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Integrated biogas utilization has experienced a rapid development in recent years in rural China, for both renewable energy production and waste treatment. On the basis of a modified Ecological Footprint (EF) indicator, this paper provides a comprehensive assessment of a “pig–biogas–fish” system, a typical household integrated biogas-utilization system in southern China, by focusing on the resources consumed and produced within the system. The method of Emergy Environmental Footprint as a combination of EF and emergy accounting is introduced to quantify the sustainability of the overall biogas system and its three subsystems. Results reveal that the resource use intensity of the “pig–biogas–fish” system, defined as the ratio of footprint investment to footprint delivered, is 0.48. Compared with the conventional animal husbandry system, the “pig–biogas–fish” system proves to be of higher sustainability. And the findings have essential policy making implications supportive to a further spread of integrated biogas-utilization modes in rural areas. [ABSTRACT FROM AUTHOR]

With the expansion of urbanization in China, the integrated biogas-utilization system has gained its popularity for both renewable energy production and multi-level utilization of organic waste. To appraise the ecological performance of the integrated biogas system, systematic accounting is undertaken for an integrated “pig–biogas–fish” system in Hubei province, China. Based on Odum's concept of embodied solar energy as a unified measure for environmental resources, human labors and purchased goods, a set of emergetic indicators are employed to quantify the system sustainability. The results reveal that in a 20-year designed lifetime scenario, 94.69% of the total emergy inputs for the “pig–biogas–fish” system are attributed to purchased social resources. Three kinds of products, namely pig, biogas, fish are taken into consideration, and transformity of the “pig–biogas–fish” system is calculated as 1.26E + 05 seJ/J. Compared with the Chinese conventional agriculture system, the integrated biogas system shows a higher sustainability. Given that most biogas systems have a lifespan less than 20 years, for the “pig–biogas–fish” system, six other scenarios with different lifespans are studied to investigate the impact of the lifespan on sustainability. The findings suggest that the “pig–biogas–fish” system should be well operated for at least 8 years to prove its advantage in ecological economy over the conventional agriculture system. This has essential policy implications that local government should strengthen subsequent management on biogas production to extend the practical service life of the biogas system. [ABSTRACT FROM AUTHOR]