Applying cumulative exergy demand (CExD) indicators to the ecoinvent database

Goal, Scope and Background Exergy has been put forward as an indicator for the energetic quality of resources. The exergy of a resource accounts for the minimal work necessary to form the resource or for the maximally obtainable amount of work when bringing the resource’s components to their most common state in the natural environment. Exergy measures are traditionally applied to assess energy efficiency, regarding the exergy losses in a process system. However, the measure can be utilised as an indicator of resource quality demand when considering the specific resources that contain the exergy. Such an exergy measure indicates the required resources and assesses the total exergy removal from nature in order to provide a product, process or service. In the current work, the exergy concept is combined with a large number of life cycle inventory datasets available with ecoinvent data v1.2. The goal was, first, to provide an additional impact category indicator to Life-Cycle Assessment practitioners. Second, this work aims at making a large source of exergy scores available to scientific communities that apply exergy as a primary indicator for energy efficiency and resource quality demand. Methods The indicator Cumulative Exergy Demand (CExD) is introduced to depict total exergy removal from nature to provide a product, summing up the exergy of all resources required. CExD assesses the quality of energy demand and includes the exergy of energy carriers as well as of non-energetic materials. In the current paper, the exergy concept was applied to the resources contained in the ecoinvent database, considering chemical, kinetic, hydro-potential, nuclear, solar-radiative and thermal exergies. The impact category indicator is grouped into the eight resource categories fossil, nuclear, hydropower, biomass, other renewables, water, minerals, and metals. Exergy characterization factors for 112 different resources were included in the calculations. Results CExD was calculated for 2630 ecoinvent product and process systems. The results are presented as average values and for 26 specific groups containing 1197 products, processes and infrastructure units. Depending on the process/product group considered, energetic resources make up between 9% and 100% of the total CExD, with an average contribution of 88%. The exergy of water contributes on the average to 8% the total exergy demand, but to more than 90% in specific process groups. The average contribution of minerals and metal ores is 4%, but shows an average value as high as 38% and 13%, in metallic products and in building materials, respectively. Looking at individual processes, the contribution of the resource categories varies substantially from these average product group values. In comparison to Cumulative Energy Demand (CED) and the abiotic-resource-depletion category of CML 2001 (CML’01), non-energetic resources tend to be weighted more strongly by the CExD method. Discussion Energy and matter used in a society are not destroyed but only transformed. What is consumed and eventually depleted is usable energy and usable matter. Exergy is a measure of such useful energy. Therefore, CExD is a suitable energy based indicator for the quality of resources that are removed from nature. Similar to CED, CExD assesses energy use, but regards the quality of the energy and incorporates non-energetic materials like minerals and metals. However, it can be observed for non-renewable energy-intensive products that CExD is very similar to CED. Since CExD considers energetic and non-energetic resources on the basis of exhaustible exergy, the measure is comparable to resource indicators like the resource use category of Eco-indicator 99 and the resource depletion category of CML 2001. An advantage of CExD in comparison to these methods is that exergy is an inherent property of the resource. Therefore less assumptions and subjective choices need to be made in setting up characterization factors. However, CExD does not coversocietal demand (distinguishing between basic demand and luxury), availability or scarcity of the resource. As a consequence of the different weighting approach, CExD may differ considerably from the resource category indicators in Eco-indicator 99 and CML 2001. Conclusions The current work shows that the exergy concept can be operationalised in product life cycle assessments. CExD is a suitable indicator to assess energy and resource demand. Due to the consideration of the quality of energy and the integration of non-energetic resources, CExD is a more comprehensive indicator than the widely used CED. All of the eight CExD categories proposed are significant contributors to Cumulative Exergy Demand in at least one of the product groups analysed. In product or service assessments and comparative assertions, a careful and concious selection of the appropriate CExD-categories is required based on the energy and resource quality demand concept to be expressed by CExD. Recommendations and Perspectives A differentiation between the exergy of fossil, nuclear, hydro-potential, biomass, other renewables, water and mineral/metal resources is recommended in order to obtain a more detailed picture of resource quality demand and to recognise trade-offs between resource use, for instance energetic and non-energetic raw materials, or nonrenewable and renewable energies. ESS-Submission Editor: Dr. Gerald Rebitzer (Gerald.Rebitzer@alcan.com)     

