Comparative carbon emission assessments of recycled and natural aggregate concrete: Environmental influence of cement content

This work examines the environmental and geochemical impact of recycled aggregate concrete production with properties representative for structural applications.The environmental influence of cement content,aggregate production,transportation,and waste landfilling is analysed by undertaking a life cycle assessment and considering a life cycle inventory largely specific for the region.To obtain a detailed insight into the optimum life cycle parameters,a sensitivity study is carried out in which supplementary cementitious materials,different values of natural-to-recycled aggregate content ratio and case-specific transportation distances were considered.The results show that carbon emissions were between 323 and 332 kgCO_(2)e per cubic metre of cement only natural aggregate concrete.These values can be reduced by up to 17%by replacing 25%of the cement with fly ash.By contrast,carbon emissions can increase when natural coarse aggregates are replaced by recycled aggregates in proportions of 50%and 100%,and transportation is not included in analysis.However,the concrete with 50%recycled aggregate presented lower increase,only 0.3%and 3.4%for normal and high strength concrete,respectively.In some cases,the relative contribution of transportation to the total carbon emissions increased when cement was replaced by fly ash in proportions of 25%,and case-specific transportation distances were considered.In absolute values,the concrete mixes with 100%recycled aggregates and 25%fly ash had lower carbon emissions than concrete with cement and natural aggregates only.Higher environmental benefits can be obtained when the transportation distances of fly ash are relatively short(15–25 km)and the cement replacement by fly ash is equal or higher than 25%,considering that the mechanical properties are adequate for practical application.The observations from this paper show that recycled aggregate concrete with strength characteristics representative for structural members can have lower carbon emissions than conventional concrete,recommending them as an alternative to achieving global sustainability standards in construction.

Life Cycle Assessment of Recycling High-Density Polyethylene Plastic Waste

Increasing production and use of various novel plastics products,a low recycling rate,and lack of effective recycling/disposal methods have resulted in an exponential growth in plastic waste accumulation in landfills and in the environment.To better understand the effects of plastic waste,Life Cycle Analysis(LCA)was done to compare the effects of various production and disposal methods.LCA shows the specific effects of the cradle-to-grave or cradle-to-cradle scenarios for landfill,incineration,and mechanical recycling.The analysis clearly indicates that increasing recycling of plastics can significantly save energy and eliminate harmful emissions of various carcinogens and GHGs into the environment.As recycling increases,the need for virgin-plastic production can be greatly reduced.Furthermore,the results of this study may help improve current mechanical recycling processes as well as potential future recycling methods,such as chemical recycling.Concerns about the current recycling/disposal methods for plastics have brought increasing attention to the waste accumulation problem.However,with the current COVID-19 pandemic,plastic accumulation is expected to increase significantly in the near future.A better understanding of the quantitative effects of the various disposal methods can help guide policies and future research toward effective solutions of the plastic waste problem.

The significance of resource recycling for coking wastewater treatment:based on environmental and economic life cycle assessment

The sustainability of the coking industry is supported by reasonable production profit and environmental quality requirements.The traditional measures substantially increased the related costs for enterprises to reach standards.This paper aims to develop a comprehensive cost combined environmental impact assessment method that is necessary for the analysis of wastewater treatment systems.Typical three coking wastewater treatment processes in China were evaluated.Results showed that eutrophication dominantly contributed to the overall environmental effect.Improving effluent quality could significantly reduce the total environmental impact.In terms of an economic perspective,the price of raw materials was the main factor that affected the operating cost of comprehensive treatment.Based on subsystem analysis,the pretreatment stage accounted for the majority of environmental and cost burdens,respectively reaching 64%-78%and 64%-86%.Optimizing the pretreatment process by enhancing the efficiency of high concentration raw material recovery and substituting toxic raw materials for extractant could reduce the environmental impact and economic cost by 43.8%and 57%,respectively,which was an effective way to improve the potential performance of coking wastewater treatment plants(WWTPs).

