Evaluation of environmental impact of cement production in Algeria using life cycle assessment

The aim of this study is the use of Life Cycle Assessment, to evaluate the impact generated by cement manufactory situated in Sour EL Ghozlane town in Algeria country, which use the dry process to produce cement Portland. The LCA method is used for compiling and examining the inputs and outputs of energy, raw material and environmental impacts directly attributable to the manufacture and functioning of a product throughout its life. It is also used to determine element and energy contributing to each impact evaluated. Potentials impacts are evaluated using the SimaProV.7.1 software and IMPACT2000+ method in this study.


INTRODUCTION
Life cycle assessment (LCA) is an important tool used to evaluate and identify the environmental impacts related to a product, service or system from a holistic standpoint that incorporates all known potential environmental impacts and follows the product, service or system from cradle to grave. It is used to understand total energy consumption, identifying energy saving opportunities, and informing decision-makers.
The LCA method has described in the ISO standards 14040 and 14044. It has developed quickly during the 1990s and has reached a definite level of harmonization and standardization. An LCA study consists of four phases: goal and scope definition, inventory analysis, impacts assessment and interpretation [1].
The LCA of a Portland cement concrete road takes into a count the raw materials and energy used in making the cement as well as the emissions from the cement manufacturing process. It includes the energy and resources consumed in mixing, transporting and the environmental consequences [2].
Regarding to the LCA of the cement industry, Huntzinger and al. [3] describes that the production of cement involves the consumption of large quantities of raw materials, energy and heat. The manufacturing process is very complex, involving a large number of materials, pyro processing (wet and dry kiln, preheating….), and fuel sources.

Cement manufacturing process
Raw materials should be mixed precisely to manufacture the cement. The cement clincker requires appropriate amount of compositions of the elements calcium, silicon, aluminum and iron. All these raw materials together with the fuel as an energy consumption must be combined to form the typical clinker composition [4].
In rotary kiln, the raw materials are calcined at temperature varying between 700 C° and 900°C, which is a combination of alumina, ferric oxide and silica with lime. Between 900-1200°C, there is formation of clinker. The clinckerisation process is following by the cooling stage.

Life cycle assessment methodology
Life cycle assessment (LCA) is a systematic way of evaluating the environmental impacts arising from resources depletion and process emissions associated with a product or service [2]. It is a method of evaluation used to assess the environmental impacts of technologies from "cradle to grave" .it has the ability to evaluate the materials and energy efficiency of a system, and to identify pollution. It consider the environmental impact of a product during its life cycle: starting with raw material acquisition, through production and use and final disposal.

Goal and scope, functional unit and system boundaries
The goal of the present study is to assess and the environmental performance of cement manufacturing by dry process. The model focuses on all steps or stages of cement production (blinding and grinding of clinker and addition of mineral components to produce cement). The functional unit of analysis in this study is the production of one ton of cement.

Data quality
The study is based on the process data supplied by cement production in Algerian manufactories (SOUR ELGHOZLANE using dry process). Data used for this study is based on data records from the plants. In this study, we have used the SimaPro7.1 software to evaluate the environmental impact of inventory aspects using IMPACT 2000+ method Inventory data for raw materials and electricity and heat generated by fuel (natural gas in this case) is obtained from those factories and from SimaPro.7, software databases (table 1-show raw materials and energy resources used in this factory).

80
ILCPA Volume 45 Table 1. Inventory of dry process of cement production.

Impacts assessment
The impacts considered in this study are shown in table 2: -Global warming expressed on Eq kg CO 2 -Aquatic eutrophication expressed on eq kg PO 4 -3 -Aquatic acidification expressed on Eqkg SO 2 -Terrestrial acid/nitrification expressed on Eq.kg SO 2 ) -Respiratory organic expressed on Eq.kgC 2 H 4 -Ozone layer depletion expressed on Eq.kgCFC-11 -Respiratory inorganic expressed on Eq.KgPM2.5) -Carcinogen expressed on Eq.kgC 2 H 3 Cl   Table 2 shows all damage categories and impact categories generated by dry process, in this evaluation, we have assessed four damage: human health, ecosystem quality, climate change and resources. Each damage has it impact category: for example damage human health, have tow impacts categories: carcinogen and respiratory inorganic. It is observed that resources cause major damage, it have an effect on global warming, aquatic eutrophication, and climate change.

RESULTS AND DISCUSSION
Damage of resources is the greatest, it generate two impacts categories; global warming at 0.882 eq kg CO 2 , and aquatic eutrophication at 7.86 E -7 Eq.kg PO 4 -3 , that's result from using resource such as natural gaz as source of heat necessary to clinckerisation and process. This process is following by height quantity of gases emitted as CO 2 , SO 2 , and NO X , which are the results of combustion process.  3.2% 9%

ILCPA Volume 45
and at 62.5% to respiratory organic which is due to gaz emission NO X , CO 2 and SO 2 . Figure  1resumes the contribution of energy to impacts categories. A study done by Ahmed Abdelmotaleb and al [5], on effect of fuel on life cycle of Egyptian cement industry: environmental impact assessment approach, results show that the decision of replacing the existing used fuels in cement industry by coal will carry an additional burden on the environment approximately by 20%. Global warming and respiratory inorganic recorded highly negative impacts of 20% and 25% respectively when using he coal compared with other fuels type. The damage human health is dominated when using the coal with a relative contribution of 30%.
In our study, for human health damage, carcinogen and respiratory inorganic, natural gaz and electricity contribute respectably at (28.5%, 61.5%) and (11.5% 11%). This damage is posed by contamination air, sol and vegetation. Marta Schuhmacher and al [6] in their study show that the incremental risk of mortality /morbidity produced by PM, and SO 2 , NO 2 , does not mean any important additional health risk for the population living in the area under evaluation. The highest annual incremental risk corresponded to particles', with mean concentrations of 4.6*10 -5 and 3.8*10 -4 for chronic mortality and morbidity, respectively (1.6*10 -4 and 1.3*10 -3 ). For a population of 80.976 inhabitants, annual increments of 37 subjects have been estimated to show health effects due to emission from plant. In relation to PCDD/ Fs, the inhalation cancer risk in this case is for maximum concentration.

CONCLUSION
Life cycle assessment is a useful tool for evaluating the environmental impact generated by system, product or service. In this case we have used LCA in order to determine and evaluate the impacts generated by cement production in Algeria, using dry process, with this tool and using SimaPro7.1 and IMPACT 2000+, we have assessed all damages categories with their impacts categories, and contribution of energy used to those impacts.
In the present study, natural gaz and electricity contribute, to each impact category such as carcinogen, respiratory organic, global warming… because during the process of production, it has generated a most quantity of gases and particles emitted through atmosphere.
So, we can make intervention in order to reduce the impact categories, by replacing energy used or minimization of energy and raw material consumption. So this tool helps to make decision in politic of environmental management.