Life cycle assessment

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There exist two primary categories of LCA:
There exist two primary categories of LCA:
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*'''Process LCA''' (also traditional LCA or SETAC LCA) as defined by [[ISO 14000]] standards, involves defining an appropriate scope and systematically accounting for all interactions of product/processes with the environment. It is generally difficult or impossible to define a complete scope, since use of materials and energy purchased from other firms implies additional use of the materials and energy used by that firm's production, transportation, and so on in a long chain.
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*'''[[Process LCA]]''' (also traditional LCA or SETAC LCA) as defined by [[ISO 14000]] standards, involves defining an appropriate scope and systematically accounting for all interactions of product/processes with the environment. It is generally difficult or impossible to define a complete scope, since use of materials and energy purchased from other firms implies additional use of the materials and energy used by that firm's production, transportation, and so on in a long chain.
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*'''Economic Input-Output LCA''', or EIO-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. 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.  
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*'''[[EIO-LCA]]''', 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. 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.  
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* '''Hybrid LCA''' describes approaches to blending data from EIO and process models.
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* '''Hybrid LCA''' describes approaches to blending data from EIO and process 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.  
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=Process LCA=
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There are four stages in the traditional process LCA approach
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*'''Scoping:''' definition of the purpose of the LCA. What is the LCA going to be used for? Comparing two similar products? Determining the effect of a new product on the environment? Is the desired information for internal or external use?
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*'''Inventory:''' quantification of inputs (energy, raw material) and outputs (environmental releases) throughout the life of the product or activity. How much energy is required to produce, distribute, use and dispose the product? What materials are consumed during all the life-cycle stages of a product? What wastes and pollutants are generated?
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*'''Impact Assessment:''' quantitative and/or qualitative assessment of the effect of the environmental loads identified in the inventory component. What are the environmental effects of producing the product? How much landfill space will be required for disposal? How do the pollutants affect the environment: Acid rain, ozone depletion?
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*'''Improvement Assessment:''' assessment of opportunities for improvement of economic impact. Can the amounts of pollutants be reduced? Can the product be reused, recycled, refurbished? Can energy be recuperated from the product by incineration?
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Life-Cycle Assessment deals with a systematic interpretation (qualitatively and quantitatively) of the ‘cradle-to-grave’ interactions between that product and its environment.  Therefore, it is important to understand the model that is used to interpret this progression of the product from cradle-to-grave.  This is the generalized Life-Cycle Model; the product system. 
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The product system is defined by a combination of unit processes that together perform one or more functions.  Unit Processes are analogous to control volumes/systems.  The complex system (product system) is modeled by viewing the life cycle as a system broken down into subsystems (unit processes) that have inputs and outputs that can be both intermediate and elemental.
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==Goal and Scope==
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In order to adequately understand, organize, and relate the results of a Life-Cycle Assessment, the goals and scope must be clearly stated, with all subsequent developments “consistent with the goal and scope”. 
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There is a very specific list of elements that define the scope of an LCA in ISO 14040/14041:
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*The functions of the product system, or, in the case of comparative studies, the systems;
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*The functional unit;
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*The product system to be studied;
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*The product system boundaries;
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*Allocation procedures;
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*Types of impact and methodology of impact assessment, and subsequent interpretation to be used;
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*Data requirements;
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*Assumptions;
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*Limitations;
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*Initial data quality requirements;
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*Type of critical review, if any;
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*Type and format of the report for the study.
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[ISO 14040:1997(E)]
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Defining the system, system function, functional unit, and reference flow is vital; inventory data gathered based on the model developed as defined by the system function is referenced to the functional unit and reference flow.  More importantly, the functional unit and reference flow allow for comparative assertions to be made when more than one system is compared. 
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System function is self-explanatory; it is simply what the system is meant to do.  The functional unit is a clearly defined, measurable unit of this function.  The reference flow is the amount of product that satisfies the intended function as quantified by the reference flow. 
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“EXAMPLE  In the function of drying hands, both a paper towel and an air-dryer system are studied.  The selected functional unit may be expressed in terms of the identical number of pairs of hands dried for both systems.  For each system, it is possible to determine the reference flow, e.g. the average mass of paper or the average volume of hot air required for one hand-dry, respectively.  For both systems, it is possible to compile an inventory of inputs and outputs on the basis of the reference flows.  At its simplest level, in the case of paper towel, this would be related to the paper consumed.  In the case of the air-dryer, this would be largely related to the energy input to the air dryer.” 
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[ISO 14041:1998(E)]
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Defining the system boundaries is accomplished by defining:
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*The unit processes to be included in the product system;
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*The emissions to be measured.
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“Several life cycle stages, unit processes and flows should be taken into consideration, e.g.:”
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*Inputs and outputs in the main manufacturing/processing sequence;
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*Distribution/transportation
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*Production and use of fuels, electricity and heat;
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*Use and maintenance of products;
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*Disposal of process wastes and products;
