Cumulative exergy extraction from the natural environment (CEENE): a comprehensive life cycle impact assessment method for resource accounting

The objective of the paper is to establish a comprehensive resource-based life cycle impact assessment (LCIA) method which is scientifically sound and that enables to assess all kinds of resources that are deprived from the natural ecosystem, all quantified on one single scale, free of weighting factors. The method is based on the exergy concept. Consistent exergy data on fossils, nuclear and metal ores, minerals, air, water, land occupation, and renewable energy sources were elaborated, with well defined system boundaries. Based on these data, the method quantifies the exergy "taken away" from natural ecosystems, and is thus called the cumulative exergy extraction from the natural environment (CEENE). The acquired data set was coupled with a state-of-the art life cycle inventory database, ecoinvent. In this way, the method is able to quantitatively distinguish eight categories of resources withdrawn from the natural environment: renewable resources, fossil fuels, nuclear energy, metal ores, minerals, water resources, land resources, and atmospheric resources. Third, the CEENE method is illustrated for a number of products that are available in ecoinvent, and results are compared with common resource oriented LCIA methods. The application to the materials in the ecoinvent database showed that fossil resources and land use are of particular importance with regard to the total CEENE score, although the other resource categories may also be significant.     

Stress-adapted extremophiles provide energy without interference with food production

How to wean humanity off the use of fossil fuels continues to receive much attention but how to replace these fuels with renewable sources of energy has become a contentious field of debate as well as research, which often reflects economic and political factors rather than scientific good sense. It is clear that not every advertized energy source can lead to a sustainable, humane and environment-friendly path out of a future energy crisis. Our proposal is based on two assertions: that the use of food crops for biofuels is immoral, and that for this purpose using land suitable for growing crops productively is to be avoided. We advocate a focus on new “extremophile” crops. These would either be wild species adapted to extreme environments which express genes, developmental processes and metabolic pathways that distinguish them from traditional crops or existing crops genetically modified to withstand extreme environments. Such extremophile energy crops (EECs), will be less susceptible to stresses in a changing global environment and provide higher yields than existing crops. Moreover, they will grow on land that has never been valuable for agriculture or is no longer so, owing to centuries or millennia of imprudent exploitation. Such a policy will contribute to striking a balance between ecosystem protection and human resource management. Beyond that, rather than bulk liquid fuel generation, combustion of various biomass sources including extremophiles for generating electrical energy, and photovoltaics-based capture of solar energy, are superbly suitable candidates for powering the world in the future. Generating electricity and efficient storage capacity is quite possibly the only way for a sustainable post-fossil and, indeed, post-biofuel fuel economy.     

Is cumulative fossil energy demand a useful indicator for the environmental performance of products?

The appropriateness of the fossil Cumulative Energy Demand (CED) as an indicator for the environmental performance of products and processes is explored with a regression analysis between the environmental life-cycle impacts and fossil CEDs of 1218 products, divided into the product categories "energy production", "material production", "transport", and "waste treatment". Our results show that, for all product groups but waste treatment, the fossil CED correlates well with most impact categories, such as global warming, resource depletion, acidification, eutrophication, tropospheric ozone formation, ozone depletion, and human toxicity (explained variance between 46% and 100%). We conclude that the use of fossil fuels is an important driver of several environmental impacts and thereby indicative for many environmental problems. It maytherefore serve as a screening indicatorfor environmental performance. However, the usefulness of fossil CED as a stand-alone indicator for environmental impact is limited by the large uncertainty in the product-specific fossil CED-based impact scores (larger than a factor of 10 for the majority of the impact categories; 95% confidence interval). A major reason for this high uncertainty is nonfossil energy related emissions and land use, such as landfill leachates, radionuclide emissions, and land use in agriculture and forestry.     

甜高粱茎秆糖度分析方法对消耗的影响

随着近年世界能源的日益紧张,化石能源使用期限的告急,因此国际各知名企业纷纷研究利用甜高粱茎秆生产可再生能源——燃料乙醇的可行性。从原料分析方法的差异对吨燃料乙醇所需原料的影响进行论述,以便于更好的与业内人士进行分享。     

界面光热转换水蒸发系统用纤维材料的研究进展

为缓解化石能源日益匮乏以及淡水资源短缺等问题,促进纤维材料在水资源利用方面的开发和应用,对以纤维材料为主要原料的界面光热转换水蒸发系统的最新研究进展进行综述。首先介绍了界面光热转换水蒸发技术的主要原理、发展历程和应用领域;然后分别分析了界面光热转换水蒸发系统中的光热转换材料和辅助材料,并以不同的功能作为切入点,详细阐述了纤维材料功能多样化、轻质、低成本和便于加工等特性,展示了其作为界面光热转换水蒸发系统主要原料的优异性能;最后针对在界面光热转换水蒸发系统中使用纤维材料所面临的挑战以及如何提升系统的实用性进行展望,希望能够推动纤维材料在界面光热转换技术中的广泛应用。     

