Electrocatalytic conversion of nitrate waste into ammonia: a review

Environmental Chemistry Letters - The electrocatalytic reduction of nitrate waste into ammonia allows both the removal of nitrate contaminants and an alternative production of ammonia compared to...     

Recycling municipal,agricultural and industrial waste into energy,fertilizers, food and construction materials,and economic feasibility: a review

The global amount of solid waste has dramatically increased as a result of rapid population growth, accelerated urbanization, agricultural demand, and industrial development. The world's population is expected to reach 8.5 billion by 2030, while solid waste production will reach 2.59 billion tons. This will deteriorate the already strained environment and climate situation. Consequently, there is an urgent need for methods to recycle solid waste. Here, we review recent technologies to treat solid waste, and we assess the economic feasibility of transforming waste into energy. We focus on municipal, agricultural, and industrial waste. We found that methane captured from landfilled-municipal solid waste in Delhi could supply 8–18 million houses with electricity and generate 7140 gigawatt-hour, with a prospected potential of 31,346 and 77,748 gigawatt-hour by 2030 and 2060, respectively. Valorization of agricultural solid waste and food waste by anaerobic digestion systems could replace 61.46% of natural gas and 38.54% of coal use in the United Kingdom, and could reduce land use of 1.8 million hectares if provided as animal feeds. We also estimated a levelized cost of landfill solid and anaerobic digestion waste-to-energy technologies of $0.04/kilowatt-hour and $0.07/kilowatt-hour, with a payback time of 0.73–1.86 years and 1.17–2.37 years, respectively. Nonetheless, current landfill waste treatment methods are still inefficient, in particular for treating food waste containing over 60% water.

     

Electrochemical conversion of biomass-derived aldehydes into fine chemicals and hydrogen: A review

Environmental Chemistry Letters - The decrease in fossil fuel usage and the projected 28% increase in the global energy demand by 2040 are calling for advanced methods to convert modern biomass...     

Assessment of key parameters in municipal solid waste management: a prerequisite for sustainability

Municipal solid waste management was studied for 1 year in a representative urban area of Lahore city for environmental sustainability. The effects of financial status of the household and the seasonal variations on generation rate and compositions of municipal solid waste (MSW) were determined. MSW generation rate and the economic status of the households were positively correlated (p < 0.05). Seasonal variations observed were significant only for organics (p = 0.001), plastics (p = 0.008) and food waste fractions (p = 0.009) in MSW. Response surface regression model developed and analysed by Minitab-15® showed that the interaction of season and different economic zones of the town on the MSW generation rate was non-significant (p = 0.334). Elemental and heating value analyses of the mixed organic fractions in kitchen waste had carbon 47.93%, hydrogen 6.20%, nitrogen 2.24%, sulphur 0.23%, oxygen 39.01%, and C and N ratio 27.78. Findings concluded that food waste was 56% of total MSW with 71.03% moisture content and a modest heating value of 5566 J/g. Existing temporary storage capacity of MSW is 51% of the total MSW generated considering the weighted MSW generation rate of 0.57 kg/person/day calculated in this study. Composting could be a possible final disposal option due to high moisture and organic content and can be studied in future research. Development of a transfer station, introduction of home composting programmes and awareness towards proper segregation and reduction of waste at the household level is suggested to attain sustainability in the MSW management system.     

城市有机生活垃圾厌氧发酵处理研究

在适当的PH值和搅拌条件下，研究了反应温度、总固体含量、pH值、碳氮比、碳磷比以及接种物量对有机牛活垃圾厌氧发酵产沼气的影响。实验结果表明：有机生活垃圾厌氧消化产沼气的适宜条件是：反应温度50～55℃，总固体含量23％～28％，pH=6．8～7．4，w(C)／w（N)=(20～30)，w(C)／w(P)=50，60％～75％的生物气，可实现能量回收；发酵剩余物可制有机肥，时间为15～20d。接种物量为25％～30％。在厌氧的条件下，可以制取含甲烷实现物质再利用。有机生活垃圾在厌氧消化反应器的停留时间为15～20d。     

垃圾填埋场渗滤液回流处理技术研究进展

垃圾渗滤液回流处理后，CODcr去除率最高达95％，在半好氧状态下NH3-N质量浓度降低至10mg/L几以下，渗滤液水质得到改善；渗滤液回流增加了湿度，使有机物的降解速率加快；渗滤液同流处产甲烷速率是不回流处产甲烷速率的2倍多：渗滤液回流处的总沉降幅度可达填埋场深度的20％，而不回流处仅为8％。回流处理技术分为直接回流至垃圾层、表面喷灌或浇灌至填埋场表面、地表下回流或内层回流技术。在填埋场处于产酸阶段早期，回流的渗滤液量宜少不宜多：在产气阶段则可逐渐增加。应将稳定化程度高的垃圾层区(产甲烷区)排出的渗滤液回流至新填人的垃圾层(产酸区)，将新垃圾层所产生的渗滤液回流至老的稳定化区。通过控制垃圾的组成、回流的时间、渗滤液的pH值等手段可改善回流处理效果。     

