This paper, co-authored by the FCRN’s Tara Garnett and John Lynch of the Oxford Livestock, Environment and People programme, identifies and discusses four challenges associated with attributional life cycle assessment.
The four challenges are:
- Detailed data on food production is often gathered from specific systems or locations and may not be reliable when scaled up to national or global levels. Many LCAs depend on the assumptions made by the modeller.
- The standard indicators used by LCAs to report health and environmental impacts do not necessarily correspond to actual harm done, since the harm done by (say) nitrogen runoff depends on many factors, such as water flows and other pollutants entering the same region.
- It can be hard to compare results from different studies because of the difficulty of choosing an appropriate functional unit, e.g. reporting impacts per kg of food, per calorie or per 100 g of protein.
- Consequential analyses of food scenarios take into account the effect of changing supply and demand as well as look at marginal opportunity costs (e.g. for the carbon stored by different land uses), in a way that attributional life cycle assessments do not.
The authors conclude that while attributional life cycle assessments do have a use, researchers must acknowledge the limitations of them.
Lynch, J. and Garnett, T., 2020. Can attributional life cycle assessment tell us how to farm and eat sustainably? Integrated Environmental Assessment and Management, 16(3).
Read the full paper here. See also the Foodsource resource The value and limitations of life cycle assessment.