Sustainability of uranium mining and milling: toward quantifying resources and eco-efficiency

The mining of uranium has long been a controversial public issue, and a renewed debate has emerged on the potential for nuclear power to help mitigate against climate change. The central thesis of pro-nuclear advocates is the lower carbon intensity of nuclear energy compared to fossil fuels, although there remains very little detailed analysis of the true carbon costs of nuclear energy. In this paper, we compile and analyze a range of data on uranium mining and milling, including uranium resources as well as sustainability metrics such as energy and water consumption and carbon emissions with respect to uranium production-arguably the first time for modern projects. The extent of economically recoverable uranium resources is clearly linked to exploration, technology, and economics but also inextricably to environmental costs such as energy/water/chemicals consumption, greenhouse gas emissions, and social issues. Overall, the data clearly show the sensitivity of sustainability assessments to the ore grade of the uranium deposit being mined and that significant gaps remain in complete sustainability reporting and accounting. This paper is a case study of the energy, water, and carbon costs of uranium mining and milling within the context of the nuclear energy chain.     

静电纺纳米纤维在界面太阳能蒸汽转化应用中的研究进展

静电纺纳米纤维因其具有高比表面积、孔隙结构可控等优点而被用作界面太阳能蒸汽发生器基底,然而由于其力学性能不足、与光热材料的结合力差等限制了其长足发展。为此,介绍了静电纺纳米纤维的特点及其与光热材料结合的主要方式,包括表面修饰、共混纺丝、Janus纳米纤维膜以及三维纳米纤维气凝胶,对其原理、性能和工艺方法等进行系统性概述;并在此基础上展望了该研究领域的未来发展趋势,以探索静电纺纳米纤维在光热能源领域中广泛应用的方法。研究认为,加强静电纺纳米纤维与光热材料结合力并赋予其抗菌、自清洁等多功能性,是提高太阳能蒸汽发生器持久使用的一大方法,探寻简易的制备方法和开发低成本材料高性能太阳能蒸汽发生器是未来的发展重点。     

Estimating resource use efficiencies in organic agriculture: a review of budgeting approaches used

The basis of organic farming is that it is environmentally, socially and economically sustainable, and it aims, wherever possible, to use renewable resources in the production system and avoid waste. Thus this review considers the use of nutrient, energy and water within the farming systems, and indices that are used to evaluate the use of these resources and hence their impact on the environment. It is crucial that the delineation of system boundaries in both time and space, including both the vertical and horizontal dimensions, is defined to assess the resources used within the system. There is increasing interest in the emergy concept, which permits different forms of energy to be compared on the same basis. Across all farming systems, there is no direct link between nutrient surplus and nutrient loss. It is important to recognise that the choice of tool used to assess the environmental consequences of the farming system, as well as whether the results are expressed on a product or an area basis, may have implications for how emissions are attributed to different parts of the production system. In order for indicators to be useful, they must be influenced by the farmer's management practices. Copyright © 2007 Society of Chemical Industry     

Environmental impacts of water use in global crop production: hotspots and trade-offs with land use

Global crop production is causing pressure on water and land resources in many places. In addition to local resource management, the related environmental impacts of commodities traded along international supply chains need to be considered and managed accordingly. For this purpose, we calculate the specific water consumption and land use for the production of 160 crops and crop groups, covering most harvested mass on global cropland. We quantify indicators for land and water scarcity with high geospatial resolution. This facilitates spatially explicit crop-specific resource management and regionalized life cycle assessment of processed products. The vast cultivation of irrigated wheat, rice, cotton, maize, and sugar cane, which are major sources of food, bioenergy, and fiber, drives worldwide water scarcity. According to globally averaged production, substituting biofuel for crude oil would have a lower impact on water resources than substituting cotton for polyester. For some crops, water scarcity impacts are inversely related to land resource stress, illustrating that water consumption is often at odds with land use. On global average, maize performs better than rice and wheat in the combined land/water assessment. High spatial variability of water and land use related impacts underlines the importance of appropriate site selection for agricultural activities.     

