Influence of the type of livestock by-products on biogas yield and composition

Abstract

The study of the effects of various types of animal waste on the quantity and composition of biogas is significant and relevant for optimising anaerobic fermentation processes, increasing the efficiency of biogas production and adapting technologies to farm conditions. The purpose of this study was to evaluate the effects of livestock by-products, specifically cattle manure, pig manure, and chicken manure, on the quantity and quality of biogas produced. The methods employed in the study included statistical analysis, gas analysis, and fermentation. The study analysed the physicochemical properties of several types of raw materials for biogas production. The study found that chicken manure had the highest potential for biogas production due to its high content of volatile solids (25-30%) and the optimum ratio of methane in the biogas composition (65%). Cattle manure was characterised by a stable average biogas yield (0.15-0.18 m3/kg volatile solids in feedstock (VT, %)), while pig manure had the lowest yield (0.12-0.14 m3/kg volatile solids in feedstock). According to the study results, the addition of carbonaceous materials (e.g., chopped straw) improved the carbon to nitrogen ratio to optimise the fermentation process. The analysis of the organic matter content before and after fermentation revealed a significant decrease for chicken manure (51%), which indicated the effectiveness of biodegradation. The study included an assessment of the composition of biogas, including methane (50-65%), carbon dioxide (30-40%), and hydrogen sulphide (1-3%). The change in pH in all types of raw materials after fermentation indicated that the environment in the bioreactors had stabilised, providing favourable conditions for microorganisms. The findings of this study can be used in practice by ecologists, agronomists, livestock technologists, and biogas producers to create energy-independent farms through the integration of biogas plants into farms.