Techno-economic analysis of a chemical looping combustion process for biogas generated from livestock farming and agro-industrial waste

Abstract

Biogas is a renewable fuel that is generated from the decomposition of organic matter through the process of anaerobic digestion. The compound that provides biogas with its energy value is CH4, which accounts for between 40% and 75% of the gas, with CO2 being the other main component of this fuel. Although the biogas valorization process is carbon neutral, the overall process can become carbon negative with the application of CO2 capture technologies, such as chemical looping combustion (CLC). This work presents a techno-economic analysis of a 5 MWth plant for the generation of biogas from livestock farming and agro-industrial waste to produce electricity + heat or heat only (base cases), or for further treatment in a CLC unit (CLC cases), where the captured CO2 is converted into a raw material, e.g. for the production of greenhouse crops. Results from the comparative study of five different oxygen carriers used in CLC are also presented.The profitability of the base cases was evaluated by means of the Levelized Cost of Electricity (LCOE) and Levelized Cost of Thermal Energy (LCOTE) metrics, whereas the economic performance of the CLC cases was measured by the Levelized Cost of CO2 (LCOCO2). LCOE gave a value of €139.90/MWh for the base case, and LCOTE was €56.50/MWh for the modified base case, where biogas was combusted in a boiler to produce only heat. With regard to the CLC cases, LCOCO2 values ranged between €148.60 per tonne for a highly reactive, synthetic Cu-based oxygen carrier and €177.10 per tonne for ilmenite.Finally, by comparing the economic results obtained in this work with those found in the literature for conventional biogas production plants and greenhouse crop production processes, it can be concluded that the implementation of CLC technology in biogas plants has the potential to become a profitable and environmentally sustainable option for the valorization of organic waste because the CO2 generated in the fuel reactor of the CLC unit can be considered a marketable, high value-added product for the niche market of the greenhouse farming of horticultural crops.