Reducing the risk level for pipelines transporting carbon dioxide and hydrogen by means of optimal safety valves spacing

In many countries where electricity generation is based on their natural resources of fossil fuels a need arises to implement new power engineering technologies that allow carbon dioxide capture. Simultaneously, efforts are made to find new energy carriers which, if fired, do not involve carbon dioxide emissions. Hydrogen is one of such fuels with this future potential which is now becoming increasingly popular. Obviously, this means that the two gases mentioned above – carbon dioxide and hydrogen – will be produced in large quantities in future, which in many cases will necessitate their transport over considerable distances. If a pipeline failure occurs, the transport of the gases may pose a serious hazard to people in the immediate vicinity of the leakage site. This paper presents an analysis of the possibility of reducing the level of risk related to pipelines transporting CO₂ and H₂ by means of safety valves. It is shown that for a 50 km long and a 0.4 m diameter pipeline transporting gas with the pressure of 15 MPa the individual risk level can be reduced from 1·10⁻⁴ to 6.5·10⁻⁷ for CO₂ and from 1·10⁻⁶ to 6·10⁻¹⁰ for H₂. The social risk can be diminished in similar proportions.     

Enhanced U(VI) bioreduction by alginate-immobilized uranium-reducing bacteria in the presence of carbon nanotubes and anthraquinone-2,6-disulfonate

Uranium-reducing bacteria were immobilized with sodium alginate, anthraquinone-2, 6-disulfonate (AQDS), and carbon nanotubes (CNTs). The effects of different AQDS-CNTs contents, U(IV) concentrations, and metal ions on U(IV) reduction by immobilized beads were examined. Over 97.5% U(VI) (20 mg/L) was removed in 8 hr when the beads were added to 0.7% AQDS-CNTs, which was higher than that without AQDS-CNTs. This result may be attributed to the enhanced electron transfer by AQDS and CNTs. The reduction of U(VI) occurred at initial U(VI) concentrations of 10 to 100 mg/L and increased with increasing AQDS-CNT content from 0.1% to 1%. The presence of Fe(III), Cu(II) and Mn(II) slightly increased U(VI) reduction, whereas Cr(VI), Ni(II), Pb(II), and Zn(II) significantly inhibited U(VI) reduction. After eight successive incubation-washing cycles or 8 hr of retention time (HRT) for 48 hr of continuous operation, the removal efficiency of uranium was above 90% and 92%, respectively. The results indicate that the AQDS-CNT/AL/cell beads are suitable for the treatment of uranium-containing wastewaters.     

Mesoporous carbon adsorbents from melamine-formaldehyde resin using nanocasting technique for CO2 adsorption

Mesoporous carbon adsorbents, having high nitrogen content, were synthesized via nanocasting technique with melamine–formaldehyde resin as precursor and mesoporous silica as template. A series of adsorbents were prepared by varying the carbonization temperature from 400 to 700°C. Adsorbents were characterized thoroughly by nitrogen sorption, X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), thermogravimetric analysis(TGA), elemental(CHN) analysis, Fourier transform infrared(FTIR) spectroscopy and Boehm titration. Carbonization temperature controlled the properties of the synthesized adsorbents ranging from surface area to their nitrogen content, which play major role in their application as adsorbents for CO_2 capture.The nanostructure of these materials was confirmed by XRD and TEM. Their nitrogen content decreased with an increase in carbonization temperature while other properties like surface area, pore volume, thermal stability and surface basicity increased with the carbonization temperature. These materials were evaluated for CO_2 adsorption by fixed-bed column adsorption experiments. Adsorbent synthesized at 700°C was found to have the highest surface area and surface basicity along with maximum CO_2 adsorption capacity among the synthesized adsorbents. Breakthrough time and CO_2 equilibrium adsorption capacity were investigated from the breakthrough curves and were found to decrease with increase in adsorption temperature. Adsorption process for carbon adsorbent–CO_2 system was found to be reversible with stable adsorption capacity over four consecutive adsorption–desorption cycles. From three isotherm models used to analyze the equilibrium data, Temkin isotherm model presented a nearly perfect fit implying the heterogeneous adsorbent surface.     

基于协调度函数的碳排放初始权区域分配模型研究

针对目前碳排放初始权区域分配模型中分配原则、指标体系不一致的问题,提出了碳排放初始权区域分配协调度概念,并确定了公平性原则、效率性原则、可持续发展原则、保障工业生产原则、保护环境原则作为碳排放初始权区域分配的具体原则,构造了基于各个分配原则下的碳排放初始权区域分配协调度子函数,建立了以碳排放初始权分配系统协调度最大为目标的协调度分配模型。将此模型应用到华东电网区域的碳排放初始权分配中,结果表明该模型合理、有效、可行性高,能较好的兼顾各个分配原则。该区域分配模型不依赖分配指标体系,能有效避免分配指标体系混乱问题,所建立的模型可以为碳排放初始权区域分配的研究提供借鉴。     

Vegetation and carbon sequestration and their relation to water resources in an inland river basin of Northwest China

In the Heihe River Basin in the arid inland area of northwest China, the distribution of water resources in vegetation landscape zones controls the ecosystems. The carbon sequestration capacity of vegetation is analyzed in relation to water resources and vegetation growing conditions. During the last 20 years, the vegetation ecosystems have degenerated in the Heihe River Basin. Simulation using the C-FIX model indicates that, at present, the total amount of NPP of vegetation accounts for about 18.16 TgC, and the average value is 106 gC/m(2)/yr over the whole basin. NPP has generally the highest value in the upperstream mountain area, middlestream artificial oases area, downstream river bank area, alluvial fan and the terminal lake depression where vegetation grows relatively well. The lowest value is found in the vast downstream desert and Gobi area. Protection of vegetation ecosystems and enhancement of carbon sequestration require such inland river basins as the Heihe River Basin to be brought under management in a comprehensive way, taking water as a key, to carry out a rational and efficient allocation and utilization of water resources.     

