life cycle environmental impact assessment of borax and boric acid production in china

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Life cycle environmental impact assessment of borax and boric acid production in China Jing An a, b, c, d, * , Xiangxin Xue a, b, c, d a College of Material and Metallurgy, Northeastern University, Shenyang 110819, Liaoning, China b Liaoning Province Higher Education Institution Key Laboratory of Boron Resources Ecological utilization technology and Boron Material, Shenyang 110819, Liaoning, China c Liaoning Province Key Laboratory of Metallurgical Resources Recycling Science, Shenyang 110819, Liaoning, China d Liaoning Province Engineering Technology Research Center of Boron Resources Comprehensive Utilization, Shenyang 110819, Liaoning, China article info Article history: Received 3 February 2013 Received in revised form 11 October 2013 Accepted 14 October 2013 Available online xxx Keywords: Life cycle assessment Borax Boric acid Cradle-to-gate abstract Borax and boric acid are important primary products in Chinas boron industry. Their characteristic production technology has been adapted to the low ore grade. To analyze the environmental impacts of different borax and boric acid production processes and to promote cleaner production of boron industry, the life cycle assessment method of cradle-to-gate was applied in this study. GaBi4.4 software was used in the assessment and the environmental impacts were classied according to the CML2001 method. To show the degree of consumption of mineral resources and energy respectively, the abiotic depletion potential was divided into the mineral resources depletion potential and fossil energy depletion po- tential. A comparison between the mineral processing and entire system studied shows that energy consumption is important in life cycle environmental impacts. Boron production industries should refrain from using coal as their main heat source and try to use clean energy. A comparison between the borax production processes shows that the boron-rich slag is the cleanest material and that blast furnace gas can be used to reduce environmental impacts further in slow cooling link. A comparison between the boric acid production processes shows that otation (I) is the cleanest process with the material of szaibelyite. Ludwigite should be processed after dressing to reduce the environmental impacts. Boron concentrate can be used to produce borax or boric acid as an alternative to szaibelyite but feasible production processes are still the focus of future research. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction China is rich in boron resources with boron reserves ranking fourth next to Turkey, the USA, and Russia (Liu et al., 2006). Compared with that of the other three countries, the grade of Chinas boron ore is low and the ore is difcult to process. For example, the main boron-containing minerals in Turkey are cole- manite, ulexite, and tincal, with a grade of at least 40% (Kuslu et al., 2010; Kunkul et al., 2012). In China, the main boron-containing minerals are szaibelyite, ludwigite, and brine. Szaibelyite in Liaoning Province is the traditional material used in the boron in- dustry and has a grade of only 12%. The remaining reserves of szaibelyite are limited as it has been used as the major mineral source in Chinas boron industry for many years. Ludwigite reserves are relatively rich and account for 58.4% of the total Chinese boron reserves, but the content of B 2 O 3 is in the range of only 6e9%. The mineral structure of ludwigite is complex because boron, iron, and magnesium are intergrown (Zheng, 2007). Therefore, there has been no large-scale exploitation of this mineral. The boron industry was established in China in the 1950s. Over the past 60 years, China has developed a fairly sophisticated boron industrial system including mining, dressing, processing, rening, and other related businesses. Approximately 50 boron-containing products can be manufactured, but the output of most ne chem- icals is still relatively small (Liu et al., 2006). Borax and boric acid are important primary products produced in large output and with high output value. Therefore, the production of borax and boric acid plays an important role in Chinas boron industry. An environmental impact assessment was conducted because borax and boric acid are important primary products in the boron industry and their production processes contribute signicantly to environmental impacts. Limited work has been conducted on the life cycle environment impact assessment of boron-containing * Corresponding author. College of Material and Metallurgy, Northeastern Uni- versity, Shenyang 110819, Liaoning, China. Tel.: þ86 24 83683176; fax: þ86 24 83687719. E-mail address: [email protected] (J. An). Contents lists available at ScienceDirect Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro 0959-6526/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jclepro.2013.10.020 Journal of Cleaner Production xxx (2013) 1e7 Please cite this article in press as: An, J., Xue, X. X., Life cycle environmental impact assessment of borax and boric acid production in China, Journal of Cleaner Production (2013), http://dx.doi.org/10.1016/j.jclepro.2013.10.020

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Page 1: Life cycle environmental impact assessment of borax and boric acid production in China

lable at ScienceDirect

Journal of Cleaner Production xxx (2013) 1e7

Contents lists avai

Journal of Cleaner Production

journal homepage: www.elsevier .com/locate/ jc lepro

Life cycle environmental impact assessment of borax and boric acidproduction in China

Jing An a,b,c,d,*, Xiangxin Xue a,b,c,d

aCollege of Material and Metallurgy, Northeastern University, Shenyang 110819, Liaoning, Chinab Liaoning Province Higher Education Institution Key Laboratory of Boron Resources Ecological utilization technology and Boron Material, Shenyang 110819,Liaoning, Chinac Liaoning Province Key Laboratory of Metallurgical Resources Recycling Science, Shenyang 110819, Liaoning, Chinad Liaoning Province Engineering Technology Research Center of Boron Resources Comprehensive Utilization, Shenyang 110819, Liaoning, China

a r t i c l e i n f o

Article history:Received 3 February 2013Received in revised form11 October 2013Accepted 14 October 2013Available online xxx

Keywords:Life cycle assessmentBoraxBoric acidCradle-to-gate

* Corresponding author. College of Material and Mversity, Shenyang 110819, Liaoning, China. Tel.: þ8683687719.

