Nuria Ortuño

Pollutant emissions during pyrolysis and combustion of waste printed circuit boards, before and after metal removal

The constant increase in the production of electronic devices implies the need for an appropriate management of a growing number of waste electrical and electronic equipment. Thermal treatments represent an interesting alternative to recycle this kind of waste, but particular attention has to be paid to the potential emissions of toxic by-products. In this study, the emissions from thermal degradation of printed circuit boards (with and without metals) have been studied using a laboratory scale reactor, under oxidizing and inert atmosphere at 600 and 850 °C. Apart from carbon oxides, HBr was the main decomposition product, followed by high amounts of methane, ethylene, propylene, phenol and benzene. The maximum formation of PAHs was found in pyrolysis at 850 °C, naphthalene being the most abundant. High levels of 2-, 4-, 2,4-, 2,6- and 2,4,6-bromophenols were found, especially at 600 °C. Emissions of PCDD/Fs and dioxin-like PCBs were quite low and much lower than that of PBDD/Fs, due to the higher bromine content of the samples. Combustion at 600 °C was the run with the highest PBDD/F formation: the total content of eleven 2,3,7,8-substituted congeners (tetra- through heptaBDD/Fs) was 7240 and 3250 ng WHO2005-TEQ/kg sample, corresponding to the sample with and without metals, respectively.

Emissions of PBDD/Fs, PCDD/Fs and PBDEs from flame-retarded high-impact polystyrene under thermal stress

The emissions of polybrominated diphenyl ethers (PBDEs), polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) and their chlorinated analogues (PCDD/Fs) during the thermal treatment of a high impact polystyrene (HIPS) TV casing were investigated. The halogenated compounds were analyzed in the original material and in the gases emitted during its treatment at temperatures between 50 °C and 250 °C. DecaBDE was the primary PBDE in the TV casing, which also contained high levels of PBDFs (ppm range). At the lower treatment temperatures, non-modified PBDEs evaporated from the samples. Conversely, at 200 °C or above, debromination reactions led to the formation of additional tri- through nonaBDE. The formation of new PBDD/Fs was also detected in the gas phase when the plastic was heated to 200 °C or 250 °C, with higher yields of furans than dioxins. This appreciably increased the toxic equivalent (TEQ) levels of the gas phase relative to those seen in the untreated sample. In all cases, the levels and TEQ contributions from PCDD/Fs were negligible compared to those for brominated analogues.

Decomposition of two types of electric wires considering the effect of the metal in the production of pollutants

Combustion runs at 700 °C in a horizontal laboratory furnace were carried out on two different electric wires (PVC and halogen-free wire). Tests were performed in the presence and in the absence of the metal conductor of the wires. The analyses of the polycyclic aromatic hydrocarbons (PAHs), chlorobenzenes (CBzs), chlorophenols (CPhs), mono- to octa-chlorodibenzo-p-dioxin and dibenzofurans (PCDD/Fs), and dioxin-like PCBs are shown. Regarding semivolatile compounds, PAHs production decreases in the presence of metal, while a higher amount of chlorinated compounds are emitted. Respect to the PCDD/Fs, the PVC wire in the presence of metal presents the highest emission, with a much more emission of furans than dioxins. The maximum emission is with 2 or 3 chlorine atom PCDD/Fs. PCBs emission correlates with PCDD/F production and represents 3-4% of total toxicity, determined by using WHO2005 factors.

De novo synthesis of brominated dioxins and furans

On the basis of laboratory experiments with model mixtures (active carbon+CuBr2 at different loads), this work studies the formation of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) by de novo synthesis. For the different samples, the temperature of the maximum carbon oxidation rate was determined by thermogravimetric analysis, and a kinetic model was proposed for the degradation of the materials in an oxidizing atmosphere (synthetic air). The effect of the addition of different amounts of CuBr2 was studied, finding that its presence accelerates the degradation of the carbonaceous structure in the presence of oxygen. The thermal degradation of the samples in air is satisfactorily described by a first-order single-reaction model. In addition, combustion runs of one of the mixtures (consisting of activated carbon+50 wt % CuBr2, pyrolyzed at 700 °C) were performed in a quartz horizontal laboratory furnace. The analysis of the emissions and the solid residue proved the formation of brominated dioxins and furans at 300, 400, and 500 °C, with a maximum yield at 300 °C (91.7 ng/g of total PBDD/Fs) and a higher bromination degree with increasing temperature.

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.

Emissions of PCDD/Fs, PBDD/Fs, dioxin like-PCBs and PAHs from a cement plant using a long-term monitoring system

The aim of the present work was to assess the emission of different persistent organic pollutants from a cement plant over a period of one year, under normal operational conditions. Thus, a long-term sampling device was installed in the clinker kiln stack of the cement plant. The factory uses petroleum coke as primary fuel, but also alternative fuels such as solid recovered fuel (SRF), automotive shredder residue (ASR), sewage sludge, waste tires, and meat and bone meal (MBM) wastes, with an energy substitution level of about 40%. Both PCDD/Fs (together with dl-PCBs) and PBDD/Fs were continuously sampled, with a total of ten samples collected in 2-4week periods. Also, PAHs were sampled during one-week periods, in order to evaluate their emissions in three different samples. The emission levels throughout the year were much lower than the set legal limits in all substances, being <10pgI-TEQ/Nm(3) in the case of PCDD/Fs. The data obtained allowed calculation of updated emission factors for the cement sector, which were 8.5ng I-TEQ/ton clinker for PCDD/Fs and 3.2ng WHO-TEQ/ton clinker for PCBs. With respect to the congener distribution, 2,3,7,8-TCDF accounts for 60 to 68% of the total toxicity for PCDD/Fs, and in PBDD/F emissions, a clear predominance of octa-substituted species (both dioxin and furan) was found.

