Life cycle assessment
From Wikipedia, the free encyclopedia
A life cycle assessment (also known as life cycle analysis, life cycle inventory, ecobalance, cradle-to-grave-analysis, well-to-wheel analysis, material flow analysis and dust-to-dust energy cost) is the assessment of the environmental impact of a given product or service throughout its lifespan.
The goal of LCA is to compare the environmental performance of products and services, to be able to choose the least burdensome one. The term 'life cycle' refers to the notion that a fair, holistic assessment requires the assessment of raw material production, manufacture, distribution, use and disposal including all intervening transportation steps. This is the life cycle of the product. The concept also can be used to optimize the environmental performance of a single product (ecodesign) or to optimize the environmental performance of a company. The term 'emergy' is often used as an analysis tool to determine embodied energy.
The pollution caused by usage also is part of the analysis. For a hydro electric power plant, for example, construction pollution is considered, but so is the decay in biomass on land flooded to create the dam because it cannot absorb CO2 anymore. This biomass decay is called "CO2 equivalent".
Common categories of assessed damages are global warming (greenhouse gases), acidification, summersmog, ozone layer depletion, eutrophication, ecotoxic and anthropotoxic pollutants, desertification, land use as well as depletion of minerals and fossil fuels.
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[edit] Life cycle assessment
The procedures of life cycle assessment (LCA) are part of the ISO 14000 environmental management standards.
In the context of the energy industry, life cycle analysis is the holistic approach of including all tangible -- and some intangible -- costs of energy production from the initial project conception to the final step of returning the land to its original -- or its next-use -- state. Examples of tangible costs include facility construction, fuel source development, post-extraction land remediation, and waste disposal. Intangible costs include the impact of release of carbon into the environment and costs due to unusually long licensing processes and political resistance for new or innovative methods of energy production.
In the past, costs due to plant decommissioning and the like were not generally figured into return on investment calculations due to lax regulatory requirements. This allowed some energy producers to hide the true lifetime costs of energy production, thus projecting a false image of profitability. An example of this cost is the reclaiming of strip-mined land in the Appalachian Mountains in North America
[edit] Well-to-wheel
Well-to-wheel is the LCA of the efficiency of fuels used for transportation. The analysis is often broken down into stages such as "well-to-station" and "station-to-wheel, or "well-to-tank" and "tank-to-wheel".
[edit] Cradle-to-grave
Cradle-to-grave is the LCA of the materials used in making a product, from the extraction of materials and energy to the return of the materials to earth when the product is finally discarded. For example, trees produce paper, which is recycled into low-energy production cellulose (fiberised paper) insulation, then used as an energy-saving device in the ceiling of a home for 40 years, saving 2,000 times the fossil-fuel energy used in its production. All inputs and outputs are considered for all the phases of the life cycle.
[edit] Cradle-to-gate
Cradle-to-gate is the LCA of the efficiency of a product or service until it is produced or delivered. It shows the environmental performance as it is. It often is used for environmental product declarations (EPD).
[edit] Cradle-to-Cradle
Cradle-to-cradle is a way of thinking about life cycles. If the grave of one cycle can be the cradle of its own or another, the life cycles are called "cradle-to-cradle".
[edit] Life cycle energy analysis
Life cycle energy analysis (LCEA) is an approach in which all energy inputs to a product are accounted for, not only direct energy inputs during manufacture, but also all energy inputs needed to produce components, materials and services needed for the manufacturing process. Early expression used for the approach is energy analysis.
With LCEA, the total life cycle energy input is established.
[edit] Energy production
It is recognized that much energy is lost in the production of energy commodities themselves, such as nuclear energy, photovoltaic electricity or high-quality petroleum products. Net energy content is the energy content of the product minus energy input used during extraction and conversion, directly or indirectly.
A controversial early result of LCEA claimed that manufacturing solar cells requires more energy than can be recovered in using the solar cell. The result was refuted.
[edit] Criticism
A criticism of LCEA is that it attempts to eliminate monetary cost analysis, that is replace the currency by which economic decisions are made with an energy currency.
A problem the energy analysis method cannot resolve is that different energy forms (heat, electricity, chemical energy etc.) have different quality and value even in natural sciences, as a consequence of the two main laws of thermodynamics. A thermodynamic measure of the quality of energy is exergy. According to the first law of thermodynamics, all energy inputs should be accounted with equal weight, whereas by the second law diverse energy forms should be accounted by different values.
The conflict is resolved in one of these ways:
- value difference between energy inputs is ignored,
- a value ratio is arbitrarily assigned, e.g. a joule of electricity is 2.6 times more valuable than a joule of heat or fuel input,
- and/or the analysis is supplemented by economic (monetary) cost analysis.
[edit] See also
[edit] References
- Thomas,J.A.G., ed: Energy Analysis, ipc science and technology press & Westview Press, 1977, ISBN 0-902852-60-4 or ISBN 0-89158-813-2
