基于生命周期方法的生活垃圾资源化利用系统生态效率分析

我国生活垃圾产量大但处理能力不足,产生多种环境危害,对其资源化利用能够缓解环境压力并回收资源。为探讨生活垃圾资源化利用策略,综合生命周期评价与生命周期成本分析方法,建立生态效率模型。以天津市为例,分析和比较焚烧发电、卫生填埋-填埋气发电、与堆肥+卫生填埋3种典型生活垃圾资源化利用情景的生态效率。结果表明,堆肥+卫生填埋情景具有潜在最优生态效率;全球变暖对总环境影响贡献最大,而投资成本对经济影响贡献最大。考虑天津市生活垃圾管理现状,建议鼓励发展生活垃圾干湿组分分离及厨余垃圾堆肥的资源化利用策略。     

城市生活垃圾的危害与处理方法浅析

随着城市生活垃圾产生量不断增长,其对环境的危害逐步扩大。城市生活垃圾在收集、运输、处置过程中垃圾所含有的和产生的有害成分会对大气、土壤、水体造成污染。解决垃圾问题的目标是使垃圾减容、减量、资源化、能源化和无害化。目前在我国乃至世界范围内广泛使用的城市生活垃圾处理方式主要有卫生填埋、焚烧和堆肥三种。     

新书介绍

内容简介:环境保护是我国的基本国策,而城市垃圾处理是城市环境保护的重要内容,也是衡量城市文明程度和城市管理水平的重要标志之一。近几年来,我国的大部分城市都正在积极的进行城市生活垃圾处理工程的探索和实践,但由于国内无系统的垃圾处理理论和少有成功的实例,而从国外引进的卫生填埋、堆肥、焚烧发电三大处理方式均不合中国国情。     

城市生活垃圾的微生物处理技术

城市生活垃圾量的日益增多严重威胁着城市的环境及人们的健康,垃圾处理成为现代社会面临的重要问题之一,因此城市生活垃圾处理技术对于城市的可持续发展起着非常重要的作用。微生物在自然界中种类繁多,在城市生活垃圾生物处理应用中占有重要地位。本文对微生物在城市生活垃圾的卫生填埋技术、生物反应器填埋技术、好氧堆肥技术、发酵降解技术及生物干燥器技术中的应用进行了综述,并对城市生活垃圾的综合处理提出建议,以期为城市生活垃圾的微生物处理技术的应用提供参考。     

中国餐厨垃圾处理的现状、问题和对策

餐厨垃圾具有高水分、高盐分、高有机质含量、组分时空差异明显、危害性与资源性并存的特点。目前国内外常用的餐厨垃圾处理技术如焚烧、卫生填埋、生态饲料、厌氧消化、好氧堆肥和蚯蚓堆肥等,通常存在着资源化利用效率低、经济效益不够理想的缺陷。总结相关文献及报道,中国在餐厨垃圾资源化处理上存在"行政瓶颈"和"技术瓶颈"两大方面的问题:"行政瓶颈"的解决之道在于完善管理及处理体系,各级政府部门切实重视、加大投入,强力推进垃圾分类投放;而对于"技术瓶颈",除综合运用多种现有处理技术外,开发新技术提高餐厨垃圾的资源化循环利用程度,是关键所在。     

基于能值的污水处理系统环境影响分析

污水处理厂及其“产物”(处理水和脱水污泥)的处理处置系统共同构成了污水处理综合系统,它从整体上涵盖了污水处理的全过程.污水处理综合系统在构建和运行的过程中主要包括两方面的环境影响:1)物质资源的消耗;2)排放污染物对环境的危害,而后者在既往有关的污水处理系统分析中往往被忽略.为了更全面地了解污水处理过程的环境影响状况,本文以能值分析理论为基础对污水处理综合系统进行分析,同时,结合生态足迹理论对系统的可持续性进行分析.结果表明:水体污染物的环境影响能值远大于大气污染物,且主要受氨氮排放量的影响;污水处理综合系统的能值消耗主要为废物流能值和本地可更新资源能值;“处理厂系统+填埋系统”的能值利用效率最高,“处理厂系统+中水回用系统+焚烧系统”的能值利用效率最低;“处理厂系统+中水回用系统+填埋系统”的环境可持续性最好,而“处理厂系统+焚烧系统”的可持续性最差.     

