ASSESSMENT OF ENERGY CONSUMPTION IN BIOMETHANE PRODUCTION

Abstract

In global practice, the development of biomethane production and use is related to the increasing need to switch to more sustainable energy in order to reduce carbon dioxide (CO₂) emissions and dependence on traditional energy sources. Biomethane production from waste contributes to the implementation of the principles of the circular economy, promoting resource efficiency, and reducing waste. During anaerobic digestion, biogas is formed from biodegradable raw materials, which usually contains 50–65% methane (CH₄), 35–50% CO₂ and a small, but technologically significant amount of hydrogen sulfide (H₂S), water vapor and other impurities. Biogas with such a composition cannot be directly used as fuel for vehicles or injected into natural gas systems. Therefore, biogas formed during anaerobic digestion must be cleaned using primary and secondary cleaning technologies. This work has conducted a study that determined the energy costs incurred during biomethane production and storage. The object of the study was an operating biogas power plant with an annual biogas production potential of 1.26 million m³ of biogas or 0.75 million m³ of biomethane, with an energy value of 7.5 GWh. The study found that in the primary purification processes of biogas, depending on the selected method and technology, energy consumption ranges from 113 to 314 thousand kWh to clean the biogas from water vapor, dust and H₂S. In the secondary purification processes, during which CO₂ is removed and the gas is compressed to the pressure required for transportation, the power plant would incur 491 thousand kWh of energy consumption if the membrane carbon dioxide separation method was selected. After assessing the entire biomethane production value chain, from 604 to 805 thousand kWh of energy would be consumed for primary and secondary purification and compression, or from 8.05 to 10.7% of the energy value of the produced biomethane.