Contribution of Biomethane from Different Substrate into Energy Sustainability and Greener Economy

The economic development depends on a large extent on energy. With the fast depletion of fossil fuels which has an impact on environmental degradation and the global climate change, the commercial production of biogas and other alternative energy gives a good drive for the development of the green/circular economy. The removal of CO₂, H₂S, and nitrogen gas from raw biogas is a necessary step before the gas can be injected in to the gas grid. The study aimed at using high temperature and pressure process as an alternative to conventional upgrading processes (water scrubbing, pressure swing adsorption, chemical and physical scrubbing) of biogas from substrates. The carbon/nitrogen (C/N) ratio of cow dung was found to be 21.12 and grass clippings to be 64.87. Laboratory experimental data from 500 ml batch anaerobic digester operating at a mesophilic temperature of 37 °C and pH of 7.7 was used. The presented process revealed that from a mixture of cow dung and grass clippings (ratio 25:35 g), a product purity of 91.3 mol% CH₄ was attainable by combining absorption (using a mixture of methyl diethanolamine, water, and calcium hydroxide), flash separation, and internal heat recovery. The process captures CO₂ in liquid form with a purity of 99.94 mol% as a by-product. The proposed hybrid process could serve as an alternative to conventional upgrading techniques due to its energy efficiency and environmentally friendly process of CO₂ removal.