填埋场植被覆盖对气态污染物的减排效应研究进展

填埋场是生活垃圾的最终处置场所,同时填埋处理是当前我国生活垃圾处理的主要方式。填埋场产生的气态污染物释放造成了较为严重的环境影响,特别是其中的恶臭化合物。植被覆盖对消减填埋场气态污染物具有一定作用,但其作用大小及影响因素很少被关注。从填埋场释放的污染物及植被的减排效用2方面对已有的文献进行疏理,并指明研究的方向。     

无公害蔬菜营养与施肥研究进展

本文综述了无公害蔬菜定义、卫生评价标准及生产环境评价标准。对无公害蔬菜生产中常用的氮肥在土壤中转化、种类和形态、用量和时期与硝酸盐关系,过量氮肥对蔬菜体内硝酸盐累积影响,对地下水质污染和人体健康的影响,磷肥过量引起流失造成水体富营养化和磷肥中镉对土壤生态环境污染的影响,以及畜禽粪肥、城市垃圾和污泥堆肥对蔬菜品质及环境影响进行了评述。对近二十年来土壤栽培条件下应用于无公害蔬菜营养诊断与平衡施肥研究的     

卫生填埋场的植被重建

随着世界各地城市市区的不断扩大,垃圾填埋场的环境影响和植被重建已成为全球所共同面临的一个相当紧迫和突出的环境问题。简述了垃圾卫生填埋的概念、填埋的方式及其带来的生态环境问题;并对影响垃圾填埋场上植物生长的各种因素,以及各国学者建议在植被重建过程中针对这些因素所应采取的措施和步骤作了详细描述。     

污水处理综合系统环境经济效益评估

污水处理、处理水处理和污泥处理是污水处理综合系统的3个基本单元.本文运用能值分析和新构建的能值指标评估了处理水回用与排放、污泥填埋与堆肥对系统整体性能的影响.该系统的价值包括环境收益和产品输出两方面.前者可通过污水处理前后的环境服务差值计算.由于系统内部物质和能量的转化数据难以获知,产品价值通过新提出的替代价值核算.结果表明： “污水处理+处理水回用+污泥填埋”的竞争力最高,“污水处理+处理水回用+蚯蚓堆肥”的可持续性能最高;处理水回用和蚯蚓堆肥均有助于提高系统可持续性;处理水回用与否应综合考虑处理水水质和当地条件;污泥蚯蚓堆肥的资源化效率还有待提高;改进的能值指标更适宜于污水处理综合系统效益评估.     

Environmental impact and cost assessment of incineration and ethanol production as municipal solid waste management strategies

Purpose

Municipal solid waste (MSW) can be handled with several traditional management strategies, including landfilling, incineration, and recycling. Ethanol production from MSW is a novel strategy that has been proposed and researched for practical use; however, MSW ethanol plants are not widely applied in practice. Thus, this study has been conducted to analyze and compare the environmental and economic performance of incineration and ethanol production as alternatives to landfilling MSW.

Methods

The ISO 14040 life cycle assessment framework is employed to conduct the environmental impact assessment of three different scenarios for the two MSW management strategies based on processing 1 ton of MSW as the functional unit. The first scenario models the process of incinerating MSW and recovering energy in the form of process heat; the second scenario also includes the process of incinerating MSW but yields in the recovery of energy in the form of electricity; and the third scenario models the process of converting MSW into ethanol. The economic impacts of each scenario are then assessed by performing benefit-to-cost ratio (BCR) and net present value (NPV) analyses.