E-mail address: [email protected] (J. An).

0959-6526/$ e see front matter � 2013 Elsevier Ltd.http://dx.doi.org/10.1016/j.jclepro.2013.10.020

Please cite this article in press as: An, J., XuJournal of Cleaner Production (2013), http:/

a b s t r a c t

Borax and boric acid are important primary products in China’s boron industry. Their characteristicproduction technology has been adapted to the low ore grade. To analyze the environmental impacts ofdifferent borax and boric acid production processes and to promote cleaner production of boron industry,the life cycle assessment method of cradle-to-gate was applied in this study. GaBi4.4 software was usedin the assessment and the environmental impacts were classified according to the CML2001 method. Toshow the degree of consumption of mineral resources and energy respectively, the abiotic depletionpotential was divided into the mineral resources depletion potential and fossil energy depletion po-tential. A comparison between the mineral processing and entire system studied shows that energyconsumption is important in life cycle environmental impacts. Boron production industries shouldrefrain from using coal as their main heat source and try to use clean energy. A comparison between theborax production processes shows that the boron-rich slag is the cleanest material and that blast furnacegas can be used to reduce environmental impacts further in slow cooling link. A comparison between theboric acid production processes shows that flotation (I) is the cleanest process with the material ofszaibelyite. Ludwigite should be processed after dressing to reduce the environmental impacts. Boronconcentrate can be used to produce borax or boric acid as an alternative to szaibelyite but feasibleproduction processes are still the focus of future research.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

China is rich in boron resources with boron reserves rankingfourth next to Turkey, the USA, and Russia (Liu et al., 2006).Compared with that of the other three countries, the grade ofChina’s boron ore is low and the ore is difficult to process. Forexample, the main boron-containing minerals in Turkey are cole-manite, ulexite, and tincal, with a grade of at least 40% (Kuslu et al.,2010; Kunkul et al., 2012). In China, the main boron-containingminerals are szaibelyite, ludwigite, and brine. Szaibelyite inLiaoning Province is the traditional material used in the boron in-dustry and has a grade of only 12%. The remaining reserves ofszaibelyite are limited as it has been used as the major mineralsource in China’s boron industry for many years. Ludwigite reserves

etallurgy, Northeastern Uni-24 83683176; fax: þ86 24

All rights reserved.

e, X. X., Life cycle environme/dx.doi.org/10.1016/j.jclepro.2

are relatively rich and account for 58.4% of the total Chinese boronreserves, but the content of B2O3 is in the range of only 6e9%. Themineral structure of ludwigite is complex because boron, iron, andmagnesium are intergrown (Zheng, 2007). Therefore, there hasbeen no large-scale exploitation of this mineral.

The boron industry was established in China in the 1950s. Overthe past 60 years, China has developed a fairly sophisticated boronindustrial system including mining, dressing, processing, refining,and other related businesses. Approximately 50 boron-containingproducts can be manufactured, but the output of most fine chem-icals is still relatively small (Liu et al., 2006). Borax and boric acidare important primary products produced in large output and withhigh output value. Therefore, the production of borax and boric acidplays an important role in China’s boron industry.

An environmental impact assessment was conducted becauseborax and boric acid are important primary products in the boronindustry and their production processes contribute significantly toenvironmental impacts. Limited work has been conducted on thelife cycle environment impact assessment of boron-containing

ntal impact assessment of borax and boric acid production in China,013.10.020

Page 2: Life cycle environmental impact assessment of borax and boric acid production in China

J. An, X. X. Xue / Journal of Cleaner Production xxx (2013) 1e72

products as researchers have been more concerned with theenvironmental risk of boron in boron-containing products andenvironmental media (Jensen, 2009; Graan et al., 1997; Batayneh,2012; Edwards et al., 2012) and its toxicity to exposed workers(Basaran et al., 2012; Duydu et al., 2012). Our research group hasevaluated the life cycle environment impacts of borax and boricacid using the AT&T matrix method (Qian et al., 2009; Xue et al.,2009). However, results from this work only show relative ratherthan absolute scores of the environmental impacts at differentborax and boric acid production stages. The aim of this study is toanalyze the environmental performance of different borax andboric acid production processes to provide a theoretical basis forimproving the processes, and to promote cleaner production inChina’s boron industry.

2. Materials and methods

2.1. System definition

In China, borax is produced mainly by the CO2-soda processwhere boron ore is decomposed by soda and CO2 (from calcinedlimestone). Boric acid is produced by the one-step and two-stepprocess. In the one-step process, the mineral is converted directlyto boric acid. Boron ore is reacted with sulfuric acid at a certaintemperature and the B2O3 in the ore is transferred to the liquidphase in the form of H3BO3. Flotation or salting-out is then used forthe separation of boric acid and magnesium sulfate liquor. In thetwo-step process, the mineral is converted to borax by the CO2-soda process and boric acid is then produced from borax and sul-furic acid. The above two steps can be completed in one or in twodifferent plants. These production processes have been adapted toChina’s characteristic low-grade boron ore and China holds intel-lectual property rights to the CO2-soda process.

