Destruction and formation of PCDD/Fs in a fluidised bed combustor co-incinerating automotive shredder residue with refuse derived fuel and wastewater treatment sludge

PCDD/Fs in indoor environments of residential communities around a municipal solid waste incineration plant in East China: Occurrence, sources, and cancer risks

Prolonged exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) can pose several adverse outcomes on human health. However, there is limited information on public health associated with indoor PCDD/F exposure in residential environments. Here, we examined PCDD/F concentrations in indoor air and indoor dust samples obtained from households near a municipal solid waste incineration (MSWI) plant. Our measurements revealed that the toxic equivalent (TEQ) concentrations of PCDD/Fs in indoor air ranged from 0.01 to 0.05 pg TEQ/m³, which were below intervention thresholds (0.6 pg TEQ/m³). Additionally, the TEQ concentrations of PCDD/Fs in indoor dust ranged from 0.30 to 11.56 ng TEQ/kg. Higher PCDD/F levels were found in household dust in the town of Taopu compared to those in the town of Changzheng. Principal component analysis (PCA) of PCDD/Fs suggested that waste incineration was the primary source of PCDD/Fs in indoor air, whereas PCDD/Fs in indoor dust came from multiple sources. The results of the health risk assessment showed the carcinogenic risk due to indoor PCDD/F exposure was higher for adults than for nursery children and primary school children. The carcinogenic risks of PCDD/Fs for age groups residing near the MSWI plant were all less than the risk threshold (10^-5). Our findings will help to better understand the levels of PCDD/F exposure among urban populations living in residential communities around the MSWI plant and to formulate corresponding control measures to reduce probabilistic risk implications.

Profile occurrences and in vitro effects of toxic organic pollutants in metal shredding facilities in Wallonia (Belgium)

End-of-life vehicles and e-waste contain several hazardous substances that can contaminate the environment during treatment processes. Occurrences and adverse effects of toxic organic pollutants emitted from 3 shredder plants located in Wallonia, Belgium, were investigated by chemical and biological analyses of fluff, dust, and scrubbing sludge sampled in 2019. Site 1 showed the highest concentrations of chlorinated compounds in sludge with 7.5 ng/g polychlorinated dibenzo-dioxins/furans and 84.5 µg/g estimated total polychlorinated biphenyls, while site 3 led the brominated flame retardant levels in dust (53.4 µg/g). The level of polycyclic aromatic hydrocarbons was highest in the sludge samples, 78 and 71 µg/g for sites 2 and 3, respectively. The samples induced significant dioxin-like activities in murine and human cells at concentrations of around 0.01-0.1 and 0.5-1 ng (sample) per ml (medium), respectively, with the efficacy similar to 2,3,7,8-tetrachlorodibenzodioxin and EC₅₀ values of around 1 and 10 ng/ml. The samples also displayed high estrogenic activities, already at 1 ng/ml, and several induced a response as efficient as 17β-estradiol, albeit a low androgenic activity. Shredder workers were estimated to be highly exposed to dioxin-like compounds through dust ingestion and dermal absorption, which is of concern.

Renewable energy from solid waste: life cycle analysis and social welfare

In this study, municipal solid waste (MSW) composition in distinct world locations is compared and a case study is assessed. Three waste-to-energy (WtE) techniques are employed within the framework of an industrial partnership. Life cycle assessment (LCA) and a brief social contextualization including the production of renewable energy from the waste generated worldwide were held to attain a holistic view and attract the interest of multiple stakeholders. Incineration depicted a sustainable profile with improved results for global warming potential and terrestrial ecotoxicity potential. Regular gasification revealed the best results for eutrophication, acidification, marine aquatic ecotoxicity and human toxicity potential. Two-stage plasma gasification showed negative values for all impact categories i.e. achieving environmental credits. The estimate of the electricity produced from the waste generated per capita showed a fair coverage of the electrical demand in distinct world areas. To the best of the authors' knowledge, there are no reports connecting the electricity use, the waste production and the renewable energy achieved from WtE for different world regions. Therefore, this study supports the replacement of fossil fuels with renewable alternatives, reducing greenhouse gas emissions while maintaining the comfort and commodities suitable for a comfortable quality of life.