Results and discussion

The results from the environmental impact assessment of each scenario reveal that scenario 2 has the highest benefits for resource availability while scenario 3 is shown to be the best alternative to avoid human health and ecosystems diversity impacts. Scenario 1 has the worst environmental performance with respect to each of these environmental endpoint indicators and has net environmental impacts. The results of the economic analysis indicate that the third scenario is the best option with respect to BCR and NPV, followed by scenarios 2 and 1, respectively. Furthermore, environmental and economic analysis results are shown to be sensitive to MSW composition.

Conclusions

It appears municipalities should prefer MSW incineration with electricity generation or MSW-to-ethanol conversion over MSW incineration with heat recovery as an alternative to landfilling. The contradiction between the environmental impact assessment results and economic analysis results demonstrates that the decision-making process is sensitive to a broad set of variables. Decisions for a specific MSW management system are subject to facility location and size, MSW composition, energy prices, and governmental policies.     

The impact of landfilling and composting on greenhouse gas emissions – A review

Municipal solid waste is a significant contributor to greenhouse gas emissions through decomposition and life-cycle activities processes. The majority of these emissions are a result of landfilling, which remains the primary waste disposal strategy internationally. As a result, countries have been incorporating alternative forms of waste management strategies such as energy recovery from landfill gas capture, aerobic landfilling (aerox landfills), pre-composting of waste prior to landfilling, landfill capping and composting of the organic fraction of municipal solid waste. As the changing global climate has been one of the major environmental challenges facing the world today, there is an increasing need to understand the impact of waste management on greenhouse gas emissions. This review paper serves to provide an overview on the impact of landfilling (and its various alternatives) and composting on greenhouse gas emissions taking into account streamlined life cycle activities and the decomposition process. The review suggests greenhouse gas emissions from waste decomposition are considerably higher for landfills than composting. However, mixed results were found for greenhouse gas emissions for landfill and composting operational activities. Nonetheless, in general, net greenhouse gas emissions for landfills tend to be higher than that for composting facilities.     

A triple bottom line evaluation of solid waste management strategies: a case study for an arid Gulf State,Kuwait

Purpose

We extend a life cycle assessment (LCA) embracing both economic and social perspectives to develop an integrated solid waste management system for Kuwait. This study considers the domestic waste generated by households and waste generated commercially. Six municipal solid waste (MSW) scenarios (SR₁, SR₂, …, SR₆) are evaluated using a triple bottom line (TBL) approach that incorporates environmental, financial, and social bottom lines (social BLs).

Methods

Within the TBL framework, the environmental BL employs LCA in accordance with ISO 14044. The financial BL is calculated using capital and operational costs as well as the associated recycling revenues. The social BL applies macro-economic indicators that examine the effects of a given MSW scenario (SR) on the inhabitants. To integrate the TBLs, we apply an analytic hierarchy process (AHP) because of its advantage of pairwise unit-free rescaling. The relative importance of each BL is determined by considering the political, legal, socio-cultural, and economic climates of the country. The relative weights are cross-multiplied with indicators from each BL to calculate a composite sustainability index (CSI) for the proposed MSW SR.

Results and discussion

The environmental BL (LCA) indicates that global warming, acidification, and human toxicity are the most adversely affected impact categories, considering the local conditions and waste composition. Environmentally, SR₁ (landfilling) scored the worst in almost all impact categories and, thus, was labeled the worst-case scenario environmentally. SR₆ (composting, recycling, and incineration) performed the best from an environmental perspective. Financially, landfilling (SR₁) is the most economical scenario. Any SR that focused on incineration (SR₂ and SR₅) was financially unfavorable. The scenarios that involved composting were scored as financially reasonable (SR₃, SR₄, and SR₆). From a social acceptability perspective, SR₂ (incineration) scored the highest, while SR₁ (landfills) scored the lowest. Finally, across the TBL framework, SR₄ (composting and incineration) had the highest CSI based on the relative importance scheme adopted for each BL.

