A case study on the life cycle assessment of recycling industrial mercury-containing waste

Accepted Manuscript A case study on the life cycle assessment of recycling industrial mercury-containing waste Congcong Qi, Xiaotian Ma, Meng Wang, Liping Ye, Yang Yang, Jinglan Hong PII:

S0959-6526(17)30948-4

DOI:

10.1016/j.jclepro.2017.05.023

Reference:

JCLP 9558

To appear in:

Journal of Cleaner Production

Received Date: 24 January 2017 Revised Date:

5 May 2017

Accepted Date: 6 May 2017

Please cite this article as: Qi C, Ma X, Wang M, Ye L, Yang Y, Hong J, A case study on the life cycle assessment of recycling industrial mercury-containing waste, Journal of Cleaner Production (2017), doi: 10.1016/j.jclepro.2017.05.023. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT A case study on the life cycle assessment of recycling industrial mercury-containing waste Congcong Qia, Xiaotian Maa, Meng Wangb, Liping Yea, Yang Yangb, Jinglan Honga,* Shandong Provincial Key Laboratory of Water Pollution Control and Resource

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a

Reuse, School of Environmental Science and Engineering, Shandong University, Jinan 250100, PR China. Medical school, Shandong University, Jinan 250012, China.

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b

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Corresponding author: Jinglan Hong Tel/Fax：+86-(0531)88362328 E-mail address: [email protected] ABSTRACT

The life cycle of the environmental impact of recycling mercury

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(Hg)-containing waste was quantified via ReCiPe H method. Uncertainty analysis was conducted to determine the credibility of the study. Recycling 1×104 tonnes Hg-containing waste with end-of-life disposal generated 0.63 CTUh, 62.33 CTUh,

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3.47×107 kg CO2 eq, and 5.44×106 kg oil eq environmental burdens of carcinogens,

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non-carcinogens, climate change, and fossil depletion categories, respectively. Results showed that the carcinogens and non-carcinogens categories that were contributed by direct atmospheric Hg emission substantially affected the overall environmental burden. Similar findings were proved by sensitivity analysis. The utilization of industrial hazardous waste (IHW) that was generated from Hg recycling process is more environmentally beneficial to the carcinogens category than landfill disposal. Effective approaches to decrease the overall environmental 1

ACCEPTED MANUSCRIPT burden of recycling Hg-containing waste include recycling Hg with end-of-life disposal, improving technology for atmospheric Hg emission, and further utilizing the IHWs that are generated from recycling Hg process. In addition, increasing the

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government supervision of relevant enterprises to avoid the illegal disposal of Hg-containing waste is crucial to protect human health and ecosystems from Hg damage.

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Keywords: Life cycle assessment; Hg-containing waste; recycling; end-life disposal;

1. Introduction 1.1 Mercury pollution

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environmental impact.

Mercury (Hg) is a silvery white metal under normal temperature and pressure.

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Hg is mainly used in electrical appliances, medical equipment, and metallurgical and chemical industries. The production of polyvinyl chloride (PVC) accounts for 60% of the total Hg consumption in China (Zhang, 2013). However, Hg poses a

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serious threat to human health and the ecosystem because of its toxicity, persistence,

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and bioaccumulation in different forms. Methylmercury, in particular, is highly toxic (Holmes et al., 2009). Methylmercury converted by inorganic Hg in an aquatic system (Hsu et al., 2013) can enter the human body via the ingestion of contaminated food which can lead to nervous system damage, severe neurological and cardiovascular diseases, and fetal damage during gestation (Ceccatelli et al., 2013; Karagas et al., 2012). In 2010, the global anthropogenic Hg emissions to air were estimated to be 1960 tonnes, accounting for approximately 30% of the total 2

ACCEPTED MANUSCRIPT atmospheric Hg emission amount (UNEP, 2013a). This mainly resulted from artisanal small-scale gold mining and coal burning (UNEP, 2013a). Moreover, China has become the world’s largest contributor of anthropogenic Hg emissions to

