Environmental impact of pyrolysis of mixed WEEE plastics part 2: Life cycle assessment

Waste electrical and electronic equipment (WEEE) contains up to 25% plastics. Extraction of higher quality fractions for recycling leaves a mix of plastic types contaminated with other materials, requiring the least environmentally harmful disposal route. Data from trials of pyrolysis, described in part 1 of this paper set, were used in a life cycle assessment of the treatment of WEEE plastics. Various levels of recycling of the sorted fraction were considered, and pyrolysis was compared with incineration (with energy recovery) and landfill for disposal of the remainder. Increased recycling gave reduced environmental impact in almost all categories considered, although inefficient recycling decreased that benefit. Significant differences between pyrolysis, incineration and landfill were seen in climate change impacts, carbon sent to landfill, resources saved, and radiation. There was no overall "best" option. Landfill had the least short-term impact on climate change so could be a temporary means of sequestering carbon. Incineration left almost no carbon to landfill, but produced the most greenhouse gases. Pyrolysis or incineration saved most resources, with the balance depending on the source of electricity replaced by incineration. Pyrolysis emerged as a strong compromise candidate since the gases and oils produced could be used as fuels and so provided significant resource saving without high impact on climate change or landfill space.     

Recycling of meat and bone meal animal feed by vacuum pyrolysis

Due to the recent bovine spongiform encephalopathy (BSE) crisis in the European beef industry, the use of animal-derived products to feed cattle is now severely restricted. Large quantities of waste animal meat and bone meal (MBM), also known as animal flour, have to be safely disposed of or transformed. One disposal option is pyrolysis. Vacuum pyrolysis of an animal flour sample has been performed in a laboratory reactor. The results obtained revealed that vacuum pyrolysis can be an attractive alternative to incineration and cement kilns. The process generated a combustible gas (15.1 wt %), a high calorific value oil (35.1 wt %), a solid residue rich in minerals (39.1 wt %), and an aqueous phase rich in organics (10.7 wt %). The gas and the aqueous phase can be used to provide heat to the vacuum pyrolysis reactor and the MBM drying unit. The oil can be used alone or mixed with petroleum products as a fuel in boilers or gas turbines. Conversion of animal waste by pyrolysis into fuels can contribute to the reduction of greenhouse gases. It is suggested to use the solid residue for agricultural soil enrichment in minerals and as a soil moisturizer.     

Volatilization behavior of fluorine in fluoroborate residue during pyrolysis

Industrial hazardous waste from the fluorine chemical industry sometimes has a high content of fluorine, and incinerating it could be very poisonous if the flue gas is not properly disposed. In this study fluoroborate residue is used to represent a typical waste from the fluorine chemical industry . Thermogravimetric analysis coupled with Fourier transform infrared analysis (TG-FTIR analysis) was used to study the evolution characteristics of gaseous products during the pyrolysis of fluoroborate residue. The pyrolysis process of fluoroborate residue could be divided into three stages according to the TG analysis: moisture loss, fast decomposition, and charring. SiF(4), BF(3), and HF are found as fluorine gas species evolved in the pyrolysis process. The evolution of SiF(4) finishes at 600 °C. The evolution of BF(3) has two peaks and most of the emission happens before 600 °C. The release of HF could be divided into two stages due to the different existence of F(-). In addition, the reforming condition of different fluorine-containing gaseous substances is verified in a thermodynamic equilibrium model and the results could explain the experiment phenomenon well.     

