CO_(2) mineralization by typical industrial solid wastes for preparing ultrafine CaCO_(3): A review

Mineral carbonation is a promising CO_(2) sequestration strategy that can utilize industrial wastes to convert CO_(2) into high-value CaCO_(3).This review summarizes the advancements in CO_(2) mineralization using typical industrial wastes to prepare ultrafine CaCO_(3).This work surveys the mechanisms of CO_(2) mineralization using these wastes and its capacities to synthesize CaCO_(3),evaluates the effects of carbonation pathways and operating parameters on the preparation of CaCO_(3),analyzes the current industrial application status and economics of this technology.Due to the large amount of impurities in solid wastes,the purity of CaCO_(3) prepared by indirect methods is greater than that prepared by direct methods.Crystalline CaCO_(3) includes three polymorphs.The polymorph of CaCO_(3) synthesized by carbonation process is determined the combined effects of various factors.These parameters essentially impact the nucleation and growth of CaCO_(3) by altering the CO_(2) supersaturation in the reaction system and the surface energy of CaCO_(3) grains.Increasing the initial pH of the solution and the CO_(2)flow rate favors the formation of vaterite,but calcite is formed under excessively high pH.Vaterite formation is favored at lower temperatures and residence time.With increased temperature and prolonged residence time,it passes through aragonite metastable phase and eventually transforms into calcite.Moreover,polymorph modifiers can decrease the surface energy of CaCO_(3) grains,facilitating the synthesis of vaterite.However,the large-scale application of this technology still faces many problems,including high costs,high energy consumption,low calcium leaching rate,low carbonation efficiency,and low product yield.Therefore,it is necessary to investigate ways to accelerate carbonation,optimize operating parameters,develop cost-effective agents,and understand the kinetics of CaCO_(3) nucleation and crystallization to obtain products with specific crystal forms.Furthermore,more studies on life cycle assessment(LCA)should be conducted to fully confirm the feasibility of the developed technologies.

Estimation of Methane Emissions from Municipal Solid Waste Landfills in China Based on Point Emission Sources

The methane(CH4) emissions from municipal solid waste(MSW) landfills in China in 2007 were estimated based on database of the three-dimensional emission factors matrix and point sources, by an IPCC recommended FOD(firstorder decay) model. The location, capacity and age of landfills constitute the three dimensions of the emission factors matrix, which were obtained by laboratory analysis and in situ investigation. Key parameters such as waste composition,degradable organic carbon ratio, CH4 correction factor, oxidation factor and recovery rate, were carefully analyzed in terms of these three dimensions. The point sources database consists of 2,107 MSW landfills in cities and towns of China in 2007. The results show that the CH4 emissions from MSW landfills were 1.186 Mt in 2007. Compared with the CH4 emissions of 2.20 Mt in 2005, the significant discrepancy mainly comes from statistical data of landfills, e.g., number of landfills and amount of waste disposed in landfills. CH4 emissions were lower than 700 t for most of the landfills, whereas there were 279 landfills with emissions larger than 1,000 t, and only 10 landfills with emissions larger than 10,000 t.Jiangsu province ranks the largest emitter with 98,700 t while Tibet is the smallest emitter with 2,100 t. In general,the emissions from eastern provinces, such as Jiangsu, Guangdong and Zhejiang, were larger than those from western provinces, such as Ningxia, Tibet and Qinghai.

Volatilization of heavy metals during incineration of municipal solid wastes

Incineration experiments with MSW, which had been impregnated with heavy metals, were presented to obtain information on the volatilization behavior of the elements cadmium(Cd), lead(Pb), and zinc(Zn) under different conditions. Experiments were carried out in a bubbling fluid bed system connected to a customized inductively coupled plasma optical emission spectroscopy(ICP-OES) for analyzing metals in the flue gas. The results indicated that the combustion temperature, the gas atmosphere, and the chlorine content in the flue gas could affect the volatilization behavior of heavy metals. In the fluidized bed combustion, a large surface area was provided by the bed sand particles, and they may act as absorbents for the gaseous ash-forming compound. Comparer with the metals Cd and Pb, the vaporization of Zn was low. The formation of stable compounds such as ZnO·Al 2O 3 could greatly decrease the metals volatilization. The presence of chlorine would enhance the volatilization of heavy metals by increasing the formation of metal chlorides. However, when the oxygen content was high, the chlorinating reaction was kinetically hindered, which heavy metals release would be delayed.