Conclusions

Although they are often overlooked in most LCA studies, the financial and social aspects are indispensable to proving feasibility and credibility at a strategic level. The complexity of financial and social formulations in LCA is inherited from the difficulty in quantifying emissions and other impacts. In addition, from a social perspective, the contingent risks and associated uncertainty vary widely across cultures, ideologies, and degrees of development and are further complicated because of the scarcity and uncertainty of the data.

     

Environmental assessment of energy production from municipal solid waste incineration

Background, Aims and Scope During the combustion of municipal solid waste (MSW), energy is produced which can be utilized to generate electricity. However, electricity production from incineration has to be evaluated from the point view of the environmental performance. In this study, environmental impacts of electricity production from waste incineration plant in Thailand are compared with those from Thai conventional power plants. Methods The evaluation is based on a life cycle perspective using life cycle assessment (LCA) as the evaluation tool. Since MSW incineration provides two services, viz., waste management and electricity production, the conventional power production system is expanded to include landfilling without energy recovery, which is the most commonly used waste management system in Thailand, to provide the equivalent function of waste management. Results The study shows that the incineration performs better than conventional power plants vis-à-vis global warming and photochemical ozone formation, but not for acidification and nutrient enrichment. Discussion There are some aspects which may influence this result. If landfilling with gas collection and flaring systems is included in the analysis along with conventional power production instead of landfilling without energy recovery, the expanded system could become more favorable than the incineration in the global warming point of view. In addition, if the installation of deNO_x process is employed in the MSW incineration process, nitrogen dioxide can be reduced with a consequent reduction of acidification and nutrient enrichment potentials. However, the conventional power plants still have lower acidification and nutrient enrichment potentials. Conclusions The study shows that incineration could not play the major role for electricity production, but in addition to being a waste management option, could be considered as a complement to conventional power production. To promote incineration as a benign waste management option, appropriate deNO_x and dioxin removal processes should be provided. Separation of high moisture content waste fractions from the waste to be incinerated and improvement of the operation efficiency of the incineration plant must be considered to improve the environmental performance of MSW incineration. Recommendations This study provides an overall picture and impacts, and hence, can support a decision-making process for implementation of MSW incineration. The results obtained in this study could provide valuable information to implement incineration. But it should be noted that the results show the characteristics only from some viewpoints. Outlook Further analysis is required to evaluate the electricity production of the incineration plant from other environmental aspects such as toxicity and land-use.     

Comparative life cycle assessment of two landfill technologies for the treatment of municipal solid waste

Goal and Scope  The potential environmental impacts associated with two landfill technologies for the treatment of municipal solid waste (MSW), the engineered landfill and the bioreactor landfill, were assessed using the life cycle assessment (LCA) tool. The system boundaries were expanded to include an external energy production function since the landfill gas collected from the bioreactor landfill can be energetically valorized into either electricity or heat; the functional unit was then defined as the stabilization of 600 000 tonnes of MSW and the production of 2.56x10⁸ MJ of electricity and 7.81x10⁸ MJ of heat. Methods  Only the life cycle stages that presented differences between the two compared options were considered in the study. The four life cycle stages considered in the study cover the landfill cell construction, the daily and closure operations, the leachate and landfill gas associated emissions and the external energy production. The temporal boundary corresponded to the stabilization of the waste and was represented by the time to produce 95% of the calculated landfill gas volume. The potential impacts were evaluated using the EDIP97 method, stopping after the characterization step. Results and Discussion  The inventory phase of the LCA showed that the engineered landfill uses 26% more natural resources and generates 81% more solid wastes throughout its life cycle than the bioreactor landfill. The evaluated impacts, essentially associated with the external energy production and the landfill gas related emissions, are on average 91% higher for the engineered landfill, since for this option 1) no energy is recovered from the landfill gas and 2) more landfill gas is released untreated after the end of the post-closure monitoring period. The valorization of the landfill gas to electricity or heat showed similar environmental profiles (1% more raw materials and 7% more solid waste for the heat option but 13% more impacts for the electricity option). Conclusion and Recommendations  The methodological choices made during this study, e.g. simplification of the systems by the exclusion of the identical life cycle stages, limit the use of the results to the comparison of the two considered options. The validity of this comparison could however be improved if the systems were placed in the larger context of municipal solid waste management and include activities such as recycling, composting and incineration.     

