Scholarly article on topic 'Recent progress and application of materials life cycle assessment in China'

Recent progress and application of materials life cycle assessment in China Academic research paper on "Materials engineering"

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Abstract of research paper on Materials engineering, author of scientific article — Zuo-ren NIE, Feng GAO, Xian-zheng GONG, Zhi-hong WANG, Tie-yong ZUO

Abstract Life cycle assessment (LCA) is a technique for systematically analyzing the environmental impacts and resources used throughout a target's life cycle, i.e. from raw material acquisition, via production and use phases, to waste management. It is an effective tool that gives a detailed information of environmental profiles of a material or a product. More importantly, the value of life cycle thinking lies in its ability to provide the decisionmaking basis for sustainable development, making the products, industries and even the whole industry chain act more in line with the principles of sustainable development. The recent developments of LCA methods and applications of materials life cycle assessment in China were reviewed. In the sections on LCA methodology, the data quality analysis, the impact of land use and abiotic resource depletion as well as the weakness in life cycle impact assessment were discussed. In relation to the applications, the Chinese materials database (SinoCenter Database) and several representative case studies such as life cycle analysis of civilian buildings and metal production in China were introduced.

Academic research paper on topic "Recent progress and application of materials life cycle assessment in China"

Recent progress and application of materials life cycle assessment in China

Zuo-ren NIE, Feng GAO, Xian-zheng GONG, Zhi-hong WANG, Tie-yong ZUO College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China Received 18 October 2010; accepted 23 December 2010

Abstract: Life cycle assessment (LCA) is a technique for systematically analyzing the environmental impacts and resources used throughout a target's life cycle, i.e. from raw material acquisition, via production and use phases, to waste management. It is an effective tool that gives a detailed information of environmental profiles of a material or a product. More importantly, the value of life cycle thinking lies in its ability to provide the decision-making basis for sustainable development, making the products, industries and even the whole industry chain act more in line with the principles of sustainable development. The recent developments of LCA methods and applications of materials life cycle assessment in China were reviewed. In the sections on LCA methodology, the data quality analysis, the impact of land use and abiotic resource depletion as well as the weakness in life cycle impact assessment were discussed. In relation to the applications, the Chinese materials database (SinoCenter Database) and several representative case studies such as life cycle analysis of civilian buildings and metal production in China were introduced. Key words: materials; life cycle assessment; LCIA methodology

1 Introduction

For the manufacture, application, and disposal of materials, rapid depletion of resource reserves and other environmental problems such as climate change have been major threats to the species during the recent years. In order to meet these challenges, many tools and indicators for assessing environmental impacts of different systems have been developed. The usual analysis methods mainly include life cycle assessment (LCA) and materials flow analysis (MFA). LCA has been extended to many aspects of production and consumption, including eco-design of products, cleaner production, environment label, green purchase, resource management, wastes management and environment strategy, etc[1-2].

With the rapid economic development of China, the confliction between economic development and environment protection becomes more and more severe. It is important to improve resources and energy efficiency and reduce pollutants emission of Chinese materials industry by performing LCA as technical and decision-making support to gain the target of energy-saving and emission-reducing. There is much progress made in Chinese LCA research in recent decade,

including the development of LCA methodology, basic database and software, as well as the establishment of environmental certification standard of typical materials under the support of the National High-Tech R&D Program, the National Basic Research Development Program, the National Key Technology Research and Development Program and the National Natural Science Foundation of China[3].

2 Development in LCA methodology

LCA is a tool for estimating and assessing the potential environmental impacts attributable to the life cycle of a product, including raw material extraction, processing, manufacture, usage, recycle and disposal. Data quality and the option of life cycle impact assessment (LCIA) methods are more concerned. The high quality data are an important premise to carry out LCA and the data reliability directly influences the capability of the results and its application. LCIA is the stage that has more difficulties and needs to be further developed.

