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Life Cycle Assessment (LCA)


The growing awareness of the importance of environmental protection, and the possible impacts associated with manufactured and consumed products, has increased the interest in developing methods to better comprehend and reduce these impacts. One of the techniques developed for this purpose is Life Cycle Assessment, LCA.

LCA studies include the environmental aspects and potential impacts throughout the products' life (i.e. cradle-to grave) from raw material acquisition through production, use and disposal. The general categories of environmental impacts that need to be considered include resource use, human health, and ecological consequences.

The life of a product is usually divided into the following life-cycle stages:


For each stage, data on inputs and outputs are collected. Transportation must also be included, either in the stage, that is responsible for the transportation or as a separate stage.

General data on production of materials, electricity production and transportation processes can be found in LCA-databases. The database will automatically calculate all emissions and waste produced in e.g. the production of 1 kg of aluminium.



Emissions are aggregated into impact categories, such as global warming and eutrophication.



Performing an LCA

Performing an LCA is structured into the following phases:




ISO (International Standards Organization) has published standards concerning LCA, ISO/EN 14040-43.


LCA phase 1: Goal and scope definition

In the goal and scope definition, the LCA is planned. Necessary prerequisites for a good outcome is to initially define the exact objective of the LCA, how the result is going to be used, for which geographical area the result should be valid and so on. Having done this, the more detailed planning can take place.

The detailed planning includes definition of the functions of the product system and the boundaries of the product system. The boundaries should be chosen sufficiently narrow, otherwise the LCA can be very time-consuming, and not necessarily more accurate, because of the uncertainties on data.

If the purpose of the LCA is to compare a number of product systems, the boundaries should be the same for all product systems, and cover all major environmental aspects. Further, the functional unit is extremely important when comparing product systems or alternatives.

The functional unit is the object of the assessment and it is introduced in order to keep the comparison fair.

Example:

If two paints are compared, it is unfair to compare one litre of each paint if their quality differs substantially. A functional unit for paint could be: The amount of paint necessary to cover 1 m2 wall for 5 years with certain specifications (of e.g. gloss).

As can be seen, life time is very important in relation to the functional unit. This is very relevant for electronics. Therefore, products cannot be compared 'one-to-one', if the expected life time or other quality parameters differ. The same thoughts should be kept in mind when comparing design alternatives at the sub-product level. If one alternative extends the life time of the product considerably, it may be desirable, even if it looks undesirable in the first place.

Another relevant issue in the goal and scope definition as well as during data collection (inventory) is allocation. Many processes result in several products, and therefore the environmental burdens from the process must be split on the different output products. Example: Several different printed circuit boards are wave-soldered in the same process during a working day. The energy use associated with the wave soldering machinery therefore has to be split on the individual PCBs.

Allocation is a hot topic among LCA specialists. It is agreed that allocation should be made as logical as possible. However, there is controversy as to what is the most logical allocation and what is most logic in different situations. For the example above, allocation could be made based on:

  1. The number of PCBs, which have been wave soldered during the day (because it takes about the same time for one PCB to move through the wave-soldering process).

  2. The area of the PCBs (especially if the PCB area is the determining parameter of the wave-soldering capacity).

  3. The amount of solder added to the PCBs (the more solder, the more the individual PCB should carry of the total load).

  4. The value of the PCBs.

The latter is perhaps not the most logical choice in this situation (but it could be in other), whereas the first three allocation principles could all be relevant.

As allocation is a source of controversy, it is difficult to give short, exact and general guidelines on the best allocation principle. However, it is extremely important to describe and argue for the choice of allocation principles each time a LCA is conducted.


LCA phase 2: Inventory analysis

The inventory analysis involves data collection and calculation of inputs and outputs of the product system. Examples of inputs and outputs are use of resources, emissions to air and water.


LCA phase 3: Impact Assessment

The inputs and outputs constitute the basis of the impact assessment. This phase aims at evaluating the significance of the environmental impacts. A typical procedure would be:


LCA phase 4: Interpretation

The combination of the results from the inventory analysis and the impact assessment facilitate that conclusions and recommendations consistent with goal and scope can be reached.




Relevant literature:

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