Sustainability and future alternatives of biogas-linked agrosystem (BLAS) in China: An emergy synthesis

The biogas-linked agriculture has experienced a rapid development in recent years in rural China, which serves both as part of the country's developmental strategies of cleaner energy and an important reaction to sustainable agriculture call. This paper provides an overview of the economic and environmental performance of biogas-linked agrosystem (BLAS) in China by focusing on efficiency, emission mitigation effect and sustainability. An emergy synthesis combing emergy accounting and emergetic ternary diagram are utilized to evaluate the overall BLAS and its four subsystems (i.e., planting subsystem, breeding subsystem, aquaculture subsystem and biogas subsystem) in terms of current status and future development. Our findings indicate that despite a high energy transformity at system scale and a great dependence on economic input, BLAS advantages itself with high biogas production efficiency and significant emission mitigation effect. Furthermore, the sustainability zone analysis shows that the overall BLAS, planting and aquaculture subsystems maintain medium-term sustainability under all policy scenarios, despite the fact that breeding and biogas subsystems stay in an unsustainable situation due to their relatively severe environmental load. Among all the studied future options, continual biogas construction and effective technological revolution instead of expanding investment in traditional agriculture are preferable routes to further improve the system performance. Last but not least, emissions mitigation, energy efficiency and system sustainability are unveiled to be positively correlated within BLAS, which entitles it a promising energy alternative to enhance biogas energy utilization in the local agriculture in face of today's energy crisis.