基于混合生命周期评价的生活垃圾处理系统生态效率分析

基于混合生命周期评价(Hybrid life cycle assessment,HLCA)提出一种改进生态效率模型,系统评价卫生填埋、卫生填埋⁃填埋气利用、焚烧发电、堆肥+卫生填埋和堆肥+焚烧发电5种我国典型生活垃圾处理情景的生态效率,并探究可持续性包含的环境、经济和社会多维权衡关系。结果表明,具有最大生态效率的生活垃圾处理情景因可持续性维度选取不同而异,如考虑人体健康损害影响,焚烧发电情景具有最大经济生态效率,而卫生填埋⁃填埋气利用情景具有最大社会生态效率。生活垃圾处理系统的可持续性评价维度之间具有显著的权衡关系,忽略某些影响类型可能带来问题转移。5种生活垃圾处理情景的环境影响各异,非焚烧情景气候变化影响和焚烧情景人体毒性影响突出。机器设备和燃料使用对资源消耗影响贡献最大,而生活垃圾处理过程对经济效益和其他环境影响贡献最大。本文提出的改进生态效率模型可以定量评价生活垃圾管理系统生态效率及权衡关系,为有效制定生活垃圾管理政策提供全面的信息支持。     

Managing municipal solid waste

Goal  

This research aims to assess the environmental effects of integrated strategies in a municipal waste management system. In particular, analysis is focused on a waste stream in Palermo, where landfill involves the prompt disposal of the most waste after collection. The current local management system is compared with two integrated waste management alternatives. Both the options comply with Italian regulations, but each one predicts adopting the available technologies in different ways.     

Composting of municipal solid waste

This paper reviews the literature on the composting process, which is one of the technological options for the processing of municipal solid wastes (MSWs). The process assumes a great significance, particularly from the point of its economic viability, capability for recycling of nutrients and waste minimization with minimum environmental problems. A number of studies on various aspects of the composting process, including process control and monitoring parameters such as temperature, pH, moisture content, aeration, and porosity are reviewed. Salient observations on microbial properties of composting are described and details of vermicomposting, as well as a detailed analysis of patents on composting of MSW, are presented.     

基于生态足迹的大学食堂餐具生态影响分析

以生态足迹为定量分析方法,以广州大学食堂为例,分析计算了一次性餐具和公用餐具对生态环境的影响,并比较分析了各种型号的餐具生态足迹.分析了一次性餐具和公用餐具生产过程中的原料消耗及能耗.广州大学食堂所用的餐具主要为塑料制餐具、不锈钢餐具、木制和竹制筷子.消耗的资源主要为钢铁、乙烯、木材和竹材等,可归于化石能源地足迹和林地足迹.调查了公用餐具洗涤过程中的资源消耗,主要为洗涤过程中的水电消耗以及废水处理能耗,可归于化石能源地足迹和可耕地足迹.最后结合学校食堂餐具的使用方案,计算了一次性餐具和公用餐具(以1a为限)的生态足迹.研究表明,公用餐具组合的足迹为3.7236×10-3gm2(全球平方米,记为gm2),使用竹筷的一次性餐具组合足迹为2.2085×10-2 gm2,使用木筷一次性餐具组合足迹为9.3781×10-2gm2.公用餐具足迹是一次性餐具的3.97%～16.8%.此外,由于竹筷的足迹是木筷23.55%,因此使用竹筷能大大降低一次性餐具对生态的影响.     