2.1 Data quality analysis

With the request of the reliability of LCA results,

Foundation item: Project (2007CB613706) supported by the National Basic Research Program of China; Project (2081001) supported by the Beijing Natural Science Foundation; Project (2007AA03Z432) supported by the National High-Tech Research and Development Program of China; Project (50525413) supported by the National Natural Science Foundation of China; Project (X0009011200902) supported by the Scientific Research Initiative Foundation of Beijing University of Technology Corresponding author: Zuo-ren NIE; E-mail: zrnie@bjut.edu.cn

the definition and evaluation of data quality have already attracted much attention. In recent years, some international organizations devoted to the study on this area. SETAC put forward a qualitative evaluation framework of LCI data quality, which recommended uncertainty analysis and sensitivity analysis, as the important parts of impact assessment, to evaluate the variety of LCA results caused by data and models. The revision of the ISO series 14040 proposed that the character of data should meet with the goal and scope of study, and date quality should be assessed by qualitative and quantitative methods, and data collection and combination methods, so as to correctly represent reliability of results[4].

The researches of LCI data quality method mainly focus on two aspects:

1) To introduce data quality indicators from representative data, such as regional and temporal data, or data collection methods.

2) To adopt the uncertainty to represent the integrated data quality and analyze the dataset uncertainty related to the process to denote the uncertainty of LCI results.

There are a number of methods to analyze the uncertainty, including Gaussian error propagation formulas, Monte Carlo simulation, stochastic simulation based on probability distribution, interval algorithm and fuzzy logic approaches[5-8] and so on.

Up to the present, appropriate methods and ideas for the data quality analysis of LCA are still not available although several methods for evaluating the consistency, continuity, sensitivity and uncertainty of the inventory data were proposed by LCA practitioners [9-10]. The primary data source of LCI study in China is public statistical data of which uncertainty is difficult to be identified and quantified. Thus, the accumulation of field monitoring data is especially important for LCI data collectors to perform the uncertainty analysis.

In view of the data deficiency of LCA research in China, the missing data are predicted and imputed logically based on the information known in life cycle inventory by using three methods: complete case analysis, linear regression analysis and Markov Chain Monte Carlo (MCMC) method. Moreover, a comparative analysis between the application of these three methods is performed. A data quality analysis system to reduce the interference from the missing data is set up[11]. Based on the grade-matrix model and the expected value methods, the transformation from determinated LCA model to stochastic LCA model was developed and an LCI stochastic model was also established for an exemplification of eco-cement production[12].

2.2 Impacts of land use

According to a report by World Resources Institute

in 1999, almost all the declines of ecosystem in the last century are related to physical changes in land utilization[13] which may also have significant impacts, whether positive or negative, in the life cycle of production system, from the exploitation of resource and energy in raw materials acquisition phase, the building for production and living in manufacture phase, the construction of road and railway in transportation phase until the landfill in final disposal phase. However, there is no consensus that how land use impacts should be incorporated in LCA, although the concern for the inclusion of land use impacts in LCA has led to many publications internationally in recent years [14-16]. A working group within the UNEP/SETAC Life Cycle Initiative has been formed and the integrated environmental assessment methods with a focus on soil quality and land use will be developed further.

In our study, a model with characterization factors was proposed to qualify the land use impact based on the land quality change presented by net primary productivity (NPP) during the land use duration, which can be incorporated into the LCA framework to improve the basis for decision making in industry and other organizations. In this model, land occupation and land transformation are considered as the basic land use activities that result in either damage or benefits to ecosystem quality (land transformation creates a change in ecosystem quality and land occupation delays changes to its quality). On the other hand, the permanent impact due to human usage is suggested to be described in quality unless the data are available. Based on this model, the characterization factors of both land occupation and land transformation are calculated using Chinese empirical information on NPP, which can be applied to Chinese LCA case study to fill an important gap in life cycle impact assessment of land use in China[17].

According to geographic position of China, the land form with the highest NPP value (evergreen broadleaved forest) is defined as natural state. As the defined natural state, the occupation in the form of evergreen broadleaved forest will not cause any environmental impact in the model, while the occupation impact of the other land types will increase with the decrease of their NPP values. The occupation factors are shown in Table 1.

For convenient usage, only transformation factors between primary land types are calculated, and the result is shown in Table 2. The transformation impact will increase with the difference of NPP value between two land types, and the factors will be negative when converted from low-NPP land type to high-NPP land type, namely, causing a beneficial impact to environment.