FORMATION MECHANISMS AND CONTROL STRATEGIES FOR DIOXINS IN INCINERATION PROCESS OF MUNICIPAL SOLID WASTES

Dioxins, which are of the most toxic materials on the earth, are principal emitted from waste incineration process. The molecular structures, toxicity parameters, such as toxicity equivalency factor, tolerable daily intake and physic-chemical properties of dioxins are briefly summarized. Three formation mechanisms of dioxins in waste incineration process, namely as de novo synthesis, mechanisms involving small organic molecular as precursors and homogenous gas phase reaction mechanism are alto reviewed. The influencing factors for dioxins formation during waste incineration process are also discussed. Three major methods for reducing dioxins emission from waste incineration process are discussed based upon the formation mechanisms and influencing factors. A new waste incineration process with low dioxins emission and low hydrogen chloride corrosion has been proposed based on multi- stage unit operation principal according to formation mechanisms of dioxins and potential production location in waste incinerators.

Assessment of Methane Flux from Municipal Solid Waste (MSW) Landfill Areas of Delhi, India

Carbon dioxide, methane and nitrous oxide are the major Greenhouse Gases (GHG’s), which emit from landfill areas and contribute significantly to global warming. Moreover, that the global warming potential of methane is 21 times higher than that of carbon dioxide and it has highest generation (60%) than other gases. Therefore, there is immense concern for its abatement or utilization from landfill areas. Compared to the west, the composition of municipal solid waste (MSW) in developing countries has higher (40% - 60%) organic waste. This would have potential to emit higher GHG’s from per ton of MSW compared to developed world. Beside that landfills areas in India are not planned or en- gineered generally low lying open areas, where MSW is indiscriminate disposed. This leads to uncontrolled emission of trace gases, foul smell, bird menace, ground and surface water pollution etc. Due to scarcity of land in big cities, mu- nicipal authorities are using same landfill for nearly 10 - 20 years. Hence, the possibility of anaerobic emission of GHG’s further increases. In the present paper we had quantified the methane emission from three MSW landfill areas of Delhi i.e., Gazipur, Bhalswa and Okhla. The results showed that the range of methane emission various in winter from 12.94 to 58.41 and in Summer from 82.69 - 293 mg/m2/h in these landfill areas. The paper has also reviewed the literature on methane emission from India and the status of landfill areas in India.

Modeling Municipal Solid Waste Management in Africa: Case Study of Matadi, the Democratic Republic of Congo

The purpose of this article is to present the key elements for best performance and profitability of Municipal Solid Waste (MSW) management in a low-income city. The research provides an overview of methods and models for integrated planning of a two-phase program: MSW collection and transportation, and MSW treatment. We present the case study of Matadi (the Democratic Republic of Congo) that has a low level of the MSW management compared to other African cities. We develop a spreadsheet model for collection and transportation of MSW which is relevant for low-income cities and enables determining the waste collection fee. A CDM decay model is used to predict the GHG emissions in disposal site. The MSW treatment plant in case of Matadi is evaluated. For the anaerobic digestion technology selected as appropriate for this plant, the key factors that ensure profitability of the plant are as follows: tipping fee from the municipality (19% of total revenue), amount of carbon credits which can sum up to 16% of the total revenue, expansion of waste collection range from 25 to 50 km. The methods of this study can be used for solving waste problem in other low-income cities where the budget for municipal services is scanty, particularly when starting from a very low level of MSW management.

Zero Waste and Conversion Efficiencies of Various Technologies for Disposal of Municipal Solid Waste

Zero waste is a philosophy and a design principle of dealing with our waste stream for the ~21st century. After reviewing the available information, the goal of zero waste from landfill is considered to be unachievable by using known and proven methods and ~approaches . The comparison of various technologies shows that the conversion efficiencies depend upon the type of system chosen for processing residual waste, and the best overall diversion rate of waste management system that can be achieved is about 71%. The maximum achievable overall diversion rate can be increased to approximate 92% if current environmental regulations to permit the routine use of the bottom ash or char for advanced thermal technologies.