勐宋Sangpabawa中棕榈藤资源的保护和持续利用

物种多样性的研究是生物多样性研究的基础,对生物多样性的保护具有重要意义。Ｓａｎｇ ｐａｂａｗａ是哈尼语“头人的藤林”,它是我国仅有的为保护棕榈藤资源而建立的自然保护区。本文通过对勐宋Ｓａｎｇｐａｂａｗａ中棕榈藤资源现状的研究,分析了棕榈藤数量锐减的原因：１．市场经济新形势下,管理不善,造成人们过度采收藤条,并且采收时滥砍乱伐;２．外界干扰影响了棕榈藤的正常自然更新;３．良种藤的栽培使非良种藤在当地处于濒危或渐危状态。并提出利用价值是衡量保护价值的一个重要标准这一原则。在此基础上,提出勐宋Ｓａｎｇｐａｂａｗａ中棕榈藤资源的保护对策：１．挖掘藤类资源的利用价值,增强人们对它的保护意识;２．加强对Ｓａｎｇｐａｂａｗａ的管理,完善村规民约,防止偷砍乱伐;３．建立棕榈藤收集区和种苗基地,保护藤类资源多样性,满足生产种植需求;４．建立商品藤生产和加工基地,满足市场需求。     

植被光能利用率:模型及其不确定性

光能利用率（Light use efficiency： LUE）指植物截获的光能转化为化学能的效率,表示为生产力和吸收光能之比。基于LUE概念的模型对模拟预测全球变化下碳循环、植被生产力及其潜力具有重要意义。全球变化和人类活动影响给植被生产力和碳循环的评估带来了巨大挑战。系统梳理了LUE模型的不确定性并分析其原因,以期提高生产力模拟预测的准确度。分析发现LUE模型准确度仅为62%-70%且模型间差异较大（32%）,误差随着植被类型、时间尺度和空间区域的不同存在显著差别。目前计算LUE的误差是模型不确定性的关键,原因主要在于LUE与影响因素尤其是水分的关系并不清楚。一方面不能准确区分水分胁迫指标对LUE的影响机制,另一方面无法准确模拟水分等影响因素与LUE关系的时空演变特征。未来该领域研究的重要方向是发展集成样地和区域尺度的叶绿素荧光、光化学指数等研究方法,厘定LUE与影响因素特别是的水分关系,并分析其时空演变特征。     

The interaction between CO2 and plant nutrition: comments on a paper by Coleman,McConnaughay and Bazzaz

Effects of CO₂ on plants are often confounded with effects of nutrition. Coleman et al. (1993) showed that nitrogen concentrations in plants grown under different CO₂ levels did not differ if plants of equal sizes were compared but varied at equal times and equal sizes for different levels of nitrogen additions. I will suggest why this must occur under the conditions of the experiment. I will also suggest why nitrogen productivity should be used to interpret experimental results rather than the dubious nitrogen use efficiency.     

Exergy‐Based Population Dynamics

This article discusses whether “sustainability” has a physical meaning in applied thermodynamics. If it has, then it should be possible to derive general principles and rules for devising “sustainable systems.” If not, then other sides of the issue retain their relevance, but thermodynamic laws are not appropriate by themselves to decide whether a system or a scenario is sustainable. Here, we make use of a single axiom: that final consumption (material or immaterial) can be quantified solely in terms of equivalent primary exergy flows. On this basis, we develop a system theory that shows that if “simple” systems are based solely on the exploitation of fossil resources, they cannot be thermodynamically “sustainable.” But as renewable resources are brought into the picture and the system complexity grows, there are thresholds below or beyond which the system exhibits an ability to maintain itself (perhaps through fluctuations), in a self‐preserving (i.e., a sustainable) state. It appears that both complexity and the degree of nonlinearity of the transfer functions of the systems play a major role and—even for some of the simplest cases—lead to nontrivial solutions in phase space. Therefore, even if the examples presented in the article can be considered rather crude approximations to real, complex systems at best, the results show a trend that is worth further consideration.     

