Assessment of the Possibilities for the Use of Selected Waste in Terms of Biogas Yield and Further Use of Its Digestate in Agriculture

Abstract

The utilization of municipal waste and sewage sludge as a source of energy is technically very difficult due to high variability of their physical and chemical properties. The aim of this study was to evaluate the efficiency of the conversion of biomass contained in the whitewater fraction of municipal waste and sewage sludge by means of methanogenesis. The second objective was to assess the chemical composition of the digestate in the context of its use for fertilizer purposes. The whitewater fraction of municipal waste and sewage sludge was subjected to methanogenesis under static experimental conditions, according to DIM DIN 38414 methodology. The methanogenesis of concentrated substrates used in agricultural biogas plants was taken as a reference to evaluate the efficiency of the process. The organic fraction of the municipal waste was characterized by approximately 30% lower value of the soluble COD, with a comparable level of total COD compared to other materials. The total biogas yield, i.e., 404 dm3 per 1 kg of dry weight of the batch, was measured in the facility with sewage sludge. In COD value, this is 0.232 dm3·g O2 COD. In the case of corn, these values were, respectively, 324 dm3 and 0.193, and for the organic sub-sieve fraction of municipal waste, 287 dm3·kg−1 dw or 0.178 dm3·g O2 COD, respectively. The type of fermented material did not affect the intensity of biogas production. The maximum level of biogas production occurred between the 13th and 15th day of the process. The digestate obtained in the process of methanogenesis of corn silage and the organic fraction of municipal waste was characterized by good parameters in terms of possible use for fertilization purposes.