Comparison of the recyclability of flame-retarded plastics

Mechanical recycling of plastics from waste from electrical and electronical equipment (WEEE) is increasingly expected by regulators and demanded by original equipment manufacturers (CEMs); however, mechanical recycling is generally recognized to be the most economically costly and technically challenging method of recovering WEEE plastics. With 12% of WEEE plastics requiring the use of flame-retardants in order to ensure appropriate levels of consumer fire safety, there is a distinct need for data from comparative tests on recyclability of various flame-retarded plastics. Ten commercially available flame-retarded plastic grades commonly used in electronic equipment (eight "halogen-free" grades and two grades containing brominated flame-retardants (BFRs)) were subjected to two different recycling scenarios. A standard recycling scenario was carried out by repeatedly extruding the materials and an accelerated hydrolysis scenario was carried out to study the influence of humidity from air during use on the process. Both, virgin and recycled materials were tested for a potential formation of polybrominated dibenzodioxins/furans (PBDD/Fs), their mechanical properties were assessed and the fire safety rating was determined. Results indicate that none of the tested materials showed a potential to form the PBDD/Fs regulated by the German Chemicals Banning Ordinance. The halogen-free plastic grades showed a significant deterioration of mechanical properties after recycling, whereas those plastics containing BFRs were able to pass all test criteria, thus maintaining their original properties. With respect to the fire safety rating, none of the eight tested halogen-free plastic grades could maintain their fire safety rating after five recycling loops, whereas both BFR plastics continued to achieve their fire safety ratings. Therefore the tested BFR containing plastic materials showed superior recycling properties compared to the tested halogen-free plastic grades with respect to all investigated parameters.     

Using crude glycerol and thin stillage for the production of microbial lipids through the cultivation of Rhodotorula glutinis

Single cell oils (SCO) produced from oleaginous microorganisms are a potential alternative oil feedstock for biodiesel production. The worldwide production of glycerol, a 10% (w/w) byproduct produced in the transesterfication process of oils converted to biodiesel, is increasing as more biodiesel is being produced. For the purposes of cost reduction, crude glycerol was regarded as a suitable carbon source for the cultivation of Rhodotorula glutinis. In addition to using renewable crude glycerol, waste solution collected from the brewing company (called thin stillage) was adopted as a substitute to replace a costly nitrogen source used in the medium. The results of using mixture of crude glycerol and thin stillage indicated about a 27% increase in total biomass as compared to that of using crude glycerol with a standard medium. Using glycerol instead of glucose as the carbon source could also alter the lipid profile, resulting in an increase in linolenic acid (C18:2) to comprise over 20% of the total lipid. Successfully using renewable crude glycerol and thin stillage for the cultivation of oleaginous microorganisms could greatly enhance the economic competition of biodiesel produced from SCO.     

食用油中邻苯二甲酸酯类增塑剂污染的途径和风险控制研究

目的对食用油中邻苯二甲酸酯类增塑剂污染的途径和风险控制进行研究。方法结合食用油的加工工艺,对原料油种籽、白土、磷酸、溶剂、活性碳、各类隐蔽密封件、塑料管、塑料桶、塑料包装物的影响进行筛查分析。结果食用油的塑化剂污染分为引入和迁移两大途径,其中引入途径主要与加工过程外采物料相关,如油料种子、加工助剂、添加剂塑化剂;迁移途径主要与加工、储存接触的塑料材质设备、工具、包装材料的塑化剂含量相关。而原料、塑料隐蔽密封件、塑料管、包装材料是食用油中邻苯二甲酸酯类增塑剂污染的主要途径;同时,食用油的脱臭工艺对塑化剂有一定的脱除作用。结论本研究提出的食用油塑化剂污染预防的控制方案,可降低食用油产品中的塑化剂风险。     

Characterization of gaseous and solid product from thermal plasma pyrolysis of waste rubber

Pyrolysis of waste rubber in thermal plasma is studied for the purpose of producing gaseous fuel and recovering carbon black filler. The plasma reactor has a dc arc nitrogen plasma generator with a maximum electric power input of 62.5 kVA and a reaction chamber of 50 mm inner diameter and 1000 mm height. The results of a series of experiments have shown that the main components of the gaseous product are H2, CO, C2H2, CH4, and C2H4; the heat value of the gas is about 5-9 MJ/Nm3. The solid product contains more than 80 wt % elemental carbon, has a surface area of about 65 m2/g, and is referred to as pyrolytic carbon black (CBp). X-ray photoelectron spectroscopy (XPS) analysis has revealed that the CBp has mainly graphitic carbon structure similar to those of commercial carbon black. The CBp may be used as semireinforcing carbon black in nontire rubber applications, or, after upgrading, as carbon black filler for tire. Thus thermal plasma pyrolysis is potentially a useful way of treating waste rubber for resource recovery.     

