Integrated anaerobic co-digestion of municipal organic waste to biogas using geothermal and CHP plants: A comprehensive analysis

In this study, the usage and comparison of two approaches comprising (1) geothermal energy (GE) system and (2) combined heat and power system with reciprocating engine (CHPRE) as a driver, is investigated in distinctive scenarios to provide heat demands of anaerobic digestion process. To make a precise analysis, a collection of reasonable assumptions, data analysis, and simulations have been conducted to find out the scale of the power plants whether geothermal energy is a proper approach to be utilized for heating purposes in the anaerobic digestion process. This study presents a comprehensive analysis which contains various cases of study ranging from electricity production to economic issues. Results of the analysis have proved that although the GE approach has some downsides, it is widely favorable to CHPRE approach through some of the subjects of analysis. Applying the GE approach for heat demands of anaerobic digestion saves a considerable portion of biogas, which ranges from 22% to 24.8% of the produced biogas in digesters. Another important discovery is that usage of the GE approach results in a reduction of greenhouse gases emissions up to 66%. Moreover, financial results indicate that the usage of GE mitigates the initial costs of an anaerobic digestion unit ranging between 23% and 25% based on the scenarios. GE approach is also more economical as the power plant of anaerobic digestion since it has less discounted payback period than the CHPRE approach, and this advantage is between 11 and 47 years depending on the scenarios from both methods.