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air at 750 tonnes in 2012 (Zhao et al., 2015). Zhang et al. (2015) reported that the predominant source of anthropogenic Hg emissions in China is industrial coal

combustion, followed by thermal power plants, nonferrous metal smelting (e.g.,

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zinc, lead, and copper), and cement production. In addition to the considerable

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amounts of atmospheric Hg emissions, large quantities of solid Hg waste are also generated by industrial processes (Horowitz, 2014). The PVC production via the calcium carbide process consumes substantial Hg and generates large amounts of Hg-containing waste. The PVC industry annually produces an average of 15,000

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tonnes waste Hg catalysts that contain 600–800 tonnes Hg with high recycling value (Wang et al., 2016). In addition, lead–zinc smelting annually generates approximately 17,000 tonnes of roasting dust (Hg, 0.1%–0.2%) as the main

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Hg-containing waste (Liu et al., 2007).

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1.2 Hg-containing waste management The National Catalogue of Hazardous Wastes in China has categorized

Hg-containing wastes, including Hg-added products (e.g., thermometers, fluorescent lamp and sphygmomanometer) and those from industrial sources (e.g., waste catalyst, chemical sludge and metallurgical slag), as hazardous wastes (Ministry of Environmental Protection, 2016). In 2014, approximately 3.63×107 tonnes industrial hazardous wastes (IHWs) were generated in China, whereas 1.14 × 107 tonnes of 3

ACCEPTED MANUSCRIPT IHWs were generated in 2004 (China Statistical Yearbook, 2005-2015). This increase indicated an annual growth rate of 12.3% for IHW. Although 56.0%, 18.76%, and 25.24% IHW utilization, storage, and disposal (i.e., incineration and

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landfill), respectively, have been reported by the government (China Statistical Yearbook, 2015), incidents of improper IHW dumping frequently occur because of the remote distance of legal IHW disposal plants and expensive disposal costs.

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Additionally, recycling Hg-containing waste produces Hg emissions and large

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quantities of hazardous waste (Lin et al., 2016), thus posing high risks of severe ecosystem damage. Furthermore, as China’s large-scale Hg mines have been discontinued because of the Minamata Convention on Mercury (UNEP, 2013b), refined Hg is mainly produced from recycled Hg-containing waste (Zeng et al.,

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2012). Accordingly, a systemic method should be utilized to build the emission inventory and determine the main factors that ameliorate the environmental impact of recycling Hg-containing waste.

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1.3 LCA analysis of Hg-containing waste disposal

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Life cycle assessment (LCA) is a systematic and widely used methodology to evaluate the environmental performance of a product, process, or activity over its entire life cycle by calculating materials used and the emissions generated (ISO 14040, 2006). Currently, the waste disposal method of utilizing recycled Hg products, such as fluorescent lamp and thermometer, has been extensively studied through LCA (Apisitpuvakul et al., 2008; Gavilán et al., 2015; Principi and Fioretti, 2014; Tan et al., 2012). Few LCA studies have evaluated the environmental burdens 4

ACCEPTED MANUSCRIPT that are generated from industrial Hg-containing waste except for that by Busto et al. (2015), which estimated the environmental impact of wastes that are generated from chlor-alkali plant. Although the aforementioned study has scientific contributions,

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no uncertainty analyses were conducted and its data sources were unclear. Based on our knowledge, few studies have utilized LCA to assess the environmental burden

from industrial Hg-containing waste in China. To address this issue and provide

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recycling was conducted in the present study.

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scientific information for policy makers, the LCA analysis of Hg-containing waste

2. Scope definition

The study was performed to evaluate the environmental impact of Hg-containing waste from industrial sources. It focused on the following objectives:

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(a) building the emission inventory to understand pollution release condition of industrial Hg waste recycling process; (b) identifying the critical environmental impact categories contributing significantly to the overall environment burden; (c)

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determining the key factors (i.e., process and substance) for reducing the potential

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environmental burden; (d) quantifying and comparing the with and without end-of-life disposal of Hg-containing waste recycling; and (e) conducting an uncertainty analysis to ensure the reliability of evaluation. 2.1 Functional unit

