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EspañolLIFE CYCLE ASSESSMENT
A 'life cycle assessment' ('LCA', also known as life cycle analysis, life cycle inventory, ecobalance, cradle-to-grave-analysis, well-to-wheel 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, smog, ozone layer depletion, eutrophication, ecotoxic and anthropotoxic pollutants, desertification, land use as well as depletion of minerals and fossil fuels.
The procedures of life cycle assessment (LCA) are part of the ISO 14000 environmental management standards: in ISO 14040:2006 and 14044:2006. (ISO 14044 replaced earlier versions of ISO 14041 to ISO 14043.)
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.
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".
The factor "Tp = Petroleum refining and distribution efficiency = 0.830" from the DOE regulation accounts for the "well-to-station" portion of the gasoline fuel cycle in the USA. To convert a standard Monroney sticker value to a full cycle energy equivalent, convert with Tp. For example, the Toyota Corolla is rated at 28mpg station-to-wheel. To get the full cycle value, multiply mpg by Tp=0.83 to account for the refining and transportation energy use - '23.2 mpg full cycle'. The same adjustment applies to all vehicles fueled completely with gasoline, therefore, Monroney sticker numbers can be compared to each other with or without the adjustment. A recent study examined well-to-wheels energy and emission effects of various vehicle and fuel systems [1]
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.
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).
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".
According to the ISO 14040 and 14044 standards4&5, a Life Cycle Assessment is carried out in four distinct phases.
In the first phase, the LCA-practitioner formulates and specifies the goal and scope of study in relation to the intended application. The object of study is described in terms of a functional unit. Apart from describing the functional unit, the goal and scope, should address the overall approach used to establish the system boundaries. The system boundary determines which unit processes that are included in the LCA, and must reflect the goal of the study. In recent years, two approaches to system delimitation have emerged. These are often referred to as ‘consequential’ modeling and ‘attributional’ modeling. Finally the goal and scope phase includes a description of the method applied for assessing potential environmental impacts and which impact categories that are included.
This second phase 'Inventory' involves modelling of the product system, data collection, as well as description and verification of data. This implies data for inputs and outputs for all affected unit processes that compose the product system. The inputs and outputs include inputs of materials, energy, chemicals and 'other' - and outputs in the form of air emissions, water emissions or solid waste. Other types of exchanges or interventions such as radiation or landuse should also be included.
The data must be related to the functional unit defined in the goal and scope definition. Data can be presented in tables and some interpretations can be made already at this stage. The results of the inventory is an LCI which provides information about all inputs and outputs in the form of elementary flow to and from the environment from all the unit processes involved in the study.
The third phase 'Life Cycle Impact Assessment' is aimed at evaluating the contribution to impact categories such as global warming, acidification etc. The first step is termed characterization. Here, impact potentials are calculated based on the LCI results. The next steps are normalization and weighting, but these are both voluntary ccording the ISO standard. Normalization provides a basis for comparing different types of environmental impact categories (all impacts get the same unit). Weighting implies assigning a weighting factor to each impact category depending on the relative importance.
T
The phase stage 'interpretation' is the most important one. An analysis of major contributions, sensitivity analysis and uncertainty analysis leads to the conclusion whether the ambitions from the goal and scope can be met. More important; what can be learned form the LCA? All conclusions are drafted during this phase. Sometimes an independent critical review is necessary, especially when comparisons are made that are used in the public domain.
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.
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.
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.
★ Anthropogenic metabolism
★ Biofuel
★ Greenhouse gas
★ Industrial Ecology
★ Carbon footprint
# Bullard, C. W., Penner, P.S. and PILATI, D.A. 1978. Net Energy Analysis: Handbook for Combining Process and Input-Output Analysis, Resources and Energy 1, 267 313,Norlh-Holland Publishing Company.
# 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
# M.W.Gilliland ed: ''Energy Analysis: A New Public Policy Tool'', AAA Selected Symposia Series, Westview Press, Boulder, Colorado, 1978., ISBN 0-89158-437-4
4ISO 14040 (2006): Environmental management - Life cycle assessment -Principles and framework, International Standard Organization (ISO), Geneve
5ISO 14044 (2006): Environmental management - Life cycle assessment -Requirements and guidelines, International Standard Organization (ISO), Geneve
★ UNEP/SETAC Life Cycle Initiative
★ The European Commission's Directory of LCA services, tools and databases
★ The European Commission's LCA database ELCD (free of charge)
★ Lifecycle.org - links to LCA sites and resources.
★ How Products Impact Natural Systems.
