• Energy Research

Abstract As a physical assessment of the sustainability of the China society, presented in this paper is an exergy-based systems account for resources use and environmental emissions of the China society in 2006 as the most recent year with statistics availability. Exergy analysis is applied to elucidate the resources flows from the natural environment into the society, between other countries or regions and the society, between the sectors of the society, and the emissions outflows into the natural environment from different sectors. For the China society broken down into seven sectors (i.e., extraction, conversion, agriculture, industry, transportation, tertiary and households) as one of the most complicated cases, systems account of environmental emissions as greenhouse gases and “three wastes” is carried out for the first time, combined with an updated resources account. The total societal exergy consumption amounts to 101.1 EJ, of which 93.6% is due to resources use accounted as 94.6 EJ, of which 23.2% is by the industry sector, 22.8% by conversion, 20.4% by households, 12.3% by agriculture, 9.0% by tertiary, 6.9% by extraction and 5.4% by transport, and 6.4% due to environmental emissions accounted as 6481.6 PJ, including greenhouse gas emissions of 5706.1 PJ, with the highly remarkable fraction of 49.05% from CH4 of the same importance as 50.91% from CO2 and only 0.04% from N2O, and “three wastes” emissions of only 775.5 PJ. The extraction sector is shown as the leading emitter with 32.6% of the total emissions, followed by the industry with 20.0%, agriculture with 17.3%, and conversion sector with 16.8%. To characterize the network performance in context of environmental resources from a systems ecological perspective, exergy-based ecological efficiency and resources conversion coefficient are found as 88.8% and 91.3% for the extraction sector, 29.0% and 30.0% for the conversion sector, 31.5% and 33.5% for the agriculture sector, 34.8% and 36.1% for the industry sector, 16.3% and 17.3% for the transportation sector, 38.4% and 38.5% for the tertiary sector, and only 1.3% and 1.3% for the households sector, respectively. Comparisons with other societies and with China society in previous years are made to further illustrate the physical sustainability of the societal system on the international and development horizons.

The thermodynamic concept of chemical exergy is introduced for water quality evaluation, to develop unified objective indicators in contrast to conventional indicators characteristic of subjectivity. While a quantity termed specific standard chemical exergy based on the global reference substances is used to evaluate the standard water quality, an indicator as specific relative chemical exergy with reference to a spectrum of substances associated with some specified water quality standard is developed for practical water quality evaluation, with related concepts of carrying deficit and carrying capacity well embodied in exergy terms. Based on the data collected in the GEMS/WATER project, water qualities of 72 rivers and 24 lakes over the world are evaluated, as a detailed case study to illustrate the adaptability of the chemical exergy based indicators for water quality evaluation.

Abstract Presented in this paper is an overview of energy consumption in rural China in view of temporal and spatial variations. Characterized by steadily decreased proportion of biomass use and increased percentage of coal and electricity use, coal and biomass are still the major energy sources in rural areas, accounting for nearly 80% of the total rural energy consumption. Moreover, the energy consumption varies significantly across provinces both in total sum and by fuel types due to diversities of geographic features, economic development levels and local energy source availability. Three statistical groups are clustered associated with quantitative change and structural change, exhibiting evident transition from noncommercial energy pattern to commercial energy pattern. Much more work need to be done to cope with the forthcoming dramatic changes associated with booming rural economy and newly released policy from the points of both energy security and environmental pressure in China.

Abstract A unified evaluation integrating various forms of energy sources and natural resources, products and services, and imports and exports is carried out systematically at the national scale for the booming Chinese economy 1978–2005, based on the ecological measure of solar emergy. The development of the economy is shown heavily dependent on the consumption of nonrenewable natural resources. Of the total resources use, the indigenous resources contribute the most, along with the increasing imports of nonrenewable resources. The development of the Chinese economy is characterized with the recovery stage during 1978–1981, transformation stage during 1981–1991, steady growth stage during 1991–2000, and accelerated increase stage after 2000, with specific distinctive systems indications.

a b s t r a c t For China as the world's third largest ethanol producer, greenhouse gas emissions of corn-ethanol pro- duction are analyzed for the entire processes of corn cultivation, ethanol conversion and wastewater treatment. Besides the greenhouse gas emissions associated with primary fossil energy use embodied in all the energy and material flows into corn-ethanol processes, the increased greenhouse gas emis- sions due to soil tilling and erosion, methane emissions from burning corn stalk and the wastewater are carefully estimated. For per kg corn-ethanol produced, a net positive greenhouse gas emission of 11.61 kg CO2-equiv. is revealed corresponding to a striking increase of 5.99 times in greenhouse emis- sions when corn-ethanol is used as a substitute for gasoline. Moreover, ethanol production might lead to a highly remarkable 98% GHG reduction compared to gasoline by an ecological systems design of the pro- duction chain with constructed wetland, biogas and combined heat and power fully employed, though existing technology is illustrated to be far from carbon neutral under various allocations for co-products.

