Anaerobic digestion of cotton yarn wastes for Biogas production: Feasibility of using sawdust to control digester temperature at room temperature

Abstract

Environmental and energy conservation pressure have led into intensive search for green sources of energy. One of the options being explored is generation of biogas from cellulosic (biodegradable) wastes. However, maintaining temperature for optimum biogas production is often an existential challenge. The materials/equipment used to control temperature is expensive as most of them require electricity. In this study, we investigated the feasibility of using a locally available material (sawdust) in anaerobic digestion (AD) of cotton yarn wastes (CYW) for biogas production. Two-liter digesters were set at room temperature, in a water bath and in sawdust using CYW as the substrate and cowdung as the inoculum. Biogas yields were recorded using water displacement method for 30 days and the effect of temperature was examined in each case. Results of the study indicated that the digester whose temperature was controlled using sawdust showed consistency in biogas production. Digester in the water bath showed the highest biogas yield compared to the digester controlled using sawdust and the one at room temperature with biogas yields of 2481.23 ± 5.50 mL per g-VS, 1856.51 ± 6.98 mL per g-VS and 1084.29 ± 5.71mL per g-VS, respectively. Similarly, the digester operated at control temperature using water bath had higher methane content 62.35% followed by di- gester in sawdust and then uncontrolled one with 52.45% and 45.28% respecively. The results of our study indicate that sawdust has the potential of regulating temperature in the range that allowed AD of CYW for biogas production. Therefore, CYW and sawdust which are readily available materials can be harnessed for biogas production at room temperature.