RECYCLING OF POLYMERIC MATERIALS USED FOR FOOD PACKAGING: CURRENT STATUS AND PERSPECTIVES

Packaging materials are currently considered an important source of environmental waste because of their great volume. Although for materials like glass, aluminum, and paperboard recycling has been rather extensively practiced, it proved to be a much more arduous task for polymeric materials because of their great variety and the coexistence/mixing of various polymers either as blends or as copolymers. Therefore, constructive approach to recycling would consist of reviewing its current status worldwide to make a comprehensive presentation of the current trends and the state of art techniques for plastic disposal, sorting, and recycling. Although mechanical, feedstock, and chemical recycling of polymers are thoroughly analyzed within the frame of this review, other alternatives such as landfill, incineration, pyrolysis, reuse and recovery, and composting are also presented and commented.     

Brominated flame retardants in waste electrical and electronic equipment: substance flows in a recycling plant

Brominated flame retardants (BFRs) are synthetic additives mainly used in electrical and electronic appliances and in construction materials. The properties of some BFRs are typical for persistent organic pollutants, and certain BFRs, in particular some polybrominated diphenyl ether (PBDE) congeners and hexabromocyclododecane (HBCD), are suspected to cause adverse health effects. Global consumption of the most demanded BFRs, i.e., penta-, octa-, and decaBDE, tetrabromobisphenol A (TBBPA), and HBCD, has doubled in the 1990s. Only limited and rather uncertain data are available regarding the occurrence of BFRs in consumer goods and waste fractions as well as regarding emissions during use and disposal. The knowledge of anthropogenic substance flows and stocks is essential for early recognition of environmental impacts and effective chemicals management. In this paper, actual levels of penta-, octa-, and decaBDE, TBBPA, and HBCD in waste electrical and electronic equipment (WEEE) as a major carrier of BFRs are presented. These BFRs have been determined in products of a modern Swiss recycling plant applying gas chromatography/electron capture detection and gas chromatography/mass spectrometry analysis. A substance flow analysis (SFA) technique has been used to characterize the flows of target substances in the recycling process from the bulk WEEE input into the output products. Average concentrations in small size WEEE, representing the relevant electric and electronic appliances in WEEE, sampled in 2003 amounted to 34 mg/kg for pentaBDE, 530 mg/kg for octaBDE, 510 mg/kg for decaBDE, 1420 mg/kg for TBBPA (as an additive), 17 mg/kg for HBCD, 5500 mg/kg for bromine, and 1700 mg/kg for antimony. In comparison to data that have been calculated by SFA for Switzerland from literature for the 1990s, these measured concentrations in small size WEEE were 7 times higher for pentaBDE, unexpectedly about 50% lower for decaBDE, and agreed fairly well for TBBPA (as an additive) and octaBDE. Roughly 60% of the total bromine input determined by SFA based on X-ray fluorescence analysis of the output materials of the recycling plant cannot be assigned to the selected BFRs. This is an indication for the presence of other brominated substances as substitutes for PBDEs in electrical and electronic equipment. The presence of BFRs, in particular PBDEs in the low grams per kilogram concentration range, in the fine dust fraction recovered in the off-gas purification system of the recycling plant reveals a high potential for BFR emissions from WEEE management and point out the importance for environmentally sound recycling and disposal technologies for BFR-containing residues.     

Efficient production of fatty acid methyl ester from waste activated bleaching earth using diesel oil as organic solvent

Fatty acid methyl ester (FAME) production from waste activated bleaching earth (ABE) discarded by the crude oil refining industry was investigated using fossil fuel as a solvent in the esterification of triglycerides. Lipase from Candida cylindracea showed the highest stability in diesel oil. Using diesel oil as a solvent, 3 h was sufficient to obtain a yield of approximately 100% of FAME in the presence of 10% lipase from waste ABE. Kerosene was also a good solvent in the esterification of triglycerides embedded in the waste ABE. Fuel analysis showed that the FAME produced using diesel oil as a solvent complied with the Japanese diesel standard and the 10% residual carbon amount was lower than that of FAME produced using other solvents. Use of diesel oil as solvent in the FAME production from the waste ABE simplified the process, because there was no need to separate the organic solvent from the FAME-solvent mixture. These results demonstrate a promising reutilization method for the production of FAME, for use as a biodiesel, from industrial waste resources containing waste vegetable oils.     