A functional unit can provide a quantified reference for all relevant products, process, and activity system. In the present study, the disposal of 1×104 tonnes of Hg-containing waste that contained 110.28 tonnes of Hg was selected as the 5

ACCEPTED MANUSCRIPT functional unit. The Hg-containing waste included waste catalyst (2143 tonnes; HgCl, 2.1%), chemical sludge (2143 tonnes; Hg, 1.6%), flue dust (1428 tonnes; Hg, 1.2%), and metallurgical slag (4286 tonnes; Hg, 0.597%). Direct air emissions (e.g.,

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particulates, mercury, sulfur dioxide, chlorine, hydrogen chloride, arsenic, antimony and lead), direct water emissions (e.g., mercury, cadmium, lead, chromium, arsenic,

chemical oxygen demand, ammonia), raw material and energy consumption, solid

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waste disposal in landfills, and road transportation were all based on this functional

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unit. 2.2 System boundary

System boundary is set with a gate to gate approach. This study considered two scenarios that are frequently applied in China: Hg-containing waste recycling with

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end-of-life disposal (Hg–D) and Hg-containing waste recycling without end-of-life disposal (Hg–ND). Figure 1 shows the system boundary of the Hg–D scenario, which involves raw material and energy production, Hg recovery and hazardous

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waste utilization, end-of-life treatment (i.e., wastewater and air pollution treatment,

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solid waste landfill), and direct pollutant emission. In this study, distillation technology was used for Hg recovery, including the pretreatment, distillation, condensation,

cleaning,

and

activated

carbon

absorption

of

tail

gas.

Hydrometallurgical technology was used to extract metals from IHWs that were generated from Hg recovery. The waste gas of IHW utilization was disposed via alkali spray, filter, and desulfurizer processes. The Hg–ND scenario is similar to the Hg–D scenario in most parts except for the end-of-life waste disposal process. 6

ACCEPTED MANUSCRIPT Municipal solid wastes (MSWs) and IHWs were assumed to be dumped directly. Wastewater and waste gas were released to the environment without any treatment. Table 1 presents the life cycle inventory of both scenarios.

Table 1 2.3 Methodology and data sources

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Fig.1

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Life cycle impact assessment (LCIA) results were quantified using the Simapro

8.2 software via ReCiPe H method (Goedkoop et al., 2009). Fifteen midpoint

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categories (Table 2) were assessed. Additionally, the characterization factors of human health and ecotoxicity categories, which were both based on China’s exposure situation, were applied (Li et al., 2016; Zhang et al., 2016) (see Supplementary notes S1). The life cycle inventory for Hg-containing waste

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recycling was built based on a Hg-containing waste disposal site in Guizhou, China. The treatment capacity for Hg-containing waste in the enterprise is approximately

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5.6×104 tonnes. However, this method simultaneously generated approximately 4.4×103 tonnes of roasting dusts and 3.96×104 tonnes of roasting slag that contained

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multiple noble metals (e.g., gold, silver, and copper) from Hg recovery. Therefore, the company established an IHW utilization production line to recover heavy metals and reduce resource waste instead of creating landfills (Fig.1). For the Hg–ND, the company’s monitoring data that are relevant to direct air, water, and soil emissions from the Hg–D scenario before pollutant treatment were used to estimate air, water, and soil emissions. The background data (e.g., sodium hydroxide production, coke production, coal-based electricity generation, MSW management, wastewater 7

ACCEPTED MANUSCRIPT treatment, hydrochloric acid production, and IHW management) were adopted from the Chinese process-based life cycle inventory database (CPLCID) (see Supplementary notes S2). Moreover, data on inorganic chemicals and buildings

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were taken from a European database (Ecoinvent centre, 2015) to compensate for the missing data in China. To reduce the regional effect generated from the European data, China’s background data (e.g., transportation, solid waste

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management, wastewater treatment, and energy consumption) in CPLCID were

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used to update the European data. 2.4 Mass balance

To further determine the dependability of the life cycle inventory, the mass balance of Hg and lead (Pb) was studied. The original mass of the treated

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Hg-containing waste was 1.0×104 tonnes, including Hg and Pb masses of 110.28 tonnes and 546.54 tonnes, respectively. In addition, Cu–Pb–Zn anode slime which contained 10.3 tonnes of Pb, was added to the IHW utilization process. Accordingly,

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the total inputs of Hg and Pb were 110.28 tonnes and 556.84 tonnes, respectively.