Szaibelyite is the traditional raw material for producing boraxand boric acid. Because of its continued exploitation over manyyears, the available reserves of szaibelyite have become limited.Some effort has been made to produce boron-containing productsusing ludwigite instead of szaibelyite. However, it is difficult toproduce borax or boric acid directly from ludwigite because of itslow grade and complex mineral structure. Based on the charac-teristics of ludwigite, the Northeastern University (Shenyang,China) has invented a separation technology by blast furnace. Afterdressing, the ludwigite ore is divided into boron concentrate andboron-containing iron concentrate. Then, boron-containing ironconcentrate is smelted in the blast furnace to obtain boron-containing pig iron while the slag is enriched with boron (Zhanget al., 1995; Cui et al., 1994). The B2O3 content in the boronconcentrate and boron-rich slag is over 12%. They can thereforesatisfy present industrial use requirements and be the materials toproduce borax or boric acid instead of szaibelyite (Liu et al., 1996;Chen et al., 1996).

The life cycle assessment (LCA) is an environmental impactassessment method from ‘cradle’ to ‘grave’ (Guinée et al., 1993a, b).Because of different evaluation scope and limitation of data, somelife cycle stages can be omitted for evaluation purposes (Neupaneet al., 2011; Memary et al., 2012). The complete life cycle for bo-ron products include raw materials production, primary productsproduction, refined chemicals production, terminal products pro-duction and application, and waste disposal and recycling. The goalof this study is to analyze the environmental impacts of borax andboric acid using different raw materials and different productionprocesses. Results will provide references for improving processesand taking measures to relieve environmental pressure. The LCAcradle-to-gate method was applied and the corresponding evalu-ation scope (see Fig. 1) includes the production of mineral

Please cite this article in press as: An, J., Xue, X. X., Life cycle environmeJournal of Cleaner Production (2013), http://dx.doi.org/10.1016/j.jclepro.2

materials, the production of borax and boric acid, and the back-ground production of coal and electricity consumed in the pro-duction process. 10,000 tons of borax and 10,000 tons of boric acidwere considered to be the functional unit with the main flowsreferring to them.

2.2. Life cycle inventory

2.2.1. Material and energy consumption inventorySixty percent of China’s boron reserves are distributed in

Liaoning and szaibelyite from Liaoning is the major raw material ofChina’s boron industry. Liaoning is also the largest production basefor boron-containing products with borax and boric acid outputs of85% and 40%, respectively. Data from Liaoning’s boron industrytherefore represent the general situation in China’s boron industry.Most of the data on the material and energy consumption forproducing borax and boric acid come from the Liaoning Boron In-dustry Association and data for the roasting of boron concentratewere obtained from Zhang et al. (2009). The consumption in-ventory for mining, dressing, borax production, and boric acidproduction is summarized in Table 1. During borax production, theraw ore should be roasted to enhance its activity and promote itsrate of utilization. The mineral structure and chemical compositionof boron concentrate and szaibelyite are different and so is theirenergy consumption during roasting. After smelting in the blastfurnace, the boron-rich slag requires slow cooling rather thanroasting to enhance its activity and this consumes limited energy.During boric acid production, the lower the ore grade and the morecomplex its structures, the more energy it consumes.

2.2.2. Pollutants discharge inventory for mining and dressingAt present, the szaibelyite grades can meet process re-

quirements without dressing. Because of the low grade of ludwigiteand the intergrown iron and boron, dressing is required to separateiron and boron. In this paper, dressing refers only to that of lud-wigite. During mining and dressing, the output of waste rocks andtailings is 100 and 538 kg/t respectively. The output of chemicaloxygen demand in wastewater is 28.6 g/t. Dust resulting from rockdrilling, blasting, ore loading, and comminuting during mining anddressing is difficult to measure accurately and is disregarded.

2.2.3. Pollutants discharge inventory for borax and boric acidproduction

The mother liquor from borax and boric acid production can berecycled by returning it to the batch feeder. The cooling water canalso be recycled. Low concentration wastewater was disregardedbecause its recycle rate is unavailable and could not be modeled.

During the actual borax and boric acid production, gaseouspollutants resulting from coal combustion and emissions arerelated to coal quantities consumed, coal characteristics, andcombustion technology and equipment. The pollutants consideredin this study include carbon dioxide, sulfur dioxide, nitrogen oxides,dust (combustion), carbon monoxide, methane, and non-methanevolatile organic compounds (NMVOC). The amount of pollutantscan be calculated using the quantity of coal consumed and theemission factors:

Pi ¼ Wc � di; i ¼ 1;/;n

where P1;/; Pn are the CO2, SO2, NOx, dust (combustion), CO, CH4and NMVOC emissions (kg); Wc is the quantity of coal consumed(t or TJ), and d1;/dn are the emission factors of CO2, SO2, NOx, dust(combustion), CO, CH4 and NMVOC (kg/t or kg/TJ).

dCO2¼ 3:67� CC � r

ntal impact assessment of borax and boric acid production in China,013.10.020

Page 3: Life cycle environmental impact assessment of borax and boric acid production in China

Fig. 1. Scope of evaluation in this study.

J. An, X. X. Xue / Journal of Cleaner Production xxx (2013) 1e7 3

dSO2¼ 1600� S

ddust ¼ 72� A

where CC, S, and A are the carbon, sulfur, and ash contents of coal,respectively and r is the carbon oxidation ratio of the coal. Thevalues and units of these parameters are given in Table 2. Theemission factors of NOx, CO, CH4, and NMVOC are obtained fromreferences and are 2.7 kg/t (MEP of China, 2008), 150 kg/TJ, 10 kg/TJ(IPCC, 1997), and 15,000 g/TJ (Klimont et al., 2002), respectively.

