• Energy Research

Abstract China has intensified the extension of family-sized biogas digesters with the Chinese National Standard in the 1990s. However, such biogas digesters have not performed well. In order to improve the current National Standard biogas digesters, the authors have designed, tested, and demonstrated 200 improved biogas digesters in a semi-arid region of China over the past 7 years and conducted a comparative study between the improved biogas digesters and traditional ones. Conclusions were drawn from the research that the improved biogas digesters are significantly better than the traditional ones in several aspects, such as less water consumption and more gas productivity.

Abstract. Deposition and accumulation of light-absorbing carbonaceous aerosol on glacier surfaces can alter the energy balance of glaciers. In this study, 2 years (December 2014 to December 2016) of continuous observations of carbonaceous aerosols in the glacierized region of the Mt. Yulong and Ganhaizi (GHZ) basin are analyzed. The average elemental carbon (EC) and organic carbon (OC) concentrations were 1.51±0.93 and 2.57±1.32 µg m−3, respectively. Although the annual mean OC ∕ EC ratio was 2.45±1.96, monthly mean EC concentrations during the post-monsoon season were even higher than OC in the high altitudes (approximately 5000 ma.s.l.) of Mt. Yulong. Strong photochemical reactions and local tourism activities were likely the main factors inducing high OC ∕ EC ratios in the Mt. Yulong region during the monsoon season. The mean mass absorption efficiency (MAE) of EC, measured for the first time in Mt. Yulong, at 632 nm with a thermal-optical carbon analyzer using the filter-based method, was 6.82±0.73 m2 g−1, comparable with the results from other studies. Strong seasonal and spatial variations of EC MAE were largely related to the OC abundance. Source attribution analysis using a global aerosol–climate model, equipped with a black carbon (BC) source tagging technique, suggests that East Asia emissions, including local sources, have the dominant contribution (over 50 %) to annual mean near-surface BC in the Mt. Yulong area. There is also a strong seasonal variation in the regional source apportionment. South Asia has the largest contribution to near-surface BC during the pre-monsoon season, while East Asia dominates the monsoon season and post-monsoon season. Results in this study have great implications for accurately evaluating the influences of carbonaceous matter on glacial melting and water resource supply in glacierization areas.

Carbonaceous aerosols (CAs) scatter and absorb incident solar radiation in the atmosphere, thereby influencing the regional climate and hydrological cycle, particularly in the Third Pole (TP). Here, we present the characteristics of CAs at 19 observation stations from the Atmospheric Pollution and Cryospheric Change network to obtain a deep understanding of pollutant status in the TP. The organic carbon (OC) and elemental carbon (EC) concentrations decreased noticeably inwards from outside to inland of the TP, consistent with their emission load and also affected by transport process and meteorological condition. Urban areas, such as Kathmandu, Karachi, and Mardan, exhibited extremely high OC and EC concentrations, with low and high values occurring in the monsoon and non-monsoon seasons, respectively. However, remote regions inland the TP (e.g., Nam Co and Ngari) demonstrated much lower OC and EC concentrations. Different seasonal variations were observed between the southern and northern parts of the TP, suggesting differences in the patterns of pollutant sources and in distance from the sources between the two regions. In addition to the influence of long-range transported pollutants from the Indo-Gangetic Plain (IGP), the TP was affected by local emissions (e.g., biomass burning). The OC/EC ratio also suggested that biomass burning was prevalent in the center TP, whereas the marginal sites (e.g., Jomsom, Dhunche, and Laohugou) were affected by fossil fuel combustion from the up-wind regions. The mass absorption cross-section of EC (MACEC) at 632 nm ranged from 6.56 to 14.7 m2 g-1, with an increasing trend from outside to inland of the TP. Urban areas had low MACEC values because such regions were mainly affected by local fresh emissions. In addition, large amount of brown carbon can decrease the MACEC values in cities of South Asia. Remote sites had high MACEC values because of the coating enhancement of aerosols. Influenced by emission, transport process, and weather condition, the CA concentrations and MACEC presented decreasing and increasing trends, respectively, from outside to inland of the TP.

Rural household energy consumption plays an essential role in the daily life of farmers, especially in developing regions. In this paper, we present a study of household energy consumption in terms of energy sources and energy end uses, and analysis of technical and economic issues associated with the use of biomass and renewable energy and the replacement of fossil fuels. Results show that energy from biomass represents the largest share of total energy supply, and that 41.15% of total energy is consumed for home heating and cooking. The average cost of household energy is 1259 RMB ($US193.6) and this expense is no longer subsidized by the government. It takes less than one year to make a solar stove profitable and less than two years to pay back the household cost of biogas digesters. An 8 m(3) digester can produce as much energy as 500-550 kg of standard coal or 940 kg of firewood, while a solar stove can generate 1.76 x 10(3) MJ heat each year. Moreover, it is estimated that in rural China the annual reduction of CO2 and SO2 emissions in 2020, due to the replacement of fossil fuel by biomass, will be 68.86 x 10(6) and 54.37 x 10(4) tons, respectively. Overall, the investigations and analyses have revealed that the structure of rural household energy consumption is undergoing a transformation from traditional low-efficiency biomass domination to integrated consumption of traditional and renewable energies. Renewable energy will significantly contribute to the sustainable development of rural households. (C) 2013 Elsevier Ltd. All rights reserved.

Abstract A comprehensive investigation was conducted to evaluate the efficiency of newly installed biogas digesters in saving biomass resources and addressing energy squandering. Compared with traditional coal-based or firewood dominated energy consumption, the biogas digesters economize on energy resources due to higher heat efficiency. Furthermore, since crop residues of straw and other domestic animal and human excreta are effectively recycled and reused as anaerobic fermentation materials of biogas digesters, greenhouse gas emissions are significantly reduced by converting the previous extensive combustion of such into a sustainable and highly efficient practice in the rural region. The results in this study show that total energy consumption is 412 kgce (kgce: 1 kg standard coal. 1 kgce = 29.31 MJ) in Xiyang Township in 2009. The construction of biogas digesters significantly contributes to the transformation of rural household energy consumption structure, though biogas as a renewable energy only accounts for 6.31% of the total household energy consumption. Per capita rural household energy consumption is 393.07 kgce in household with biogas digesters and 437.60 kgce in household without biogas digesters. In addition, application of biogas dregs, slurry, and marsh liquid to the agricultural crops have greatly reduced the expenditure of buying chemical fertilizers. The average commercial fertilizer per mu (0.067 ha) in rural households using biogas digesters is 12.43 kg and the cost per mu is 29.53 yuan (1 yuan = 0.1523 dollar), while rural households without biogas digesters use 25.22 kg of commercial fertilizers and cost 59.71 yuan per mu. The utilization of biogas in rural semi-arid regions of China is a potentially clean development mechanism (CDM) and has profound implications for applied energy.