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The mass products of Hg and Pb were 100.18 tonnes and 546.54 tonnes. In the Hg–D scenario, the total output of Hg and Pb were 102.18 tonnes and 546.55 tonnes, respectively. This result indicated that 8.97% Hg and 1.85% Pb were lost. Similarly, in the Hg–ND scenario, the total output of Hg and Pb were 108.36 tonnes and 547.45 tonnes, respectively. Accordingly, 1.74% Hg and 1.69% Pb were lost in the Hg–ND scenario. The mass loss may be attributed to measurement error, transportation loss, and missing inventory data. 8

ACCEPTED MANUSCRIPT Fig.2 3. Results 3.1 LCIA results and uncertainty analysis

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The LCIA midpoint assessment results are presented in Table 2. The Hg–ND scenario exhibited a significantly high potential impact on carcinogens, non-carcinogens, freshwater ecotoxicity, and particulate matter formation compared

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with the Hg–D scenario. To estimate the degree of confidence on whether the

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environmental burden of the Hg–ND scenario was higher than that of the Hg–D scenario, uncertainty analysis was conducted using the Monte Carlo method. The squared geometric standard deviation (GSD2) and probability results are shown in Table 2. For the carcinogens category, the GSD2 for Hg–D and Hg–ND were 1.41

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and 1.37, respectively. These values indicated that the potential impacts were 0.45–0.89 and 16.56–31.09 CTUh for Hg–D and Hg–ND, respectively. The probability that the Hg–D scenario exhibited a high impact on carcinogens was 0%,

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implying that the carcinogens score of the Hg–D scenario is significantly lower than

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that of the Hg–ND scenario. This analogy was equally applicable to other categories, including non-carcinogens, freshwater ecotoxicity, and particulate matter formation. Therefore, the scores obtained from the Hg–D scenario were lower than those from the Hg–ND scenario. By contrast, the climate change, ozone depletion, freshwater eutrophication, marine eutrophication, photochemical oxidant formation, agriculture land occupation, urban land occupation, water depletion, and fossil depletion scores obtained from the Hg–D scenario were considerably higher than those acquired 9

ACCEPTED MANUSCRIPT from the Hg–ND scenario. This finding was mainly caused by the additional energy and raw material input for waste disposal. In addition, the results of the metal depletion category acquired for both scenarios were identical with a probability

Table 2 3.2 Normalized LCIA results

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score of 66.2%.

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Figure 3 shows the normalized LCIA results. For both scenarios, the impacts of

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carcinogens and non-carcinogens played a dominant role to the overall environmental burden. In addition, for Hg–D scenario, the impact caused by climate change and fossil depletion categories had an indistinctive contribution to overall environmental impacts, whereas for Hg–ND scenario these contributors were

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freshwater ecotoxicity and particulate matter formation. For both scenarios, the burden attributed by the remaining categories played a comparatively small role. Notably, the median value attributed by Hg–ND scenario was significantly higher

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than that of Hg–D scenario in the key categories (i.e., carcinogens and

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non-carcinogens) because of the absence of pollution control system. Fig. 3

3.3 Main contributors The significant processes contributing most to the overall environmental

burden are illustrated in Figure 4. For both scenarios, direct emissions were the dominant contributor to carcinogens and non-carcinogens categories. Figure 5 indicates that the atmospheric Hg emissions were the dominant source contributing 10

ACCEPTED MANUSCRIPT significantly to the key categories. In addition, IHW landfill substantially contributed to most categories except for ozone depletion and metal depletion, which was mainly attributed to chemical consumption for the Hg–D scenario. For

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the Hg–ND scenario, direct emissions were the most significant contributor to freshwater ecotoxicity, terrestrial acidification, and particulate matter formation in

addition to the key categories. Chemical and coal-based electricity consumption had

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Fig.4

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an important contribution to the remaining categories.