Solid wastes are generated in both borax production and boricacid production with output mainly related to boron ore grade.

Table 1Consumption inventory of every production process.

Process Materials (grade) Quantities consumed

Mineral (t/t) Coal (109 J/t)

Mining e e 0Dressing Ludwigite ore (7%) 6.67 0Borax productionCO2-soda(I) Szaibelyite ore (12%) 3.85 20.52CO2-soda(II) Boron concentrate (12%) 3.85 29.31CO2-soda(III) Boron-rich slag (12%) 3.85 20.22Boric acid productionFloatation(I) Szaibelyite ore (16%) 4.80 30.77Floatation(II) Boron concentrate (12%) 5.83 34.29Salting-out Ludwigite ore (10.5e11%) 6.40 52.75Two-stepa Borax (�) 1.60 23.45

a Includes only boric acid production from borax.

Please cite this article in press as: An, J., Xue, X. X., Life cycle environmeJournal of Cleaner Production (2013), http://dx.doi.org/10.1016/j.jclepro.2

The lower the ore grade, the more solid wastes are produced. Thesolid waste resulting from borax production is boron mud. It isalkaline, hard to dissolve, has a pH value in the range of 8e11, andcontains 40% magnesia. Currently, limited boronmud is reused as asecondary resource while the rest is stockpiled. Large stockpiles ofboron mud therefore exist in the major regions that produce borax.These occupy land and pollute water, soil, and the atmosphere. Thesolid waste resulting from boric acid production is termed slag andcontains serpentine, forsterite, gypsum, and some H3BO3. The slagcan be used to produce boric magnesium fertilizer or brick, butmost slag is stockpiled around production plants.

The pollutants discharge inventory for the borax and boric acidproduction is shown in Tables 3 and 4, respectively.

Electricity(kW h/t)

Sodium carbonate(t/t)

Limestone(t/t)

Sulfuric acid(92.5%)(t/t)

35 e e e

23.08 e e e

350 0.35 0.40 e

527 0.35 0.40 e

350 0.35 0.40 e

1150 e e 4.081250 e e 3.271330 e e 2.88

94 e e 0.40

ntal impact assessment of borax and boric acid production in China,013.10.020

Page 4: Life cycle environmental impact assessment of borax and boric acid production in China

Table 2Values and units of some parameters.

Parameters CC r S A

Units kg/TJ % % %Values 26.3 � 103a 90 1 15

a Average value of anthracite and bitumite (UNCTAD, 2004).

J. An, X. X. Xue / Journal of Cleaner Production xxx (2013) 1e74

2.2.4. Pollutants discharge inventory for background energyproduction

The main types of energy used in borax and boric acid pro-duction are coal and electricity. The pollutants discharge inventoryfor raw coal and electricity is given in Table 5. The product back-ground emissions were calculated from the energy consumptionquantity and the emissions per unit of energy.

2.3. Impact methodology

The environmental impacts were classified according to theCML2001 method. To show the consumption of mineral resourcesand energy, the environmental impact of abiotic depletion potentialwas divided into the mineral resources depletion potential andfossil energy depletion potential and their characterization factorsderived from Gao et al. (2009). In the assessment of fossil energydepletion potential, electricity consumed was converted into fossilfuels based on the fact that 76.61% of the electricity supply wasderived from hard coal in China (Itten et al., 2013) and that theconsumption coefficient of the coal power supply was 0.334 kg/(kW h) in 2007. Because of the large amount and serious environ-mental pollution resulting from solid wastes generated during theproduction process, ‘solid wastes’ measured by the mass of solidwastes were added to the environmental impacts.

2.4. Software

GaBi, an effective software tool that has been used extensively inLCAs (Stichnothe and Schuchardt, 2010; Amienyo et al., 2013), isdeveloped and distributed by PE International. It can be used totrack all materials, energy, and emission flows automatically andcan provide instant performance accounting in dozens of envi-ronmental impact categories. With a modular and parameterizedarchitecture, GaBi allows for the rapid modeling of complex pro-cesses and offers different production options. The version used inthis study is 4.4.

Table 3Pollutants discharge inventory for borax production (kg/t).

Techniques CO2 SO2 NOx Dust (comb

CO2-soda (I) 1.37 � 103 1.08 � 101 1.82 � 100 7.29 � 100

CO2-soda (II) 2.14 � 103 1.68 � 101 2.84 � 100 1.14 � 101

CO2-soda (III) 1.36 � 103 1.07 � 101 1.80 � 100 7.21 � 100

Table 4Pollutants discharge inventory for boric acid production (kg/t).

Techniques CO2 SO2 NOx Dust (com

Floatation(I) 2.67 � 103 2.10 � 101 3.54 � 100 1.42 � 101

Floatation(II) 2.98 � 103 2.34 � 101 3.95 � 100 1.58 � 101

Salting-out 4.58 � 103 3.60 � 101 6.08 � 100 2.43 � 101

Two-stepa 2.03 � 103 1.60 � 101 2.70 � 100 1.08 � 101

a Only includes boric acid production from borax.