基于生态足迹的生态地租分析

以李嘉图地租理论和生态足迹为基础,分析了生态地租的内涵,并运用相关测算方法以中国数据为例进行实证,计算了生态地租的数量。在一定时段内,由于土地的稀缺特性以及技术进步的有限性,土地生物承载力有一定的限度。为了能够获取超过土地生物承载力的产出,必然需要更多的生产要素投入,这相当于为消除生态赤字而增加的成本,相应地会导致边际产品产出价格增加。但保持在土地生物承载力范围之内的产出,其产出成本中可以避免为消除生态赤字而增加的投入,从而能够获取超额利润,即性质上属于李嘉图租的生态地租。构建生态足迹与各产业的对应关系,将投入产出模型运用于生态地租的测算,计算出2007年中国单位经济产出的生态地租量为0.082,生态地租总额为7258711×10⁶元,相当于当年经济总产出增加值的27.3%。在不同行业中,农林牧渔业单位产出的生态地租量最高,电、热及水生产和供应业次之,但工矿业能够获取的生态地租总量最大。研究表明消除生态赤字的两条可行途径为,要么将最终总需求保持与生物承载力一致的水平,如果要使经济产出水平与生物承载力保持一致,那么需要减少60.7%的最终需求;要么征收与生态地租等值的生态税,征收的生态税应该用于治理生态环境,以维持土地生物性生产能力的稳定。因此,如果充分考虑生态地租的影响,将导致社会产品价格的上涨,意味着人类生活成本大为增加,但这却是为维持生态平衡必须支付的代价。     

生态足迹分析方法研究进展

作为可持续发展的指标,生态足迹模型得到了广泛的关注和应用.同时,对生态足迹理论和方法的研究也不断深化,出现了将生态足迹分析与物流能流分析、产品生命周期分析、投入产出分析相结合的适用于宏观和微观尺度的各种方法,尤其是最近出现了分配足迹到最终需求类型的“标准化”方法.本文介绍了生态足迹不同方法的产生情况,指出生态足迹分析方法分为过程分析和投入产出分析两套体系,并具体介绍了各种分析方法的特点、适用范围、研究进展和应用情况,建立了较为明晰的生态足迹发展的方法框架.针对当前国内外生态足迹方法的应用现状和趋势,提出重点把握3个方向:统一综合法在国家和区域尺度的研究;探索投入产出法、成分法等方法在国内的应用;加强时间序列研究和多情景预测分析.     

垃圾堆肥基质对不同草坪植物生态及质量特征的影响

通过田间实验,研究了城市生活垃圾堆肥基质对高羊茅和黑麦草不同品种草坪植物生态及质量特征的影响。结果表明:堆肥能明显促进草坪植物生长,提高地上和地下生物量。与一茬草相比,垃圾堆肥对二茬草的促进作用更为明显,说明了垃圾堆肥营养具有缓释效应。另外,垃圾堆肥能加快草坪植物返青,对越年草坪植物盖度、株高以及生物量具有明显促进作用。不同品种草坪植物对垃圾堆肥的生长响应存在明显差异,在生长速度和生物量指标上,3种高羊茅品种表现较好。采用美国国家草坪评比体系NTEP(9分法)作为评比标准,对各草坪综合质量进行评定。结果垃圾堆肥建植的草坪综合质量均明显好于对照;不同草坪植物之间比较,以爱神综合质量为最佳,尤其表现在密度、颜色和质地方面。     

Bioreactor landfill technology in municipal solid waste treatment: An overview

In recent years, due to an advance in knowledge of landfill behaviour and decomposition processes of municipal solid waste, there has been a strong thrust to upgrade existing landfill technologies for optimizing these degradation processes and thereafter harness a maximum of the useful bioavailable matter in the form of higher landfill gas generation rates. Operating landfills as bioreactors for enhancing the stabilization of wastes is one such technology option that has been recently investigated and has already been in use in many countries. A few full-scale implementations of this novel technology are gaining momentum in landfill research and development activities. The publication of bioreactor landfill research has resulted in a wide pool of knowledge and useful engineering data. This review covers leachate recirculation and stabilization, nitrogen transformation and corresponding extensive laboratory- and pilot-scale research, the bioreactor landfill concept, the benefits to be derived from this bioreactor landfill technology, and the design and operational issues and research trends that form the basis of applied landfill research.     