In order to gain experiences in using and comparing the different methods in practice, some case studies closely related to the impact of land use, such as sintered

Table 1 Characterization factor of land occupation in China

Primary land type Secondary land type LUFocc/(g(C)-m-2-a-1)

Subtropical evergreen coniferous forest 66

Temperate evergreen coniferous forest 223

Evergreen broadleaved forest -

Forest Deciduous needle-leaf forest 247

Deciduous broadleaved forest 185

Temperate mixed forest 191

Tropical/ subtropical mixed forest 115

High-density shrub 137

Low-density shrub 441

Meadow-herb swamp 266

Grassland High-density grassland 218

Low-density grassland 502

One crop annually 312

Farmland Two crops annually 261

Paddy-upland rotation annually 240

Double cropping rice 169

Semidesert 597

Desert Harsh desert 562

Sand desert 608

City_City_476

Table 2 Characterization factor of land transformation in China (103g(C)-m 2-a ')

Land type Forest Shrub Grassland Farmland Desert City

Forest - -3.04 -8.38 -6.10 -16.2 -11.8

Shrub 3.04 - -5.34 -3.06 -13.2 -8.79

Grassland 8.38 5.34 - 2.28 -7.83 -3.46

Farmland 6.10 3.06 -2.28 - -10.1 -5.74

Desert 16.2 13.2 7.83 10.1 - 4.37

City 11.8 8.79 3.46 5.74 -4.37 -

brick production, agricultural products and waste reusage are conducted.

2.3 Abiotic resource depletion

Abiotic resource depletion is one of the most important categories in life cycle impact assessment. The current level of recognition for the mineral resource depletion issue, however, is still far lower than that for the issues, such as the greenhouse effect, and acidification effects, that arise in the process of developing and utilizing mineral resources [18]. There also exists much controversy on the characterization methods of the abiotic resource depletion impacts, and the focus of this controversy is largely centered on a number of fields, such as the determination of resources function parameters, the rationality of choosing the characteristic factors of resource depletion, as well as the impacts caused by resource extraction, substitution and recycling technology on resource depletion[19-21].

At present, there are mainly three kinds of models for resource depletion.

1) Use the ratio of resources extraction volumes to reserves to measure the level of the abiotic resources depletion. These methods use a number of characteristic factors, such as 1/R, U/R and U/R2, among them R represents the reserves of a certain resource while U denotes the current volumes of use or extraction of this kind of resource. The CML method developed by the group of Leiden University in Netherlands, reflects this view[22-23].

We chose the CML method, combined with Chinese characteristics of resources and statistical data, so as to modify important parameters involved in this model, and thus calculated Chinese characterization factor set of mineral resource depletion as well as normalization factor of resource depletion in 2004. The comparison with the original method highlights the fact that geographical distribution differences of resources are

unavoidable in the LCA study. Through case studies, the differences between the modified model and the CML model in the application are comparatively illustrated in Table 3 and the causes for these differences are discussed, thereby a feasible basis for suggesting the modified model as the characterization method assessing Chinese mineral resource depletion provided[24].

Table 3 Summary of characterization results for resources category from two LCIA procedures

Resource CML (kg antimony eq.) Modified method (kg antimony eq.)

Dolimite 0 47.1

Silica 6.52x10-8 1.31x10" -2

Iron(from ore) 2.23x10-5 1.20x10" -3

Fluorite 6.50x10-1 1.89

Coal 1.20x102 1.02x10" -3

Crude oil 2.05 1.44x10" -2

Natural gas 1.43 9.05x10" -6

2) Use the expected results generated by resource exploitation as a basis for characterization. This point of view suggests that mankind's current extraction of high-grade resources will cause more serious environmental and economic impacts when exploiting low-grade resources in the future. Such kind of views are represented by the Eco-indicator 99 method[25], which uses the energy demand required for exploiting low-grade resources as the damage factor to measure resource depletion, and which believes that this kind of "additional energy" is able to interlink the functionality with technical development of the abiotic resources, rather than directly relying on estimates of hardly-predictable resources reserves and annual consumption volumes in the future.

The Eco-indicator 99 method uses a large number of theoretical assumptions, and the calculation of parameters requires the support of a large amount of data, in particular the need for continuous statistical data of ore extraction volumes and ore grade in a longer period of time. According to the current actual statistical situation of Chinese mineral resources, the statistical data of ore grade of the majority of non-metallic mineral resources cannot be obtained, thereby limiting the general applicability of this model. Furthermore, the calculation process is relatively complicated, and has higher requirements for data quality, thus affecting the operation of the model.