Evaluating the Effects of the Concentration of Large Scale Municipal Solid Waste Incineration Facilities Using Geographical Information System

In Japan, each municipality generally has its own municipal solid waste incineration facilities because of the principle of self-management in the respective territories. Typically, a small municipality often owns a small facility. However, a large facility which can run continuously at high temperature with stability would be preferable if the dioxin generation mechanism is to be considered. Accordingly, municipalities in contiguous areas should cooperate mutually by using a large facility. To evaluate the effect of the concentration of large facilities, the authors created a GIS （Geographic Information System） based database of combustible waste generation at town level in Shizuoka Prefecture. Focusing on large facilities in Shizuoka City and superannuated facilities in Shida area, the authors evaluated the effect of the concentration of large facilities in Shizuoka city on utilization rate of facilities, energy balance and CO2 emissions. Our results showed the amount of light oil consumption and CO2 emissions increased because the mileage distance of garbage collection trucks becomes longer. However, the utilization rates of facilities and the amount of energy recovery from waste are improved. From these standpoints, the authors conclude that the concentration of large facilities is better compared to a single municipality based facility.

GHG Emissions Estimation from Household Solid Waste Management in Jakarta, Indonesia

This study defines and compares four scenarios for MSW （municipal solid waste） management： Scenario 1, unsorted waste taken to a landfill （baseline scenario）; Scenario 2, sorted waste used for home or communal composting; Scenario 3, sorted waste used for anaerobic digestion; and Scenario 4, sorted waste taken to a composting centre. The results of this study suggest that Scenario 1 would emit the highest levels of GHG （greenhouse gas） emissions, 692 x 103 tonnes CO2eq per year. Scenario 3 would have the lowest levels of GHG emissions, 195 x 103 tonnes CO2eq per year. Compared with the baseline scenario, it yields a 72% reduction of GHG emissions with a total savings of 498 ~ 103 tonnes CO2eq per year. The second-best option is Scenario 2, followed closely by Scenario 4, both yield 66.6% reductions with deviation by 0.03%. The deviation is due to transportation, which emission is negligibly small. The amounts of GHG savings for Scenario 2 and 4 are 461.3 ×10^3 tonnes CO2eq per year and 461×10^3 tonnes CO2eq per year, respectively It is evident from these results that anaerobic digestion has the highest potential for reducing GHG emissions.

Novel energy recovery from an integrated municipal solid waste and leachate treatment system

Population growth,waste generation,and massive waste mismanagement have led to environmental catastrophe.Management of municipal solid waste(MSW)requires an efficient and sustainable integrated system.The integrated thermal processing of MSW is one of the best waste management techniques.In this study,energy analysis of MSW is carried out based on the material and energy balance of 2000 kg wet MSW,which contains 50%leachate.Once the leachate is removed,the dry MSW is sent for carbon content enhancement in carbonization to produce MSW-based char.Thereafter,the combustion of MSW-based char provided high heat and syngas to be used in a hydrothermal process for MSW leachate treatment.The result shows that the char fuel of MSW produces a sufficient amount of energy,13501.29 MJ(84.55%),in the form of synthetic gas by-product,which has a big potential as an energy source.The novelty of the proposed integrated thermal system is to produce 84.55%synthetic gas by-product,which is used for electricity production,cooking,food,and heat energy for industrial purposes.The proposed applications of this paper offer insightful information for policymaking regarding novel MSW techniques,which are economical,energy-efficient,and environmentally friendly.Thus,it increases the effectiveness of MSW utilization.

Evaluation of the efficiency of urban solid waste management in Brazil by data envelopment analysis and possible variables of influence

This article has the general objective of estimating the efficiency of urban solid waste management in 940 Brazilian munici-palities through Data Envelopment Analysis(DEA)technique and has specific objectives:(i)to estimate efficiency scores;(ii)to compare the performance between different groups of municipalities;and(ii)to analyze the profile of efficient munici-palities from the perspective of the guidelines of Law 12,305/2010 and socio-economic and environmental indicators.The technique used was DEA with output-oriented and variable scale to return modeling.The results showed higher efficiency scores in the municipalities with populations above 500,000 inhabitants.The score variation ranged from 0.5(municipalities with populations<10,000 inhabitants)to 0.9(municipalities with more than 500,000 inhabitants).Of the sample set,only 12.34%of the municipalities were considered efficient,and when analyzing the efficient group,it was found that adherence to legislation was not a major factor in achieving efficiency.