Determination of fungal succession during municipal solid waste composting using a cloning‐based analysis

Aims: The microbiota at industrial full‐scale composting plants has earlier been fragmentarily studied with molecular methods. Here, fungal communities from different stages of a full‐scale and a pilot‐scale composting reactors were studied before and after wood ash amendment. Methods and Result: The portion of fungal biomass, determined using phospholipid fatty acid analysis, varied between 6·3% and 38·5% in different composting phases. The fungal internal transcribed spacer (ITS) area was cloned and sequenced from 19 samples representing different stages of the composting processes. Altogether 2986 sequenced clones were grouped into 166 phylotypes from which 35% had a close match in the sequence databases. The fungal communities of the samples were related with the measured environmental variables in order to identify phylotypes typical of certain composting conditions. The fungal phylotypes could be grouped into those that dominated the mesophilic low pH initial phases (sequences similar to genera Candida, Pichia and Dipodascaceae) and those found mostly or exclusively in the thermophilic phase (sequences clustering to Thermomyces, Candida and Rhizomucor), but a few were also present throughout the whole process. Conclusions: The community composition was found to vary between suboptimally and optimally operating processes. In addition, there were differences in fungal communities between processes of industrial and pilot scale. Significance and Impact of the Study: The results of this study reveal the fungal diversity with molecular methods in industrial composting process. This is also one of the first studies conducted with samples from an industrial biowaste composting process.     

The biofuel potential of municipal solid waste

The world in the 21st century is facing a dual crisis of increasing waste and global climate change. Substituting fossil fuels with waste biomass‐derived cellulosic ethanol is a promising strategy to simultaneously meet part of our energy needs, mitigate greenhouse gas (GHG) emissions, and manage municipal solid waste (MSW). However, the global potential of MSW as an energy source is as yet unquantified. Here, we report increasing trends of MSW generation, and waste biomass‐derived cellulosic ethanol potentials in relation to socio‐economic development across 173 countries, and show that globally, up to 82.9 billion litres of waste paper‐derived cellulosic ethanol can be produced worldwide, replacing 5.36% of gasoline consumption, with accompanying GHG emissions savings of between 29.2% and 86.1%.     

Effects of biodrying process on municipal solid waste properties

In this paper, the effect of biodrying process on municipal solid waste (MSW) properties was studied. The results obtained indicated that after 14 d, biodrying reduced the water content of waste, allowing the production of biodried waste with a net heating value (NHV) of 16,779 ± 2,074 kJ kg⁻¹ wet weight, i.e. 41% higher than that of untreated waste. The low moisture content of the biodried material reduced, also, the potential impacts of the waste, i.e. potential self-ignition and potential odors production. Low waste impacts suggest to landfill the biodried material obtaining energy via biogas production by waste re-moistening, i.e. bioreactor. Nevertheless, results of this work indicate that biodrying process because of the partial degradation of the organic fraction contained in the waste (losses of 290 g kg⁻¹ VS), reduced of about 28% the total producible biogas.     

Anaerobic digestion of municipal solid waste as a treatment prior to landfill

Anaerobic digestion of organic fraction of municipal solid waste was conducted in pilot-scale reactor based on high-solid combined anaerobic digestion process. This study was performed in two runs. In Run 1 and Run 2, pre-stage flushing and micro-aeration were conducted to determine their effect in terms of enhancing hydrolysis and acidification in ambient condition. In Run 2, after pre-stage, the methane phase (methanogenesis) was started-up after pH adjustment and inoculum addition in mesophilic condition. Acidified leachate produced in pre-stage was used for percolation during active methane phase. At the end of methane phase, air flushing was conducted before unloading the digesters. Hydrolysis and acidification yield of 140 g C/kg TS and 180 g VFA/kg TS were achieved, respectively in pre-stage. Micro-aeration exhibited an equivocal result in terms of enhancing hydrolysis/acidification; however it showed a positive effect in methane phase performance and this needed further investigation. Leachate percolation during methane phase showed an enhanced methanization when compared to the reactors without leachate percolation. After 60 days, 260 l CH(4)/kg VS was obtained. Based on the waste methane potential, 75% biogas conversion and 61% VS degradation were achieved.     