14th congress of combustion by-products and their health effects—origin, fate, and health effects of combustion-related air pollutants in the coming era of bio-based energy sources

The 14th International Congress on Combustion By-Products and Their Health Effects was held in Umeå, Sweden from June 14th to 17th, 2015. The Congress, mainly sponsored by the National Institute of Environmental Health Sciences Superfund Research Program and the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, focused on the “Origin, fate and health effects of combustion-related air pollutants in the coming era of bio-based energy sources”. The international delegates included academic and government researchers, engineers, scientists, policymakers and representatives of industrial partners. The Congress provided a unique forum for the discussion of scientific advances in this research area since it addressed in combination the health-related issues and the environmental implications of combustion by-products. The scientific outcomes of the Congress included the consensus opinions that: (a) there is a correlation between human exposure to particulate matter and increased cardiac and respiratory morbidity and mortality; (b) because currently available data does not support the assessment of differences in health outcomes between biomass smoke and other particulates in outdoor air, the potential human health and environmental impacts of emerging air-pollution sources must be addressed. Assessment will require the development of new approaches to characterize combustion emissions through advanced sampling and analytical methods. The Congress also concluded the need for better and more sustainable e-waste management and improved policies, usage and disposal methods for materials containing flame retardants.

Pollutant formation in the pyrolysis and combustion of materials combining biomass and e-waste

Combustion and pyrolysis runs at 850°C were carried out in a laboratory scale horizontal reactor with different materials combining biomass and waste electrical and electronic equipment (WEEE). Analyses are presented of the carbon oxides, light hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), polychlorinated benzenes (ClBzs), polychlorinated phenols (ClPhs), polybrominated phenols (BrPhs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Results showed that gas emissions were mainly composed of CO and CO2; the high level of CO found in the pyrolytic runs was easily transformed into CO2 by reaction with oxygen. The total amount of light hydrocarbons emitted was higher in the samples containing WEEE, methane being the most abundant light hydrocarbon in all the runs. However, the presence of WEEE reduced the emission of PAHs which decreased with the increase of the oxygen. The total amount of BrPhs increased in the decomposition of the samples containing WEEE, reaching its maximum in pyrolysis runs. Emission of PCDD/Fs was enhanced in pyrolytic conditions and easily decreased in the presence of oxygen.

Volatile and semivolatile emissions from the pyrolysis of almond shell loaded with heavy metals

Heavy metal-loaded almond shell was subjected to pyrolysis to understand the effect of the presence of different heavy metals on its thermal degradation. Pyrolysis behavior of native and metal-loaded samples was studied by thermogravimetric analysis. Similar shapes of thermogravimetric curves indicate that the presence of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni) and lead (Pb) did not change the main degradation pathways of almond shell. However, the temperature at which the decomposition in each stage takes place at a higher rate and char yield was considerably modified by the presence of Cr and Ni. Then, pyrolysis tests of the almond shell samples were performed in a moving tubular reactor at 700°C. Gases and volatile organic compounds were collected using Tedlar bags and semivolatile organic compounds were collected using a resin as adsorbent. Significant changes were obtained in the composition of the gaseous fraction as a result of the metal impregnation. The main changes in the composition of the gas were observed for Ni-loaded sample, which presented the highest H2 and CO yields. Also, the yields of most of the light hydrocarbons decrease in the presence of metal, while the rest remain quite similar. The total PAH yields reached 103μg/g for nickel-loaded sample (NiAS), 164μg/g for copper-loaded sample (CuAS), 172μg/g for lead-loaded sample (PbAS), 245μg/g for native sample (AS), 248μg/g for cadmium-loaded sample (CdAS) and 283μg/g for chromium-loaded sample (CrAS). Nickel is the most effective in the higher aromatic tar reduction, followed by Cu and Pb, whereas the presence of Cd does not affect the total emissions of PAHs. Finally, the carcinogenic potency of the samples was calculated. Native sample and the sample loaded with Cr presented slightly higher values associated to the presence of small amounts of benzo(a)pyrene.

Emissions of toxic pollutants from co-combustion of demolition and construction wood and household waste fuel blends

Four different types of fuel blends containing demolition and construction wood and household waste were combusted in a small-scale experimental set-up to study the effect of fuel composition on the emissions of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs), chlorobenzenes (PCBzs), chlorophenols (PCPhs) and polycyclic aromatic hydrocarbons (PAHs). Two woody materials, commercial stemwood (ST) and demolition and construction wood (DC) were selected because of the differences in their persistent organic pollutants (POPs), ash and metals content. For household waste, we used a municipal solid waste (MSW) and a refuse-derived fuel (RDF) from MSW with 5-20 wt% and up to 5 wt% food waste content respectively. No clear effect on the formation of pollutants was observed with different food waste content in the fuel blends tested. Combustion of ST-based fuels was very inefficient which led to high PAH emissions (32 ± 3.8 mg/kgfuel). The use of DC clearly increased the total PCDD and PCDF emissions (71 ± 26 μg/kgfuel) and had a clear effect on the formation of toxic congeners (210 ± 87 ng WHO2005-TEQ/kgfuel). The high PCDD and PCDF emissions from DC-based fuels can be attributed to the presence of material contaminants such as small pieces of metals or plastics as well as timber treated with chromated copper arsenate preservatives and pentachlorophenol in the DC source.