with methane yield of 199, 250, 256, 284, and 332 ml？CH4/g？VS at 3, 3.5, 4, 4.5, and 5.0？g？VS/l. For cashew apple waste single-stage fermentation inhibited biogas production. However, phase separation showed methane yield of 60.7？ml？CH4/g？VS and 64.6？ml？CH4/g？VS at 3.5 and 4.0？g？VS/l, respectively. The anaerobic biodegradability of coconut oil cake was evaluated in fed batch mode in a 5？L anaerobic reactor at 4？g？VS/L per batch, and the maximum methane yield was found to be 320？ml？CH4/g？VS. 1. Introduction In the light of rapidly rising costs associated with energy supply, waste disposal, and increasing concerns with environmental quality degradation, conversion of wastes to energy is becoming an economically viable solution [1]. Anaerobic digestion (AD) is a biological process in which bacteria break down organic matter producing biogas as the end product. AD is a sequence of chemical reactions during which organic matter is decomposed through the metabolic pathways of naturally occurring microorganisms in an oxygen depleted environment. AD is a promising technology which could effectively address the problem of waste disposal yielding valuable outputs like biogas and fertilizer. AD without any pretreatment but with energy recovery is the most attractive method for treating solid wastes [2]. AD of organic wastes and energy crops to produce methane would benefit society by providing a clean fuel from renewable feed stocks. This could substitute fossil fuel-derived energy and reduce environmental impact including global warming and acid rain [3]. Agro wastes and energy crops represent an important source of biomass that can serve as a substrate in anaerobic digestion, resulting in the production of renewable energy. The wastes selected for our study are coconut oil cake (residue obtained after oil extraction), cashew apple waste (crushed apple waste obtained after extraction of “Feni”—“Feni” is a form of liquor i.e., distilled from the pure fermented juice of cashew apple without addition of spirit), and