Solvent-extractable polycyclic aromatic hydrocarbons in biochar: influence of pyrolysis temperature and feedstock

Despite the increasing agricultural use of biochar as a way of combining the utilization of biomass for energy production with the removal of CO(2) from the atmosphere, it is not known how variations in pyrolysis temperature and feedstock type affect concentration and composition of polycyclic aromatic hydrocarbons (PAHs) that inevitably form and associate with biochar. To close this knowledge gap, we quantified 11 unsubstituted three- to five-ring PAHs as well as alkylated forms of phenanthrene and anthracene in grass and wood chars produced in 100 °C increments across a temperature range (100 to 700 °C). Our results show that solvent-extractable PAH concentrations in biochars produced at heat treatment temperatures (HTTs) of 400 and 500 °C greatly exceed those observed at higher and lower temperature, supporting a low HTT solid-phase formation mechanism operable at temperatures commonly used for industrial biochar production. The maximum extractable yield of 'pyrolytic' unsubstituted PAHs for grass (22 μg g(-1) at HTT = 500 °C) greatly exceeds the value for wood (5.9 μg g(-1)). Moreover, PAH signatures (e.g., total monomethylphenanthrene to phenanthrene ratios, MP/P ～2-3) at intermediate temperatures (400 °C) resemble those of fossil oils rather than that commonly attributed to pyrolytic products. Further research is needed to characterize the PAH evolution in modern pyrolysis reactors and assess the fate of biochar-bound PAHs in soils and sediments. Various commonly applied PAH ratios and indicator compounds show promise as markers for specific feedstock materials and pyrolysis conditions of biochars in environmental systems.     

Energy balance and emissions associated with biochar sequestration and pyrolysis bioenergy production

The implications for greenhouse gas emissions of optimizing a slow pyrolysis-based bioenergy system for biochar and energy production rather than solely for energy production were assessed. Scenarios for feedstock production were examined using a life-cycle approach. We considered both purpose grown bioenergy crops (BEC) and the use of crop wastes (CW) as feedstocks. The BEC scenarios involved a change from growing winter wheat to purpose grown miscanthus, switchgrass, and corn as bioenergy crops. The CW scenarios consider both corn stover and winter wheat straw as feedstocks. Our findings show that the avoided emissions are between 2 and 5 times greater when biochar is applied to agricultural land (2--19 Mg CO2 ha(-1) y(-1)) than used solely for fossil energy offsets. 41--64% of these emission reductions are related to the retention of C in biochar, the rest to offsetting fossil fuel use for energy, fertilizer savings, and avoided soil emissions other than CO2. Despite a reduction in energy output of approximately 30% where the slow pyrolysis technology is optimized to produce biochar for land application, the energy produced per unit energy input at 2--7 MJ/MJ is greater than that of comparable technologies such as ethanol from corn. The C emissions per MWh of electricity production range from 91-360 kg CO2 MWh(-1), before accounting for C offset due to the use of biochar are considerably below the lifecycle emissions associated with fossil fuel use for electricity generation (600-900 kg CO2 MWh(-1)). Low-temperature slow pyrolysis offers an energetically efficient strategy for bioenergy production, and the land application of biochar reduces greenhouse emissions to a greater extent than when the biochar is used to offset fossil fuel emissions.     

食用植物油与餐厨废油脂中三酰甘油氧化聚合物含量的研究

为了探寻餐厨废油脂的标志性氧化产物,采用正相硅胶柱制备色谱预分离油脂中极性物,联用高效体积排阻色谱方法测定三酰甘油氧化聚合物(oxidized triacylglycerol polymers,TGP),统计分析了12种常见品种44个新鲜食用植物油样品和具代表性的三大类61个来源不同、精炼程度各异的餐厨废油脂样品的TGP含量,显示食用植物油中TGP平均质量分数为(0.68±0.37)%,精炼餐厨废油脂中平均质量分数为(6.10±3.44)%,二者TGP含量具极显著差异(P<0.01)。结果表明TGP可望成为鉴别源于餐厨废弃食用油的二次油的指标。     

废纸制浆工艺与技术装备的发展

回顾总结了建国60年来我国造纸工业在废纸回收和利用方面工艺技术的演变、装备的进步以及废纸制浆过程中化学助剂的应用、废水与废渣的处理,重点阐述了有代表性的引进的废纸处理设备和国产废纸处理设备的研发成果,对今后废纸制浆技术装备的发展具有导向作用.     

