Weak alkaline treatment of wheat and pearl millet straw for enhanced biogas production and its economic analysis

Abstract

Wheat and pearl millet are the major cereals cultivated in Rajasthan. These cereals generate huge amount of residual biomass (straw). The surplus fraction of the residual biomass is either burnt or left unutilized. The organic content of the residues may be utilized for production of biogas through anaerobic digestion process. In this research, effect of weak alkaline pretreatment using lime (Ca(OH)2) on biogas production was studied. Both the straw were pretreated with Ca(OH)2 for 8 h at ambient temperature at loading of 0%, 20%, 40%, and 60% (w/w). In the range of 0–60% Ca(OH)2 loading, increase in the biogas yield ranged between 14 and 42% for wheat straw and 9–33% for pearl millet straw. Analytical methods such as scanning electron microscopy, fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray diffraction analysis were performed to study the impact of treatment and increase in biogas production due to treatment. The feasibility of the pretreatment was evaluated by performing energy and economic analysis by estimating the electricity and revenue generated using biogas in combined heat and power plant.