Fig.5

3.4 Sensitivity analysis

Table 3 presents the sensitivity results of the main contributors to ascertain the

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variability of LCIA results. For the carcinogens category, decreasing direct emission by 5% would produce 4.07% and 4.98% environmental benefits in the Hg–D and Hg–ND scenarios, respectively. For the remaining processes, a parallel analogy can

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be concluded by considering the sensitivity results shown in Table 3. Decreased

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direct emission exhibited the largest environmental benefit in both scenarios, with a significant variability in the dominant categories. In addition, electricity consumption efficiency showed the lowest variability in both scenarios. Table 3

4. Discussion Lin et al. (2016) reported that the recycling process of Hg-containing waste is a significant contributor of Hg release to air. In this study, the Hg emissions of Hg–D 11

ACCEPTED MANUSCRIPT and Hg–ND scenarios were 0.18 tonnes and 8.00 tonnes, respectively (Table 1), illustrating that the Hg removal rate was 97.75%. According to Zhao et al. (2013), the removal effect in this study is better than that of other processes but still has a

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certain gap compared with more advanced technology (99.8%). Figure 5 shows that atmosphere Hg was the dominant substance contributing significantly to the carcinogens and non-carcinogens categories for both scenarios. For the Hg–D

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scenario, direct emissions accounted for 81.29% and 97.77% of the carcinogens and

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non-carcinogens categories, respectively. Therefore, controlling the Hg emissions to air was an efficient method to reduce the overall environmental burden of Hg-recycling process. Several researchers have developed new technologies, such as carbonization charging with oxygen and injecting inert gas, to prevent Hg vapor

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from escaping and almost entirely eliminating direct Hg air emissions (Maslennikova et al., 2014; Xie and Wang, 2016). Therefore, updating the tail gas treatment technology is highly necessary.

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In addition to atmospheric pollution, the Hg recovery process also generated

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large quantities of IHWs, which are treated in landfills by companies that are qualified for IHW disposal (Fig. 1). Hong et al. (2016) reported that IHW disposal to landfill presents the highest environmental burden on carcinogens categories. To dispose of the IHWs that are generated from Hg recycling, the Hg recycling site in this study utilized IHWs to extract rare metals (e.g., silver, copper, lead, gold) and produce inorganic chemicals (e.g., zinc sulfate, copper sulfate, sodium sulfate). Figure 6 compares the LCIA midpoint results of IHW utilization and landfill. IHW 12

ACCEPTED MANUSCRIPT utilization exhibited the highest environmental benefits in carcinogens, ozone depletion, and urban land occupation categories because it replaced the environmental impact of synthetic inorganic chemical products. Additionally, the

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impacts contributed by IHW utilization were lower than those of the IHW landfill scenario in most categories except for non-carcinogens, climate change, marine eutrophication, agriculture land occupation, metal depletion, and fossil depletion.

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This result is attributed to the additional input of energy, chemicals, and metals

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during recycling. Notably, IHW utilization also produces many abundant metals, such as Pb and Ag. However, the study did not replace the environmental impact generated from metal production because of the lack of relevant data. If the entire metal products are considered in this study, then the overall environmental impact

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caused by IHW utilization will be further reduced. Fig. 6

Currently, companies that are qualified for Hg-containing waste recycling are

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located in remote areas (e.g., Guizhou, Xinjiang), leading to some companies

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paying large amounts for the transportation and disposal cost of Hg-containing waste. This condition results in illegal dumping or recycling by companies without proper business licenses. Companies that illegally recycle Hg-containing waste are small scale, use simple techniques, and generally recover Hg without pollution control (Wang et al., 2016). Although Hg–ND has relatively lower LCIA scores than Hg–D in most categories (Table 2), Hg–ND has higher environmental impact on the key categories (i.e., carcinogens and non-carcinogens, Fig.3), thus 13

ACCEPTED MANUSCRIPT significantly contributing to overall environmental burden. When a pollution control system was implemented, the impacts of Hg-containing waste recycling on carcinogens and non-carcinogens decreased by 97% and 98%, respectively.

discharge during recycling is highly important.

