Life cycle assessment

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"Cradle-to-grave" redirects here. For other uses, see Cradle to the Grave (disambiguation).

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.

Contents

[edit] 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.

A classic example of an LCA is to determine whether beverage packaging made of glass is more or less burdensome to the environment than plastic bottles. All life cycle phases for both options need to be investigated. For glass bottles those phases are the mining of glass minerals from the lithosphere, bottle production, bottling, all transports, and final disposal. For plastic bottles they are raw oil production, oil refining, polymer production, bottle production, bottling, transports, and final disposal. For all necessary auxiliary materials or services similar process chains need to be considered: for example, a catalyst needed during the polymer production needs to be included with its life cycle pro rata. Ecological interventions generated along these complex process chains are inventoried, like emissions to air, water or soil, resources taken from the biosphere, or land uses. These interventions are then interpreted relating to their severity and compared for both options to make a fair and holistic judgement. Simultaneously it is possible to establish which processes in a product's life cycle are important contributors to damages and gain an understanding on the major determinants of environmental performance of the assessed products.

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.)

[edit] Four main phases

According to the ISO 14040[1] and 14044[2] standards, a Life Cycle Assessment is carried out in four distinct phases.

[edit] 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. For the example of comparing glass vs. plastic bottles, the functional unit could be “1 liter bottle container for refrigerated juices”. Comparing 1 kg of plastic bottles directly with 1 kg of glass bottles, disregarding the packed volume, would not be an appropriate functional unit for the desired functionality of bottles. 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.

[edit] 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 and within study boundaries unit processes that compose the product system. Example 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.

[edit] 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.

[edit] 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 importantly: 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.

[edit] LCA uses and tools

Based on a survey of LCA practitioners carried out in 2006 [3] 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%).

[edit] Variants

[edit] Cradle-to-grave

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.

[edit] Cradle-to-gate

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).

[edit] Cradle-to-Cradle

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).

[edit] Well-to-wheel

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 [1]

[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.[citation needed]

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.

[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.[citation needed]

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

energy Portal
Sustainable development Portal

[edit] References

  1. ^ ISO 14040 (2006): Environmental management - Life cycle assessment -Principles and framework, International Organisation for Standardisation (ISO), Geneve
  2. ^ ISO 14044 (2006): Environmental management - Life cycle assessment -Requirements and guidelines, International Organisation for Standardisation (ISO), Geneve
  3. ^ Cooper, J.S., J. Fava "Life Cycle Assessment Practitioner Survey: Summary of Results," Journal of Industrial Ecology (2006)

[edit] Further reading

  1. 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
  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
  3. Center for Life Cycle Analysis, Columbia University, New York www.clca.columbia.edu
  4. J. Guinée, ed:, Handbook on Life Cycle Assessment: Operational Guide to the ISO Standards, Kluwer Academic Publishers, 2002.

[edit] External links



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