A steam dried municipal solid waste gasification and melting process

Considering high-moisture municipal solid waste (MSW) of China, a steam dried MSW gasification and melting process was proposed, the feasibility was tested, and the mass and energy balance was analyzed. Preliminary experiments were conducted using a fixed-bed drying apparatus, a 200 kg per day fluidized-bed gasifier, and a swirl melting furnace. Moisture percentage was reduced from 50% to 20% roughly when MSW was dried by slightly superheated steam of 150°C?C350°C within 40 min. When the temperature was less than 250°C, no incondensable gas was produced during the drying process. The gasifier ran at 550°C?C700°Cwith an air equivalence ratio (ER) of 0.2?C0.4. The temperature of the swirl melting furnace reached about 1240°C when the gasification ER was 0.3 and the total ER was 1.1. At these conditions, the fly ash concentration in the flue gas was 1.7 g·(Nm³)^?1, which meant over 95% fly ash was trapped in the furnace and discharged as slag. 85% of Ni and Cr were bound in the slag, as well as 60% of Cu. The mass and energy balance analysis indicates that the boiler heat efficiency of an industrial MSW incineration plant reaches 86.97% when MSW is dried by steam of 200°C. The boiler heat efficiency is sensitive to three important parameters, including the temperature of preheated MSW, the moisture percentage of dried MS Wand the fly ash percentage in the total ash.     

Leaching toxicity characteristics of municipal solid waste incineration bottom ash

The continuously increasing production of municipal solid waste incineration bottom ash (MSWIBA) has promoted its utilization as construction material and raised environmental concern. The physico-chemical properties and leaching behavior of MSWIBA were studied, and ecotoxicological testing using a luminescent bacterium bioassay was performed to assess the ecological pollution risks associated with its leached constituents. The MSWIBA was leached by two types of leachants, H₂SO₄/HNO₃ and HAc solution, at different liquid to solid ratios and contact times. The concentrations of heavy metals and anions in the leachates were analyzed. Multivariate statistical analyses, including principle component analysis, Pearson's correlation analysis and hierarchical cluster analysis, were used to evaluate the contributions of the constituents to the toxicity (EC₅₀) of the MSWIBA leachate. The statistical analyses of the ecotoxicological results showed that the Ba, Cr, Cu, Pb, F⁻ and total organic carbon (TOC) concentrations were closely correlated with the EC₅₀ value, and these substances were the main contributors to the ecotoxicity of the MSWIBA leachate. In addition, the cluster of these variables indicated similar leaching behaviors. Overall, the research demonstrated that the ecotoxicological risks resulting from MSWIBA leaching could be assessed before its utilization, which provides crucial information for the adaptation of MSWIBA as alternative materials.     

Environment and economic feasibility of municipal solid waste central sorting strategy: a case study in Beijing

Although Beijing has carried out municipal solid waste (MSW) source separation since 1996, it has largely been ineffective. In 2012, a “Green House” program was established as a new attempt for central sorting. In this study, the authors used material flow analysis (MFA) and cost benefit analysis (CBA) methods to investigate Green House’s environment and economic feasibility. Results showed that the program did have significant environmental benefits on waste reduction, which reduced the amount of waste by 34%. If the Green House program is implemented in a residential community with wet waste ratio of 66%, the proportion of waste reduction can reach 37%. However, the Green House is now running with a monthly loss of 1982 CNY. This is mainly because most of its benefits come from waste reduction (i.e., 5878 CNY per month), which does not turn a monetary benefit, but is instead distributed to the whole of society as positive environmental externalities. Lack of government involvement, small program scale, and technical/managerial deficiency are three main barriers of the Green House. We, thus, make three recommendations: involve government authority and financial support, expand the program scale to separate 91.4 tons of waste every month, and use more professional equipment/technologies. If the Green House program can successfully adopt these suggestions, 33.8 tons of waste can be reduced monthly, and it would be able to flip the loss into a profit worth 35034 CNY.