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*Recovery of used products (including reuse, recycling and energy recovery);
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*Manufacture of ancillary materials;
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*Manufacture, maintenance and decommissioning of capital equipment;
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*Additional operations, such as lighting and heating;
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*Other considerations related to impact assessment (if any).
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[ISO 14041:1998(E)]
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ISO gives a qualitative impression of how boundaries can be drawn: “Resources need not be expended on the quantification of such inputs and outputs that will not significantly change the overall conclusions of the study.” [ISO 14041:1998(E)]  In addition, cutoffs can be made by marking a threshold of mass, energy, or specific emissions as a percentage of the total for a unit process, and excluding inputs and outputs that do not meet that threshold. 
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Data quality is an important issue for LCA, and ISO makes reference to the following as issues to address in the scope:
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*Time
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*Geography
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*Technology
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*Source
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*Measured/Calculated/Estimated
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*Precision
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*Completeness
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*Representativeness
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*Consistency
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*Reproducability
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==Life Cycle Inventory Analysis==
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The goal and scope provide the framework for the inventory. During preparation for data collection, the full and detailed sequence of unit processes with inputs and outputs is developed.  Any other relevant issues for data collection must also be addressed (units, responsibility, data categories, etc.).  ISO 14041 contains a sample data collection sheet. 
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Data collection itself is carried out, through data gathering on site or through published sources (which must of course be properly referenced). 
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“Following the data collection, calculation procedures are needed to generate the results of the inventory of the defined system for each unit process and for the defined functional unit of the product system that is to be modeled.” [ISO 14041:1998(E)]  Calculating is broken down into the following:
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*'''Validation:'''
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**Mass/energy balances (as a check);
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**Comparative analyses of emissions factors (as a check);
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**Reporting and treatment of data gaps.
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*'''Relating data to unit processes:'''
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**“For each unit process, an appropriate reference flow shall be determined (e.g. 1 kg of material or 1 MJ of energy).  The quantitative input and output data of the unit process shall be calculated in relation to this reference flow.”  [ISO 14041:1998(E)]
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*'''Relating data to functional unit and data aggregation:'''
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**“ … normalizing the flows of all unit processes in the system to the functional unit.  The calculation should result in all system input and output data being referenced to the functional unit.” [ISO 14041:1998(E)]
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*'''Refining the system boundaries:'''
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**Sensitivity analysis should be used to validate scope decisions;
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**Refine and re-collect relevant data if necessary.
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Allocation deals with the inherent nature of coupled life cycles in industrial activity.  Multiple product systems exist within any system to be studied, and allocation procedures define how they are linked to one product versus another.  Allocation must be done according to a more rigid set of rules than most of the other elements in the LCI according to ISO.  As such, consult the standard itself for further information.
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==Life Cycle Impact Assessment==
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The purpose of the Life-Cycle Impact Assessment (LCIA) is to assign quantities of environmental relevance to the Life-Cycle Inventory Results.  ISO defines the following stages in the progression from LCI results to indicator results:
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*'''Selection of:'''
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**Impact categories;
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**Category indicators;
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**Characterization models;
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**Category endpoints.
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*'''Classification:'''
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**“Assignment of LCI results to the impact categories.”  [ISO 14042:2000(E)]
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*'''Characterization:'''
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**Calculation of category indicator results;
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*'''Optional:'''
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**Normalization (“Calculation of the magnitude of category indicator results relative to reference information” [ISO 14042:2000(E)]);
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**Grouping;
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**Weighting;
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**Data quality analysis.
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The standard discusses in detail criteria for the selection of impact categories, category indicators, and characterization models.  It is best to access the standard for this information. 
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LCI results are assigned to impact categories (classification) in order to make the environmental issues embedded within the inventory apparent. 
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Characterization: “The calculation involves the conversion of LCI results to common units [through characterization factor] and aggregation of converted results within the impact category [aggregation results in the indicator result].”  [ISO 14042:2000(E)]
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With a body of indicator results compiled from the inventory, a full Life-Cycle Impact Profile is composed. 
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The optional activities are left to the standard.
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==Life Cycle Interpretation==
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“The objectives of life cycle interpretation are to analyse results, reach conclusions, explain limitations and provide recommendations based on the findings of the preceding phases of the LCA or LCI study and to report the results of the life cycle interpretation in a transparent manner.”  [ISO 14043:2000(E)]
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The elements of a Life-Cycle Interpretation are defined as:
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*Identification of the significant issues based on the results of the LCI and LCIA phases of LCA;
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*Evaluation which considers completeness, sensitivity and consistency checks;
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*Conclusions, recommendations and reporting.
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[ISO 14043:2000(E)]
