Study on preliminary economic availability of electric energy use from drying bed sludge by biogas from anaerobic digestion and incineration in Brazil

Abstract

This study aimed to analyze electrical energy generation derived from anaerobic biogas digestion and the incineration of drying bed sludge (DBS) from an Upflow Anaerobic Sludge Blanket (UASB) reactor using samples from a Wastewater Treatment Plant in Itajubá, Minas Gerais, Brazil. Some data including Automatic Methane Potential Test System (AMPTS II) were obtained from Moni Silva et al. (2021). An experimental apparatus comprised of a biodigester and gasometer was elaborated to conduct quali-quantitative evaluation of DBS biogas generation. Economic analysis was conducted on the Thermal Power Plant (TPP) electrical generation system, powered by biogas with data from i. experimental apparatus, and ii. AMTPS, as well as an incineration power plant. Greenhouse Gas (GHG) emission reductions were assessed. The results demonstrate that TPP from biogas with biodigestion without temperature control (experimental apparatus) was not economically feasible, even when considering ICMS tax exemptions; nonetheless, it would be capable of mitigating GHG emissions. Biodigestion with temperature control enabled TPP projects economic viability with payback in 20 years (178.67 kW, 9% IRR) considering a minimum population of 3,000,000 inhabitants. In all cases, the ICMS taxation reduces project feasibility.