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91.
Jeffrey I. Steinfeld 《Sustainability Science》2006,1(1):123-126
Global energy demand is expected to increase from the current 400 ExaJ per year to as much as 700–1,000 ExaJ per year by the middle of this century. If fossil carbon resources continue to make up the bulk of the energy supply, not only will atmospheric carbon dioxide increase to levels not seen for the past 30–35 million years, but depleting fossil carbon resources will become increasingly less available for other purposes, particularly the production of chemicals on which society now depends. The chemical process industries are heavily dependent on the availability of low-price petroleum as a feedstock. Recent life-cycle analyses suggest that pursuing both strategies of renewable energy sources and renewable feedstocks (i.e. biomass) will be required to meet these competing demands. Reducing the global use of both energy and manufactured chemicals will be a challenge for sustainable development. Education of the next generation of chemists and chemical engineers will have to change significantly from its current emphasis on petrochemical-based manufacturing to include a much greater emphasis on renewable resources and bio-based processes.Brief accounts of this work were presented at the 7th International Symposium on Green Chemistry in China (Zhuhai, People’s Republic of China, May 2005) and at the Joint US–China Green Chemistry Workshop (Beijing, People’s Republic of China, May 2005; this workshop was supported by US National Science Foundation grant CHE-0522369). 相似文献
92.
2006年8月10日-8月21日,分别对扎龙湿地内的植被种类和植被类型进行调查,并在植被调查的基础上划分4处样地共20个样方调查野生芦苇群落的生物量。结果表明,火烧因子与缺水干旱因子对湿地内草本植物的生境、种类、植株数量、植被类型、单位面积生物量和株高影响明显。植被生境明显恶化,植被种类减少、植株数量下降、类型单一化,野生芦苇群落单位面积生物量降低。 相似文献
93.
94.
Jonatas S. RomanoMariane S. Miranda Meiri B.R. OliveiraFlávio A. Rodrigues 《Journal of Cleaner Production》2011,19(11):1224-1228
Metals can be stabilized into cement matrix by solidification/stabilization process. Rice hull is an agricultural residue containing about 10-20% (weight) of silica. It can be used to synthesize β-Ca2SiO4, an important component of Portland cement. Furthermore it is possible to prepare β-Ca2SiO4 doped with heavy metals. Here we describe the synthesis of β-Ca2SiO4 doped with zinc and the behavior of mortars prepared using this material. Products were analyzed by X-ray diffraction, differential thermal analysis and scanning electron microscopy coupled to energy-dispersive spectroscopy. The maximum amount of zinc that can be inserted into β-Ca2SiO4, without affecting the crystalline structure, is limited to 2% (molar basis). In comparison with conventional mortars, zinc-modified mortars show a similar behavior, regarding porosity, resistance to acidic attack and compressive strength. The synthesis of β-Ca2SiO4 doped with zinc presents a new possibility for safety enhancement in solidification/stabilization processes. 相似文献
95.
96.
《International Journal of Sustainable Engineering》2013,6(4):240-247
ABSTRACTThe biogas constituting majorly CH4 and CO2 has been produced by Ca(OH)2 pre-treated wheat straw with pre-digested cow dung. Some of the key thermodynamic parameters like specific heat capacity, density and heating capacity of the biogas produced have also been calculated per day as well as throughout the hydraulic retention time. The governing equations of biogas with appropriate phase and interfacial conditions describing the physics of the biogas have been derived. The control volume approach has been used to predict the total volume (ml) of biogas, CH4 and CO2 throughout the experiment and on the daily basis. The effects of feedstock, temperature and pressure on the production of biogas, CH4 and CO2 in anaerobic digestion have also been studied. The average number of molar fraction and conversion ratio of CH4 and CO2 are correlated with number of carbon atoms available in feedstock. Numerical calculations by using developed model and Modified Gompertz model have shown proficient agreement with the experimental observations. 相似文献
97.
Yuan Cheng Qinqin Yu Jiumeng Liu Youwen Sun Linlin Liang Zhenyu Du Guannan Geng Wanli Ma Hong Qi Qiang Zhang Kebin He 《Frontiers of Environmental Science & Engineering》2022,16(2):18
98.
