LCAs are used for informing business strategies, research and development, design, labelling and product declarations. The report includes an analysis of the energy costs, and attempts to come to a conclusion by weighting the various impacts by various categories, such as human toxicity, smog, global warming, eutrophication.
Life Cycle Impact Assessment
The Life Cycle Impact Assessment (LCIA) is the third phase of four in a formal LCA.
The LCIA allocates the results of the LCI (Life Cycle Inventory) to a number of different impact categories. These include: climate change, eutrophication, human toxicity, acidification, ozone depletion, ecotoxicity, ionising radiation, photochemical ozone formation, landuse, water depletion, and resource depletion.
This phase includes (usually implicit) an evaluation of the emissions, usually allocated to an impact category. A process of normalisation can be used to adjust the importance of the impacts, relative to, for example, the number of inhabitants of the affected area. This last step makes the presentation of the results simpler and more meaningful in context.
In order to answer the question of how great the impact on the environment resulting from this product or service is, the impact assessment of the results of the inventory are grouped by scientific criteria into different impact categories.
The major impact categories are: global warming, ozone depletion, acidification, eutrophication, photochemical ozone creation, abiotic depletion potential (Abiotic Depletion Factor, ADF) for non-fossil and fossil resources.
The modelling can be based on a selection of so-called mid-points (impact categories), or end-points, such as human health, protection of natural resources, and ecosystem quality. These end-points can be weighted to provide a means of aggregating the impacts of different types.
The ecological scarcity method is used in this capacity for a "difference to tolerance" calculation.
[Environment: LCA] Eco-Points (EP). In an LCA using the Ecological Scarcity Method, the eco-point system allows weighting of the ecological factors per unit of impact.
A by-product is not the intended aim of the process, but has a net value to the producer, so is not discarded, as is the case with waste, which is a net cost. The revenue from by-products are used to off-set the costs of the primary product. An example is flue scrubbing: the primary aim is the removal of pollutants from exhaust air, and a saleable by-product of calcium carbonate (building plaster) may result.
Cumulative Energy Demand
Cumulative Energy Demand is a method employed in LCA to simplify energy flows to predict and evaluate the environmental burden of a process, such as commodity production. The calculation of the CED is useful when making comparative studies of primary energy consumption of technical processes and product cycles.
VDI Guideline 4600:
In ISO 14040 the term "product" is replaced by "economic good", which can be either a product or a service.
CED = CEDM + CEDU + CEDD
where M = manufacture, U = use, D = disposal. The transport, as well as "half-finished, auxiliary and operating materials", should be included. Use includes maintenance.
CED = CPE + CNE
where CPE = cumulative process energy cost
CNE = cumulated non-energy cost
VDI Guideline 4600 defines CNE as:
CNE = NEU + CBE
where NEU = non-energy use (of energy resources)
CBE = compound-bonded energy content (of materials)
Comments: primary energy assessments for both groups, with distinction made between energy resources and combustible materials. CNE calculates the two sub-divisions together. The weighting factors are derived from the effective use (e.g. if 80% of the primary energy is lost as heat during a process, then gt = 0.2 ).