Life cycle environmental and economic impact of a food waste recycling-farming system: a case study of organic vegetable farming in Japan

Purpose

Bio-based recycling systems and agricultural production using recycled materials are often evaluated separately. This study performs an environmental and socio-economic life cycle assessment (LCA) of a food waste treatment and spinach farming system in Japan. The environmental and economic tradeoffs of introducing a recycling system and the net environmental benefit of the substitution of market fertilizer considering operation changes are also examined.

Methods

Three scenarios were developed and compared. In the conventional (CV) scenario, food waste is collected, incinerated, and disposed of in landfill, and the farmer uses market organic fertilizer. The on-site composting (OC) scenario processes food waste using an on-site garbage disposer and transports compost to a nearby spinach farmer. Food waste in the centralized composting (CC) scenario is transported to a centralized composting facility and resultant compost is sent to the farm. Primary data were obtained from field experiments and interviews. Non-greenhouse gas (GHG) emissions from the field and nitrogen leaching to water systems were simulated using the denitrification–decomposition (DNDC) model.

The environmental LCA targeted climate change, eutrophication, and waste landfill. An input–output analysis estimated socio-economic indicators, namely gross added value and employment inducement effect.

Results and discussion

The scenario with the lowest impact is the CC scenario. Climate change and eutrophication impacts are highest in the OC scenario and waste landfill impacts are most significant in the CV scenario. The weighted impact by LIME2 can be reduced by 47% in the CC scenario and 17% in the OC scenario due to the recycling of food waste instead of dumping in the landfill. The difference in socio-economic indicators between the scenarios was relatively small, although the CV scenario encouraged more employment. The substitution effect of composting, as well as the environmental impact reduction of replacing market organic fertilizer with compost, will result in 28.7% of the avoided impacts in GHG emissions.

Conclusions

Both composting scenarios are feasible from an environmental and socio-economic perspective when compared with conventional organic production, although there is a tradeoff between waste landfill and GHG emissions for the on-site composting system. However, the OC scenario needs to save electricity to improve its environmental competitiveness with the CV scenario. When considering the substitution effect of composting, it is recommended to take into account that agricultural operation also changes.

     

LCA application to integrated waste management planning in Gipuzkoa (Spain)

Goal, Scope and Background  Gipuzkoa is a department of the Vasque Country (Spain) with a population of about 700,000 people. By the year 2000 approximately 85% of municipal solid waste in this area was managed by landfilling, and only 15% was recycled. Due to environmental law restrictions and landfill capacity being on its limit, a planning process was initiated by the authorities. LCA was used, from an environmental point of view, to assess 7 possible scenarios arising from the draft Plan for the 2016 time horizon. Main Features  In each scenario, 9 waste flows are analysed: rest waste, paper and cardboard, glass containers, light packaging, organic-green waste, as well as industrial/commercial wood, metals and plastics, and wastewater sludge. Waste treatments range from recycling to energy recovery and landfilling. Results  Recycling of the waste flows separated at the source (paper and cardboard, glass, light packaging, organic-green waste, wood packaging, metals and plastics) results in net environmental benefits caused by the substitution of primary materials, except in water consumption. These benefits are common to the 7 different scenarios analysed. However, some inefficiencies are detected, mainly the energy consumption in collection and transport of low density materials, and water consumption in plastic recycling. The remaining flows, mixed waste and wastewater sludge, are the ones causing the major environmental impacts, by means of incineration, landfilling of partially stabilised organic material, as well as thermal drying of sludge. With the characterisation results, none of the seven scenarios can be clearly identified as the most preferable, although, due to the high recycling rates expected by the Plan, net environmental benefits are achieved in 9 out of 10 impact categories in all scenarios when integrated waste management is assessed (the sum of the 9 flows of waste). Finally, there are no relevant differences between scenarios concerning the number of treatment plants considered. Nevertheless, only the effects on transportation impacts were assessed in the LCA, since the plant construction stage was excluded from the system boundaries. Conclusions  The results of the study show the environmental importance of material recycling in waste management, although the recycling schemes assessed can be improved in some aspects. It is also important to highlight the environmental impact of incineration and landfilling of waste, as well as thermal drying of sludge using fossil fuels. One of the main findings of applying LCA to integrated waste management in Gipuzkoa is the fact that the benefits of high recycling rates can compensate for the impacts of mixed waste and wastewater sludge. Recommendations and Outlook  Although none of the scenarios can be clearly identified as the one having the best environmental performance, the authorities in Gipuzkoa now have objective information about the future scenarios, and a multidisciplinary panel could be formed in order to weight the impacts if necessary. In our opinion, LCA was successfully applied in Gipuzkoa as an environmental tool for decision making.     