Abstract This study presents a network simulation of the global embodied energy flows in 2007 based on a multi-region input–output model. The world economy is portrayed as a 6384-node network and the energy interactions between any two nodes are calculated and analyzed. According to the results, about 70% of the world’s direct energy input is invested in resource, heavy manufacture, and transportation sectors which provide only 30% of the embodied energy to satisfy final demand. By contrast, non-transportation services sectors contribute to 24% of the world’s demand-driven energy requirement with only 6% of the direct energy input. Commodity trade is shown to be an important alternative to fuel trade in redistributing energy, as international commodity flows embody 1.74E + 20 J of energy in magnitude up to 89% of the traded fuels. China is the largest embodied energy exporter with a net export of 3.26E + 19 J, in contrast to the United States as the largest importer with a net import of 2.50E + 19 J. The recent economic fluctuations following the financial crisis accelerate the relative expansions of energy requirement by developing countries, as a consequence China will take over the place of the United States as the world’s top demand-driven energy consumer in 2022 and India will become the third largest in 2015.

The resource consumption of the Chinese society is investigated by ecological footprint (EF) as an aggregate indicator. Based on the theory of ecological thermodynamics, a modified calculation of ecological footprint termed as exergetic ecological footprint (EEF) in contrast to the conventional one is performed and related overall trends of the Chinese society are analyzed. The annual policy for the individual sector is described in detail corresponding to the variations of the EF and EEF components. Comparison of the conventional EF and the EEF is outlined. The EF intensity and EEF intensity are also presented to depict the resource consumption level corresponding to unit economic output. Finally, EEF is suggested to serve as a supplemented indicator of EF towards illustrating the productions of the resource, environment, population, and thereby reflecting the ecological overshoot of the general ecological system.

Abstract Fossil energy burning is one of the most important sources of atmospheric mercury emissions, which poses great threats to both environment and human health. Urban regions are dominant energy consumers; however, the information on the resultant mercury emissions in urban regions has been lacking. Therefore, in light of environmentally extended input–output analysis, this study used Beijing as a case to investigate embodied (direct plus indirect) mercury emissions induced by fossil energy consumption in urban regions. The results show that embodied mercury emissions caused by Beijing׳s fossil energy consumption amounted to 5.86 tonnes, which is over 1.5 times the direct emissions, indicating that the conventional direct emission accounting method will lead to significant emission leakage. Coal combustion takes the major responsibility for energy-related mercury emissions. As a net importer of embodied mercury emissions, Beijing avoided a considerable amount of mercury emissions. Sectors like construction which play key role in embodied mercury emissions are also identified in this study. To comprehensively reduce mercury emissions from energy consumption the Beijing government should devote efforts to develop clean coal technology and high efficiency mercury removal devices, shift investment from infrastructure construction to tertiary industries and optimize green consumption among the residents, especially the urban residents. The method and findings may be useful for compilation of overall urban mercury emissions inventory as well as have important policy implications for global cities to control mercury emissions.

Abstract The livestock sector represents major challenges to safeguarding environmental integrity. Therefore, we comprehensively analyze twelve environmental impacts of the livestock sector from 1995 to 2016 and project them until 2030. Our findings show livestock production impacts land resources, freshwater use, energy demand, climate change, nitrogen and phosphorus flows, and atmospheric aerosol loading. The livestock sector alone will likely exceed the planetary boundary of GHG emissions by 2030 and pose threats to other boundaries. Continuation of the current patterns of livestock production will also preclude limiting global warming well below 2°C, as the Paris Agreement aims. The impacts from the livestock sector are unevenly distributed worldwide, with spillover effects from developed to developing regions. Livestock footprints, i.e., environmental impacts of the livestock sector, are concentrated in emerging economies of Asia & the Pacific and South America. In contrast, per-capita livestock footprints are highest in developed economies such as the US and the EU. The livestock sector represents targeted opportunities for climate change mitigation and global environmental change. Adopting a less meat-based diet can reduce livestock footprints.