Consequential and attributional approaches to LCA: a guide to policy makers with specific reference to greenhouse gas LCA of biofuels

Apr 2008

Policies for climate change mitigation are increasingly being informed by the results of greenhouse gas life cycle assessments (GHG-LCAs) of alternative energy carriers and delivery pathways. GHG-LCAs are of particular relevance to the biofuel sector because, within the EU, it is expected that incentives (in the form of obligation certificates) will be related to the life cycle GHG savings relative to conventional fossil fuels. The current use of GHG-LCA for biofuel carbon reporting tends not to distinguish between two different LCA approaches: consequential LCA (CLCA) and attributional LCA (ALCA). These two approaches aim to answer different questions, and failure to distinguish them can result in the wrong method being applied, a mixture of the two approaches within a single assessment, or misinterpretation of results.
Attributional LCA (ALCA) provides information about the impacts of the processes used to produce (and consume and dispose of) a product, but does not consider indirect effects arising from changes in the output of a product. ALCA generally provides information on the average unit of product and is useful for consumption-based carbon accounting.
Consequential LCA (CLCA) provides information about the consequences of changes in the level of output (and consumption and disposal) of a product, including effects both inside and outside the life cycle of the product. CLCA models the causal relationships originating from the decision to change the output of the
product, and therefore seeks to inform policy makers on the broader impacts of policies which are intended to change levels of production.
This paper describes the key differences between CLCA and ALCA. It then discusses the extent to which the Renewable Fuels Agency (RFA) and Renewable Energy Directive (RED) carbon reporting guidelines use an attributional or consequential approach, or a combination of the two.

 
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