Life-cycle assessment (LCA) studies the environmental aspects and potential impacts throughout a product's life from raw material acquisition, through production, use and disposal.

Different aspects and limitations of LCA methodology are discussed. New methods for describing landfilling and incineration of solid waste in LCAs are suggested. A new method for characterising resource depletion is developed based on exergy consumption. Exergies of several metal ores and other natural resources are calculated. Life-cycle inventory data from different databases are compared in order to evaluate the uncertainties involved in typical LCAs and rules of thumb are suggested. Values involved in the valuation element of an LCA are discussed.

Existing case studies are evaluated and results are compared, with the aim of evaluating and determining the type of information current LCAs can and can not produce. LCAs on recycling and incineration with energy recovery of paper packaging materials are used as an example. It is shown that some results are consistent in all studies. Other apparently conflicting results turn out to be consistent if consideration is given to some key assumptions made. In a smaller study, some recent LCAs on flooring materials are also reviewed.

Results of LCAs can have direct policy implications and be useful in identifying areas for improvement. None of the case studies can however show the overall environmental preference for any of the alternatives compared, and it is suggested that this is typical. It is argued that even in situations where one product actually is environmentally preferable to another, this will normally not be possible to show by any method. This has some policy implications. For example, if policy changes require that it must be shown that one product is more (or less) environmentally preferable to another before any action can be taken, then it is likely that no action will ever take place. It must therefore be possible to take decisions on a less rigid basis.