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Life Cycle Assessment is an assessment of the environmental impact of a product's life cycle (Samasundaran, 2007). It is the best tool to combine both the long term environmental and the economical evaluations of building designs (Nannan Wang, 2010).
Besides, Arena from Argentina state that the LCA is an environmental management tool used to assess the environmental impacts of a product or process from the "cradle to the grave". These mean that this tool consider on every stage of building life, from extraction of raw materials, manufacturing of building materials and components, construction on site, operation, demolition and finally is disposal. It examines the contribution of the product or process onto global and regional environmental issues, such as global warming, ozone depletion and energy use (A.P.Arena, 2003).
Process for refinement
Waste and emission to air and water
Figure 1.1: A model of building life cycle
The Society of Environmental Toxicology and Chemistry(SETAC) define that the LCA is an objective procedure for evaluating the energetic and environmental loads results from the product or process by identifying the materials and energy used and the wastes released in the natural environment. The evaluation is performed for the whole life cycle of the product or process, which include the extraction and treatment of raw materials, the fabrication, transport, distribution, use, recycling, reuse and final disposal (A.P.Arena, 2003).
In additional to, M. Asif from Scotland state that Life cycle assessment is a process to evaluate the environmental burdens associated with a product or process by identifying and quantifying energy and materials used and wastes released to the environment. Besides, LCA also assess the impact of those energy and materials used and releases to the environment and to identify and evaluate opportunities to affect environmental improvements. The assessment includes the entire life cycle of the product, process or activity, encompassing, extracting and processing raw materials: manufacturing, transportation and distribution: use, re-use, maintenance: recycling, and final disposal (M.Asif, 2007).
ISO 14040 (1997) defines LCA as a technique for assessing the potential environmental aspects associated with a product or process by compiling an inventory of relevant inputs and outputs, evaluating the potential environmental impacts associated with these inputs and outputs, and interpreting the results of the inventory and impact phases in relation to the objectives of the study (M.Asif, 2007).
The name of " life cycle assessment" was created in SETAC meeting at year 1990. After that, the general principles and guidelines started to be developed and well known to the whole world. Thus, LCA is an assessment tool which has a flow or procedure to undergo.
Generally there are four interactive steps necessary for a complete life cycle study in LCA procedure which is planning, inventory analysis, impact assessment and interpretation.
Figure 1.2: LCA procedures
Planning: This is the first step in the LCA procedure. This step include defines the goals and objectives of the LCA framework and definition of the purpose of the study. In the LCA framework, it will include the investigation boundaries (e.g. which input would be included, and which ones would be excluded from the study), scope of study and the functional unit (the unit to which all data and calculations are referred).
Inventory analysis: This is the second step in the LCA procedure. This step include data collection and calculation procedures of relevant quantitative inputs and outputs of the product or process. For the example the use of resources like energy and raw material which will releases to air, water and land associated with the system as water-borne effluent and solid waste. Besides, in this inventory stage, the process for estimating and characterising the e1ects of the environmental burdens is identified.
Impact assessment: This is the third step in the LCA procedure. This step evaluates how the product or process affects the environment. A qualitative and quantitative approach is used to analyse how raw material use, energy generation, water production, effluent output, air emission and solid waste affect the environment.
Interpretation: This is the last step in the LCA procedure. This step involves making improvements to reduce environmental impacts result from the product or process through taking an objective view of the entire life cycle and assessing the impact that changes would have on the environment. This is also a systematic procedure to evaluate information from the conclusions of the previous phases, checking that the requirements of the application as described in the goal and scope of the study are met.
As a powerful environmental assessment tool, life cycle assessment has been widely used in many areas such as solar PV system, municipal solid waste management system and chemicals (Nannan Wang, 2010).
Case study 1: Life cycle assessment for sustainable design options of a commercial building in Shanghai
Shanghai is a huge city with many building construction which has significant impact on the environment during their life cycle. Thus, sustainable building designs which include the life cycle assessment is urgent task for the construction industry in China. In order to investigate these problems, a case study is developed base on life cycle assessment approach for the strategic design of a Flagship Store in Shanghai.
First step is planning. They generate the structure of the life cycle assessment tool which is sustainable design 'shopping list'. In this study, the life cycle assessment tool is a sustainable design tools which are designed for the general guidance of building design. It is focus on the environmental impact of the buildings and the capital cost of the design options. Besides, the life cycle costs and the practitioners' opinion have been concern because they are as equally important as the environmental impact. This is because the design of buildings practically can reduce the life cycle costs and improve the sustainability of the buildings.
Second step is inventory analysis. This step involves the qualitative evaluation from practitioners and the quantitative data from technical engineers and quantity surveyors. Industrial practitioners is invited to give their sustainable design opinions on this study. In the first section, it involves a group decision making process. A questionnaire is designed for the workshops to help the practitioners to rank the options according to the retailer's priorities. In the question, there is a due-priority matrix has been designed to collect the group decisions for the workshop. In the second section, the output from the workshops and the quantitative analysis are integrated to an overall score for each design option.This multi-criteria decision making produced a final score and ranking of each option. Besides, another data collection step involves technical evaluation of the life cycle costs and risk levels of the design options. The experts evaluated the options against these criteria based on their experience and historical data.
