Bioconversion of livestock by-products into biogas: Experimental study of optimal fermentation conditions

Abstract

The bioconversion of organic waste into biogas is a substantial part of the company's strategy for sustainable development and reducing its environmental impact. The key factors affecting the efficiency of this process are fermentation temperature, carbon-to-nitrogen (C/N) ratio and substrate type. The study aimed to investigate the effect of temperature conditions, C/N ratio and different types of organic waste on biogas yield, particularly methane concentration, during anaerobic fermentation. Two temperature conditions were compared in the experiment: mesophilic (35°C) and thermophilic (55°C), using three types of organic waste: poultry manure, cattle manure and pig manure. The optimal C/N ratio was also studied to improve the energy efficiency of the process. Under thermophilic conditions, an increase in biogas yield by 20-28% and an increase in methane concentration by 5-10% were recorded compared to the mesophilic regime. The highest biogas yield (0.42 m3/kg of organic dry matter (OSR)) and methane concentration (70%) were achieved with poultry manure. In the thermophilic regime, the time to achieve stable gas production was also reduced to 7-8 days, which confirmed the effectiveness of this approach for industrial use. The thermophilic fermentation mode is more efficient for biogas production and increases the energy efficiency of the process. Optimisation of the C/N ratio and co-fermentation of different substrates further improved the efficiency. Poultry manure proved to be the most efficient substrate for bioconversion, which opens prospects for its use on an industrial scale. The results of the study can be used to optimise biogas fermentation technologies to improve the performance of biogas plants and reduce energy costs