The influence of system boundaries and baseline in climate impact assessment of forest products
This article aims to explore how different assumptions about system boundaries and setting of baselines for forest growth affect the outcome of climate impact assessments of forest products using life cycle assessment (LCA), regarding the potential for climate impact mitigation from replacing non-forest benchmarks. This article attempts to explore how several assumptions interact and influence results for different products with different service life lengths.
Four products made from forest biomass were analysed and compared to non-forest benchmarks using dynamic LCA with time horizons between 0 and 300 years. The studied products have different service lives: butanol automotive fuel (0 years), viscose textile fibres (2 years), a cross-laminated timber building structure (50 years) and methanol used to produce short-lived (0 years) and long-lived (20 years) products. Five calculation setups were tested featuring different assumptions about how to account for the carbon uptake during forest growth or regrowth. These assumptions relate to the timing of the uptake (before or after harvest), the spatial system boundaries (national, landscape or single stand) and the land-use baseline (zero baseline or natural regeneration).
Results and discussion
The implications of using different assumptions depend on the type of product. The choice of time horizon for dynamic LCA and the timing of forest carbon uptake are important for all products, especially long-lived ones where end-of-life biogenic emissions take place in the relatively distant future. The choice of time horizon is less influential when using landscape- or national-level system boundaries than when using stand-level system boundaries and has greater influence on the results for long-lived products. Short-lived products perform worse than their benchmarks with short time horizons whatever spatial system boundaries are chosen, while long-lived products outperform their benchmarks with all methods tested. The approach and data used to model the forest carbon uptake can significantly influence the outcome of the assessment for all products.
The choices of spatial system boundaries, temporal system boundaries and land-use baseline have a large influence on the results, and this influence decreases for longer time horizons. Short-lived products are more sensitive to the choice of time horizon than long-lived products. Recommendations are given for LCA practitioners: to be aware of the influence of method choice when carrying out studies, to use case-specific data (for the forest growth) and to communicate clearly how results can be used.
KeywordsBiogenic carbon Carbon footprint Carbon storage Dynamic LCA Timing of emissions Wood-based product
Cumulative climate impact relative to the impact of 1 kg CO2 emission at year 0
Global warming potential
Indirect land-use change
Intergovernmental Panel for Climate Change
Life cycle assessment
Product environmental footprint
This publication is the result of a project carried out within the collaborative research program Renewable transportation fuels and systems (Förnybara drivmedel och system) [Project no. 39588-1]. The authors would also like to thank the anonymous reviewers for their valuable input.
The project has been financed by the Swedish Energy Agency and f3 – Swedish Knowledge Centre for Renewable Transportation Fuels (see www.f3centre.se/samverkansprogram). Additional work by the corresponding author has been carried out with financial support from Formas (project EnWoBio 2014-172).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- Cherubini F, Peters GP, Berntsen T, Strømman AH, Hertwich E (2011) CO2 emissions from biomass combustion for bioenergy: Atmospheric decay and contribution to global warming. GCB Bioenerg 3(5):413–426. https://doi.org/10.1111/j.1757-1707.2011.01102.x
- Cherubini F, Bright RM, Strømman AH (2012) Site-specific global warming potentials of biogenic CO2 for bioenergy: contributions from carbon fluxes and albedo dynamics. Environ Res Lett 7(4). https://doi.org/10.1088/1748-9326/7/4/045902
- European Commission (2010) Communication from the Commission on the practical implementation of the EU biofuels and bioliquids sustainability scheme and on counting rules for biofuels, 2010/C 160/02. http://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:52010XC0619(02)&from=EN. Accessed July 2015
- European Commission (2013) Commission recommendation of 9 April 2013 on the use of common methods to measure and communicate the life cycle environmental performance of products and organisations. (2013/179/EU). http://eur-lex.europa.eu/legal-content/EN/ALL/?uri=OJ:L:2013:124:TOC. Accessed July 2015
- IPCC (2006) Guidelines for national greenhouse gas inventories. Prepared by the National Greenhouse Gas Inventories Programme. In: Eggleston HS, Buendia L, Miwa K, Ngara T, Tanabe K (eds) Volume 4—Agriculture, forestry and other land use, Chapter 4—forest land, Table 4.12. IGES, JapanGoogle Scholar
- IPCC (2014) Climate change 2014: synthesis report. In: Core Writing Team, Pachauri RK, Meyer LA (eds) Contribution of working groups I, II and III to the fifth assessment report of the intergovernmental panel on climate change. IPCC, Geneva 151 pGoogle Scholar
- Matthews R et al (2014) Review of literature on biogenic carbon and life cycle assessment of forest bioenergy. Final Task 1 report, DG ENER project, ‘Carbon impacts of biomass consumed in the EU’. https://ec.europa.eu/energy/sites/ener/files/2014_biomass_forest_research_report_.pdf. Accessed May 2015
- Methanol Institute (2011) How is methanol made? http://www.methanol.org/methanol-basics/overview/how-is-methanol-made-.aspx. Accessed August 2015
- Oerlikon Textile (2010) The fiber year 2009/10. A world survey on textile and nonwovens industry. http://www.indotextiles.com/download/Fiber%20Year%202009_10.pdf. Accessed August 2015
- Sandin G, Røyne F, Peñaloza D, Staffas L, Svanström M (2015) The method’s influence on climate impact assessment of biofuels and other uses of forest biomass. f3 report 2015:10, f3 The Swedish Knowledge Centre for Renewable Transportation Fuels, Sweden. Available at www.f3centre.se. Accessed January 2015
- Skogsstyrelsen (2015) Forest and forestry in Sweden. Figure: “Annual cut and annual forest increment” (page 5). Available at: https://www.skogsstyrelsen.se/globalassets/in-english/forests-and-forestry-in-sweden_2015.pdf, Stockholm, Sweden
- Soimakallio S, Brandão M, Ekvall Cowie A, Finnveden G, Erlandsson M, Koponen K, Karlsson PE (2016) On the validity of natural regeneration in determination of land use baseline [Letter to the editors]. Int J Life Cycle Assess 20(10):1–3Google Scholar