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Accordingly, increasing government supervision to prevent direct pollution

In 2013, China signed the Minamata Convention on Mercury, a treaty aimed to

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protect human health and the environment from Hg pollution. According to the

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provisions of the convention, primary Hg mining is prohibited. Moreover, Hg-containing waste must only be recycled, recovered, reclaimed, reused, or disposed of properly in the environment (UNEP, 2013b). Therefore, the recovery of Hg from Hg-containing waste has become important in China. However, many

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problems still exist during recovery, including: (1) the large amounts and complicated types (e.g. waste catalyst, smelting wastes, chemical reagent, and SFL) of Hg-containing waste; (2) the low rate of Hg recycling. For example, the rate of

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overall cyclic Hg use is approximately 50% in the calcium carbide process in the

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PVC industry (Wang et al., 2016); (3) the serious environment pollution generated by the recycling sector. This situation, however, has not attracted enough attention in China (Lin et al., 2016); and (4) compared with that in other developed countries, Hg management in China remains in its infancy despite established Hg management systems and issued technology guidelines(Ministry of environmental protection of China, 2011 and 2014). To address these problems, the following suggestions are recommended: classification and collection of different types of Hg waste to use the 14

ACCEPTED MANUSCRIPT most appropriate technology for recycling; the establishment of a dynamic information management platform to understand Hg flow and monitor the disposal and movement of Hg waste to avoid illegal handling; and the improvement of the

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recovery technology and the enhancement of the pollution control system. These methods are fundamental to decreasing environmental pollution during recycling.

Improving the existing law, executive standards, and environmental economic

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policies, such as environmental tax and financial subsidies, is important. Promoting

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the recycling of Hg-containing waste is also necessary. 5. Conclusion

This study evaluated the environmental impact of Hg-containing waste recycling with and without end-of-life disposal. The life cycle inventory and key

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factors that primarily affect environmental burden were identified. The main findings indicated that the Hg–ND scenario had a significantly higher impact on key categories (i.e., carcinogens and non-carcinogens) than the Hg–D scenario. This

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disadvantage could be attributed to direct Hg emission without a pollution control

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mechanism. Compared with Hg–ND, approximately 98% of environmental benefits were generated on key categories in Hg–D due to waste treatment, especially atmospheric Hg control. Consequently, recycling Hg-containing waste with end-of-life disposal and improving waste control technology can efficiently decrease environmental impact. This scientific information will be helpful for decision makers and relevant enterprises for recycling Hg-containing waste. However, this research has several limitations. First, the recovery technology, 15

ACCEPTED MANUSCRIPT materials, and pollution control system were based on a case study. Thus, this study cannot completely reflect national level of the recycling industry for Hg-containing waste. Second, given that Hg waste can severely damage ecosystems and human

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health, scientific and systematic assessment methods, including the environmental, economic, and social LCA of Hg-containing waste disposal, must be performed.

Finally, the national pollution emission inventory of this industry must be studied in

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the future.

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Acknowledgments

We gratefully acknowledge financial support from National Natural Science Foundation of China (Grant no. 71671105), China Energy Conservation and Emission Reduction Co. Ltd (GJN-14-07), and The Fundamental Research Funds of

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Zhao, Y., Zhang, H., Zhang, J., Nielsen, C.P., 2015. Evaluating the effects of China’s

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pollution controls on inter–annual trends and uncertainties of atmospheric

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mercury emissions. Atmos. Chem. Phys. 15, 4317–4337.

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ACCEPTED MANUSCRIPT Table 1 Life cycle inventory of Hg-containing waste recycling process. Values are presented per functional unit. Table 2 LCIA midpoint results and uncertainty analysis.

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Table 3 Sensitivity analysis of main contributors. Values are presented per functional

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unit.