城市污水处理生态系统能值分析

脱水污泥的污染问题影响了城市污水处理厂的生存和发展,中水的不同处置方式对当地的水资源和水环境影响也不一样,将污水处理、脱水污泥和中水处置结合起来构建污水处理生态系统有利于研究污水处理的综合效益、探索促进污水处理事业可持续发展的途径.能值分析方法可作为分析这一复合系统的工具,传统能值分析方法由于对废物处理处置和排放的影响没有考虑,因此提出了针对污水处理生态系统的改进的能值分析方法和指标体系,以明镜滩污水处理生态系统作为案例用两种方法进行了对比分析.结果表明,改进的能值分析方法更适合于污水处理生态系统的实际情况;不可更新资源能值流比值(NR)和废物排放能值流比值(WR)对污水处理生态系统的可持续性影响最大,其次是中水回用能值流比值(IR),污水处理生态系统的可持续性最终取决于NR、WR和IR三者的共同贡献;废物利用可提高污水处理生态系统的可持续性.不同废物利用方式由于对废物利用的程度不同以及对不可更新资源的消耗不同,因此对污水处理生态系统的可持续性影响不一样;在提出的8个方案中,"脱水污泥填埋 中水排放"方案的可持续性最低,而"脱水污泥制堆肥 中水回用"方案的可持续性最高.     

纸张生态足迹

自1960年代以来,由于废纸浆在全球造纸浆中比例不断提高,原有的纸张生态足迹计算方法--以原木浆纸的木材消耗量为计算基础--需要改进.通过分析纸浆结构的变化、纸浆与纸的关系、纸浆耗木量、废纸成浆率等,定量地表征了废纸回收对纸张木材消耗的影响,得出1t纸消耗的木材应为3.879 m3而略小于原来的4 m3的结论.在此基础上,重新计算纸张的生态足迹,得出1t纸的生态足迹为2.569 hm2森林.     

基于改进模型的东营市生态足迹动态分析

考虑了水热条件的时空差异性,用净初级生产力对传统生态承载力模型进行了改进,并针对传统生态足迹模型中水生态帐户仅考虑渔业功能的不足,增加了水资源生态足迹的计算,最后用改进的生态足迹模型对1996—2003年间东营市生态足迹动态进行了分析.结果表明：1996—2003年间,传统模型计算的东营市人均生态足迹由1.766 hm²增至2.644 hm²,人均生态承载力由0.889 hm²降至0.813 hm²;改进模型计算的东营市人均生态足迹则由2.819 hm²增至3.776 hm²,人均生态承载力由1.935 hm²降至1.865 hm²;与传统模型相比,改进的生态足迹模型计算的研究区生态压力较小.加大对水资源的利用可缓解区域的生态压力,改进模型能更准确地反映研究区自然资源利用状况.     

Biostabilization-biodrying of municipal solid waste by inverting air-flow

The process of biodrying could be a good solution for municipal solid waste management, allowing the production of fuel with an interesting energy content. Previous work (Adani, F., Baido, D., Calcaterra, E., Genevini, P.L., 2002. The influence of biomass temperature on biostabilization-biodrying of municipal solid waste. Bioresource Technology 83 (3), 173-179) has indicated that appropriate management of the processing parameters (air-flow rate and biomass temperatures) could achieve biomass drying in very short times (8-9 days). However, the data of that work also evidenced that if the conditions do not consider pile turning, and the air-flow is always from one direction, temperature gradients arise within the biomass, resulting in a lack of homogeneity in the moisture and energy content of the final product. Therefore, a new laboratory study was conducted on municipal solid waste biodrying-biostabilization in an effort to obtain homogeneous final products. Our proposal to solve this lack of homogeneity is to periodically invert the air-flow direction. Thus, in line with a previous study, two trials, A and B, were carried out, dividing the biomass into three layers to study temperature and moisture gradients throughout the process, and a third trial (C) simulating air-flow inversion at regular intervals was introduced. The results suggest that the daily inversion of air-flow eliminates marked temperature differences and leads to a homogeneous final product.     