Abstract A series of mesocosms was exposed to a suite of light treatments and nutrient enrichment in order to generate algal communities of varying biomass. the influence of this biomass on the speciation of copper (II) was studied. Distribution coefficients ( Kd,Lkg?1) were relatively high (log Kd = 5 to 7), indicative of robust trace metal sequestration, and were likely controlled by the particulate organic carbon content (foc). Differences in Kd over time and among treatments were significant, as was the relationship between Kd and foc. Fluorescence quenching was used to determine binding capacities ( Lt , M) and their associated binding constants ( Kcond ,M?1) in order to model the solid phase copper speciation. the Kcond ranged between 2.1 and 5.2 × 1012M?1, indicating a very strong copper-ligand complex, and was higher in mesocosms that received more light. the light Lt increased over time, dramatically after the nutrient enrichment, but did not vary systematically among light treatments. Lt ranged from 7.2 × 10? 7 to 4.9 × 10? 5 M. the large magnitudes of Kd , Kcond and Lt ensured that greater than 97% of total copper in the mesocosms was complexed by organic matter. the total copper concentration ([Cu]T, M) needed to reach a target dissolved copper concentration of 10?12.5 M (pCu = 12.5) was determined for each mesocosm over time. [Cu]T was between 8.02 × 10?5 and 3.41 × 10?2 M, and increased over time. the [Cu]T normalized to the target pCu (Effective Dose Ratio, EDR) increased directly with increases in algal biomass, indicating a direct link between system productivity and copper exposure. Approximately 45% of the variance in EDR was explained by variance in total biomass, while the residual variance in EDR was due likely to differences in the strengths of particle associations and magnitude of binding capacities. 相似文献
99.
Motomu Toda Masayuki Yokozawa Akihiro Sumida Tsutomu Watanabe Toshihiko Hara 《Ecological modelling》2009
A simulation study was carried out to investigate simultaneously the effects of eco-physiological parameters on competitive asymmetry, self-thinning, stand biomass and NPP in a temperate forest using an atmosphere–vegetation dynamics interactive model (MINoSGI). In this study, we selected three eco-physiological relevant parameters as foliage profiles (i.e. vertical distribution of leaf area density) of individual trees (distribution pattern is described by the parameter η), biomass allocation pattern in individual tree growth (χ) and the maximum carboxylation velocity (Vmax). The position of the maximal leaf area density shifts upward in the canopy with increasing η. For scenarios with η < 4 (foliage concentrated in the lowest canopy layer) or η > 12 (foliage concentrated in the uppermost canopy layer), a low degree of competitive asymmetry was produced. These scenarios resulted in the survival of subordinate trees due to a brighter lower canopy environment when η < 4 or the generation of spatially separated foliage profiles between dominant and subordinate trees when η > 12. In contrast, competition between trees was most asymmetric when 4 ≤ η ≤ 12 (vertically widespread foliage profile in the canopy), especially when η = 8. In such cases, vertically widespread foliage of dominant trees lowered the opportunity of light acquisition for subordinate trees and reduced their carbon gain. The resulting reduction in carbon gain of subordinate trees yielded a higher degree of competitive asymmetry and ultimately higher mortality of subordinate trees. It was also shown that 4 ≤ η ≤ 12 generated higher self-thinning speed, smaller accumulated NPP, litter-fall and potential stand biomass as compared with the scenarios with η < 4 or η > 12. In contrast, our simulation revealed small effects of χ or Vmax on the above-mentioned variables as compared with those of η. In particular, it is notable that greater Vmax would not produce greater potential stand biomass and accumulated NPP although it has been thought that physiological parameters relevant to photosynthesis such as Vmax influence dynamic changes in forest stand biomass and NPP (e.g. the greater the Vmax, the greater the NPP). Overall, it is suggested that foliage profiles rather than biomass allocation or maximum carboxylation velocity greatly govern forest dynamics, stand biomass, NPP and litter-fall. 相似文献
100.
Xiangyu Yang Qiang He Fucheng Guo Xiaobo Liu Yi Chen 《Frontiers of Environmental Science & Engineering》2021,15(6):138