ACCEPTED MANUSCRIPT Table 1 Life cycle inventory of Hg-containing waste recycling process. Values are presented per functional unit. Unit

t t t t t t kWh t t t t t t t t

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963.89

963.89

1.23×103 2.32 62.25 2.85×103 18.41 2.57×104 3.21×106 107.14 96.10 35.71 10.77 1.10×103 2.65×103 12.00 9.72×103

1.23×103 2.32 62.25 2.85×103 18.41 2.57×104 3.21×106 107.14 96.10 35.71 10.77 1.10×103 2.65×103 12.00 9.72×103

Particulates Mercury Sulfur dioxide Nitrogen dioxide Sulfuric acid Mercury chloride Chlorine Hydrogen chloride Arsenic Antimony Lead

t t t t t kg kg kg kg kg kg

3.69 0.18 1.36 0.13 0.015 24.20 9.09 2.27 4.09 8.18 8.18

295 8.00 30 0.15 1.62 251.3 199.6 241.2 450 900 900

Mercury Cadimium Lead Chromium VI Arsenic Chemical oxygen demand Ammonia

kg kg kg kg kg kg kg

-

2.83 0.03 0.07 5.72×10−3 7.07×10−4 71.30 1.41

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Direct air emission

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Coal Activated carbon Lime Chemicals inorganic Chemicals organic Tap water Electricity Cu–Pb–Zn Anode slime Zinc Oxygen Iron Coke Wastewater Solid waste Hazardous waste

m2

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Land occupation

Hg-ND Amount

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Raw materials and resources

Hg-D Amount

Direct emissions from wastewater

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-

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kg kg kg kg kg kg kg kg kg kg kg

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Arsenic Barium Beryllium Cadimium Chromium Copper Fluoride Lead Mercury Nickel Zinc

0.46 2.70 0.11 0.48 4.81 1.92 22.60 9.61 0.04 3.84 1.07

ACCEPTED MANUSCRIPT Table 2 LCIA midpoint results and uncertainty analysis. Unit

Hg-D

Carcinogens Non-carcinogens Freshwater ecotoxicity

CTUh CTUh CTUe

Amount GSD2 0.63 1.41 62.33 1.49 7 2.61×10 1.44

Climate change Ozone depletion Terrestrial acidification Freshwater eutrophication Marine eutrophication Photochemical oxidant formation Particulate matter formation

kg CO2 eq kg CFC-11 eq kg SO2 eq kg P eq kg N eq

3.47×107 0.14 7.50×104 132.09 5.15×103

kg NMVOC

8.63×104

m

2a

Urban land occupation

m

2a

Water depletion

m3

Agricultural land occupation

Metal depletion Fossil depletion

kg Fe eq kg oil eq

1.17×107 0.11 5.74×104 39.72 2.07×103

1.36 1.74 1.17 2.05 1.39

100 100 5 100 100

2.89×104

1.35

100

1.33

1.03×105

1.27

0

2.72

5.90×10

4

2.63

100

4

1.54

99.5

1.38 1.86 1.36 2.09 1.37 1.41

4.71×10 9.99×10

4

1.67

5.25×10

2.75×105

1.77

1.05×105

1.27

100

1.36 1.27

5

1.39 1.21

66.2 99.9

5

9.91×10 5.44×106

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% 0 0 0

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GSD2 means the squared geometric standard deviation

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GSD2 1.37 1.37 1.37

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3.03×104

Amount 22.69 2.68×103 4.11×108

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kg PM10 eq

Probability of Hg-D >=Hg-ND

Hg-ND

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Category

9.22×10 3.13×106

ACCEPTED MANUSCRIPT Table 3 Sensitivity analysis of main contributors. Values are presented per functional unit.

Variation (%) Carcinogens (%) Nom-carcinogens (%)

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Hg-D Hg-ND Hg-D Hg-ND

Direct Hazardous Chemicals emissions waste landfill 5 5 5 4.07 0.47 0.35 4.98 0.01 4.89 0.01 0.07 -4 5.00 1.87×10 -

Electricity 5 0.02 6.06×10-4 0.01 3.01×10-4

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Category

ACCEPTED MANUSCRIPT Figure captions Fig.1. System boundary and mass flow of Hg-D scenario. Fig. 2. Mass balance of Hg and Pb.

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Fig.3. Normalized LCIA mid-point results. Fig.4. Contributions of dominant processes to the mid-point results: a) Hg-D; b) Hg-ND.

