Research on yield of biogas during methane fermentation of cow manure with addition of granulated straw with slaked lime

Abstract

Cattle manure is often used to produce biogas, from which electricity and heat are generated. However, due to presence of a large amount of crude fiber in manure, the yield of biogas when it is fermented using biogas plants is relatively low. Therefore, an urgent task is to increase the yield of biogas from cattle manure through the use of various additives stimulating methane fermentation. Polyethylene bags were used as digesters, which were sealed with special devices. A calibrated cylinder was used to determine the biogas yield. The acidity of the substrate was measured with a pH meter. The novelty of the chosen topic lies in the use of chemical processing of biomass in combination with extrusion. The research results showed that pretreatment of wheat straw with different concentrations of Ca(OH)2 leads to the breakdown of lignocellulose, an increase in biogas yield and electricity generation. The optimal loading at rate of 100 kg CaO(t-1 into the reactor in the form of straw pellets has significant advantages and is the optimal solution, since the biogas yield in this case is practically the same as the yield obtained from wheat straw pellets at the rate of 150 kg CaO(t-1 of straw, but it is more cost effective. In addition, the year round use of straw pellets with the optimal addition of slaked lime for a biogas plant makes it possible to obtain high quality biological organic fertilizers; ensure high stable and trouble-free operation of the entire system as a whole; to increase gas recovery from bioraw materials of plant origin due to the decomposition of cellulose. This makes it easier to switch to other types of raw materials, and also increases the specific load of the entire line. It can be seen from the calculations that the highest methane yield (0.342 m3(kg-1 of dry matter) was obtained from wheat straw pellets, which were processed after extrusion with a Ca(OH)2 solution at rate of 100 kg CaO(t-1, 40% more than the control experiment.