餐厨废弃油脂生物柴油对船舶柴油机性能、排放特性以及燃烧特性的影响北大核心CSCD

为探讨生物柴油应用于船舶柴油机的可行性,将餐厨废弃油脂生物柴油与柴油混合,在船舶柴油机上进行试验,测试其对船舶柴油机性能、排放特性和燃烧特性的影响。结果表明:生物柴油混合物的高黏度以及低热值会降低有效热效率,并导致燃油消耗率略有升高;由于生物柴油的高含氧量促进完全燃烧,相比于柴油,燃烧生物柴油混合物后,一氧化碳排放量最高下降17%,二氧化碳排放量最高下降5.1%,二氧化硫排放量最高下降41%,碳烟排放量最高下降36%;生物柴油过快的燃烧速率提高了气缸内的燃烧温度,以及高含氧量促进了氮氧化物的排放;生物柴油混合物燃烧时的缸内压力与柴油非常接近。餐厨废弃油脂生物柴油对船舶柴油机的性能、燃烧特性和排放特性均具有较好的表现,可以作为柴油的替代燃料用于船舶柴油机。     

RoHS regulated substances in mixed plastics from waste electrical and electronic equipment

The disposal and recovery of plastics from waste electrical and electronic equipment (WEEE) are of considerable importance, both from an environmental and an economic perspective. This paper presents the results of a study investigating current concentrations of hazardous substances in mixed plastics from WEEE and their implications for an environmentally sound recovery. The study included 53 sampling campaigns for mixed plastics from WEEE. The samples were analyzed with regard to heavy metals (cadmium, chromium, mercury, and lead) and flame retardants (PentaBDE, OctaBDE, DecaBDE, DecaBB) regulated in the RoHS Directive. Besides these substances, other brominated flame retardants known to occur in electronics (HBCD, TBBPA) as well as the total bromine and phosphorus contents were considered. Results show that no mixed plastics fraction from WEEE is completely free from substances regulated in the RoHS Directive. The lowest number and average concentrations were found in flat screen monitors. The highest concentrations were found in mixed plastics from CRT monitors and TVs. Mixed plastics fractions with high average concentrations of heavy metals originate from the treatment of small household appliances (cadmium), ICT equipment (lead), and consumer equipment (lead). Mixed plastics fractions with high average concentrations of brominated flame retardants mainly originate from the treatment of small household appliances for high temperature applications (DecaBDE), CRT monitors (OctaBDE and DecaBDE) and consumer equipment (DecaBDE), in particular CRT TVs (DecaBDE). To avoid a dissipation of hazardous substances into plastics and the environment, it is recommended that mixed plastics from WEEE are subject to a strict quality management.     

Tobacco waste/industrial sludge based desulfurization adsorbents: effect of phase interactions during pyrolysis on surface activity

Industrial waste derived adsorbents were obtained by pyrolysis of tobacco waste with either metal sludge or waste oil sludge from a shipyard. The materials were used as media to remove hydrogen sulfide at room temperature in the presence of moisture. The initial and exhausted adsorbents after the breakthrough tests were characterized using sorption of nitrogen, thermal analysis, XRD, elemental analysis, and surface pH measurements. It was found that mixing tobacco and industrial sludges results in a strong synergy, enhancing the catalytic properties of adsorbents. This synergy is observed in both surface chemistry and porosity. During pyrolysis, new mineral phases are formed as a result of solid-state reactions between the components of the sludges. They are highly dispersed on the surface of mesopores. A high volume of these pores is a result of activation of the carbon phase in the composite by alkaline earth metals and also by the release of water from the decomposition of an inorganic phase that is in the predominant quantity. A high temperature of pyrolysis is beneficial for the adsorbents due to the enhanced activation of the carbonaceous phase and the chemical stabilization of the inorganic phase. Samples obtained at low temperatures are sensitive to water, which deactivates their catalytic centers.     