Concentrations, spatial distributions, and congener profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans around original plastic solid waste recovery sites in China

The concentrations, profiles, and spatial distributions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in soil and sediment samples from several typical plastic solid waste (PSW) recovery sites (particularly from areas in which PSW is burned openly) in China were investigated. The results showed that burning PSW directly influenced PCDD/F concentrations immediately around the burning area. All of the samples in which soil contained black burning residue, collected from immediately around burning areas, had PCDD/F concentrations (mean 21708 ng kg^-1) and toxic equivalent (TEQ) concentrations (mean 2140 ng I-TEQ kg^-1 or 1877 ng WHO₂₀₀₆-TEQ kg^-1) more than 100 times higher than the concentrations in samples collected away from burning areas (mean 222 ng kg^-1, 8.75 ng I-TEQ kg^-1, 7.96 ng WHO₂₀₀₆-TEQ kg^-1). Principal component analysis and hierarchical cluster analysis indicated that the PCDD/F concentrations in seven soil samples from near PSW burning areas were influenced by PSW burning but that the PCDD/Fs in these soil samples may have had other or multiple sources. PCDD/F distributions at PSW recovery sites have been investigated in few previous studies. The results presented here indicate that appropriate measures should be taken to decrease the ecological risks posed by PSW recovery and to prevent, control, and remediate PCDD/F and other chemical contamination caused by PSW recovery.

Destruction and formation of polychlorinated dibenzo-p-dioxins and dibenzofurans during pretreatment and co-processing of municipal solid waste incineration fly ash in a cement kiln

During a three-day industrial trial, municipal solid waste incineration fly ash (FA) was co-processed in a cement kiln after water-washing pretreatment for waste-to-resource conversion. All inputs and outputs were sampled to obtain the dioxin fingerprints. During washing, the relative contents of polychlorinated dibenzo-p-dioxins and dibenzofurans in FA, washed FA and sludge were basically the same and only a simple physical migration resulted. During drying, only physical processes resulted, which included volatilization and migration. Minimal dioxins residue remained in the clinker, cement kiln dust and flue gas, and the dioxins degraded completely. Through co-processing, the dioxins degraded obviously. The main compounds synthesized include 1,2,3,4,7,8-hepta-chlorodibenzo-p-dioxin, 2,3,7,8-tetra- chlorodibenzofuran and octa-chlorodibenzofuran. A comparison of dioxins fingerprints in the clinker, cement kiln dust and flue gas under baseline and co-processing conditions showed that co-processing had no effect on the cement kiln production. The baseline sample also contained a certain amount of dioxins, possibly because of the 'memory effect' and heterogeneous formations. The dioxins concentrations in the clinker and FA were far lower than the national standards. Thus, no environmental risk results during co-processing.

Pollutant formation in the pyrolysis and combustion of Automotive Shredder Residue

The present work has been carried out to verify the feasibility of thermal valorization of an automobile shredder residue (ASR). With this aim, the thermal decomposition of this waste has been studied in a laboratory scale reactor, analyzing the pollutants emitted under different operating conditions. The emission factors of carbon oxides, light hydrocarbons, PAHs, PCPhs, PCBzs, PBPhs, PCDD/Fs, dioxin-like PCBs and PBDD/Fs were determined at two temperatures, 600 and 850°C, and under different oxygen ratios ranging from 0 (pure pyrolysis) to 1.5 (over-stoichiometric oxidation). After analyzing all these compounds, we conclude that thermal valorization of ASR is a clean way to treat this waste.