The characterization model of abiotic resource depletion was modified and improved in terms of localization in our study. However, the characteristic factors of the abiotic resource depletion need to be expanded in terms of both time span and resource

category with the development of exploration technology, and the expansion of human demand, because some important parameters, such as resources reserves and extraction volumes, are regionally different and sensitively time-bound. And the degree of correlation between characterization factors of abiotic resource depletion and economic-social factors still needs to be further studied.

3) Exergy-based model. Exergy, which is defined as the work potential of energy at a stated surrounding, is an appropriate function to express the quality of energy. The exergy model for elements was proposed by Szargut[26], who selected reference species at atmosphere for 9 kinds of elements, hydrosphere for 23 kinds of elements, lithosphere for 53 kinds of elements, and calculated the exergy values of elements. Subsequently, methods and data based on this exergy model were developed for natural resources in life-cycle assessment by Finnveden and ostlund[27]. In order to fill the gap of the lack of exergy consumption data, a series of Cumulative Exergy Demand (CExD) indicators were set up to assess exergy scores for a large number of materials and processes[28]. It is likely that CExD indicators could suitablely assess energy and resource demand in product life cycle assessments.

The exergy for some Chinese minerals was calculated to describe the depletion of exergy caused by the use of natural minerals. For the non-aluminum-containing minerals, there is no distinct difference between the results from Szargut's and Rivero's data[29] of element exergy, but for the aluminum-containing minerals, especially for the minerals which contain a large number of aluminum, it will cause a significant difference on the results when using different models. The main reason for this significant difference is the choice of standard mole Gibbs's free energy of formation for aluminum reference species (sillimanite). And the element exergy from Rivero's results is inappropriate to calculate the exergy for some aluminum-containing minerals, which will get some unreasonable results[30].

2.4 Development of methodology of life cycle impact assessment

So far, the development of the methodology and the benchmark system of the life cycle impact assessment (LCIA) phase is still in progress, and there are several models used to calculate the characteristic indicators connecting inventory data with environmental impact categories. However, widely accepted uniform standard is still not available. Internationally, a variety of methods have been proposed to implement impact assessment, which can basically be divided into two types: midpoint methods[31] and endpoint methods[32]. The former focuses on the environmental impact categories and their

function mechanism, using characteristic factors to describe the relative importance of various environmental disturbance factors. And the latter focuses more attention on the causality of the environmental impact issue.

Although significant progress has been made in the LCIA characteristic methods, their scientific connotation still need to be continuously improved and enriched mainly in the following several areas[33]:

1) To quantify the uncertainties of impact indicators. In the decision making process, the uncertainty analysis method needs to be established to improve the accuracy and reliability of LCA results.

2) The differences of environmental impacts caused by spatial and temporal differentiation need to be identified.

3) In accordance with the requirements for consistency and comparability, the depth and breadth of simulating environment mechanism need to be increased. The correlation between the characterization results and the environment needs to be further proved so as to enable the potential environmental impact assessment results to facilitate integrated decision making.

4) Related disciplines need to be further developed to improve the development of the method for comparing the impact categories, such as resource depletion, human health, land use, and water use, thereby providing better support for integrated decision making.

3 LCA database and software

Generally, not only large numbers of environment burden data with high regional limitation but also different LCA models are involved in LCA application. These data with the properties of universality, regionality and complexity, are the basis for each LCA study and supposed to be managed effectively. Therefore, owing to the advantage of database technology in data management area, the development of LCA database and evaluation software has become one of the most important directions of LCA research recently.

3.1 Research status of international LCA database

and software

For promoting the communion of LCA information, a current format for data exchange was established by Society for Promotion of Life-cycle Assessment Development (SPOLD), which performed a detailed meta-data division on each inventory record in order to assure the independence, handleability and procurability of life cycle inventory. Moreover, the SPOLD format is an open source and can be embedded in different LCA software for the data exchange between these tools.

Furthermore, an international standard (ISO

14048)[34] for LCA data exchange is formulated by International Organization for Standardization (ISO), which put forward a normative information format including process information, model information and management information. Whereas, more detailed criterions for data selection and technology requirement are demanded for actual LCA study.

Several national and international public databases, such as the Swiss ecoinvent database[35], the European Reference Life Cycle Database (ELCD)[36], the Japanese JEMAI database [37], the US NREL database[38], and the Australian LCI database[39], have been released in recent years. These databases evolved from publicly funded projects cover a variety of inventory data on products and basic services including raw materials, electricity generation, and transport forms as well as waste disposals and services.