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Fig.5. Contributions of significant substances to key categories: a) carcinogen; b)

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non-carcinogen.

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Fig.6. Net LCIA of IHW utilization and landfill at midpoint.

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Transport

Distillation Condensation Cleaning

Wastewater treatment 2.1×103 t Recycle MSW sanitary landfill 5.4t

Hazardous waste 7.9×103 t

Bag filter Two alkali spray system

Desulfurizer Wet filter reduction

Hazardous waste landfill 9.7×103 t

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Hydrometallurgical technology used

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Pretreatment

Activated carbon absorption

Coal 1234 t Land occupation 786 m2a Activated carbon 2.14 t Lime 62.14t Chemicals inorganic 7.5 t Sulfuric acid 1.1 t Tap water 7.0×103 t Transportation 8.1×105 t/km Electricity 2.3×106 kWh Cu-Pb-Zn Anode slime 107 t Occupation 178m2 Sulfuric acid 1648 t Oxygen 36 t Chemicals inorganic 381 t Chemicals organic 18 t Sodium hydroxide 42 t Hydrochloric acid 114t Zinc 96 t Sodium carbonate 318 t Chlorine 2.2 t Transportation 7.1×105 t/km Nitric acid 335t Iron 10.8 t Tap water1.8×104 t Electricity 8.9 ×105 kWh Coke 1102 t

MSW sanitary landfill 6.6 t

Wastewater treatment 578 t Recycle

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Raw materials and energy production

Mercury-containing waste 1.0×104 t

Dry filter reduction

Hg (100 t; 99.99%), Zinc sulfate(1842 t ), Copper sulfate(1631 t), Sodium sulfate (795 t), Pb-Bi-Alloy (580 t), Chemicals inorganic (111t), Se(119 t), General metal(20 t) for sale

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Fig.1. System boundary and mass flow of Hg-D scenario.

PM, Hg SO2 …

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Cu-Pb-Zn Anode slime 107.14 t (Pb:10.3t)

Hg:100.18 t

Industrial hazardous waste utilization

Pb-Bi-Alloy 580.36 t (Pb 546.54 t)

Hg-ND

Direct emissions to air: Hg 8.18 t; Pb 0.90t Direct emissions to water: Hg 2.83×10−3 t; Pb 7.00×10 − 5 t Solid waste open dumping: Hg 4.0×10 − 5 t; Pb 9.61×10 − 3 t

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(Hg: 110.28 t) (Pb :546.54t)

Hg-D

Mercury recycling process

Direct emissions to air: Hg (0.20 t); Pb (8.18 ×10−3 t)

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Hg-containing waste 1.0×10 4 t

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Fig.2. Mass balance of Hg and Pb.

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Fig.3. Normalized LCIA mid-point results.

ACCEPTED MANUSCRIPT 140%

1

120%

Direct emissions

IHW landfill

Chemicals

Primary zinc production

Coke production

Electricity

Transport

Others

a)

100% 80%

40% 20% 0% 140%

1

120%

Direct emissions Transport Coke production

Electricity Primary zinc production Others

Chemicals Tap water

b)

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100%

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60%

80% 60%

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40% 20%

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0%

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Hg-ND.

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Fig.4. Contributions of dominant processes to the mid-point results: a) Hg-D; b)

ACCEPTED MANUSCRIPT 100%

a)

80% Others 60% Mercury, air

0% 100%

b)

80% Others 60% Mercury, air

20% 0% Hg-D

Hg-ND

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20%

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40%

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non-carcinogens.

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Fig.5. Contributions of significant substances to key categories: a) carcinogens; b)

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IHW utilization

100

IHW landfill

60

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%

20 -20 -60

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Fig.6. Net LCIA of IHW utilization and landfill at midpoint.

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Life cycle assessment of mercury-containing waste recycling is quantified.




Direct mercury emission highly contributes to the overall environmental burden.




End-of-life disposal is an important process of recycling mercury-containing

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waste.


Enhancement of control technology for atmospheric mercury emission is crucial.




Prohibiting illegal recycling company of mercury-containing waste is highly

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needed.