Characterisation of polycyclic aromatic hydrocarbons in flue gas and residues of a full scale fluidized bed combustor combusting non-hazardous industrial waste

This paper studies the fate of PAHs in full scale incinerators by analysing the concentration of the 16 EPA-PAHs in both the input waste and all the outputs of a full scale Fluidized Bed Combustor (FBC). Of the analysed waste inputs i.e. Waste Water Treatment (WWT) sludge, Refuse Derived Fuel (RDF) and Automotive Shredder Residue (ASR), RDF and ASR were the main PAH sources, with phenanthrene, fluoranthene and pyrene being the most important PAHs. In the flue gas sampled at the stack, naphthalene was the only predominant PAH, indicating that the PAHs in FBC's combustion gas were newly formed and did not remain from the input waste. Of the other outputs, the boiler and fly ash contained no detectable levels of PAHs, whereas the flue gas cleaning residue contained only low concentrations of naphthalene, probably adsorbed from the flue gas. The PAH fingerprint of the bottom ash corresponded rather well to the PAH fingerprint of the RDF and ASR, indicating that the PAHs in this output, in contrast to the other outputs, were mainly remainders from the PAHs in the waste inputs. A PAH mass balance showed that the total PAH input/output ratio of the FBC ranged from about 100 to about 2600 depending on the waste input composition and the obtained combustion conditions. In all cases, the FBC was clearly a net PAH sink.

Viability study of automobile shredder residue as fuel

Car Fluff samples collected from a shredding plant in Italy were classified based on particle size, and three different size fractions were obtained in this way. A comparison between these size fractions and the original light fluff was made from two different points of view: (i) the properties of each size fraction as a fuel were evaluated and (ii) the pollutants evolved when each size fraction was subjected to combustion were studied. The aim was to establish which size fraction would be the most suitable for the purposes of energy recovery. The light fluff analyzed contained up to 50 wt.% fines (particle size<20 mm). However, its low calorific value and high emissions of polychlorinated dioxins and furans (PCDD/Fs), generated during combustion, make the fines fraction inappropriate for energy recovery, and therefore, landfilling would be the best option. The 50-100 mm fraction exhibited a high calorific value and low PCDD/F emissions were generated when the sample was combusted, making it the most suitable fraction for use as refuse-derived fuel (RDF). Results obtained suggest that removing fines from the original ASR sample would lead to a material product that is more suitable for use as RDF.

Environmental and human exposure to soil chlorinated and brominated polycyclic aromatic hydrocarbons in an urbanized region

Nine chlorinated and brominated polycyclic aromatic hydrocarbons (Cl/BrPAHs) and five parent polycyclic aromatic hydrocarbons (PAHs) were measured in urban surface soil and fly ash samples collected from Shenzhen, south China in winter 2010. The concentrations of total Cl/BrPAHs and PAHs in soil ranged from below the reporting limit to 142 ng/g and from 4.34 to 158 µg/g, respectively, and in fly ash they ranged from 17.7 to 19.5 ng/g and 26.1 to 28.3 µg/g, respectively. Concentrations of Cl/BrPAHs and parent PAHs were not significantly correlated with each other in soil or in fly ash, suggesting that Cl/BrPAHs were formed mainly by mechanisms other than direct halogenation of parent PAHs. Estimated mass inventories of 2-BrFlu varied from 68.1 kg in commercial land to 669 kg in countryside land, the highest among all Cl/BrPAHs. Loss fluxes via soil erosion accounted for only small proportions of total soil mass inventories of Cl/BrPAHs. Average daily human intake via soil ingestion decreased with increasing age, with 2-BrFlu as the main contributor. Children of 0 to 8 years old were the most sensitive subgroup (13.7 pg/kg body wt/d for total Cl/BrPAHs), and females were more sensitive than males in the same age group. The mean dioxin-like toxic equivalency quotient (TEQ) concentration of total Cl/BrPAHs (0.008 ng-TEQ/g) was lower in soil than in fly ash (0.06 ng-TEQ/g). Conversely, the mean TEQ concentration of total parent PAHs (2.23 ng-TEQ/g) was higher in soil than in fly ash.