Rapid assessment of the adulteration of virgin olive oils by other seed oils using pyrolysis mass spectrometry and artificial neural networks

Curie-point pyrolysis mass spectra were obtained from a variety of extra-virgin olive oils, prepared from various cultivars using several mechanical treatments. Some of the oils were adulterated (according to a double-blind protocol) with different amounts of seed oils (50–500 ml of soya, sunflower, peanut, corn or rectified olive oils per litre of mixed oil). Canonical variates analysis indicated that the major source of variation between the pyrolysis mass spectra was due to differences between the cultivars. rather than whether the oils had been adulterated. However, artificial neural networks could be trained (using the back-propagation algorithm) successfully to distinguish virgin oils from those which had been adulterated.     

Primary measures for reduction of PCDD/F in Co-combustion of lignite coal and waste: effect of various inhibitors

Co-combustion of coal and waste in power plants poses both environmental and economic challenges, especially because of the high polychlorinated dibenzo-p-dioxin and furan (PCDD/F) emissions from solid waste. In this study, we performed a series of experiments focusing on the prevention of PCDD/F formation by the use of various inhibitors added to the fuel before combustion. A mixture of lignite coal, solid waste, and poly(vinyl chloride) (PVC) was thermally treated in a laboratory-scale furnace at 400 degrees C. Twenty different additives were investigated at a level of 10 wt% of the total fuel during the experiments. We have divided them into four general groups according to their chemical nature: metal oxides, N-containing compounds, S-containing compounds, and N- and S-containing compounds. The resulting values showed a significant reduction of PCDD/F levels when N- and S-containing compounds were used as additives to the fuel. Principle component analysis (PCA) was used to illustrate the effect of the 20 different inhibitors on the congener patterns emitted. As a result, the most effective inhibitors for PCDD/F formation in flue gases were determined to be (NH4)2SO4 and (NH4)2S2O3; they are inexpensive and nontoxic materials. Both compounds can suppress the formation of toxic compounds such as PCDD/Fs by more than 98-99%, and the most toxic PCDD/F congeners were not detectable in most of the samples. Thus, these compounds were also studied as a lower percentage of the fuel. (NH4)2SO4 resulted in a greater than 90% reduction of PCDD/F even when composing only 3% of the fuel combusted. However, less than 5% (NH4)2S2O3 resulted in far weaker inhibition. The PCDD/F homologue distribution ratio for samples with varying percentages of (NH4)2SO4 and (NH4)2S2O3 was also investigated. Higher percentages of the inhibitors produced a lower percentage of lower chlorinated PCDDs. The opposite effect was found for PCDFs.     

Novel incineration technology integrated with drying, pyrolysis, gasification, and combustion of MSW and ashes vitrification

The conventional mass burn systems for municipal solid waste (MSW) emit large amount of acidic gases and dioxins as well as heavy metals due to the large excess air ratio. Additionally, the final process residues, bottom ash with potential leachability of heavy metals and fly ash with high level of heavy metals and dioxins, also constitute a major environmental problem. To deal with these issues more effectively, a novel MSW incineration technology was developed in this study. MSW drying, pyrolysis, gasification, incineration, and ash vitrification were achieved as a spectrum of combustion by the same equipment (primary chamber) in one step. In practice, the primary chamber of this technology actually acted as both gasifier for organic matter and vitrifying reactor for ashes, and the combustion process was mainly completed in the secondary chamber. Experiments were carried outto examine its characteristics in an industrial MSW incineration plant, located in Taiyuan, with a capability of 100 tons per day (TPD). Results showed that (1) the pyrolysis, gasification, and vitrification processes in the primary chamber presented good behaviors resulting in effluent gases with high contents of combustibles (e.g., CO and CH4) and bottom ash with a low loss-on-ignition (L.o.l), low leachability of heavy metals, and low toxicity of cyanide and fluoride. The vitrified bottom ash was benign to its environment and required no further processing for its potential applications. (2) Low stack emissions of dioxins (0.076 ng of TEQ m(-3)), heavy metals (ranging from 0.013 to 0.033 mg m(-3)), and other air pollutants were achieved. This new technology could effectively dispose Chinese MSW with a low calorific value and high water content; additionally, it also had a low capital and operating costs compared with the imported systems.