• Energy Research

It is commonly assumed that renewable energy based systems have the potential to mitigate greenhouse gas emissions and save fossil energy from the grid. Nevertheless, any energy conversion systems need extra energy to deliver energy into society. It is necessary to estimate the total direct and indirect fossil energy cost and associated greenhouse gas emissions by any system over its entire life cycle. For the first MW class solar tower power plant in China, nonrenewable energy cost and greenhouse gas emissions are accounted respectively as 0.95 MJ/MJ and 0.04 kg CO2-eq/MJ during its expected 20 years of operating life, corresponding to a net nonrenewable energy saving of 3.92E+08 GJ and greenhouse gas emission mitigation of 4.17E+04 tonne CO2-eq compared to conventional thermal power systems in China.

Abstract For the greenhouse gas (GHG) emissions in China, little attention has been given to CH4 emissions and related emission mitigation. This paper presents a detailed bottom-up estimation and comparison analysis of China's CH4 and CO2 emissions for the first time. China's CH4 emissions are shown with comparable importance to the CO2 emissions at the national and regional levels. The national total CH4 emission in 2008 amounts to 39 Tg, equivalent to about 1/8, 1/3 and 3/5 of the total CO2 emission by the 100-year global warming potential (GWP) factor, the 20-year GWP factor and the global thermodynamic potential factor, respectively. Increasing CH4 emissions could compromise China's efforts to mitigate its GHG emissions. In contrast to energy-dominated emission pattern for CO2, the major sources of China's CH4 emissions are coal mining, enteric fermentation, rice cultivation and waste management. Meanwhile, there exists a large gap between the eastern coastal regions and the western and central inland regions in the emission magnitude and emission intensity for CH4 and CO2, with different mitigation flexibilities. Reducing CH4 emissions should be integrated into the national and regional policies for GHG emission mitigation. In some central and western regions such as Shanxi, Henan, Sichuan, Guizhou, Qinghai and Tibet, the inclusion of CH4 emission intensity reduction can be more cost-effective than only setting a target for CO2 emission intensity to reduce the regional GHG emission intensity.

Abstract To facilitate the aggregation of both quantity and quality of waste emissions, the concept of chemical exergy combining the first and second laws of thermodynamics is introduced for a unified account of gas pollutants and greenhouse gases, by a case study for the Chinese transportation system 1978–2004 with main gas pollutants of NO, SO 2 , CO and main greenhouse gases of CO 2 and CH 4 . With chemical exergy emission factors concretely estimated, the total emission as well as emission intensity by exergy of the overall transportation system and of its four modes of highways, railways, waterways and civil aviation are accounted in full detail and compared with those by the conventionally prevailing metrics of mass, with essential implications for environmental policy making.

Abstract Energy-related greenhouse gas emission is emerging as a major concern to be addressed. The structure of the urban economy, as the center of energy consumption, has therefore arrested widespread attention on the globe. By employing input–output model as a dynamic approach to simulate urban metabolism processes, structure decomposition analysis is undertaken as a unified framework to clarify the underlying reasons behind increment of GHG emission in Beijing with the latest data. The eight components classified into three categories of changes, i.e., intensity structure, production linkage, and final demand are investigated from the perspectives of comparative contribution and hierarchical structure, identifying the crucial components for total changes and the characteristics within each category at the aggregated and sectoral levels. The asymmetries of contribution across the components and the essential implications for policy makers are presented.

An overview of energy consumption pattern by available data and the analysis of some relevant aspects of energy policy in rural China are presented in this paper. The most obvious trend is the steady decreased proportion of biomass use, from 70.79% to 30.95%, and increased percentage of coal and electricity use, whereas coal and biomass are the major energy sources in rural areas, accounting for more than 70% of the total rural energy consumption even in 2007. Moreover, the energy consumption varies tremendously across provinces both in total and by fuel types, due to diversities of geographic features, economic development levels and local energy source availability. The rural energy policy and strategy of China have been somewhat unique, characterized by multi-resources, multi-assortments and multi-distribution channels. Some evident transition features can be found for both the rural energy consumption structure and the rural energy policy during the concerned period, that is, from noncommercial energy to commercial energy and from just satisfying energy demand to multi-purposes considering more factors as rural development and environmental protection.

This study presents an ecological analysis of Chinese agriculture for the period from 1980 to 2000, on the basis of Odum's well-known concept of emergy in ecological economy. Emergy analysis methods are explained, illustrated and used to diagram the agro-ecosystem, to evaluate environmental and economic inputs and harvested yield, and to assess the sustainability of the Chinese agriculture as a whole. Detailed structure of the input/output and system indicators are examined from a historical perspective for the contemporary Chinese agriculture in the latest two decades after China's Reform and Open in the late 1980s. Temporal variation of indices such as increasing environmental load ratio (ELR), decreasing emergy self-support ratio (ESR) and decreasing emergy yield ratio (EYR) illustrate a weakening sustainability of the Chinese agro-ecosystem characteristic of profound transition from a self-supporting tradition to a modern industry based on non-renewable resource consumption.

Comprehensive inventory of cities' greenhouse gas emissions (GHG) is the basis for cities to make appropriate mitigation plans. However, previous studies on cities' GHG emissions consider emissions occurring within the city boundary (Scope 1) and out of boundary electricity emissions (Scope 2), but neglect indirect emissions associated with commodities consumed by cities (Scope 3), resulting in emission leakage. To cope with this problem, a systematic accounting covering all 3 scopes is presented in a case study of Macao for the years 2005–2009, based on the latest embodied emission intensity databases for China and for the world. The results show that total emissions are dominated by indirect emissions mainly embodied in imports, which is 3–4 times direct emissions during the period concerned. It is verified that accounting under Scopes 1 and 2 cannot capture the full picture of cities' emissions, especially cities like Macao which are dominated by service industry and inevitably sustained by massive materials and services from other regions. Our study suggests that Macao should adjust its current GHG mitigation policies which consider only its emissions occurring within its border, as Macao is a net GHG emissions importer. This work is the first assessment of Macao's embodied GHG emissions.

Abstract Nonrenewable energy cost is accounted for the believed renewable biofuel of corn-ethanol in China. By a process-based energy analysis, nonrenewable energy cost in the corn-ethanol production process incorporating agricultural crop production, industrial conversion and wastewater treatment is conservatively estimated as 1.70 times that of the ethanol energy produced, corresponding to a negative energy return in contrast to the positive ones previously reported. Nonrenewable energy cost associated with wastewater treatment usually ignored in previous researches is shown important in the energy balance. Denoting the heavy nonrenewability of the produced corn-ethanol, the calculated nonrenewable energy cost would rise to 3.64 folds when part of the nonrenewable energy cost associated with water consumption, transportation and environmental remediation is included. Due to the coal dominated nonrenewable energy structure in China, corn-ethanol processes in China are mostly a conversion of coal to ethanol. Validations and discussions are also presented to reveal policy implications against corn based ethanol as an alternative energy in long term energy security planning.

The resource consumption of the Chinese society from 1981 to 2001 is investigated using ecological footprint (EF) and emergetic ecological footprint (EEF). The latter is a newly development modification of ecological footprint based on ecological thermodynamics. Individual sectors in society are described in detail corresponding to the EF and EEF components based on different views of ecological production. The EF and EEF intensities are also presented to depict the resource consumption level corresponding to unit economic output. Finally, EEF is suggested to serve as a modified indicator of EF to illustrate the resource, environment, and population activity, and thereby reflecting the ecological overshoot of the general ecological system.