Life cycle assessment

Life cycle assessment

A life cycle assessment (LCA, also known as life cycle analysis, ecobalance, and cradle-to-grave analysis) is the investigation and valuation of the environmental impacts of a given product or service caused or necessitated by its existence.

Common procedures

The goal of LCA is to compare the full range of environmental damages assignable to 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 necessary or caused by the product's existence. The sum of all those steps - or phases - 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. Common categories of assessed damages are global warming (greenhouse gases), acidification, smog, ozone layer depletion, eutrophication, eco-toxicological and human-toxicological 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.)

Four main phases

According to the ISO 14040 [ISO 14040 (2006): Environmental management - Life cycle assessment -Principles and framework, International Organisation for Standardisation (ISO), Geneve] and 14044 [ISO 14044 (2006): Environmental management - Life cycle assessment -Requirements and guidelines, International Organisation for Standardisation (ISO), Geneve] standards, 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 so-called "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 are included in the LCA and must reflect the goal of the study. In recent years, two additional 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 data collection and modeling of the product system, as well as description and verification of data. This encompasses all data related to environmental (e.g. CO2) and technical (e.g. intermediate chemicals) quantities for all relevant unit processes within the study boundaries that compose the product system. Examples of inputs and outputs quantities 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 land use can also be included.

Usually Life Cycle Assessments inventories and modeling are carried out using dedicated software packages. Depending of the software package used it is possible to model life cycle costing and life cycle social impacts in parallel with environmental life cycle.

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 according 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.


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 importantly: what can be learned from 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.

LCA uses and tools

Based on a survey of LCA practitioners carried out in 2006 [ Cooper, J.S., J. Fava "Life Cycle Assessment Practitioner Survey: Summary of Results," Journal of Industrial Ecology (2006) ] most life cycle assessments are carried out with dedicated software packages. 58% of respondents used GaBi software, 31% used SimaPro and 11% a series of other tools. According to the same survey, LCA is mostly used to support business strategy (18%) and R&D (18%), as input to product or process design (15%), in education (13%) and for labeling or product declarations (11%).



Cradle-to-grave is the full Life Cycle Assessment from manufacture ('cradle') to use phase and disposal phase ('grave'). 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. After 40 years the cellulose fibers are replaced and the old fibres are disposed of, possibly incinerated. All inputs and outputs are considered for all the phases of the life cycle.


Cradle-to-gate is an assessment of a "partial" product life cycle from manufacture ('cradle') to the factory gate, i.e. before it is transported to the consumer. The use phase and disposal phase of the product are usually omitted. Cradle-to-gate assessments are sometimes the basis for environmental product declarations (EPD).


Cradle-to-cradle is a specific kind of cradle-to-grave assessment, where the end-of-life disposal step for the product is a recycling process. From the recycling process originate new, identical products (e.g. glass bottles from collected glass bottles), or different products (e.g. glass wool insulation from collected glass bottles).


Gate-to-Gate is a partial LCA looking at only one value-added process in the entire production chain.


Well-to-wheel is the specific LCA of the efficiency of fuels used for road 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 28 mpg 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 []

Economic Input-Output Life Cycle Assessment

EIOLCA, or Economic Input-Output LCA involves use of aggregate sector-level data on how much environmental impact can be attributed to each sector of the economy and how much each sector purchases from other sectors. [Hendrickson, C. T., Lave, L. B., and Matthews, H. S. (2005). "Environmental Life Cycle Assessment of Goods and Services: An Input-Output Approach", Resources for the Future Press.] Such analysis can account for long chains (for example, building an automobile requires energy, but producing energy requires vehicles, and building those vehicles requires energy, etc.), which somewhat alleviates the scoping problem of process LCA; however, EIO-LCA relies on sector-level averages that may or may not be representative of the specific subset of the sector relevant to a particular product.

Hybrid LCA describes approaches to blending data from EIO and process-based models. For example, one might use process LCA to capture all of the aspects that can be measured within the scope of the study and use EIOLCA to capture the supply chain outside of the system boundary.

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. Fact|date=January 2008

Another new concept that flows from life cycle assessments is Energy Cannibalism. Energy Cannibalism refers to an effect where rapid growth of an entire energy-intensive industry creates a need for energy that uses (or cannibalizes) the energy of existing power plants. Thus during rapid growth the industry as a whole produces no energy because new energy is used to fuel the embodied energy of future power plants.


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.Fact|date=December 2007

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.

ee also

* Anthropogenic metabolism
* Biofuel
* Carbon footprint
* Design for Environment
* End-of-life (product)
* Greenhouse gas
* GREET Model
* Industrial Ecology
* ISO 15686


Further reading

# 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
# Center for Life Cycle Analysis, Columbia University, New York
# J. Guinée, ed:, "Handbook on Life Cycle Assessment: Operational Guide to the ISO Standards", Kluwer Academic Publishers, 2002.
# Hendrickson, C. T., Lave, L. B., and Matthews, H. S. (2005). "Environmental Life Cycle Assessment of Goods and Services: An Input-Output Approach", Resources for the Future Press.

External links

* [ EIME, Bureau Veritas' leading Ecodesign/Life Cycle Assessment Tool for consumer and industrial products]
* [ 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)]
* [ - links to LCA sites and resources] .
* [ Department Life Cycle Engineering] - LBP – University of Stuttgart.
* [ How Products Impact Natural Systems] .
* [ Embodied Energy: Life Cycle Assessment] . Your Home Technical Manual. A joint initiative of the Australian Government and the design and construction industries.
* [ LCA research at the Center for Environmental Sciences, Leiden University]
* [ Economic Input-Output Life Cycle Assessment Model at Carnegie Mellon University]

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