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Release of elements from municipal solid waste incineration fly ash

The element-release behavior of municipal solid waste incineration fly ash was explored through leaching test with continuous set-point pH (pH_stat test) and serial single reaction cell (SSRC) tests. First, the relationship between element release and acid neutralizing capacity (ANC) consumption was examined with a pH_stat test. Four types of release behaviors were identified which are characteristic for different elements: (1) release curves that were almost linear with ANC consumption (Ca, Zn, and Cd); (2) release that was significantly faster than ANC (Na, K, and Cl); (3) curves that featured a strong increase with ANC consumption, after a transient release, followed by an almost equal decrease (Si and S); and (4) release that is strongly retarded compared with ANC consumption (Cr, Cu, and Pb). In the SSRC system, it the existence of a pH front and a wash-out phenomenon is demonstrated. Combining the results from the SSRC test with the kinetic analysis of the ANC system in the pH_stat test, it was inferred that less than one-third of the ANC measured from a batch pH titration plays a neutralization role in a field situation. The methodologies described may provide a powerful set of tools for systematic evaluation of element release from solid wastes.     

Densification of waste biomass for manufacturing solid biofuel pellets: a review

Environmental Chemistry Letters - The demand for bioenergy is increasing due to the diminishing popularity of fossil fuels and rising greenhouse gas emissions. However, according to recent reports,...     

Carbon discharge through municipal solid waste in Haikou,China

With rapid urban development, municipal solid waste (MSW) has become a pressing issue. Estimation of carbon discharge through municipal solid waste provides a way to assess environmental load of solid waste from the viewpoint of the carbon cycle. With few studies on carbon research and provides insights into human impacts on the carbon cycle. Based on a comprehensive fieldwork investigation of a typical Chinese tourist city – Haikou City, Hainan Island – the characteristics of MSW carbon discharge and human activities that influenced it were analysed. The results indicated that, in 2001, the total carbon discharge from 261.9 Gg of MSW was 105.1 GgC per year, and 174.6 kgC per capita per annum. Carbon is discharged in the form of food scraps (24%), plastics (20%), wood (17%), fabrics (14%), paper (13%), and dust and stone (12%). If landfill received all the waste, 4.7% of MSW carbon would be transformed into methane, with a value of 4.9 GgC. Between 1991 and 1999, Haikou's per capita MSW carbon discharge increased by 59.9%, and total MSW carbon discharge increased by 124.9%. MSW carbon discharge in Haikou is significantly affected by the growth of residential expenditure and urbanisation. Local characteristics of tourism also influence Haikou's MSW carbon discharge, not only in terms of its yearly variation, but also its monthly variation. Integrating data on carbon discharge with carbon consumption will provide a systematic view of the carbon metabolism in urban ecosystems, and further insights into the generation of urban environmental pollution.     

Fates and partitioning of heavy metals in municipal solid waste incineration process

The fate and partitioning of heavy metals (including Hg, Cd, Pb, Zn, As, Cr, Ni, and Cu) from MSW incinerators located in Taiwan were determined. Results of stack sampling indicate that most Hg and As (more than 80%) exists in the gas phase while other metals partition differently among bottom ash, fly ash, and flue gases. Removal efficiencies of existing air pollution control devices for Hg and As are lower (about 70%) than other metals. Bottom ash contains higher concentration of Cd compared with European incinerators. In addition, strong enrichment of Cd on fly ash particles is observed.     

城市生活垃圾处理技术现状与管理对策

近年来,我国城市生活垃圾产生量每年以约10%的速度迅猛增长,而城市生活垃圾处理能力发展相对滞后。客观评述城市生活垃圾常用的填埋、焚烧、堆肥3种处理技术的优缺点和在国内的应用现状,并针对城市生活垃圾在收运、处理以及管理等环节中存在的突出问题,提出了明确的建议与措施：首先,完善相关法规政策,实施分类收集,加强源头控制;其次,创新管理体制,推行市场化运作机制,政府加强政策引导和监督;再次,按照＂谁污染,谁付费＂的原则,建立健全垃圾收费体系;最后,充分利用各种媒介,加大宣传力度,提高公众环保意识。同时,还探讨了城市生活垃圾处理技术发展的趋势。焚烧处理将是今后一段时期我国最有发展潜力的技术,气化熔融焚烧技术是一种高效资源化、污染物接近零排放的新型焚烧技术;生物反应器填埋技术可减少渗滤液处理量、降低垃圾处理成本,具有广阔的发展前景;堆肥技术可作为焚烧或填埋之前的预处理手段;城市生活垃圾综合处理集多种处理技术的优点于一体,在节约处理成本,提高经济效益的同时,实现了垃圾的减量化、资源化、无害化,是未来我国生活垃圾处理的优先发展方向。     

Control of chlorinated aromatic compounds from a municipal solid waste incinerator using limestone addition

In this study, limestone powder was directly added to synthetic MSW, which was fed into a small‐scale fluidized bed incinerator. The concentration of CBzs and CPs in the flue gas were measured before and after a secondary combustion air injection. Finally, the PCDDs and PCDFs concentrations were also measured in the flue gas after the secondary combustion zone. The CaCO₃ added to synthetic MSW not only controls HCl in the flue gas, but suppresses the formation of chlorinated aromatic compounds like CBzs, CPs, PCDDs, and PCDFs. The main mechanisms to control the formation of chlorinated aromatic compounds was more likely related to the suppression of catalytic capability of flyash than the HCl reduction in the flue gas. However, the NO concentration was increased by catalytic reaction of limestone in the fluidized bed.     