蒸馏/反渗透海水淡化及其耦合工艺研究

海水淡化是解决淡水危机的重要途径,新工艺、新型膜材料及新能源的利用,有望进一步降低海水淡化成本.介绍了多效蒸发、多级闪蒸、压气蒸馏、反渗透等海水淡化工艺以及基于膜技术的海水淡化集成工艺的最新进展,分析了利用风能、太阳能、核能和化学热能等可替代能源进行海水淡化的可能性,在此基础上,提出了海水淡化未来的发展方向.     

燃料油植物资源研究现状与发展对策

能源危机是人类即将面临的巨大挑战,可再生植物能源的开发利用已成为当今世界应对能源危机的对策之一。我国燃料油植物资源丰富,并且有大量的宜林荒山荒地,积极发展燃料油植物,不仅可解决部分石化能源的枯竭问题,而且可以改善生态环境,增加农民收入,逐步加强我国在能源方面的独立性。概述了国内外燃料油植物研究现状,分析了我国开发利用燃料油植物存在的问题,指出加强燃料油植物资源培育及开发利用的发展策略的重要性,提出今后的研究发展方向。     

Advanced exergoenvironmental analysis of a near-zero emission power plant with chemical looping combustion

Carbon capture and storage (CCS) from power plants can be used to mitigate CO(2) emissions from the combustion of fossil fuels. However, CCS technologies are energy intensive, decreasing the operating efficiency of a plant and increasing its costs. Recently developed advanced exergy-based analyses can uncover the potential for improvement of complex energy conversion systems, as well as qualify and quantify plant component interactions. In this paper, an advanced exergoenvironmental analysis is used for the first time as means to evaluate an oxy-fuel power plant with CO(2) capture. The environmental impacts of each component are split into avoidable/unavoidable and endogenous/exogenous parts. In an effort to minimize the environmental impact of the plant operation, we focus on the avoidable part of the impact (which is also split into endogenous and exogenous parts) and we seek ways to decrease it. The results of the advanced exergoenvironmental analysis show that the majority of the environmental impact related to the exergy destruction of individual components is unavoidable and endogenous. Thus, the improvement potential is rather limited, and the interactions of the components are of lower importance. The environmental impact of construction of the components is found to be significantly lower than that associated with their operation; therefore, our suggestions for improvement focus on measures concerning the reduction of exergy destruction and pollutant formation.     

蒸馏／反渗透海水淡化及其耦合工艺研究

海水淡化是解决淡水危机的重要途径，新工艺、新型膜材料及新能源的利用，有望进一步降低海水淡化成本。介绍了多效蒸发、多级闪蒸、压气蒸馏、反渗透等海水淡化工艺以及基于膜技术的海水淡化集成工艺的最新进展，分析了利用风能、太阳能、核能和化学热能等可替代能源进行海水淡化的可能性，在此基础上，提出了海水淡化未来的发展方向。     

Cradle-to-Gate Life Cycle Assessment for a Cradle-to-Cradle Cycle: Biogas-to-Bioplastic (and Back)

At present, most synthetic organic materials are produced from fossil carbon feedstock that is regenerated over time scales of millions of years. Biobased alternatives can be rapidly renewed in cradle-to-cradle cycles (1-10 years). Such materials extend landfill life and decrease undesirable impacts due to material persistence. This work develops a LCA for synthesis of polyhydroxybutyrate (PHB) from methane with subsequent biodegradation of PHB back to biogas (40-70% methane, 30-60% carbon dioxide). The parameters for this cradle-to-cradle cycle for PHB production are developed and used as the basis for a cradle-to-gate LCA. PHB production from biogas methane is shown to be preferable to its production from cultivated feedstock due to the energy and land required for the feedstock cultivation and fermentation. For the PHB-methane cycle, the major challenges are PHB recovery and demands for energy. Some or all of the energy requirements can be satisfied using renewable energy, such as a portion of the collected biogas methane. Oxidation of 18-26% of the methane in a biogas stream can meet the energy demands for aeration and agitation, and recovery of PHB synthesized from the remaining 74-82%. Effective coupling of waste-to-energy technologies could thus conceivably enable PHB production without imported carbon and energy.     

A biorefinery for mobility?