Removal of Se(IV) from aqueous solution using sulphuric acid-treated peanut shell

A carbonaceous sorbent was prepared from peanut shell via sulphuric acid treatment. Se(IV) removal from aqueous solution on the sorbent was studied varying time, pH, Se(IV) concentration, temperature and sorbent status (wet and dry). Se(IV) removal was faster using the wet sorbent than the dry sorbent following a pseudo-first-order model. Se(IV) removal increases at low pH values, and decreases as pH increases until pH 7. Sorption was found to fit the Langmuir equation and sorption capacity for the wet sorbent was higher than that for the dry one. Both sorbents showed an increased selenium sorption by rising the temperature. Redox processes between Se(IV) and the carbon sorbent are involved. Analysis by scanning electron microscope and X-ray powder diffraction for the sorbent after the reaction with acidified Se(IV) confirmed the availability of elemental selenium as particles on the sorbent surface as a result of Se(IV) reduction. Physicochemical tests showed an increase in sorbent acidity, cation exchange capacity (CEC) and surface functionality after the reaction with acidified Se(IV), indicating the oxidation processes occurring on the sorbent surface. Due to its reduction properties, the sorbent seems efficient for Se(IV) removal from aqueous solution.     

Wood carbon content of tree species in Eastern China: interspecific variability and the importance of the volatile fraction

Data on the mass density and carbon content of tree organs, and in particular stem wood, are essential for accurate assessments of forest carbon sequestration. However most available data, including that for East Asia, has neglected the volatile C fraction. Wood samples were collected and assayed for C content from 14 native tree species in Jilin Province, NE China. C content showed statistically significant variation among species, ranging from 48.4% to 51.0%. The volatile C fraction was non-negligible, averaging 2.2%, and showed high variation among species. As found in prior studies, wood C content was appreciably higher in conifer than hardwood (angiosperm) species (50.8+/-0.1% vs. 49.5+/-0.2%, respectively). Wood carbon density (gC/cm(3)) showed very high inter-specific variation, due mainly to differences in wood specific gravity. Our analyses, in conjunction with recently published data from North America, indicate a global mean value of 47.5+/-0.5% wood C content exclusive of volatile C; the widely used 50% figure corresponds more closely to total wood C inclusive of the volatile fraction. Failure to include volatile C or to use species- or higher-taxon-specific C content values in forest C assessments is likely to introduce biases on the order approximately 4-6%. In addition, the stocks and flows of the volatile C fraction in wood are in themselves an important and sorely neglected aspect of forest C processes likely to be strongly impacted by harvests and other management practices.     

Hyperautomobility and Governmentality in Auckland

Abstract

A number of cities around the world are associated with very high levels of private motor car usage, and Auckland provides an example of one of these ‘hyperautomobile’ cities. There are many problems with this system of transportation and dependence on the private car, including environmental, social and city design dimensions. Though there is a clear aspiration to move towards reduced levels of car usage in the city's transport and spatial planning strategies, there are major difficulties in implementation terms. We develop and consider future scenarios to 2041 to reduce these levels of motorization, and subsequent transport CO₂ emissions, with a much greater use of public transport, walking and cycling, urban planning, and low emission vehicles. The current implementability of such a ‘sustainable mobility’ future is however questioned in the current political and social context, and critically debated in terms of the available governance mechanisms and the limited attempts to shape the behaviour of the public. We conclude by calling for a reconsideration of the policy measures being considered, including the range and levels of application and investment; with a much wider framing of the transport planning remit, and carried out within a much stronger participatory framework for decision-making.     

基于生物质能的芒属（Miscanthus）植物碳动态和收支研究进展

生物质能（Biomass energy）是最为广泛的可再生能源，其中多年生芒属C4植物（Miscanthus）由于具有巨大碳固定能力而成为潜力巨大的生物质能植物。中国是芒属植物芒草起源中心，但相对于欧洲国家应对能源危机和温室效应而采取的芒草研究与应用来说，仍处于起步阶段。我国长期以来传统的草地利用模式，决定了在南方草地的研究显著少于北方，近年来芒草在华南地区的运用研究集中于生态修复，对草本植物群落基于生态系统水平的 CO2气体交换能力的研究仍然相当缺乏，在二氧化碳浓度持续增长及全球变暖背景下，生物质能植物及其碳汇功能的相关研究尤显重要。我国南方近6700万hm2退化丘陵草坡急待恢复或处于恢复中，草坡地芒属植物符合生物质能植物标准，施肥少，害虫少，农药输入少，能够有效地利用光、水等自然资源。考虑到C4植物具有比C3植物更强的光合作用能力，高光能利用率C4芒属植物的碳固定能力及能源潜力值得重视，但缺乏科学的碳动态和碳收支评估。综述了国内外芒草生物量特征与生物质能潜力研究现状，重点论述芒属植物生态系统水平的碳动态和收支能力研究，探讨了系统水平更客观评估芒属碳源汇（Carbon sequestration）功能的方法，基于生物量过程的研究结果及华南地区草坡研究历史和现状，为草坡地生物质能的合理开发利用提出了相关对策，强调在我国南方开发和利用芒属植物资源具有重要能源价值和经济、环境效益。