Third step is impact assessment. The design options with positive scores selected in workshops are analysed by the technical engineers and quantity surveyors for the technical evaluation on costs and risks. The high level cost estimates were produced by professional engineers and quantity surveyors. The options were categorised as falling into one of 5 cost 'bands' for both additional capital expenditure and ongoing operational cost.
Finally is interpretation. The life cycle assessment tool demonstrated by a case study was proven to be a simple, practical and efficient design tool and therefore it is suitable for the design of other projects to assist the decision makers. However, this tool has disavantages which is requests a range of expertise and time consuming. Besides, the research is based on a real project in Shanghai. Therefore the 'shopping list' has been shortened to be suitable to the specific project environment. It is not a generic option list suitable for all projects. As this is only the initial stage of a new research area, it is recommended for future researches to discuss the suitability of other decision making tools based on this research.
Case study 2: Life cycle assessment of energy and environmental implications of the implementation of conservation technologies in school buildings in Mendoza- Argentina
This study is concern on the comparison of traditional and energy-conservative technologies applied in a rural school buildings in Mendoza (Argentina) for obtainaining thermal comfort with minimum fossil energy consumption, by using life cycle analysis (LCA) as a tool.
First step is planning. The study was conducted choosing a representative segment of the building, keeping in mind the evaluation of the conservative technologies. Only locally available technologies were taken into consideration. The functional unit, i.e. the basis for comparison, was defined taken into consideration that the compared technologies have the same area, and that the school rooms are completely equivalent in both cases. Starting with the processes involved and the components used during the construction of the school building, the upstream processes, components and materials have been included. As a necessary step to accomplish this aim other objectives were reached, like collecting environmental data for building materials and components, adapting a foreign software tool to the local conditions, and solving methodological problems which came up when applying LCA to this case.
Second step is inventory analysis. For all calculations regarding the inventory, impact assessment and normalization phases the SBID database has been used, from the Danish Building Research Institute. In Petersen details about the SBID model can be found. For comparing the technologies two intermediate rooms have been taken into account, one from the northern block and the other from the southern one. Only the conservative technologies designed for reducing the heating energy consumption have been considered, leaving aside those related with day lighting or passive cooling.
Third step is impact assessment. The impact assessment phase of the LCA has been completed with a normalization method to compare the di1erent alternatives. No overall environmental score has been used, such as eco-indicators.
Finally is interpretation. More conservative and passive solar strategies will be studied
as the research advances but, as remarked before, a great e1ort will be necessary to improve data availability for the production of new materials, which is very poor at the moment in Argentina. A further step will be the LCA of a full school building, excluding the demolition=disposal phase due to the previously commented reasons. When different end-of-life scenarios and data will be available for our country, the full life cycle will be considered.
Case study 3: Life cycle assessment: A case study of a dwelling home in Scotland
This study is concern on the life cycle assessment (LCA) of a 3-bed room semi detached house in Scotland. Detailed LCA of five main construction materials i.e. wood, aluminium, glass, concrete and ceramic tiles have been provided to determine their respective embodied energy and associated environmental impacts.
First step is planning. The present work has addressed eight different materials that were of significance in the construction of the studied house. These materials include: timber, glass, concrete, ceramic tiles, aluminium, plasterboard, slat and damp course. Out of these eight materials, detailed life cycle assessment has been provided for five main materials that are more important in terms of their embodied energy and environmental impacts characteristics. These materials include: timber, glass, concrete, ceramic tiles and aluminium.
Second step is inventory analysis. The work undertaken provides LCA of a three-bedroom semi detached dwelling home in Scotland. The involved materials were quantified through investigating the inventory reports, direct observations, and interviewing the contractors and local housing association personnel.
Third step is impact assessment. A number of different materials were used in the construction of the studied home. This section provides a brief detail of the environmental impacts associated with the key materials used in the construction process.
Table 1.1: Environmental impacts associated with the material used in the construction of home
The production of concrete is quite complex and environmentally impacting process as it releases various pollutants such as, carbon dioxide, heavy metals, organic hydrocarbons, carbon monoxide, sulphur dioxide, Nitrogen oxides and alkaline wastewater.
Timber is considered to be a recyclable material since at the end of its service life, a timber product can be down-cycled and can be used for many purposes for example, in chipboard production, animal bedding or garden projects.
The two main environmental factors associated with glass production are the high primary energy consumption with related energy pollution and the material pollution.
They have huge environmental impacts associated with their production. Potential polluting elements released as a direct result of their production include carbon dioxide, sulphur dioxide, fluorine and possible chromium.
It requires a great deal of energy to be produced. This energy consumption in itself brings environmental burdens besides the large amounts of pollutants released during the production process. The pollutants resulting from aluminium production process include substances like carbon dioxide (CO2), acidic sulphur dioxide (SO2), polyaromatic hydrocarbons (PAHs), and gases having global warming potential
Finally is interpretation. Concrete is the most significant construction material employed in the studied home not only in terms of quantity consumed but also for the embodied energy and associated environmental impacts. It has smaller values of embodied energy and environmental impacts as compared to other construction materials involved such as glass, aluminium and ceramic tiles. However since concrete is used in a very large quantity proportion in any construction, it becomes responsible for a large share of the gross embodied energy and environmental impacts. Results indicate that concrete and mortar are responsible for 99% of the total CO2 resulting from the home construction.