Life Cycle Assessment and Life Cycle Cost of Waste Management—Plastic Cable Waste

The main driver for recycling cable wastes is the high value of the conducting metal, while the plastic with its lower value is often neglected. New improved cable plastic recycling routes can provide both economic and environmental incentive to cable producers for moving up the “cable plastic waste ladder”. Cradle-to-gate life cycle assessment, LCA, of the waste management of the cable scrap is suggested and explained as a method to analyze the pros and cons of different cable scrap recycling options at hand. Economic and environmental data about different recycling processes and other relevant processes and materials are given. Cable producers can use this data and method to assess the way they deal with the cable plastic waste today and compare it with available alternatives and thus illuminate the improvement potential of recycling cable plastic waste both in an environmental and in an economic sense. The methodology applied consists of: cradle-to-gate LCA for waste material to a recycled material (recyclate);quantifying the climate impact for each step on the waste ladder for the specific waste material;the use of economic and climate impact data in parallel;climate impact presented as a span to portray the insecurities related to which material the waste will replace;and possibilities for do-it-yourself calculations. Potentially, the methodology can be useful also for other waste materials in the future.

A Review of the Life Cycle Analysis for Plastic Waste Pyrolysis

Pyrolysis is a rapidly expanding chemical-based recyclable method that complements physical recycling. It avoids improper disposal of post-consumer polymers and mitigates the ecological problems linked to the production of new plastic. Nevertheless, while there is a consensus that pyrolysis might be a crucial technology in the years to come, more discussions are needed to address the challenges related to scaling up, the long-term sustainability of the process, and additional variables essential to the advancement of the green economy. Herein, it emphasizes knowledge gaps and methodological issues in current Life Cycle Assessment (LCA), underlining the need for standardized techniques and updated data to support robust decision-making for adopting pyrolysis technologies in waste management strategies. For this purpose, this study reviews the LCAs of pyrolytic processes, encompassing the complete life cycle, from feedstock collection to end-product distribution, including elements such as energy consumption, greenhouse gas emissions, and waste creation. Hence, we evaluate diverse pyrolysis processes, including slow, rapid, and catalytic pyrolysis, emphasizing their distinct efficiency and environmental footprints. Furthermore, we evaluate the impact of feedstock composition, process parameters, and scale of operation on the overall sustainability of pyrolysis-based plastic waste treatment by integrating results from current literature and identifying essential research needs. Therefore, this paper argues that existing LCA studies need more coherence and accuracy. It follows a thorough evaluation of previous research and suggests new insights into methodologies and restrictions.

黏结钕铁硼磁体生产和回收生命周期评价

关于钕铁硼磁体回收的研究越来越受到重视,但在起步阶段回收制备技术是否能够真正带来环境效益是不确定的。采用ReCiPe评价方法,选取制备1 kg黏结钕铁硼磁体为功能单位,分别对黏结钕铁硼磁体直接制备和回收制备流程的环境影响进行评价并对比。结果表明:直接制备流程中对环境影响最大的关键阶段为熔炼阶段,环境影响主要由钕和电力产生;回收制备流程中对环境影响最大的关键阶段为去除有机物阶段和热压固化阶段,环境影响主要由次氯酸钠和电力产生。生产1 kg黏结钕铁硼磁体,直接制备工艺对人体健康损害、生态健康损害和资源耗竭的环境损害分别是回收制备工艺的158.40%、180.63%、63.37%。

围绕产业链和生命周期的包装废弃物治理初探

包装废弃物问题的治理,根本在于明晰包装产业链及生命周期与包装废弃物产生的关系,构建闭环的包装废弃物回收体系与回收模式。为此,在揭示包装废弃物形成和产生的要素与环节的基础上,试图阐明减少包装废弃物产生与便利回收处理之间的逻辑关系。提出包装废弃物治理必须秉承材料撷取是基础,包装设计是关键,制品生产工艺优化是重点,回收体系与模式是保障的思路和原则,绿色低碳是目标。在大力研发和推广应用新型绿色包装材料的同时,应建立严格的包装制品设计规范和审批制度,淘汰工艺技术落后产能,着力打造由政府主导、政策支持、区域协同、效益驱动、自主与约束相结合的回收体系与模式,建立从回收到分类再到加工处理的完整产业链,从而对包装废弃物实现标本兼治。