Characterization of humic substances in bio-treated municipal solid waste landfill leachate

Considerable organic matter remains in municipal solid waste landfill leachate after biological treatments. Humic substances (HSs) dominate the organic matter in bio-treated landfill leachate. In this study, the HSs from landfill leachate treated by membrane bioreactor (MBR-HSs) were analyzed via elemental analysis, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, and charge polarized magic-angle spinning-¹³C-nuclear magnetic resonance. The characteristic absorption in the UV wavelength range indicated the presence of high C=C and C=O double bonds within the MBR-HSs. Compared with commercial HSs, MBR-HSs had lower carbon content [48.14% for fulvic acids (FA) and 49.52% for humic acids (HA)], higher nitrogen content (4.31% for FA and 6.16% for HA), lower aromatic structure content, and higher carbohydrate and carboxylic atoms of carbon content. FA predominantly had an aliphatic structure, and HA had less condensed or substituted aromatic ring structures than natural HA. The aromatic carbon content of MBR-HSs was lower than that of humus-derived HSs but higher than that of waste-derived HSs, indicating that MBR-HSs appeared to be more similar to humus-derived HSs than waste-derived HA.     

垃圾填埋场空气微生物污染及评价

用撞击法采集某垃圾填埋场不同区域空气微生物样品,通过微生物浓度评价不同区域污染状况,并对优势菌落PCR产物经同源性比对分析了空气微生物的优势菌群。结果表明,填埋场的主要污染区域为裸露的填埋区和垃圾运输路段,达到轻微污染程度,其它区域均达到较清洁以上程度。风沙、扬尘大的春季微生物总浓度明显高于夏季。填埋场的空气微生物污染主要为细菌的超标,污染区域空气中的细菌总量比清洁区高13.5倍,空气微生物总浓度相差10.7倍,而霉菌的数量变化相对较小。垃圾填埋场空气中优势细菌以芽孢杆菌属（Bacillus）、节杆菌属（Arthrobacter）和微球菌属（Micrococcus）为主,其中以枯草芽孢杆菌（Bacillus subtilis）,短小芽孢杆菌（Bacillus pumilus）和黄金节杆菌（Arthrobacter aurescens）出现的频率较高;优势真菌菌群为青霉属（Penicillium）、曲霉属（Aspergillus）、链格孢属（Alternaria）等。     

Assessment of the impacts of municipal solid waste dumps on soils and plants

The study aimed at evaluating the impacts of open municipal solid wastes dumps on soil and vegetation near the main roads linking major cities in Nigeria. We hypothesised that the metals from the wastes exerted substantial impacts at the dump sites which affect the soil and plants. Data were analysed from five dump sites and five control sites. The result revealed that the effects of the heavy metals (HM) were significant and higher at the dump sites where their concentrations were far above the EU, and Canadian environmental quality permissible limits for agricultural soils and vegetation. In contrast with dump sites, a significant relationship (R²?=?0.70; p??Cr?>?Pb at both dump sites and control sites. Further study on the effects of more HM on soil and plant is recommended in the area. Recycling and bio-phytoremediation processes should also be introduced.     

Biochar from municipal solid waste for resource recovery and pollution remediation

Environmental Chemistry Letters - Open dumping of municipal solid waste is a common method of waste disposal in developing countries, thus leading to pollution by gaseous emissions and landfill...     

Spatial distribution of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in soil around a municipal solid waste incinerator

Municipal solid waste incinerators (MSWIs) are usually considered to be important sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). To examine the influence of PCDD/Fs emissions from a MSWI on the surrounding environment, 21 soil samples were collected from various sampling sites distributed at distances of 300–1,700 m away from the stack of a MSWI. International Toxic Equivalent (I-TEQ) concentrations ranged from 0.47 to 2.07 pg I-TEQ g^?1, with average and median concentrations of 1.08 and 1.05 pg I-TEQ g^?1, respectively. Comparison of the results presented herein with other worldwide studies suggested that the concentrations of PCDD/Fs in the ambient soil were relatively low, indicating a limited impact on the surrounding environment. The emission concentrations from the incinerator were the critical factor in generating an environmental impact on the surrounding environment. An exponential function was developed, indicating a slight decline in TEQs of PCDD/Fs with increasing distance from the MSWI stack. The ordinary kriging interpolation technique was selected to create a contour map, which intuitively showed that a limited surrounding area (≤1,000 m from the stack) was obviously influenced by the MSWI.