The efficiency of LCA implement can be improved and the cost of time and manpower can be reduced by the application of LCA software which is often divided into three groups: general software for LCA experts and consultants, professional software for the decision of engineering design, sale or environment and waste management, application software for specific users (mainly the enterprise users). At present, the amount of LCA software related to material and production is more than twenty worldwide, the environment database exceeds one thousand, and over three thousand commercial softwares with embedded default database are sold, in which some famous tools (such as Simapro[40], Gabi[41], Team[42]) have been widely applied in LCI, LCIA, Eco-design and cost analysis.

3.2 Research status of Chinese LCA database

In recent year, the research of LCA in China developed rapidly due to the high attention from the public and government, although started relatively late. In the support of National High-Tech R&D Program, which was initiated by Beijing University of Technology (BJUT) and co-operated with other colleges, research institutes and material corporations, the environment burden data of main material production (steel, cement, aluminum, engineering plastics, architectural coatings, ceramic, etc) was collected and processed, and based on these data a basic material life cycle assessment (MLCA) database and related softwares with independent intellectual property were also developed[43]. As a result of the exploration and development within recent ten years, a research and consultation platform of LCA with the largest data quantity which covered the widest range of materials in China was established in BJUT, involving six servers, firewalls and routers, eleven workstations and related professional evaluation softwares (Gabi4.0, Simapro7.0, UmberTo4.0[44], Team3.0, etc).

Furthermore, the website of Center for National Materials Life Cycle Assessment (CNMLCA, www.cnmlca.com.cn) has been opened to society and public in order to propagandize the development and application of LCA, introduce the latest research trend and result around home and abroad, promote the formation and wide development of ECO-material think and evaluation, and most importantly, support the LCA and ECO-design performance in China. By far, the practice of life cycle assessment in China has attracted attention with several international LCA institutions. The research center has widely cooperated with ISO and PRe Consultants, and participated in the establishment of global LCA union.

SinoCenter system established by Windows Advance Server and MSQL Server Enterprise version is an internet oriented platform that focused on research and development, which consisted of several connected sub-database, and management tools[45], etc (Fig. 1). The majority of database systems are based on unit process data representing specific technologies of Chinese materials industry. Presently, more than one hundred thousand records are involved and the concrete classification includes energy supply (primary energy and secondary energy), transportation, mineral resources, materials (metal materials, building materials, chemical materials, etc), LCA methods and standards.

4 Representative case studies

The development of China economy will spur a significant growth in energy and raw materials industries. Using LCA methods to adjust industrial layout and to choose, optimize and design technique processes, such as energy supply as well as the production and manufacturing of materials, will be able to provide scientific decision making and technical guidance for Chinese materials industry to achieve cleaner production and to carry out energy-saving and emission-reducing targets.

4.1 Energy

The life cycle inventory (LCI) of the production of primary energy and the major secondary energy is the fundamental data to carry out LCA for the materials industry and even all industrial products. In order to further develop Chinese materials LCA database, we have worked out the inventories of primary energy, including the energy consumption and emissions involved in the extraction process of coals, crude oils and natural gas, and have compiled a full data inventory from "cradle to gate" of several major downstream products derived from coals and crude oils, such as cleaned coal, coke, gas, petrol, diesel oil and fuel oil[46]. The inventory of energy consumption of power generation, as well as the emissions of gaseous pollutants, liquid pollutants and solid wastes were also investigated. The comparison with emissions related to 1 kW-h of electricity distributed between the Japan's electricity industry and Chinese is shown in Fig.2[47]. These fundamental energy inventories have already been applied in Chinese environmental impact assessment of materials and products as well as in international comparative studies. With the enlargement of Chinese

Fig.1 Structure and function of SinoCenter platform

These unit process data provide the possibility for choosing the technologies that are appropriate in the case investigated, and allowing the LCA practitioner to review underlying details of the process data and methodological choices for environmental assessment of a product or service. Quality and consistency are key issues related to inventory data. The SinoCenter database is also designed to address inventory data and to help support the exchange of data amongst the many LCA tools and databases in the contexts of consistency and quality assurance building on existing achievements, e.g. the ISO TC 14048.

