Construction and Economic Analysis of a Biogas Fermentation Multi-Energy Complementary System

Amid the global renewable energy transition and rural revitalization, efficient organic waste use is critical for circular economy and carbon neutrality—core pillars of global sustainability. This study addresses unrecovered biogas slurry waste heat and biomass boiler thermal instability in Lindian County’s agricultural waste project. Using a small-scale experiment with MATLABR2023a simulations, it analyzed key parameters’ influence on mesophilic dry anaerobic fermentation, validating waste heat recovery and heat source optimization—measures closely aligned with sustainability goals. A novel multi-energy system for biogas fermentation integrated solar, biomass, and carbonization furnace residual heat. Experiments and simulations assessed heat demand, heating allocation, and economic performance. Findings showed 17-fold peak–valley heat demand fluctuations with seasonal patterns; 200 MJ load increments captured system dynamics. The multi-energy system outperformed single-energy setups in investment and operational costs. Optimal cost-effectiveness came with a 50%, 35%, and 15% heat load distribution among the solar, charcoal furnace, and biomass subsystems, cutting operational expenses. Results provide a robust framework for optimized biogas project design, aiding cost reduction, competitiveness, and circular economy and supporting China’s energy transition, rural revitalization, and the achievement of the sustainable development goals.