Stable forest carbon stocks support current assumption of biogenic carbon neutrality in the case of European-manufactured beverage cartons

Abstract

Purpose: Life cycle assessments (LCAs) of forest-based products, such as beverage cartons, generally demonstrate lower greenhouse gas emissions than fossil fuel-based alternatives and often contain the implicit assumption that removal of carbon dioxide (CO2) by a growing forest and emission of CO2 at the end of a product’s life cancel each other out such that the net emission is zero. This study aims to test the validity of this assumption of biogenic CO2 neutrality in relation to beverage cartons by examining whether carbon stocks of the source forests are stable. The fact that over 95 % of the cartonboard used in their manufacture is sourced from the boreal forests of Sweden and Finland provides a scenario with a straightforward relationship between forest and product thus avoiding issues surrounding the complexities of global supply chains. Methods: The reviewed LCAs conclude that beverage cartons have lower greenhouse gas emissions than alternatives, although non-forest-derived components such as plastic caps and aluminium laminate often contribute disproportionately to those emissions. We discuss issues surrounding the assumption of biogenic CO2 neutrality and explore the factors that influence carbon stocks in boreal forests that supply much of the raw material for beverage cartons. Results and discussion: An analysis of published rates of carbon sequestration in the managed forests of Finland and Sweden reveals that forest carbon is stable under current harvest rates. This lends support to the assumption of biogenic CO2 neutrality in the case of beverage cartons produced from these forests. We conclude that greenhouse gas emissions would not change if an LCA included forest carbon. However, future forest dynamics and thus carbon stocks are predicted to alter in response to climate change, for example, which will have knock on effects for greenhouse gas emissions from packaging derived from forests. Conclusions: This review combines current thinking on inclusion of forest carbon in LCAs with an analysis of issues that will influence carbon stocks in managed forests. Although current assumptions of biogenic CO2 neutrality are valid in the case of European-manufactured beverage cartons, we argue that this assumption needs to be explicitly addressed in LCAs. While there is no accepted methodology for integrating biogenic forest carbon uptake into LCA, our assessment of current trends in forest carbon stocks allows for assumptions of biogenic CO2 neutrality to be tested, although our approach may not be practical for more complex supply chains.