Please cite this article in press as: An, J., Xue, X. X., Life cycle environmeJournal of Cleaner Production (2013), http://dx.doi.org/10.1016/j.jclepro.2

3. Results and discussion

Results from the ‘cradle’ to ‘gate’ LCA on borax and boric acid aregiven in Tables 6 and 7. The results are based on the process flowand pollutants discharge inventory and were obtained using theGaBi4.4 software. Since many borax and boric acid productionplants are concentrated in the boron ore origin, to determine theimpact of mineral processing (including mining, dressing, andborax and boric acid production) on local environment, the per-centage of a specific environmental impact resulting from mineralprocessing accounting for the life cycle environmental impact inthat category was calculated as shown in Tables 6 and 7.

The life cycle environmental impacts of borax and boric acidresult from not only mineral processing (on-site) but also frombackground energy production (off-site). As shown in Tables 6 and7, the impacts of MRDP, FEDP, and SWP are all or mostly derivedfrom mineral processing, but the contribution of mineral process-ing to the other environmental impacts is relatively low with arange of 36.52e71.73% for borax and 27.67e76.34% for boric acid.The energy consumption quantity therefore plays an important rolein assessing the total environmental impacts of the study system.Reducing the energy consumption quantity not only lowers theextent of depletion of the fossil energy and the environmentalimpacts caused by using energy in mineral processing, but alsolowers the environmental impacts caused by background energyproduction. Coal is the main heat source in the Chinese boron in-dustry. Production enterprises should therefore try to use cleanenergy such as natural gas and coal gas to reduce environmentalimpacts.

To facilitate comparison and analysis, internal normalizationwas applied in the assessment results. The largest value in a specificcategory is used to normalize all other values in that category. Thenormalization results of mineral processing (on-site) and those ofcradle-to-gate (on-site and off-site) for borax are shown in Figs. 2and 3. The normalization results of mineral processing (on-site)and those of cradle-to-gate (on-site and off-site) for boric acid areshown in Figs. 4 and 5.

As shown in Fig. 2, except for MRDP, the environmental impactsof mineral processing resulted from CO2-soda (II) with the materialof boron concentrate are the highest in the three borax productionprocesses. The impacts resulted from CO2-soda (I) are as high asthose from CO2-soda (III) and less than those resulted from CO2-soda (II). The energy consumed in boron concentrate roasting is themain reason for the environmental impacts. Ludwigite is inactiveand must be roasted to increase its activity. Ludwigite has not been

ustion) CO CH4 NMVOC Boron mud

2.37 � 100 1.58 � 10�1 2.37 � 10�1 3.85 � 103

3.70 � 100 2.47 � 10�1 3.70 � 10�1 3.85 � 103

2.35 � 100 1.56 � 10�1 2.35 � 10�1 3.85 � 103

bustion) CO CH4 NMVOC Slag

4.62 � 100 3.08 � 10�1 4.62 � 10�1 2.40 � 103

5.14 � 100 3.43 � 10�1 5.14 � 10�1 3.50 � 103

7.91 � 100 5.28 � 10�1 7.91 � 10�1 4.48 � 103

3.52 � 100 2.34 � 10�1 3.52 � 10�1 0

ntal impact assessment of borax and boric acid production in China,013.10.020

Page 5: Life cycle environmental impact assessment of borax and boric acid production in China

Table 5Pollutants discharge inventory for background energy production.

Energytype

Unit CO2 SO2 NOx Dust(combustion)

CO CH4 NMVOC COD Petroleum Solid waste

Raw coal kg/t 6.19 � 100 7.45 � 10�3 4.29 � 10�2 9.07 � 10�1 5.17 � 10�3 9.32 � 100 e 5.20 � 10�2 2.29 � 10�3 4.92 � 101

Electricity kg/kW h 1.07 � 100 9.93 � 10�3 6.46 � 10�3 2.02 � 10�2 1.55 � 10�3 2.60 � 10�3 4.87 � 10�4 2.17 � 10�5a 9.56 � 10�7a 1.48 � 10�1

a Calculated by the author from data of the MEP of China (2008). Other data derived from Yuan et al. (2006), Di et al. (2005), and the MEP of China (2008).

Table 6LCA results of 10,000 t of borax.

Impacts category Unit Life cycle environmental impacts Mineral processing %-contribution

CO2-soda (I) CO2-soda (II) CO2-soda (III) CO2-soda (I) CO2-soda (II) CO2-soda (III)

Acidification potential (AP) kg SO2 eq 2.12 � 105 3.30 � 105 1.91 � 105 65.57% 65.45% 71.73%Eutrophication potential (EP) kgPO3�

4 eq 6.50 � 103 1.01 � 104 5.34 � 103 36.39% 36.75% 43.81%Freshwater aquatic ecotoxitity potential (FAETP) kg DCB eq 2.34 � 102 3.64 � 102 2.01 � 102 50.00% 50.27% 57.71%Global warming potential 100 years (GWP) kg CO2 eq 2.13 � 107 3.30 � 107 1.97 � 107 64.32% 65.15% 69.04%Human toxicity potential (HTP) kg DCB eq 1.19 � 105 1.85 � 105 1.00 � 105 42.27% 42.43% 49.70%Marine aquatic ecotoxicity potential (MAETP) kg DCB eq 4.65 � 101 7.23 � 101 3.99 � 101 50.11% 50.35% 57.89%Photochem ozone creation potential (POCP) kg C2H4 eq 1.20 � 104 1.86 � 104 1.08 � 104 60.08% 60.22% 66.11%Terrestric ecotoxicity potential (TETP) kg DCB eq 2.67 � 101 4.15 � 101 2.29 � 101 50.19% 50.36% 58.08%Mineral resources depletion potential (MRDP) kg Sb eq 4.66 � 105 4.66 � 105 4.66 � 105 100.00% 100.00% 100.00%Fossil energy depletion potential (FEDP) kg Sb eq 5.28 � 10�1 7.67 � 10�1 4.95 � 10�1 81.16% 80.00% 85.45%Solid waste potential (SWP) kg 4.34 � 107 6.68 � 107 3.94 � 107 97.70% 97.60% 97.72%

J. An, X. X. Xue / Journal of Cleaner Production xxx (2013) 1e7 5

exploited extensively as it is difficult to control roasting processconditions. Boron concentrate is a product from dressing ludwigiteand is inactive even though the boron content is increased.Although new flash roasting technology improves the activationrate and utilization efficiency of boron resources, the high energyconsumption in this technology results in significant environ-mental impacts. Therefore, roasting technologies and equipmentare required to increase resource utilization efficiency and reduceenvironmental impacts.

As shown in Fig. 3, the life cycle environmental impacts fromCO2-soda (II) are still the highest. The proportion of environmentalimpacts from CO2-soda (III) declines slightly compared with that inFig. 2. The main reason for this occurrence is that boron-rich slagfrom the smelting of ludwigite in a blast furnace is reused as waste.The materials and energy consumed and the pollutants dischargedin the production of boron-rich slag were not considered in thisstudy. Furthermore, less energy is consumed in the slow coolingprocess. So the environmental impacts from background energyproduction are therefore lower. The production of boron-rich slagcomes into being with the blast furnace smelting. To reduce theenvironmental impacts further, blast furnace gas and other cleanenergy can be taken into consideration in slow cooling. Throughthis analysis it is found that boron-rich slag is a suitable material forborax production from the point of cleaner production.

Table 7LCA results of 10,000 t of boric acid.

Impacts category Unit Life cycle environmen

Floatation(I)

Floatati(II)

Acidification potential (AP) kg SO2 eq 4.63 � 105 5.42 �Eutrophication potentialn (EP) kgPO3�

4 eq 1.54 � 104 1.86 �Freshwater aquatic ecotoxitity potential (FAETP) kg DCB eq 5.37 � 102 6.38 �Global warming potential 100 years (GWP) kg CO2 eq 4.44 � 107 5.14 �Human toxicity potential (HTP) kg DCB eq 2.76 � 105 3.31 �Marine aquatic ecotoxicity potential (MAETP) kg DCB eq 1.06 � 102 1.27 �Photochem ozone creation potential (POCP) kg C2H4 eq 2.62 � 104 3.06 �Terrestric ecotoxicity potential (TETP) kg DCB eq 6.11 � 101 7.26 �Mineral resources depletion potential (MRDP) kg Sb eq 5.81 � 105 7.05 �Fossil energy depletion potential (FEDP) kg Sb eq 9.05 � 10�1 1.04 �Solid waste potential (SWP) kg 3.00 � 107 7.83 �a Results include borax production from szaibelyite and boric acid production from bo

Please cite this article in press as: An, J., Xue, X. X., Life cycle environmeJournal of Cleaner Production (2013), http://dx.doi.org/10.1016/j.jclepro.2

As shown in Fig. 4, during boric acid production, the environ-mental impacts of mineral processing from salting-out are thehighest followed by the two-step process except for FEDP and SWP.Impacts from the flotation process are lower than those from theother two processes and minimal impacts result from flotation (I)with the material of szaibelyite. Ludwigite with a grade ofapproximately 11% is the raw material of the salting-out process.The low grade and complex mineral structure of ludwigite leads toits low acidolysis efficiency and high environmental impact. Thetwo-step production process includes borax production and boricacid production from borax. The longer process and higher con-sumption of coal (mainly in borax production) leads to greaterenvironmental impacts during mineral processing, especially forthe FEDP and SWP.

As shown in Fig. 5, for the life cycle environmental impacts ofboric acid, the highest environmental impacts still result from thesalting-out process and the proportion of environmental impactsresulting from the two-step process declines significantlycompared with that in Fig. 4. Some impacts resulting from the two-step process are lower than those from flotation (II), such as EP,EAETP, HTP, MAETP, and TETP. Less electricity is consumed in thetwo-step production process and lower environmental impactsresult from background electricity production. This is the mainreason for the decline in the proportion of environmental impacts.

tal impacts Mineral processing %-contribution

on Salting-out Two-step Floatation(I)

Floatation(II)

Salting-out Two-stepa

105 7.02 � 105 5.60 � 105 58.21% 55.49% 65.91% 76.34%104 2.13 � 104 1.48 � 104 29.85% 27.77% 37.13% 49.39%102 7.72 � 102 5.72 � 102 42.64% 39.91% 50.78% 63.31%107 6.92 � 107 5.80 � 107 60.31% 58.12% 66.39% 73.06%105 3.90 � 105 2.81 � 105 35.41% 32.96% 43.05% 55.19%102 1.53 � 102 1.14 � 102 42.64% 39.91% 50.78% 63.31%104 3.94 � 104 3.14 � 104 53.59% 50.97% 61.03% 70.83%101 8.78 � 101 6.51 � 101 42.64% 39.91% 50.78% 63.31%105 7.74 � 105 7.45 � 105 100.00% 100.00% 100.00% 100.00%100 1.43 � 100 1.35 � 100 71.13% 68.79% 77.40% 86.86%107 5.50 � 107 7.00 � 107 91.98% 96.26% 94.15% 96.81%

rax.

ntal impact assessment of borax and boric acid production in China,013.10.020

Page 6: Life cycle environmental impact assessment of borax and boric acid production in China

Fig. 2. Internally normalized results of mineral processing (on-site) for the comparison of alternative processing technologies for the production of borax.