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, smog, ozone layer depletion, eutrophication, ecotoxic and anthropotoxic pollutants, desertification, land use as well as depletion of minerals and fossil fuels.
Life cycle assessment
The procedures of life cycle assessment (LCA) are part of the ISO 14000 environmental management standards: in ISO 14040:2006 and 14044:2006. (ISO 14044 replaced earlier versions of ISO 14041 to ISO 14043.)
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.
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".
The factor "Tp = Petroleum refining and distribution efficiency = 0.830" from the DOE regulation accounts for the "well-to-station" portion of the gasoline fuel cycle in the USA. To convert a standard Monroney sticker value to a full cycle energy equivalent, convert with Tp. For example, the Toyota Corolla is rated at 28mpg station-to-wheel. To get the full cycle value, multiply mpg by Tp=0.83 to account for the refining and transportation energy use - '23.2 mpg full cycle'. The same adjustment applies to all vehicles fueled completely with gasoline, therefore, Monroney sticker numbers can be compared to each other with or without the adjustment. A recent study examined well-to-wheels energy and emission effects of various vehicle and fuel systems [1]
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.
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).
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".
The Four Main Phases of Life Cycle Assessment
According to the ISO 14040 and 14044 standards4&5, a Life Cycle Assessment is carried out in four distinct phases.
Goal and Scope
In the first phase, the LCA-practitioner formulates and specifies the goal and scope of study in relation to the intended application. The object of study is described in terms of a functional unit. Apart from describing the functional unit, the goal and scope, should address the overall approach used to establish the system boundaries. The system boundary determines which unit processes that are included in the LCA, and must reflect the goal of the study. In recent years, two approaches to system delimitation have emerged. These are often referred to as ‘consequential’ modeling and ‘attributional’ modeling. Finally the goal and scope phase includes a description of the method applied for assessing potential environmental impacts and which impact categories that are included.
Life Cycle Inventory
This second phase 'Inventory' involves modelling of the product system, data collection, as well as description and verification of data. This implies data for inputs and outputs for all affected unit processes that compose the product system. The inputs and outputs include inputs of materials, energy, chemicals and 'other' - and outputs in the form of air emissions, water emissions or solid waste. Other types of exchanges or interventions such as radiation or landuse should also be included.
The data must be related to the functional unit defined in the goal and scope definition. Data can be presented in tables and some interpretations can be made already at this stage. The results of the inventory is an LCI which provides information about all inputs and outputs in the form of elementary flow to and from the environment from all the unit processes involved in the study.
Life Cycle Impact Assessment
The third phase 'Life Cycle Impact Assessment' is aimed at evaluating the contribution to impact categories such as global warming, acidification etc. The first step is termed characterization. Here, impact potentials are calculated based on the LCI results. The next steps are normalization and weighting, but these are both voluntary ccording the ISO standard. Normalization provides a basis for comparing different types of environmental impact categories (all impacts get the same unit). Weighting implies assigning a weighting factor to each impact category depending on the relative importance.
T
Interpretation
The phase stage 'interpretation' is the most important one. An analysis of major contributions, sensitivity analysis and uncertainty analysis leads to the conclusion whether the ambitions from the goal and scope can be met. More important; what can be learned form the LCA? All conclusions are drafted during this phase. Sometimes an independent critical review is necessary, especially when comparisons are made that are used in the public domain.
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.
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.
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.
See also
★ Anthropogenic metabolism
★ Biofuel
★ Greenhouse gas
★ Industrial Ecology
★ Carbon footprint
References
# Bullard, C. W., Penner, P.S. and PILATI, D.A. 1978. Net Energy Analysis: Handbook for Combining Process and Input-Output Analysis, Resources and Energy 1, 267 313,Norlh-Holland Publishing Company.
# 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
# M.W.Gilliland ed: ''Energy Analysis: A New Public Policy Tool'', AAA Selected Symposia Series, Westview Press, Boulder, Colorado, 1978., ISBN 0-89158-437-4
4ISO 14040 (2006): Environmental management - Life cycle assessment -Principles and framework, International Standard Organization (ISO), Geneve
5ISO 14044 (2006): Environmental management - Life cycle assessment -Requirements and guidelines, International Standard Organization (ISO), Geneve
External links
★ UNEP/SETAC Life Cycle Initiative
★ The European Commission's Directory of LCA services, tools and databases
★ The European Commission's LCA database ELCD (free of charge)
★ Lifecycle.org - links to LCA sites and resources.
★ How Products Impact Natural Systems.
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