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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]

Hydropower fuels the overall societal development by contributing a notable proportion to the whole global power generation. Although much attention has been paid to the development of hydropower, few of them attempted to gather global systematic data and conduct a large-scale review of scientific studies. In such situation, a bibliometric approach is employed in this study to quantitatively evaluate global scientific research on hydropower sustainable development, with a long time span ranging from 1991 to 2012. 434 publications in accordance with the search criteria from Science Citation Index Expanded (SCI-Expanded) database are analyzed statistically, and assessments on research development, current trends, and future directions are conducted in regard to eight categories. By synthetically analyzing the keywords, the dominant hotspots of hydropower sustainable research could be concluded as “Turkey”, “Eco-”, “Small hydro-”, and “Fish”. Along with a comparable number of publications to the United State, the keyword “Turkey” has exhibited a notable increase since 2000, revealing its predominance in the research on the hydropower sustainable development. Increasing attention has also been directed to the prefixes “Small hydro-” and “Eco-” in recent years. The keywords related to fish are identified from the keyword analyses as well, suggesting that the significance of fish studies has been recognized by researchers. Given the trend during the past several years, these topics are likely to become primary research focuses in the coming period. [ABSTRACT FROM AUTHOR]