Biofuels are considered as a carbon neutral alternative to hydrocarbons in the transport sector and this approach has triggered concerns about the impact the production of biofuels might have on land usage. Another option that might also lead to reduced emissions in the transport sector is electricity based on renewable energy sources such as biomass. Below, we assess the benefits and drawbacks of the joint production of ethanol and electricity in a sugar cane based refinery, and the use of both energy forms in privately owned automobiles. In this analysis, we have considered technology for energy production that is currently available and cost competitive. The results show that the amount of land that is required to power our current automobile use needs is less than what is typically stated. According to our results that are based on 2010 values, 2 million ha of land are sufficient to power the Brazilian automobile fleet, 25 million ha are enough to satisfy the needs of the U.S. fleet, and 67 million ha are sufficient to cover the global autofuel requirements. When minor efficiency gains are considered, 19 million ha will be enough to satisfy the fuel needs of the U.S. fleet in 2030, whereas land required to supply the Brazilian and global fleet remain basically unchanged. Our analysis shows that the harvested energy density of sugar cane is 306 GJ/ha/yr, which is 1.7 times the value usually reported in the literature for biofuels. As a result, taking advantage of the primary energy potential of sugar cane, only 4% of the world's available cropland area would be sufficient to produce fuels that would power the global car fleet.     

Hydrothermal Pretreatment of Lignocellulosic Materials for Improving Bioethanol Production

With the continued depletion of non-renewable energy resources,it is essential to seek new methods of harnessing clean and renewable energy.In this regard,second-generation bioethanol derived from lignocellulosic biomass has attracted increasing attention in recent years.The choice of the pretreatment method of lignocellulose is critical to the subsequent bioconversion processes.Compared with other conventional chemical pretreatment methods,hydrothermal pretreatment is a simple,low-cost,and economically feasible process that requires water as the only reagent.This paper reviews the research efforts that have been made toward hydrothermal pretreatment of lignocellulosic biomass and focuses on the transformations involving cellulose,hemicellulose,and lignin during this process.     

Domestic wastewater treatment as a net energy producer--can this be achieved?

In seeking greater sustainability in water resources management, wastewater is now being considered more as a resource than as a waste-a resource for water, for plant nutrients, and for energy. Energy, the primary focus of this article, can be obtained from wastewater's organic as well as from its thermal content. Also, using wastewater's nitrogen and P nutrients for plant fertilization, rather than wasting them, helps offset the high energy cost of producing synthetic fertilizers. Microbial fuel cells offer potential for direct biological conversion of wastewater's organic materials into electricity, although significant improvements are needed for this process to be competitive with anaerobic biological conversion of wastewater organics into biogas, a renewable fuel used in electricity generation. Newer membrane processes coupled with complete anaerobic treatment of wastewater offer the potential for wastewater treatment to become a net generator of energy, rather than the large energy consumer that it is today.     

纤维素类物质生产乙醇研究进展

纤维素类物质是可再生资源,资源丰富,利用纤维素类物质制备燃料乙醇是发展新能源重要途径。该文综述利用纤维素类物质生产乙醇研究进展,重点介绍预处理、糖化、发酵等工序。     

Heat, electricity, or transportation? The optimal use of residual and waste biomass in Europe from an environmental perspective

The optimal use of forest energy wood, industrial wood residues, waste wood, agricultural residues, animal manure, biowaste, and sewage sludge in 2010 and 2030 was assessed for Europe. An energy system model was developed comprising 13 principal fossil technologies for the production of heat, electricity, and transport and 173 bioenergy conversion routes. The net environmental benefits of substituting fossil energy with bioenergy were calculated for all approximately 1500 combinations based on life cycle assessment (LCA) results. An optimization model determines the best use of biomass for different environmental indicators within the quantified EU-27 context of biomass availability and fossil energy utilization. Key factors determining the optimal use of biomass are the conversion efficiencies of bioenergy technologies and the kind and quantity of fossil energy technologies that can be substituted. Provided that heat can be used efficiently, optimizations for different environmental indicators almost always indicate that woody biomass is best used for combined heat and power generation, if coal, oil, or fuel oil based technologies can be substituted. The benefits of its conversion to SNG or ethanol are significantly lower. For non-woody biomass electricity generation, transportation, and heating yield almost comparable benefits as long as high conversion efficiencies and optimal substitutions are assured. The shares of fossil heat, electricity, and transportation that could be replaced with bioenergy are also provided.     

The energetics of British agriculture

An analysis is presented firstly of the biological energetics of UK agriculture in which the ultimate yield of edible food is related to primary plant production and solar radiation incidence. Secondly, the industrial energetics of British agriculture are dealt with in which agriculture is regarded as an industry in which the input is of materials which have required, for their production, energy as fossil fuel and the output is again edible food. The results show that primary plant output is 0.18% of solar radiation receipt and of this 12% is recovered as human food. This meets 57% of the requirements of the population for dietary energy and the labour of one man supports the dietary requirement of 48 people. UK agriculture accounts for 3.9% of the total UK primary fuel consumption and the farm gate output relative to total fossil fuel input is 0.6 : 1 while the edible food output is 0.3 : 1. The results of the analysis are discussed taking both a short term and long term view.