Heliothermal Conversion of Municipal Household Waste into Biogas: A Sustainable Approach for Environmental Protection and Resource Recovery

Abstract

The current global energy crisis and the growing threat of climate change necessitate significant innovation within the energy sector, as well as a swift transition to a green economy in both developed and developing nations. In this context, thermal power plants (TPPs) remain one of the main contributors to greenhouse gas emissions due to their dependence on fossil fuels, despite having traditionally formed the basis of electricity generation. Consequently, international and national energy strategies are focusing more and more on introducing technologies that reduce the environmental impact of TPPs, increase the efficiency of heat-to-energy systems, and cut emissions. Significant attention is being paid to adapting to climate-related challenges, decarbonising thermal energy infrastructure, and developing sustainable 'green growth' models that integrate renewable energy sources, waste-to-energy technologies, and advanced heat efficiency technologies into power generation systems. The depletion of traditional fossil fuel reserves, coupled with the environmental problems caused by their combustion, has led to a surge in global interest in environmentally friendly, waste-free energy technologies. At the same time, the world’s population is growing rapidly and consumer production is expanding, leading to a significant increase in municipal solid waste generation and putting pressure on land and water ecosystems. This study aims to develop and evaluate a sustainable method of recovering waste gas from household solid waste through heliothermal (solar-assisted) anaerobic processing. The proposed system incorporates solar energy into the degradation process of waste, thereby reducing the need for conventional fossil fuels and minimising environmental emissions. A pilot-scale heliothermal reactor with a working volume of 1 m³ was designed. It features a dual-layer structure measuring 1.2 × 1.0 m, as well as a mechanical mixer, filter, gas holder and transparent top cover connected to a solar air heater (SAH). Experimental results under thermophilic conditions (50÷55°C) showed that 469 kg of household waste produced 95 m³ of waste gas and 365 kg of biogas. Introducing water and coal powder at a ratio of 3:1 increased waste gas generation efficiency by up to 138.9%. Furthermore, using previously fermented substrates as inoculum accelerated the onset of anaerobic digestion by 2–3 days. The developed heliothermal processing system offers a sustainable approach to waste treatment that reduces land pollution and enhances the recovery of renewable energy in municipal waste management.