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==Some Criticisms of (Process) LCA==
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* There is lack of comprehensive data for LCA.
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* Data reliability is questionable.
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* Defining problem boundaries for LCA is controversial and arbitrary. Different boundary definitions will lead to different results.
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* LCA is too expensive and slow for application in the design process.
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* There is no single LCA method that is universally agreed upon and acceptable.
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* Conventional, SETAC-type LCA usually ignores indirect economic and environmental effects.
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* Published LCA studies rarely incorporate results on a wide range of environmental burdens; typically only a few impacts are documented.
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* Equally credible analyses can produce qualitatively different results, so the results of any particular LCA cannot be defended scientifically.
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* Modeling a new product or process is difficult and expensive.
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* LCA cannot capture the dynamics of changing markets and technologies.
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* LCA results may be inappropriate for use in eco-labeling because of differences in interpretation of results.
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=Economic Input-Output LCA=
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Economic Input-Output LCA, or EIO-LCA involves use of aggregate sector-level data quantifying how much environmental impact can be directly attributed to each sector of the economy and how much each sector purchases from other sectors in producing its output. Combining such data sets can enable accounting 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 traditional process [[LCA]]. The EIO-LCA software traces out the various economic transactions, resource requirements and environmental emissions (including all the various manufacturing, transportation, mining and related requirements) required for producing a particular product or service.
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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. To the extent that the good or service of interest is representative of a sector, EIOLCA can provide very fast estimates of full supply chain implications for that good or service. The [http://www.eiolca.net eiolca.net] website is a freely available software implementation of EIOLCA.
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==Background==
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Economic input-output analysis was developed by Wassily Leonteif (who won a Nobel Price in 1973). It quantifies the interrelationships among sectors of an economic system, enabling identification of direct and indirect economic inputs of purchases. The [[Green Design Institute]] extended this concept by including data about environmental and energy analysis from each sector.
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Input-output transactions tables, which track flows of purchases between sectors, are collected by the federal government in the United States. EIO works as follows: If <math>X_{ij}</math> represents the amount that sector <math>j</math> purchases from sector <math>i</math> and <math>y_i</math> is the "final demand" for output from sector <math>i</math> (i.e., the amount of output purchased for consumption, as opposed to purchased by other businesses as supplies for more production), then the total output <math>x_i</math> from sector <math>i</math> includes final demand plus output sold to other sectors:
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<math>x_i = y_i + \sum_jX_ij</math>
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If we define <math>A_{ij}</math> as the normalized production for each sector, so that <math>A_{ij} = X_{ij}/x_j</math>, then
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<math>x_i = y_i + \sum_jA_{ij}x_j</math>
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In vector notation
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<math>\mathbf{x} = \mathbf{y} + \mathbf{Ax}</math>
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<math>\mathbf{y} = (\mathbf{I - A})\mathbf{x}</math>
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<math>\mathbf{x} = (\mathbf{I - A})^{-1}\mathbf{y}</math>
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This result indicates that knowing only final output from each sector <math>\mathbf{y}</math> and the normalized IO matrix <math>\mathbf{A}</math>, one can calculate the total implied production <math>\mathbf{x}</math> from each sector of the economy. If data are available on a particular emission (or other attribute of interest) from each sector of the economy, then a vector <math>\mathbf{r}</math> can be compiled to represent emissions per $ output from each sector. Total emissions <math>z</math> associated with a final demand of <math>\mathbf{y}</math> can then be calculated as:
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<math>z = \mathbf{r}^T\mathbf{x} = \mathbf{r}^T(\mathbf{I - A})^{-1}\mathbf{y}</math>
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For a set of emissions and other attributes, <math>\mathbf{r}</math> becomes a matrix <math>\mathbf{R}</math> (rows are sectors and columns are environmental attributes of interest), and the output is a vector
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<math>\mathbf{z} = \mathbf{R}^T\mathbf{x} = \mathbf{R}^T(\mathbf{I - A})^{-1}\mathbf{y}</math>
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This simple result enables very quick analysis taking into account the entire supply chain requirements needed to provide a specific output. The equations are based on average data in the current economy, but they can be used to make predictions for marginal changes in output (such as one more unit of a particular product) if
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# average output and marginal output are assumed to be sufficiently close (i.e., the impact of ''one more unit'' = the impact of ''the average unit''), and
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# the marginal change in final output <math>\mathbf{y}</math> is representative of the product of interest (ex: if the product will use electricity from wind energy exclusively, then using the electricity sector, which is dominated by coal, would yield a poor estimate).
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==EIOLCA Software==
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The Economic Input Output-Life Cycle Assessment software, available at [http://www.eiolca.net], traces out the various economic transactions, resource requirements and environmental emissions associated with the production of a particular product or service. The model captures all the various manufacturing, transportation, mining and related requirements to produce a product or service. For example, you might wish to trace out the implications of purchasing $ 46,000 of reinforcing steel and $ 104,000 of concrete for a kilometer of roadway pavement. Environmental implications of these purchases can be estimated using EIO-LCA. The current (1997) model is based upon the Department of Commerce's 491 sector industry input-output model of the US economy.
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The page on [[using EIOLCA to evaluate a product]] contains an introductory guide.
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=Hybrid LCA=
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Hybrid LCA refers to combining process LCA and EIOLCA. One example might be to 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.  
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* 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.
* 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.
* [[ISO 14000]] Standards
* [[ISO 14000]] Standards
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* [[Design for environment]]
[[category:design analysis tools]]
[[category:design analysis tools]]
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[[category:green design]]