城市建筑代谢研究方法及其展望

建筑代谢是当前城市代谢研究领域中的一个新兴热点问题,其研究着重关注建筑系统中物质能量流动可能对周围环境产生的压力及其有害影响。本文在阐明城市建筑代谢内涵的基础上,综述了国内外建筑代谢研究方法的进展情况,分析了目前城市建筑代谢研究方法的适用范围及其特点,指出了城市建筑代谢研究方法在未来应从以下几个方面发展:开发跨城市边界的代谢研究方法;注重建筑代谢中非物质性代谢流研究;制定适合乡土建筑地域特点的代谢研究方法;综合物质量和价值量的建筑代谢研究,全面认识和评价建筑的可持续性。     

自然资源持续利用的理论分析

自然资源持续利用的理论分析赵景柱（中国科学院生态环境研究中心,北京１０００８５）ＴｈｅｏｒｅｔｉｃａｌＡｎａｌｙｓｉｓｏｎＳｕｓｔａｉｎａｂｌｅＵｓｅｏｆＮａｔｕｒａｌＲｅｓｏｕｒｃｅｓ￥ＺｈａｏＪｉｎｇｚｈｕ（ＲｅｓｅａｒｃｈＣｅｎｔｅｒｆｏｒＥｃ...     

The effects of nitrogen, light and water availability on tropic leaf movements in soybean (Glycine max)

Abstract. Rapid, tropic leaf movements and photo-synthetic responses of the heliotropic plant, soybean, Glycine max cv. Cumberland, grown under two different nitrogen, three different light and two different water treatments were examined. Measurements of leaf orientation during midday periods outdoors, and tropic reorientation of leaflets in response to vertical illumination indoors, revealed a positive, linear relationship between leaf water potential and the cosine of the angle of incidence between the leaf and the direct beam of the excitation light. This relationship was altered by nitrogen availability, such that a lower cosine of incidence (lower leaf irradiance) for a given leaf water potential was measured for plants grown under low nitrogen compared to those grown under high nitrogen. Additionally, plants grown under low nitrogen and low water availability showed more rapid rates of leaf movement compared to plants receiving high levels of these resources. Light regime during growth had no effect on the relationship between the cosine of incidence and leaf water potential. Reduced water and nitrogen availabilities during growth resulted in lower photosaturated rates of photosynthesis and stomatal conductance, as well as alterations in the relationship between these parameters. Thus, higher values for the ratio of intercellular CO₂/ambient CO₂ were measured for low-N grown plants (higher nitrogen use efficiencies) and lower values of this ratio for water stressed plants (higher water use efficiencies). The results show that environmental growth conditions other than water availability have the potential to modify leaf orientation responses to vectorial light in heliotropic legumes such as soybean. This has implications for the potential of heliotropic movements to minimize environmental stress-induced damage to the photosynthetic apparatus, and to modulate leaf-level resource use efficiencies.     

安徽省植被净初级生产力估算——基于改进的CASA模型

定量估算植被净初级生产力(NPP)对预测陆地碳循环趋势具有重要意义,目前广泛应用于NPP估算的CASA模型其精度仍有待提高。在已有CASA模型优化的基础上,考虑最大光能利用率(LUE_max)的动态变化来改进CASA模型,对改进前后的模拟结果进行比较,并利用改进后的模型估算2001—2020年安徽省植被NPP。结论如下：(1)改进的CASA模型可应用于研究区的植被NPP估算,NPP模拟值与实测值之间的相关性达到显著水平(R²=0.736,P<0.01)。(2)改进后模拟的安徽省植被NPP在空间表达上能够呈现更多细节,时间上较改进前在生长季NPP值更高,非生长季值更低,拉大了NPP的年内变化。(3)2001—2020年安徽省植被NPP整体呈波动上升趋势,多年平均值为547.61 gC m^-2 a^-1,年均增长量达2.18 gC m^-2 a^-1,2016—2020年间NPP增长最快。年内NPP具有明显的季节差异,表现为夏季>秋季>春季>冬...     

砒砂岩区不同施氮水平下5种潜在适生植物氮素利用比较研究

鄂尔多斯高原砒砂岩区土壤贫瘠、水土流失强烈,土壤氮素养分也是该区域植被恢复重建的主要限制因子.该研究以3种乡土种芨芨草(Achnatherum splendens)、长柄扁桃(Amygdalus pedunculata)和沙棘(Hippo-phae rhamnoides)与2种外来种掌叶大黄(Rheum palmatu...