Biogenic Carbon and Temporary Storage Addressed with Dynamic Life Cycle Assessment

Abstract

Key words:carbon footprint carbon storage climate change global warming industrial ecology time Summary A growing tendency in policy making and carbon footprint estimation gives value to temporary carbon storage in biomass products or to delayed greenhouse gas (GHG) emissions. Some life cycle-based methods, such as the British publicly available specification (PAS) 2050 or the recently published European Commission's International Reference Life Cycle Data System (ILCD) Handbook, address this issue. This article shows the importance of consistent consideration of biogenic carbon and timing of GHG emissions in life cycle assessment (LCA) and carbon footprint analysis. We use a fictitious case study assessing the life cycle of a wooden chair for four end-of-life scenarios to compare different approaches: traditional LCA with and without consideration of biogenic carbon, the PAS 2050 and ILCD Handbook methods, and a dynamic LCA approach. Reliable results require accounting for the timing of every GHG emission, including biogenic carbon flows, as soon as a benefit is given for temporarily storing carbon or delaying GHG emissions. The conclusions of a comparative LCA can change depending on the time horizon chosen for the analysis. The dynamic LCA approach allows for a consistent assessment of the impact, through time, of all GHG emissions (positive) and sequestration (negative). The dynamic LCA is also a valuable approach for decision makers who have to understand the sensitivity of the conclusions to the chosen time horizon.Volume 17, Number 1 potentials (GWPs) with a fixed time horizon. Another topical issue regarding the assessment of GHG emissions is the consideration of biogenic carbon, for which there is no consensus among different methods. Using a fictitious case study comparing different approaches, the objective of this article is to show that the results of a life cycle GHG assessment are sensitive to the assumptions regarding the timing of emissions and the consideration of biogenic carbon, and that dynamic LCA is the preferred approach to address these issues consistently.

Exploring the climate impact effects of increased use of bio-based materials in buildings

“…This is consistent with the results obtained by Fouquet et al [14] and Levasseur et al. [15], where it was also found that timing of the forest growth significantly affects the outcome of this kind of study. Similarly, in the study by Fouquet et al [15] where single-family houses were analyzed, the difference between a concrete house and a timber alternative varies when a dynamic approach is applied to calculate climate impacts, even though the ranking between them stays the same, which is also consistent with the results obtained in this study.…”

“…[15], where it was also found that timing of the forest growth significantly affects the outcome of this kind of study. Similarly, in the study by Fouquet et al [15] where single-family houses were analyzed, the difference between a concrete house and a timber alternative varies when a dynamic approach is applied to calculate climate impacts, even though the ranking between them stays the same, which is also consistent with the results obtained in this study. This study and the study by Fouquet et al [14] differ not only in the type of building analyzed but also in the assumptions explored besides the time horizon and timing of the forest carbon sequestration.…”

Comparative assessment for biogenic carbon accounting methods in carbon footprint of products: a review study for construction materials based on forest products

“…There are however, some differences if only the carbon contained in the harvested stem is included or if other pools like below-ground carbon are included. Levasseur et al (2013) requires the inventory result (sum of the positive and negative emissions) of the given GHG for each year (in kg) for the time horizon.…”

“…The methodology developed in Levasseur et al (2010) and applied in Levasseur et al (2013), proposes the inclusion of time series in the LCA calculations. This is defined by the authors as a dynamic LCA.…”

Climate Change Mitigation Potential of Wood Use in Civil Engineering in Japan Based on Life-Cycle Assessment

“…As a result, the biogenic carbon balance was agreed to be consequently omitted. However, this widely used assumption about carbon neutrality is criticized because it ignored a significant time lag between biogenic carbon absorption and emissions that is caused by temporary carbon storage [4,15,18,[39][40][41]. Regarding time change, wood continues to store carbon for a certain period, and the timing of wood incineration or biodegradation and growth in forests varies.…”