Fig.2 Comparison of emissions related to 1 kW-h of electricity distributed between China and Japan

economy scale and the rapid increase of energy requirement in recent years, the inventory data of energy consumption especially the electricity generation have been updated to reflect the tendency of changing situation. A carbon footprint analysis of thermal power, which is 81.83% of Chinese electricity generation in 2006, showed that the carbon emission of 1 kW-h net thermal power is a little higher than that of 2002.

4.2 Design of eco-cement and structural adjustment of Beijing cement industry

The cement industry accounts for about 15% total amount of carbon emission in China, which is in the third place preceded only by steel and power industry. In addition, millions of tons of cement kiln dust and other gaseous emissions each year were released to contribute to respiratory and human health risks. A process-oriented method to calculate CO2 emissions due to cement manufacture was established and a case study for a certain plant was provided for eco-cement products design[48].

Combining the process LCA analysis and the regional material flow analysis (MFA), under the premise that guarantees both the cement demands of Olympic construction and environmental protection requirements, we put forward the 2008 Beijing's cement industry layout adjustment program. Under the circumstance that keeps the cement output basically unchanged, the overall consumption volume of materials and energy in Beijing's cement plants, through adjustment, combination and technological upgrading, was basically the same as in 2001, but the emissions of atmospheric pollutants, including soot, fumes and sulfur dioxide, were decreased by 50%, 11% and 2%, respectively, compared to 2001 (Fig.3). This program provides an extremely important reference for significant

Fig.3 Comparison of materials and energy consumption between 2001 and 2008 for Beijing cement production

improvement of the atmospheric environment quality in Beijing and for the phased objective achievement of reducing and controlling air pollution[49].

4.3 LCA analysis of civilian buildings

The green building system currently advocated is to consider, from the perspective of sustainable development, the impacts on resources, energy and environment during a whole life cycle of buildings. The total floor area of buildings in China has reached over 40*109 m2, and the direct energy consumption during the construction and use of buildings accounts for 30% of the total amount consumed by the whole society. In order to meet the urgent demand for the development of energy-saving buildings and green materials, we have cooperated with Canada Wood Group to jointly analyze the environmental impacts produced by three different types of construction structures of multi-story and multi-residential civilian buildings in Beijing, including concrete framework construction (CFC), light gauge steel framework construction (SFC) and wood framework construction (WFC), during the stages of building materials production, construction and use. In this analysis, the life cycle inventory of a wide range of materials, including metal materials, gypsum materials, cement and concrete materials, materials for doors and windows and vinyl materials, as well as fossil energy, electricity and transportation are all derived from the SinoCenter database. Through the calculation of characteristic indicators of 11 types of environmental impacts as well as the uncertainty and sensitivity analysis of the results, we determined that, among these three different kinds of construction structures, wood structure shows very obvious advantages because it ranks lowest in 8 kinds of environmental impact category, especially in the climate change, radiation effects, ozone depletion and land resources damages, all of 4 are closely related to human survival and life (Fig.4).

4.4 Iron and steel

Environmental load data of iron and steel materials derive from research into the production situation of more than 70 major Chinese iron and steel manufacturing plants as well as from industry statistical reports. The scope of the data covers the life cycle stages ranging from "cradle-to-gate", representing the environmental load of enterprises in different regions and with different levels of technology. Through the assessment of energy-saving and wastes recycling and reuse technology during the iron and steel production process, a program for large-scale integrated iron and steel enterprise to carry out the practice of recycling economy was put forward[50]. For a large-scale integrated iron and steel enterprise with an annual

compounds (PFCs), carbon tetrafluoride (CF4) and carbon hexafluoride (C2F6) to decrease by 75% in 2006 compared to that in 2003. When the overall energy consumption for alumina production is reduced to 700 kg coal eq per ton, GHG emissions will be able to basically reach the world average level in 2000. With the decline of overall electricity consumption for electrolytic aluminum, the greenhouse gas (GHG) emissions from the aluminum industry in 2010 and 2020, in comparison with that in 2006, will decrease by 6.2% and 12.3%, respectively[59].

Fig.4 LCIA comparison of impact categories for CFC, SFC and WFC in their life cycle where the largest score of each category is set to 100%

production output of 10*106 t, the use of the new recycled iron and steel production process is able to, annually, absorb from the market 1.2*106 t of scrap steels and 2*105 t of waste plastics, generate 9*109 kW-h of electrical power, and produces 3*106 t of high-grade cement through digesting wastes produced by itself, thereby yielding huge economic and social benefits.

