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Technical–Economic Analyses of Electric Energy Generation by Biogas from Anaerobic Digestion of Sewage Sludge from an Aerobic Reactor with the Addition of Charcoal
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Cornélio Ribeiro Garcia, Michael Danilo Vargas Hincapie, Regina Mambeli Barros, Maxi Estefany Huamán Córdova, Hellen Luisa de Castro e Silva, Ivan Felipe Silva dos Santos, Electo Eduardo Silva Lora, Geraldo Lucio Tiago Filho, João Victor Rocha de Freitas, Adriele Maria de Cássia Crispim and Aylla Joani Mendonça de Oliveira Pontes
Methane 2024, 3(4), 595-616; https://doi.org/10.3390/methane3040034 (registering DOI) - 2 Dec 2024
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Abstract
This study aimed to obtain the energy recovery potential of the biogas produced from anaerobic digestion (AD) of the sludge from a wastewater treatment plant (WWTP), including the use of biochar as an additive for substrate co-digestion and catalyst for methane production. We
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This study aimed to obtain the energy recovery potential of the biogas produced from anaerobic digestion (AD) of the sludge from a wastewater treatment plant (WWTP), including the use of biochar as an additive for substrate co-digestion and catalyst for methane production. We carried out the following steps: chemical–physical laboratory analyses of sludge samples; the building, operation, and monitoring of an experimental prototype of a batch bioreactor of 2.5 L for the AD of the sludge (with and without the addition of charcoal); qualitative measurements of biogas; the study of charcoal morphology; and the projection of useful energy generation from the AD sludge after treatment. A study on the economic viability and avoided greenhouse gas (GHG) emissions was performed based on the experimental results. The substrate showed alterations in all the physicochemical parameters evaluated after AD, such as a reduction of 35% in the biochemical oxygen demand (BOD) analysis; the experiment carried out using biochar showed positive results regarding the speed of CH
4 production and a greater potential for energy recovery. Enterprises from 2000 kW onwards would present an internal rate of return (IRR) equal to or higher than the minimum attractiveness rate (MAR) of 15%. The USD 95.28/MWh tariff presented economic feasibility for the studied scenarios. WWTPs that produce enough sludge to generate power of 2000 kW would need to process the waste of 117,200 inhabitants with charcoal addition and 136,000 without charcoal. It would be possible to avoid the emission of 2307.97 tCO
2/year (2000 kW). According to the results obtained, this study revealed that using alternative energies based on anaerobic digestion and biochar can generate positive results regarding methane production, and its application as an energy source in a WWTP proved to be economically viable at a specific level of power production.
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