Fig. 3. Internally normalized results of cradle-to-gate (on-site and off-site) for the comparison of alternative processing technologies for the production of borax.

J. An, X. X. Xue / Journal of Cleaner Production xxx (2013) 1e76

The flotation (I) process using szaibelyite is the cleanest processfrom the point of cleaner production.

4. Conclusions

In this study, LCA theory and methodology was adopted toevaluate systematically the environmental impacts of borax and

Fig. 4. Internally normalized results of mineral processing (on-site) for the compa

Please cite this article in press as: An, J., Xue, X. X., Life cycle environmeJournal of Cleaner Production (2013), http://dx.doi.org/10.1016/j.jclepro.2

boric acid in China. The impacts from different raw materials anddifferent processes were compared and analyzed from the point ofcleaner production.

The environmental impacts from background energy produc-tion cannot be ignored. Energy consumption is important forstudying the whole assessment system of life cycle environmentalimpacts. Production enterprises in the boron industry should

rison of alternative processing technologies for the production of boric acid.

ntal impact assessment of borax and boric acid production in China,013.10.020

Page 7: Life cycle environmental impact assessment of borax and boric acid production in China

Fig. 5. Internally normalized results of cradle-to-gate (on-site and off-site) for the comparison of alternative processing technologies for the production of boric acid.

J. An, X. X. Xue / Journal of Cleaner Production xxx (2013) 1e7 7

refrain from using coal as the main heat source and try to use cleanenergy such as natural gas or coal gas.

During borax production with CO2-soda, the boron-rich slag isthe cleanest material and blast furnace gas can be used to reducethe environmental impacts in slow cooling. During boric acid pro-duction, flotation (I) is the cleanest process with the material ofszaibelyite. Ludwigite should be processed after dressing to reduceits environmental impacts. Flotation (I) with the material of boronconcentrate is therefore recommended instead of salting-out withthe material of ludwigite.

Because the available reserves of szaibelyite are limited, boronconcentrate can be used to produce borax or boric acid as analternative to szaibelyite. However, feasible production processesfor borax and boric acid from boron concentrate are the focus offuture research.

There are some shortcomings in the evaluation conducted inthis study. For example, because of limited available data, dustresulting from some processes and the ecological impacts ofvegetation damage, water loss and soil erosion were not consid-ered. In addition, because the emissions from Chinese electricitymixes and grid are not available, emissions from coal-fired powerwere used based on the fact that most electricity is supplied bycoal-fired power in China.

Acknowledgments

Gratitude goes to the staff of Boron Industry Association ofLiaoning Province who provided this study with detailed data. Inaddition, thanks go to the support by Central University Basic Sci-entific Research Special Funds (N11030200).

References

Amienyo, D., Gujba, H., Stichnothe, H., Azapagic, A., 2013. Life cycle environmentalimpacts of carbonated soft drinks. Int. J. Life Cycle Assess. 18 (1), 77e92.

Basaran, N., Duydu, Y., Bolt, H.M., 2012. Reproductive toxicity in boron exposedworkers in Bandirma, Turkey. J. Trace Elem. Med. Biol. 26 (2e3), 165e167.

Batayneh, A.T., 2012. Toxic (aluminum, beryllium, boron, chromium and zinc) ingroundwater: health risk assessment. Int. J. Environ. Sci. Technol. 9 (1), 153e162.

Chen, J., Liu, S.L., Zhang, X.P., 1996. Study of carbonate-alkaline leaching boron-richslag for borax preparation. J. Northeast. Univ. (Natural Science) 17 (5), 508e511.

Cui, C.M., Zhang, X.P., Liu, S.L., 1994. Pig iron containing boron and boron-rich slagmade from ludwigite in blast furnace. Mining Metall. 3 (4), 68e72.

Di, X.H., Nie, Z.R., Zuo, T.Y., 2005. Life cycle emission inventories for the fuelsconsumed by thermal power in China. China Environ. Sci. 25 (5), 632e635.

Duydu, Y., Basaran, N., Ustundag, A., Aydin, S., Undeger, U., Ataman, O.Y., Aydos, K.,Duker, Y., Ickstadt, K., Waltrup, B.S., Golla, K., Bolt, H.M., 2012. Assessment ofDNA integrity (COMET assay) in sperm cells of boron-exposed workers. Arch.Toxicol. 86 (1), 27e35.