盐冻循环下粉煤灰再生混凝土性能劣化规律及寿命预测

为研究粉煤灰再生混凝土在高寒、盐渍土地区的耐久性问题,以质量分数为3%的NaCl和5%的Na_(2)SO_(4)混合溶液为冻融介质,采用快冻法对不同粉煤灰掺量的再生混凝土进行冻融循环试验,测定各组试件的质量损失、抗压强度以及相对动弹性模量的数据,研究粉煤灰再生混凝土在盐冻耦合作用下的性能劣化规律,并通过抛物线损伤模型预测再生混凝土的耐久性寿命。研究结果表明:在盐冻侵蚀作用下,不同掺量粉煤灰再生混凝土的相对动弹性模量和抗压强度变化均呈现前期平缓下降,后期快速下降的趋势,而质量损失率则前期缓慢增长,后期快速增加;抛物线模型能较好表征粉煤灰再生混凝土在复合盐环境下的冻融损伤,其模型拟合曲线与试验结果符合较好,具有较高的精度;当粉煤灰掺量为20%时,再生混凝土的抗冻耐久性寿命最长。

不同再生骨料生产模式的环境影响评价——以浙江省为例

建筑废弃物的资源化过程与其生产方式密切相关,由于处理过程和运输距离的差异,采用集中式处理工厂和移动式破碎站生产再生骨料时,两者的环境影响具有明显差异。立足于浙江省基于三维数字地球确定运输距离,科学定量地给出了2种再生骨料生产方式的生命周期环境影响清单,开展了相应的生命周期环境负荷和环境效益评价。研究结果表明:集中式处理工厂环境负荷主要产生于材料运输阶段,占总环境负荷的53.42%;移动式破碎站的环境负荷则主要来源于骨料外运和残渣的焚烧与填埋,分别占总环境负荷的37.26%和25.54%。虽然移动式破碎站生产1 t再生骨料的环境负荷低于集中式处理工厂,但集中式处理工厂具有更高的生产效率、年产量和生产能力,极大地提高了其年环境效益,利用集中式生产再生骨料其年环境效益比移动式高44.44%。因此,在碳达峰碳中和背景下,可大力推广采用集中式生产再生骨料。

再生水回用对典型污水处理工艺生态效应的影响

再生水回用是降低水污染、改善水环境、提高水资源利用率的重要途径,但这一过程同步增加了药剂和能源的消耗,以及温室气体排放等。研究再生水回用对典型污水处理工艺的生态效应影响,可为污水处理策略的全过程优化提供支持。文中采用生命周期评价法,从元素资源消耗(ADPE)、化石燃料消耗(ADPF)、臭氧层耗竭(ODP)、全球变暖(GWP)、酸化(AP)、富营养化(EP)、淡水生态毒性(FAETP)、陆地生态毒性(TETP)和人类毒性(HTP)9种环境效应,对比分析了常规污水处理工艺AAO和再生水处理工艺AAO+MBR的生态效应。结果表明,AAO+MBR工艺对EP的削减效果是AAO工艺的1.1倍,污水处理效果优于单独使用厌氧/缺氧/好氧(AAO)工艺;AAO+膜生物反应器(MBR)工艺对ADPE、ADPF、ODP、GWP、AP、FAETP、TETP、HTP的负面影响均高于AAO工艺;进一步在20%、40%、60%、80%和100%不同再生水回用率情景下比较AAO工艺和AAO+MBR工艺对9种环境效应的影响,发现再生水回用率显著影响ADPE、ADPF、FAETP、ODP,当再生水回用率为100%时,对环境影响下降45%~100%;对AP、GWP、TETP、HTP的影响较小,当再生水回用率为100%时,对环境影响下降17%~25%;对EP影响则不显著,随着再生水回用率变化,EP基本保持不变。研究可为污水处理决策优化提供支持。

区块链技术应用对企业绿色创新的影响

在“碳达峰、碳中和”愿景和数字经济发展的双重背景下,区块链技术作为数字经济时代的关键技术之一,是否具有绿色创新效应值得重点关注。基于战略选择理论,选取中国A股611家上市企业为研究对象,实证检验区块链技术应用对企业绿色创新的影响,并探讨在不同高管团队多元化程度和企业生命周期情境下区块链技术的绿色创新效应。研究发现:企业应用区块链技术能够显著促进绿色创新;区块链技术的绿色创新赋能效应,在高管团队职能背景多元化程度高、人口特征背景多元化程度低的企业中更显著;相较于成长期和衰退期企业而言,成熟期企业应用区块链技术能够促进绿色创新。研究结论有助于拓宽区块链技术的应用场景,为区块链技术助力企业实现可持续发展提供理论支撑和实践借鉴。

