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

Amid global renewable energy transition and rural revitalization, efficient organic waste use is critical for circular economy and carbon neutrality. 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 MATLAB simulations, it analyzed key parameters' influence on mesophilic dry anaerobic fermentation, validating waste heat recovery and heat source optimization. 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 50%, 35%, 15% heat load distribution among 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, supporting China’s energy transition and rural revitalization.