Please cite this article in press as: An, J., Xue, X. X., Life cycle environmeJournal of Cleaner Production (2013), http://dx.doi.org/10.1016/j.jclepro.2

Edwards, A.C., Coull, M., Sinclair, A.H., Walker, R.L., Watson, C.A., 2012. Elementalstatus (Cu, Mo, Co, B, S and Zn) of Scottish agricultural soils compared with asoil-based risk assessment. Soil Use Manage. 28 (2), 167e176.

Gao, F., Nie, Z.R., Wang, Z.H., Gong, X.Z., Zuo, T.Y., 2009. Characterization andnormalization factors of abiotic resource depletion for life cycle impactassessment in China. Sci. China Ser. E: Technol. Sci. 52 (1), 215e222.

Graan, A.G., Myres, A.W., Green, D.W., 1997. Hazard assessment of boric acid in toys.Regul. Toxicol. Pharmacol. 26 (3), 271e280.

Guinée, J.B., Udo de Haes, H.A., Huppes, G., 1993a. Quantitative life cycle assessmentof products: 1: goal definition and inventory. J. Clean. Prod. 1 (1), 3e13.

Guinée, J.B., Heijungs, R., Udo de Haes, H.A., Huppes, G., 1993b. Quantitative lifecycle assessment of products: 2. Classification, valuation and improvementanalysis. J. Clean. Prod. 1 (2), 81e91.

Intergovernmental Panel on Climate Change (IPCC), 1997. Revised 1996 IPCCGuidelines for National Greenhouse Gas Inventories: Reference Manual, vol. 3.Available at: http://www.ipcc-nggip.iges.or.jp/public/gl/invs6.html (accessed05.04.12.).

Itten, R., Frischknecht, R., Stucki, M., 2013. Life Cycle Inventories of Electricity Mixesand Grid. Available at: http://www.esu-services.ch/fileadmin/download/publicLCI/itten-2012-electricity-mix.pdf.

Jensen, A.A., 2009. Risk assessment of boron in glass wool insulation. Environ. Sci.Pollut. Res. 16 (1), 73e78.

Klimont, Z., Streets, D.G., Gupta, S., Cofala, J., Fu, L.X., Ichikawa, Y., 2002. Anthro-pogenic emissions of non-methane volatile organic compounds in China.Atmos. Environ. 36 (1), 1309e1322.

Kunkul, A., Aslan, N.E., Ekmekyapar, A., 2012. Boric acid extraction from calcinedcolemanite with ammonium carbonate solutions. Ind. Eng. Chem. Res. 51 (9),3612e3618.

Kuslu, S., Disli, F.C., Colak, S., 2010. Leaching kinetics of ulexite in borax pentahydratesolutions saturated with carbon dioxide. J. Ind. Eng. Chem. 16 (5), 673e678.

Liu, R., Xue, X.X., Liu, X., Wang, D.S., Zha, F., Huang, D.W., 2006. Progress on China’sboron resource and the current situation of boron-bearing materials. Bull. Chin.Ceram. Soc. 25 (6), 102e107.

Liu, S.L., Chen, J., Zhang, X.P., 1996. Study on leaching boron-rich slag with H2SO4.J. Northeast. Univ. (Natural Science) 17 (4), 378e380.

Memary, R., Giurco, D., Mudd, G., Mason, L., 2012. Life cycle assessment: a time-series analysis of copper. J. Clean. Prod. 33, 97e108.

Ministry of Environmental Protection of the People’s Republic of China, 2008. TheFirst Pollution Source Census Data Base of China (Stand-alone Version). Avail-able at: http://cpsc.mep.gov.cn/pwxs/ (accessed 05.04.12.).

Neupane, B., Halog, A., Dhungel, S., 2011. Attributional life cycle assessment ofwoodchips for bioethanol production. J. Clean. Prod. 19 (6e7), 733e741.

Qian, H.W., Xue, X.Y., Xu, Y.X., An, J., 2009. AT&T matrix comparative study of boricacid production process. Res. Environ. Sci. 22 (4), 501e505.

Stichnothe, H., Schuchardt, F., 2010. Comparison of different treatment options forpalm oil production waste on a life cycle basis. Int. J. Life Cycle Assess. 15 (9),907e915.

United Nations Conference on Trade and Development (UNCTAD), 2004. A Manualfor the Preparers and Users of Eco-efficiency Indicators (version 1.1). Availableat: http://unctad.org/en/Docs/iteipc20037_en.pdf (accessed 05.04.12.).

Xue, X.X., Qian, H.W., Jiang, T., An, J., 2009. Resource depletion and environmentalimpact in evolution of alkali carbonate process for borax preparation.J. Northeast. Univ. (Natural Science) 30 (3), 384e387.

Yuan, B.R., Nie, Z.R., Di, X.H., Zuo, T.Y., 2006. Life cycle inventories of fossil fuels inChina (Ⅱ): Final life cycle inventories. Mod. Chem. Ind. 26 (4), 59e61.

Zhang, J.Y., Cheng, J., Li, Z.L., Xiao, R., 2009. A new technology for flash-calciningpaigeite. Inorg. Chemicals Ind. 41 (3), 42e44.

Zhang, X.P., Lang, J.F., Cui, C.M., Liu, S.L., 1995. Comprehensive utilization of lowgrade ludwigite ore with blast furnace smelting. Iron and Steel 30 (12), 9e11.

Zheng, X.J., 2007. Production and Application of Boron Compounds. Chemical In-dustry Press, Beijing, p. 29.

ntal impact assessment of borax and boric acid production in China,013.10.020