黑水虻利用有机固废开发新型饲料蛋白与碳减排研发现状和展望

黑水虻作为一种重要的资源昆虫,可以处理多种有机固废,收获虫体生物质。黑水虻虫体富含蛋白质、脂肪等营养物质,在畜禽与水产的饲料中可有效替代鱼粉和豆粕而作为新型饲料蛋白资源。黑水虻幼虫处理有机固废还可以有效减少处理过程中的碳排放,将更多的碳元素以有机物的形式固定在虫体生物质上。文章从以下几个方面进行了综述:黑水虻转化不同有机固废,及其不同废弃物搭配对黑水虻转化及黑水虻营养的影响;微生物对黑水虻转化有机固废获得黑水虻生物质、蛋白的影响;黑水虻转化有机固废的无害化;黑水虻替代鱼粉和豆粕,是极具潜力的新型“开源”饲料蛋白;黑水虻中功能性蛋白(肽)的开发利用-用于饲料蛋白“节流”;黑水虻在固碳减排方面的作用;同时对黑水虻未来研究与开发方向进行了展望,以期为黑水虻资源的开发利用提供参考。

基于注意力模块化神经网络的城市固废焚烧过程氮氧化物排放预测

氮氧化物(nitrogen oxides,NO_(x))浓度的实时精准检测是实现脱硝过程闭环控制的前提,对提高城市固废焚烧(municipal solid waste incineration,MSWI)过程脱硝效率具有重要意义。为此,提出了一种基于注意力模块化神经网络(attention modular neural network,AMNN)的MSWI过程NO_(x)排放预测方法。首先,模拟脑网络“分而治之”处理复杂任务的特性,利用模糊C均值(fuzzy C-means,FCM)聚类算法将待预测任务划分为多个子任务,从而降低预测任务复杂度;其次,针对各子任务,设计一种自组织模糊神经网络(self-organizing fuzzy neural network,SOFNN)构建子模型,通过神经元增删机制和二阶学习算法提高子模型的学习效率和学习精度;然后,提出了一种基于注意力机制的子模型整合策略,进一步提高预测模型的泛化性能;最后,通过基准实验Mackey-Glass时间序列预测和北京某MSWI厂实际数据验证了AMNN的可行性和有效性。

某调度通信楼空调系统节能减碳改造设计实践

重点介绍了某调度通信楼空调系统的节能减碳改造设计,通过综合运用余热回收、可再生能源、固体蓄热、高效制冷机房等多项技术,构建了安全可靠、绿色低碳、高效节能的空调系统。采用HDY-SMAD空调负荷计算及分析软件模拟了建筑物全年的空调能耗,并对优化前后空调系统的运行能耗和碳排放进行了测算。结果显示,优化方案空调系统全年节约电量100万kW·h,全年碳减排573 t,节能减碳效果显著。

不同管理阶段生活垃圾处理处置碳减排潜力研究——以厦门市为例

我国快速城市化带来了大量的城市生活垃圾。为了破解“垃圾围城”的普遍性难题,我国不断完善生活垃圾管理体系,经历了以填埋为主的无害化、以焚烧为主的无害化和减量化、垃圾强制分类在全国主要城市的全面推广、分类垃圾综合处理处置等不同发展阶段。以厦门市为例,分析不同生活垃圾管理阶段的碳排放特征。结果表明:厦门市2000—2009年(无害化阶段)的碳排放总量由25.49万t直线上升至76.38万t,年均增长13.19%;2010—2016年(无害化和减量化阶段)由于填埋气收集效率提升和持续推进垃圾焚烧减量,吨垃圾碳排放强度逐年下降,但排放总量仍然从27.95万t增长至49.30万t;2017年至今全市推行垃圾四分类并开展餐厨垃圾分类和低值可回收物试点,碳排放强度从324.74 kg/t下降至178.11 kg/t,其中每分出1 t厨余垃圾、可回收物、餐厨垃圾和低值可回收物,碳排放分别减少5.69、302.58~328.75、83.19、884.66 kg。未来,随着低值可回收物分类和再生资源中心建设的推广,生活垃圾碳排放总量和强度将进一步降低,推动城市绿色低碳发展。