Fig.5 Comparison of GHG emissions between China and world average level

4.5 Aluminum

It is a complex system for primary aluminum production. The development of this industry has been restrained to a large extent by the issues related to resources, energy and environment. With the initiation and promotion by the International Aluminum Institute (IAI), LCA has been introduced into the environmental assessment system for aluminum and aluminum products[51-58]. At present, China has become the world's largest aluminum producer. Because of the characteristics of nationwide bauxite resources and the energy consumption, especially the structure of the electricity industry, the specific overall energy consumption of China aluminum production is 50% higher than that of the world average level, thereinto the aluminum smelting 45% higher, and alumina production 56% higher.

The life cycle analysis result showed that the global warming potential (GWP) of China primary aluminum production in 2003 is nearly 1.7 times higher than that of the world average level in 2000, and the contribution of the process shown in Fig.5 is also different. The efforts of raising the control level of electrolytic pots and reducing the coefficient of anode effects from 0.5 to 0.2 enabled the GWP caused by two perfluorocarbon

4.6 Magnesium

Since 1990s, China magnesium industry has gained a rapid development, and China is the largest primary magnesium producer and supplier in the world. So far, the international LCA research on both the production of primary magnesium and the magnesium products is still underway[60-62], and it also needs to further study the environmental impacts on the extensive use of the magnesium products.

According to the actual situation of China magnesium production, we analyzed the environmental impacts on the directly coal-burning technics. The results showed that the reduction process accounts for 50% for the global warming potential, followed by the calcination process, being at 45%. For the acidification potential, the contribution of the refinement process and the reduction process accounts for 56% and 35%, respectively. The human toxicity potential mainly occurs in the reduction process which accounts for 95%. Based on different fuel use strategies, the environmental impacts of three scenarios were analyzed and compared (Fig.6). The direct coal-burning (Scenario 1) showed the poorest environmental performance. The overall environmental load of producer gas (Scenario 2) as the main fuel decreased by 1.9%, but the GWP were 14% higher

compared with the direct coal-burning. The environmental load using coke oven gas as major fuel for magnesium production (Scenario 3) decreased by 17.5% compared with that of the direct coal-burning. This means that a positive and environment-friendly improvement can be achieved by integrated a sort of production networks based on the materials flow and supply, by-product exchange and the waste heat utilization[63].

Fig.6 Final single results for three scenarios of magnesium production

4.7 Other materials

LCA of the materials industry is a cross/multi-disciplinary research area, involving several aspects of science, including materials science, environmental science and management. With respect to the case study of specific materials or products, there will still be a large number of useful research and exploration, such as environmental impacts produced by pyrometallurgical and hydrometallurgical process of copper production[64], as well as environmental impacts during the smelting process in typical lead and zinc plants[65-66]. Furthermore, the accumulated fundamental data and case studies of LCA for a wide range of materials, including several kinds of macromolecule materials[67], glass, ceramics, lead-free solders and biodegradable plastics, play a positive role in the improvement of the LCA database and its application in the materials industry.

5 Summary

As a quantitative tool, life cycle assessment aims at making a comprehensive assessment of the environmental impacts of products and services in a life-cycle perspective and plays an important role in materials and products eco-design, cleaner production, decision making and industry structure layout. The review presented in this paper shows several areas where the development has been active during the last years in China. These include suitable impact assessment models

for China situation, and databases for the inventory analysis, and examples of energy and materials life cycle analysis. However, some areas including LCA tools, and methods for assessment of impacts on ecosystem from land use and water use, and weighting methods still need to be further developed. In general, the applications of LCA in China are still limited in several demonstration fields and there is still a wide gap between evaluation results and the criteria people expected. Therefore, the development of LCA study should not only extend the application range of industry and agriculture fields, but also improve LCA methodology in economic and social aspects.

Although the researches of LCA methods and its application still need to make a deep investigation, it has been accepted and made important progress in the definition of goal and scope, framework, and the challenge of LCA. It is an effort for Chinese materials industry to perform the work of energy-saving and emission-reducing, and we think that LCA method is a great potential tool to provide the decision-making and technical support for the achievement of the target.

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