Reconstruction of a closed-loop ecological cycle system anchored by large-scale load-balancing biogas and its economic viability assessment

Biogas can be used for complementary load-balancing with renewable intermittent power, thus maintaining overall energy output stability. However, biogas load balancing is typically used in small-scale distributed energy systems, constrained by factors such as technology and land requirements, making it challenging to scale up. Therefore, this study proposes a closed-loop ecological cycle system, where biogas provides load leveling support for large-scale intermittent power sources in desertified regions dominated by animal husbandry. The biogas slurry and residue produced are used for land restoration and subsequent cultivation of high-quality economic crops, with the resulting straw used for the next round of biogas production. This study conducts an economic assessment of the aforementioned system and analyzes a case study of a load-balancing biogas project in Northwest China. Accounting results indicating that the system's net present value is 0.108 million yuan/m³, internal rate of return is 0.60%, and payback period is 22 years. Additionally, sensitivity backward deduction analysis identified the reasonable value ranges for key system parameters. According to the results, we offer management recommendations to promote the proposed system, supporting innovative biomass energy utilization and enhancing renewable energy stability.<i>Implications</i>: This research introduces a novel closed-loop ecological cycle system that integrates large-scale peak-shaving biogas with renewable energy sources, offering a sustainable solution for enhancing energy stability and environmental sustainability in desertified areas. The study's economic evaluation reveals the critical role of ecological restoration costs in the overall viability of such systems, indicating the necessity for policy support to make them economically attractive. Our findings suggest that targeted subsidies, based on the quantified ecological benefits, are essential for incentivizing the adoption of this model. By providing specific conditions under which the system is economically feasible, this work informs policymakers on how to design effective incentive structures, thereby promoting the wider application of biogas and contributing to the goals of sustainable development and climate resilience. The research underscores the importance of integrating economic and ecological considerations to achieve long-term sustainability, making it a valuable reference for future energy policies and practices.