中国城市生活垃圾处理碳排放时空分布特征及减排潜力

传统垃圾处理方式(填埋、焚烧等)是温室气体尤其是CH4排放的重要来源。基于此,该研究采用IPCC碳排放计算方法,分析了2006—2021年中国297个地级及以上城市的城市生活垃圾处理结构和温室气体排放时空分布特征,并结合灰色预测模型,对2030年和2060年的排放情况进行预测。结果表明:①在处理方式层面,绝大多数城市不再以填埋为唯一垃圾处理方式,垃圾焚烧逐步替代填埋成为主流。②在排放量层面,中国城市生活垃圾处理的碳排放总量快速增长,在2019年到达7940.66万t后趋于稳定,北京、上海、广东深圳等超大城市的总碳排放量最高;中国城市生活垃圾处理净碳排放量经历先升后降的过程,且净碳排放量较高地区向三四线城市转移;城市生活垃圾处理碳排放呈现随城市人口规模扩大和经济发展水平提升而显著增加的变化规律。③预测结果表明,中国城市生活垃圾处理总碳排放量将于2030年达到6575万~9942万t;在直辖市和省会城市中,仅甘肃兰州可以实现垃圾处理碳排放达峰;垃圾分类对净零排放存在较大影响,如采取垃圾分类措施,大部分城市未来可实现碳中和。最后,作者提出城市生活垃圾“三步走”分级管理策略:对于仍采用填埋为主要处理方式的城市,应推动从填埋到焚烧的转型;对于已实现垃圾零填埋的城市,应加快推进垃圾分类工作;对于已实施垃圾分类政策的城市,应进一步减少垃圾产生并落实源头减量措施。

多重视角下工业固体废物资源化利用路径优化——以铜冶炼渣为例

为降低工业固体废物处理处置过程对环境和气候变化影响,提高资源利用率,基于环境资源交互属性、生命周期评价和有价资源价值评估3项指标,建立多维度工业固体废物资源化利用路径优化方法。结果表明:通过升级回收和降级回收的资源化途径,工业固体废物的生态毒性和人体健康毒性较填埋途径分别降低96.86%和98.53%,能够减少土壤污染,维护土壤生态安全。预计2035年铜冶炼渣升级回收、降级回收和原级回收的比例分别达到30%、50%和10%时,可以实现最优目标,但升级回收占比的提高会导致碳排放升高和综合效益下降。研究结果表明,短期内降级回收能够大规模消纳工业固体废物,但受到建筑行业和产品质量管理制约。因此,远期规划需合理分配工业固体废物资源化途径占比,以获得最大化环境效益和经济效益。

生活垃圾气炭分离燃烧污染物排放特性研究

为了研究生活垃圾挥发分和热解碳分离燃烧污染物排放特性,探索通过改变燃烧方式来降低生活垃圾燃烧污染物排放,利用固定床装置对生活垃圾直接燃烧和热解后的挥发分、热解炭单独燃烧进行了试验对比。结果表明:与直接燃烧相比,气炭分离燃烧生成CO、HCl、SO_(2)、NO_(2)、NH_(3)、HCN、HNCO等污染物的总量明显减少,NO和N_(2)O生成量略有增加;不同的燃烧方式产生的NO_(x)组分有较大的区别,直接燃烧产生的NO_(x)主要是NO和NO_(2),气炭分离后燃烧产生的NO主要是NO不同燃烧方式下,过量空气系数α对污染物的生成量均有影响,随着α的增加,直接燃烧时产生的CO、N_(2)O、SO_(2)、NH_(3)有所减少,NO、NO_(2)、HCN、HNCO有所增加,挥发分燃烧产生NO明显增加,HCN和HNCO略有减少,HCl、N_(2)O、NO_(2)、NH_(3)生成量很小变化不明显;热解炭燃烧时各污染物生成量均较低。

“双碳”目标下城市生活垃圾制氢技术研究进展

在全球碳减排的背景下,中国提出了实现“碳达峰碳中和”的“双碳”目标。利用城市生活垃圾中的生物质能制氢符合“双碳”目标要求。目前,城市生活垃圾制氢技术包括热化学转化、生物转化等直接制氢技术和结合甲烷重整制氢技术与城市生活垃圾厌氧发酵技术的间接制氢技术两大类。间接制氢技术因成熟可靠而成为当下城市生活垃圾制氢的主流工程化应用方向。城市生活垃圾前端分类、中端收运及末端处置系统的完善,将对生活垃圾制氢技术发展起到积极推动作用。

重庆市生活垃圾处理碳排放及影响因素分析

核算了2007—2021年重庆市生活垃圾处理碳排放量,运用LMDI模型分析了重庆市生活垃圾处理碳排放的影响因素。结果表明:2007—2021年重庆市生活垃圾处理碳排放量表现出先增后降的趋势;经济产出效应、城市化率和常驻人口规模对垃圾处理碳排放始终起正向驱动作用,经济产出效应的驱动作用最大,贡献率达86.6%;生活垃圾处理结构强度对碳排放具有抑制作用,贡献率达-24.8%。利用灰色GM(1,1)模型预测出2022—2030年重庆市的垃圾清运量和垃圾处理碳排放量将持续走高。