Solid waste treatment and disposal: effects on public health and environmental safety

The safety and acceptability of many widely used solid waste management practices are of serious concern from the public health point of view. Such concern stems from both distrust of policies and solutions proposed by all tiers of government for the management of solid waste and a perception that many solid waste management facilities use poor operating procedures. Waste management practice that currently encompasses disposal, treatment, reduction, recycling, segregation and modification has developed over the past 150 years. Before that and in numerous more recent situations, all wastes produced were handled by their producers using simple disposal methods, including terrestrial dumping, dumping into both fresh and marine waters and uncontrolled burning. In spite of ever-increasing industrialisation and urbanisation, the dumping of solid waste, particularly in landfills, remains a prominent means of disposal and implied treatment. Major developments have occurred with respect to landfill technology and in the legislative control of the categories of wastes that can be subject to disposal by landfilling. Even so, many landfills remain primitive in their operation. Alternative treatment technologies for solid waste management include incineration with heat recovery and waste gas cleaning and accelerated composting, but both of these technologies are subject to criticism either by environmentalists on the grounds of possible hazardous emissions, failure to eliminate pathogenic agents or failure to immobilise heavy metals, or by landfill operators and contractors on the basis of waste management economics, while key questions concerning the effects of the various practices on public health and environmental safety remain unanswered. The probable and relative effects on both public health and environmental safety of tradition and modern landfill technologies will be evaluated with respect to proposed alternative treatment technologies.     

Ranking municipal solid waste treatment alternatives based on ecological footprint and multi-criteria analysis

The selection of a municipal solid waste (MSW) treatment alternative is a complex task in which a widespread set of criteria must be taken into account. Additionally to economic or social aspects, the decision process should consider the environmental perspective. With the purpose of quantifying the environmental burdens, a wide variety of environmental and sustainability indicators have been developed in the last years. Furthermore, integrative frameworks have been highlighted as the best option to achieve more comprehensive assessments.In this work, four different options of MSW treatment were ranked from an environmental point of view applying two methods: (1) the ecological footprint (EF) as single composite indicator and (2) multi-criteria analysis (MCA) integrating the EF together with other material flow indicators related to water consumption, emissions to air and water and occupied landfill volume. The MCA methods selected were a combination of Analytic Hierarchy Process (AHP) and Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE) aided by Geometrical Analysis for Interactive Aid (GAIA). The objective was twofold: on the one side, the identification of the most beneficial waste treatment alternative (including thermal plasma gasification which as yet has not been assessed systematically) from an environmental perspective and, on the other side, the comparison of the results yielded by the two ranking methods proposed.The ranking obtained in both cases was (from best to worst): thermal plasma gasification, biological treatment of organic fraction with energy recovery from refuse derived fuel, incineration with energy recovery and landfilling. Hence, the EF proved to be a good screening indicator although it did not provide a comprehensive measure of environmental impacts associated to the waste treatment options considered. Besides, the combined application of AHP and PROMETHEE/GAIA as MCA methodology was found to be a suitable way, not very complex at user level, to integrate the information provided by a set of environmental criteria and to aid decision making.