Product specific emissions from municipal solid waste landfills

For the inventory analysis of environmental impacts associated with products in Life Cycle Assessment (LCA) there is a great need for estimates of emissions from waste products disposed at municipal solid waste landfills (product specific emissions). Since product specific emissions can not be calculated or measured directly at the landfills, they must be estimated by modeling of landfill processes. This paper presents a landfill model based on a large number of assumptions and approximations concerning landfill properties, waste product properties and characteristics of various kinds of environmental protection systems (e.g. landfill gas combustion units and leachate treatment units). The model is useful for estimation of emissions from waste products disposed in landfills and it has been made operational in the computer tool LCA-LAND presented in a following paper. In the model, waste products are subdivided into five groups of components: general organic matter (e.g. paper), specific organic compounds (e.g. organic solvents), inert components (e.g. PVC), metals (e.g. cadmium), and inorganic non-metals (e.g. chlorine,) which are considered individually. The assumptions and approximations used in the model are to the extent possible scientifically based, but where scientific information has been missing, qualified estimates have been made to fulfill the aim of a complete tool for estimation of emissions. Due to several rough simplifications and missing links in our present understanding of landfills, the uncertainty associated with the model is relatively high.     

Microbial characterization during composting of municipal solid waste

This study investigates the prevailing physico-chemical conditions and microbial community; mesophilic bacteria, yeasts and filamentous fungi, bacterial spores, Salmonella and Shigella as well as faecal indicator bacteria: total coliforms, faecal coliforms and faecal Streptococci, present in a compost of municipal solid waste. Investigations were conducted in a semi-industrial pilot plant using a moderate aeration during the composting process. Our results showed that: (i) auto-sterilization induced by relatively high temperatures (60–55°C) caused a significant change in bacterial communities. For instance, Escherichia coli and faecal Streptococci populations decreased, respectively, from 2×10⁷ to 3.1×10³ and 10⁷ to 1.5×10³ cells/g waste dry weight (WDW); yeasts and filamentous fungi decreased from 4.5×10⁶ to 2.6×10³ cells/g WDW and mesophilic bacteria were reduced from 5.8×10⁹ to 1.8×10⁷ bacteria/g WDW. On the other hand, the number of bacterial spores increased at the beginning of the composting process, but after the third week their number decreased notably; (ii) Salmonella disappeared completely from compost by the 25th day as soon as the temperature reached 60°C; and (iii) the bacterial population increased gradually during the cooling phase. While Staphylococci seemed to be the dominant bacteria during the mesophilic phase and at the beginning of the thermophilic phase, bacilli predominated during the remainder of the composting cycle. The appearance of gram-negative rods (opportunistic pathogens) during the cooling phase may represent a serious risk for the sanitary quality of the finished product intended for agronomic reuse. Compost sonication for about 3 min induced the inactivation of delicate bacteria, in particular gram-negatives. By contrast, gram-positive bacteria, especially micrococcus, spores of bacilli, and fungal propagules survived, and reached high concentrations in the compost.     

Product specific emissions from municipal solid waste landfills

This paper presents and verifies the computer tool LCA-LAND for estimation of emissions from specific waste products disposed in municipal solid waste landfills in European countries for use in the inventory analysis of LCA. Examples of input data (e.g. distribution of the waste product in different countries, composition of the product and physical/chemical/biological properties of waste product components) and output data (e.g. estimated emissions to atmosphere and water) are given for a fictive waste product made of representative types of components (toluene, cellulose, polyvinylchloride (PVC), copper and chloride). Since waste products from different processes in the product system may be disposed at different landfills where they are mixed with waste originating outside the product system, the estimated emissions from specific waste products cannot be compared with measured emissions from true landfills. Hence, the computer tool is verified in terms of mass balances and sensitivity analyses. The mass balances agree exactly and the sensitivity analyses show that different types of waste product components behave differently in different types of landfills. Emission of e.g. toluene is significantly reduced in the presence of landfill top-cover, landfill gas combustion units and leachate treatment units. Generally, the sensitivity analysis shows good agreement between the relative proportions of various types of emissions (based on properties of the waste and properties of landfills) and good agreement with emission levels that would be expected based on a general understanding of landfill processes.