Current revision

Example processes involved in the life cycle of a coffee maker (image used with permission)
Example processes involved in the life cycle of a coffee maker (image used with permission)

Life Cycle Assessment is a technique for assessing the environmental aspects and potential impacts associated with a product or service, by

  • compiling an inventory of relevant inputs and outputs of the system;
  • evaluating the potential environmental impacts associated with those inputs and outputs;
  • interpreting the results of the inventory analysis and impact assessment phases in relation to the objectives of the study.
Example showing the network of processes involved in producing a product or service. Process LCA requires defining a system boundary, which means ignoring processes that fall outside the boundary. EIO-LCA includes the entire supply chain using sector averages.
Example showing the network of processes involved in producing a product or service. Process LCA requires defining a system boundary, which means ignoring processes that fall outside the boundary. EIO-LCA includes the entire supply chain using sector averages.

There exist two primary categories of LCA:

  • Process LCA (also traditional LCA or SETAC LCA) as defined by ISO 14000 standards, involves defining an appropriate scope and systematically accounting for all interactions of product/processes with the environment. It is generally difficult or impossible to define a complete scope, since use of materials and energy purchased from other firms implies additional use of the materials and energy used by that firm's production, transportation, and so on in a long chain.
  • EIO-LCA, 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. 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 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.


Links

Retrieved from "https://wiki.ece.cmu.edu/ddl/index.php/Life_cycle_assessment"
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