基于生命周期评价法模型的废旧轮胎翻新的环境效益评价

对废旧轮胎进行翻新是减少资源消耗和环境污染,促进产业循环经济发展的重要手段。本文选择全钢巨胎为研究对象评价了废旧轮胎翻新的环境效益。研究发现,在全钢巨胎生产过程中,原材料投入是环境影响的主要来源。如果按全球平均水平(6.00%)进行翻新,环境总影响将减少4.20%,而按照北美平均水平(47.00%)进行翻新,环境总影响将减少32.90%。这表明,在全钢工程轮胎生产中引入废旧轮胎回收工艺具有较强的环境友好性。鉴于目前我国对废旧轮胎翻新的重视不足,本研究还给出了相应的政策建议。

Nitrogen doping induced by intrinsic defects of recycled polyethylene terephthalate-derived carbon nanotubes

The indiscriminate utilization of nondegradable polyethylene terephthalate(PET)-based products has triggered serious environmental pollution that has to be resolved vigorously.A simple synthesis of N-doped carbon nanotubes from recycled PET(NCNTs_(r-PET))was developed by a nitric acid-assisted hydrothermal method.Experimental results and theoretical calculations show that the intrinsic defects in CNTs_(r-PET)would induce N-doping by NH_(3)generated from nitric acid during the hydrothermal process,thus producing the NCNTs_(r-PET).The life cycle assessment proves that the developed method for N-doped CNTs using r-PET as the carbon source is more environmentally friendly than the conventional chemical vapor deposition using acetylene as the carbon source.As a typical application,the NCNTs_(r-PET)delivered an impressive sodium storage capacity with an ultralong lifespan.This work not only provides a new route to upcycling waste plastics into valuable carbonaceous materials in an ecofriendly manner,but also reveals a basic understanding of the N-doping mechanism in carbonaceous materials.

源于钛基铅酸电池的再生钛基体作为板栅集电体的研究

钛基铅酸电池能够大幅度提高铅酸电池的能量密度,并且解决了传统铅酸电池正极板易腐蚀和软化的问题,商业化潜力巨大.然而,相比于传统铅酸电池成熟的回收工艺和再生铅的利用,钛基铅酸电池的回收方法以及回收材料的应用途径是未来钛基铅酸电池应用和发展的关键.本文制备了源于钛基铅酸电池的再生钛基的正负极板栅,将正极板栅组成为再生钛基体/锡锑中间层/铅,将负极板栅组成为再生钛基体/铜/铅.通过研究源于钛基铅酸电池的再生钛基体用于板栅集电体的电化学性能,讨论了循环应用的可能性.结果表明,基于再生钛基正极板的活性物质放电比容量为72.4mA·h/g,相应电池在0.5C100%DoD(放电深度)下的循环寿命为180次;基于再生钛基负极板的活性物质放电比容量为98mA·h/g,相应电池在0.5C100%DoD下的循环寿命达到332次,用再生钛基体制备的板栅及电池的性能与纯钛基体相同.

基于B/S架构的军校教材管理系统分析与设计

近年来,军校教材呈现爆发式增长,旧的教材管理系统已不能有效进行信息化管理,工作效率低。根据军校对教材管理的特定需求,对系统和技术可行性进行客观分析,提出一种基于B/S架构的军校教材管理系统设计,并探讨系统运行性能指标,对系统的拓扑结构、运行环境、功能实现等进行全面设计,充分利用军校现有的校园网络系统实现每册教材的全生命周期管理。

退役三元锂电池回收方法的生命周期评估

开发了一个生命周期评价框架,分析使用中国工厂实施的传统湿法冶金技术回收镍钴锰(NCM)和镍钴铝(NCA)电池对环境的影响。结果表明,回收NCA电池带来的温室效益类指标要低于NCM电池,但其淡水生态毒性、人类致癌毒性、海洋生态毒性这三个指标却高于NCM电池,因此传统的湿法冶金方法需要被完善。两种电池的回收过程对环境的影响均为负增长,而且在回收最开始的阶段对环境影响最大。研究结果可为动力电池回收企业技术更新提供参考。

