Life cycle Assessment

Transcription

1 Life cycle Assessment

2 Life Cycle Assessment LCA is a 'cradle to grave' method of assessing environmental impact. It is an analysis which covers the entire life cycle of a product or function, from the extraction and processing of the raw materials needed to make the product to its recycling and disposal.

3 Life Cycle Assessment In recent years life cycle thinking has become a key focus in environmental policy making. A clear example is the concept of IPP (Integrated Product Policy) as communicated by the EU, but also in Asia (China: Circular Economy) and the America s many countries develop strategies that promote life cycle thinking as a key concept. Another development is the sustainability reporting movement. The majority of the Fortune 500 companies now report on the sustainability aspects of their operations.

4 Life Cycle Assessment There are four ISO standards specifically designed for LCA application: ISO 14040: Principles and framework ISO 14041: Goal and Scope definition and inventory analysis ISO 14042: Life Cycle Impact assessment ISO 14043: Interpretation Currently, in early 2006, two draft standards had been published that replaced these four standards: ISO/DIS 14040: Principles and Framework ISO/DIS 14044: Requirements and Guidelines

5 The Life Cycle Concept An LCA of a product includes all the production processes and services associated with the product through its life cycle, from the extraction of raw materials through production of the materials which are used in the manufacture of the product, over the use of the product, to its recycling and/or ultimate disposal of some of its constituents. Such a complete life cycle is also often named cradle to grave". Transportation, storage, retail, and other activities between the life cycle stages are included where relevant. This life cycle of a product is hence identical to the complete supply-chain of the product plus its use and end-of-life treatment. A framework for LCA has been standardized by the International Organization for Standardization (ISO) in the ISO series.

6 Life Cycle Assessment It consists of the following elements: Goal and scope Life Cycle Inventory analysis, LCI Life Cycle Impact Assessment, LCIA Interpretation

7 Goal and Scope It defines the goal and intended use of the LCA, and scopes the assessment concerning system boundaries, function and flow, required data quality, technology and assessment parameters. Common categories of assessed damages are global warming (greenhouse gases), acidification, smog, ozone layer depletion, eutrophication, eco-toxicological and human-toxicological pollutants, habitat destruction, desertification, land use as well as depletion of minerals and fossil fuels. The life of a product is usually divided into the following life-cycle stages:

8 Life Cycle Inventory analysis, LCI LCI is an activity for collecting data on inputs (resources and intermediate products) and outputs (emissions, wastes) for all the processes in the product system. 'Inventory' involves data collection and modelling of the product system, as well as description and verification of data.

9 Life Cycle Impact Assessment, LCIA LCIA is the phase of the LCA where inventory data on inputs and outputs are translated into indicators about the product systems potential impacts on the environment, on human health, and on the availability of natural resources. Life Cycle Impact Assessment is aimed at evaluating the contribution to impact categories such as global warming, acidification, etc.the three steps involved are classification/characterization, normalization and evaluation/weighting. Assessing the impacts on human health and the environment associated with energy and raw material inputs and environmental releases quantified by the inventory.

10 Interpretation Interpretation is the phase where the results of the LCI and LCIA are interpreted according to the goal of the study and where sensitivity and uncertainty analysis are performed to qualify the results and the conclusions. Quantifying the energy and raw material inputs and environmental releases associated with each stage of production.

11 Computer Chip Life Cycle The first step is silicon mining and purification. Energy is one of the inputs of the mining and purifying process. The output is purified silicon.

12 Computer Chip Life Cycle The computer chip factory takes the purified silicon and makes it into a crystal wafer form. Only about 43% of the pure silicon crystal used in the process becomes part of the chip. The silicon that does not end up in a chip either comes out as a recyclable output or as waste.

13 Computer Chip Life Cycle Then the factory "etches" circuits on the silicon wafer and cleans the etched wafer, and places the transistors and other circuits on the chips. The input for this process are chemicals to etch the silicon and water to flush it out. For a 2-gram, 32- megabyte memory chip and its plastic package, about 70.5 pounds of water is used (Williams, et al, 2002). The water used in the process must be purified before it can be used. It is then used to wash the silicon wafers and is passed out of the system as waste, or effluent. This effluent contains the chemicals it washed off the wafers, and therefore has to be disposed according to federal and state regulations. About 0.16 pounds of chemicals are used for each pound chip produced, which is about 40 times the weight of the chip.

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15 Computer Chip Life Cycle Finally, the factory cuts the wafer up into the actual chips that are packaged in a form ready for assembling in other products. Through every step of the production process, energy is required as an input. The silicon crystal that is used must be extremely pure creating the absolute clean environments required to produce such pure substances is energy-intensive. It has been calculated that the equivalent of 3.5 pounds of fossil fuels are used in the production of the memory chip and its packaging.

16 To manufacture a computer chip, we have: Raw Material Extraction: inputs, outputs and processes required to produce a supply of energy and silicon, including mining of materials. Material Production: inputs, outputs and processes to produce crystalline silicon, including the crystallization of purified liquid silicon. Part Production: inputs, outputs and processes to manufacture a chip, including etching circuits on a silicon wafer. Assembly: inputs, outputs and processes to produce the final packaged chip, including the plastic or ceramic case with metal pins that encases the chip.

17 Computer chips have a high environmental impact relative to their weight. For every gram of a microchip, 630 grams of fossil fuels are used, whereas for every gram of an automobile, only 2 grams of fossil fuels are used. This is due to the fact that making very pure, organized and hence low entropy structures from high entropy materials require large energy inputs. Automobiles, while made with heavy materials, do not require the level of purity and sophistication of materials as a microchip. The energy used in producing nine or ten computers is enough to produce an automobile.