硅灰对再生混凝土抗盐冻性能及微观结构的影响

为研究硅灰对内蒙河套盐碱地区的再生混凝土微观结构和抗盐冻性能的影响,以硅灰掺量为变量对再生混凝土(RAC)进行了冻融循环试验、抗氯离子渗透试验和电镜扫描试验(SEM)。结果表明:通过SEM能看出球状硅灰颗粒可以使结构变得致密,RAC的质量损失率、立方体抗压强度损失率和氯离子迁移系数均随硅灰掺量的增加呈现先减后增的趋势,但硅灰掺量为10%和15%的RAC相对动弹性模量却相差不大;综合来看硅灰掺量为10%时抗盐冻性能最好,90次冻融循环后RC10组的质量损失率、立方体抗压强度损失率和氯离子迁移系数分别仅为RC0组的54.3%、50.3%和49.81%;同时建立了以硅灰掺量和冻融循环次数为参数的冻融损伤模型,并对内蒙盐碱地区的RAC进行了寿命预测。研究成果有助于推动再生混凝土的合理利用。

“双碳”背景下我国废钢资源高质循环利用战略研究

废钢是再生绿色资源,也是钢铁工业不可或缺的铁素资源。在“双碳”战略背景下,重构废钢循环利用技术体系和创新废钢资源管理模式,从根本上破解废钢高质循环利用的瓶颈问题对钢铁工业的绿色低碳转型至关重要。本文对比分析了全球废钢行业的发展现状,科学预测了我国粗钢产量和废钢资源量的变化趋势,提出了2060年左右可能存在的全废钢冶炼这一中国特色问题;凝练了废钢行业规范化、信息化、数字化、智能化发展方向;系统梳理了我国废钢循环利用在标准制度体系、精确分类回收、基于生产者责任延伸(EPR)制度的材料设计和数字化标识解析等方面存在的问题与挑战;在此基础上,创新提出了废钢资源“四全五化”高质循环利用新模式,清晰给出了组织框架和实施策略方案,即面向可能到来的全废钢时代,从钢铁材料全生命周期、全生产流程、全产业链(“四全”)协同贯彻EPR制度,实现废钢资源的科学分类管理、循环和再利用,同时加强全流程生产管理的数字化、信息化、标识化、网络化,并逐渐过渡到优质废钢拆解回收机器人化(“五化”)。研究建议:完善钢铁领域贯彻EPR的制度、技术和管理体系,加强废钢行业标准体系建设,加强钢铁材料全生命周期全产业链数字化标识解析,强化重点行业废钢分类回收和循环利用等,为全面实施废钢资源“四全五化”高质循环利用新模式做好坚实保障。

An Analysis of Contemporary Copper Recycling in China

Copper consumption increased very quickly in China in recent years,which could not be met by inland copper industry.In order to achieve a sustainable development of copper industry,an analysis of copper recycling in China was necessary.For the life cycle of copper products a copper-flow diagram with time factor was worked out and the contemporary copper recycling in China was analyzed,from which the following data were obtained.The average life cycle of copper products was 30 years.From 1998 to 2002,the use ratio of copper scraps in copper production,the use ratio of copper scraps in copper manufacture,the materials self-support ratio in copper production,and the materials self-support ratio in copper manufacture were 26.50%,15.49%,48.05% and 59.41%,respectively.The materials self-support ratios in copper production and manufacture declined year by year in recent years on the whole,and the latter dropped more quickly.The average index of copper ore and copper scrap from 1998 to 2002 were 0.8475 t/t and 0.0736 t/t,respectively;and copper resource efficiency was 1.1855 t/t.Some efforts should be paid to reduce copper ores consumption and promote copper scraps regeneration.Copper scraps were mostly imported from foreign countries because of shortage in recent years in China.Here the reasons related to copper scraps deficiency were also demonstrated.But we can forecast:when copper production was in a slow rise or in a steady state in China,the deficiency of copper scraps may be mitigated;when copper production was in a steady state for a very long time,copper scraps may become relatively abundant.According to the status of copper industry in China,the raw materials of copper production and manufacture have to depend on oversea markets heavily in recent years,and at the same time,the copper scraps using proportion and efficiency in copper industry should be improved.