Comparison of 16 national methods in the life cycle
assessment of carbon storage in wood products in a
reference building

C M Ouellet-Plamondon, M Balouktsi, L Delem, G Foliente, N Francart, A Garcia-Martinez, E Hoxha, T Lützkendorf, F Nygaard Rasmussen, Bruno Peuportier, et al.

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► To cite this version:

C M Ouellet-Plamondon, M Balouktsi, L Delem, G Foliente, N Francart, et al. Comparison of 16 national methods in the life cycle assessment of carbon storage in wood products in a reference building. World Sustainable Built Environment 2024, Jun 2024, Virtual conference, Australia. pp.012059, 10.1088/1755-1315/1363/1/012059. [hal-04869501](https://hal.science/hal-04869501v1)

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Comparison of 16 national methods in the life cycle assessment of carbon storage in wood products in a reference building

To cite this article: C M Ouellet-Plamondon et al 2024 IOP Conf. Ser.: Earth Environ. Sci. 1363 012059

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# Comparison of 16 national methods in the life cycle assessment of carbon storage in wood products in a reference building

C M Ouellet-Plamondon<fnref n="1" />*, M Balouktsi<fnref n="2" />,<fnref n="11" />, L Delem<fnref n="3" />, G Foliente<fnref n="4" />, N Francart<fnref n="5" />,<fnref n="11" />, A Garcia-Martinez<fnref n="6" />, E Hoxha<fnref n="7" />,<fnref n="11" />, T Lützkendorf<fnref n="2" />, F Nygaard Rasmussen<fnref n="8" />, B Peuportier<fnref n="9" />, J Butler<fnref n="10" />, H Birgisdottir<fnref n="11" />, L Bragança<fnref n="12" />, D Dowdell<fnref n="10" />, M Dixit<fnref n="13" />, V Gomes<fnref n="14" />, M Gomes da Silva<fnref n="15" />, J Carlos Gómez<fnref n="6" />, M Kjendseth Wiik<fnref n="16" />, M Carmen Llatas Olivier<fnref n="6" />, R Mateus<fnref n="12" />, L M Pulgrossi<fnref n="14" />, M Röck<fnref n="7" />,<fnref n="17" />, M Ruschi Mendes Saade<fnref n="7" />, A Passer<fnref n="7" />, D Satola<fnref n="8" />, S Seo<fnref n="4" />, B Soust-Verdaguer<fnref n="6" />,<fnref n="7" />, J Veselka<fnref n="18" />, M Volf<fnref n="18" />, X Zhang<fnref n="19" />,<fnref n="20" />, R Frischknecht<fnref n="21" />

**Abstract.** Wood and bio-based construction products are perceived as a way to use
renewable resources, to save energy and to mitigate greenhouse gas (GHG)-emissions

<figure><img src="image_5.png" /></figure>

<footnote n="1">¹ École de technologie supérieure, Montréal, Canada</footnote>

<footnote n="2">² Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany</footnote>

<footnote n="3">³ Belgian Building Research Institute, 1000 Bruxelles, Belgium</footnote>

<footnote n="4">⁴ The University of Melbourne, Parkville VIC 3010, Australia</footnote>

<footnote n="5">⁵ KTH - Royal Institute of Technology, 114 28 Stockholm, Sweden</footnote>

<footnote n="6">⁶ Universidad de Sevilla, 41004 Sevilla, Spain</footnote>

<footnote n="7">⁷ Graz University of Technology, 8010 Graz, Austria</footnote>

<footnote n="8">⁸ Norwegian University of Science and Technology, 7491 Trondheim, Norway</footnote>

<footnote n="9">⁹ MINES Paris, PSL Research University, CEEP, 75272 Paris, France</footnote>

<footnote n="10">¹⁰ BRANZ, Judgeford 5381, New Zealand</footnote>

<footnote n="11">¹¹ Aalborg Universitet København, Aalborg Universitet København</footnote>

<footnote n="12">¹² University of Minho, 4710-057 Braga, Portugal</footnote>

<footnote n="13">¹³ Texas A&M University, College Station, TX 77843, United States</footnote>

<footnote n="14">¹⁴ University of Campinas, 13083-852, Campinas, Brazil</footnote>

<footnote n="15">¹⁵ Federal University of Espirito Santo, 29075-910, Vitoria, Brazil</footnote>

<footnote n="16">¹⁶ SINTEF, 0373 Oslo, Norway</footnote>

<footnote n="17">¹⁷ KU Leuven, 3001 Leuven, Belgium</footnote>

<footnote n="18">¹⁸ University Centre for Energy Efficient Buildings, Czech Technical University in Prague, 273 43, Bustehrad, Czechia</footnote>

<footnote n="19">¹⁹ Technology Assessment Group, Laboratory for Energy Systems Analysis, Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland</footnote>

<footnote n="20">²⁰ ETH Zürich, Institute of Construction and Infrastructure Management (IBI), Chair of Sustainable Construction, Stefano-Francini-Platz 5, 8093 Zürich, Switzerland</footnote>

<footnote n="21">²¹ Treeze Ltd, CH-8610 Uster, Switzerland</footnote>

<footnote>*Corresponding author: Claudiane.Ouellet-Plamondon@etsmtl.ca</footnote>
during production and to store carbon during the entire service life of the building. This
article compares the carbon footprint per kilogram of wood products (softwood beams,
plywood, oriented strand board panel, and fibre board) from the perspective of the life
cycle assessment methodology for greenhouse gas (GHG) emissions of practitioners
from 16 countries participating in the IEA Annex 72. These materials are used in PAL6
softwood structure multi-residential building. This article aims at comparing the carbon
footprint accounting methods from 16 countries for PAL6 multi-residential building.
Each national team applied the reference study period (RSP), life cycle modules
covered, modelling rules, the geographical scope of inventory data as well as the LCA
database according to its specific national method. The results show that there are three
types of methodology to assess a building with biogenic content (0/0, -1/+1, -1/+1*).
The results were more variable plywood, oriented strand board, and fibreboard than the
softwood beams due to the variability in the wood transformation processes among the
countries. A net negative carbon balance was obtained for the softwood beam for the
countries using -1/+1* with a clear assumption of the fraction of the carbon permanently
stored at the end-of-life (EoL). The carbon storage is only possible if it is secured at the
EoL. Participating countries apply different definitions of permanence and EoL
scenarios. Guideline on assessing, monitoring, and legally reporting carbon storage at
the EoL are needed, based on concertation between standard, life cycle assessment,
wood industry, and climate experts.

**1. Introduction**

Efficient design, construction, retrofit of buildings are part of the key adaptation and mitigation measures to achieve climate resilient urban systems [1]. Substitution of greenhouse gas (GHG) emission intensive material to material having less impact or offer the potential to permanently store carbon is part of the solution for the built environment. Wood construction is often proposed as a strategy to reduce to the embodied greenhouse gas emissions (GHG) of buildings [2, 3]. A systematic literature review of the life cycle assessment (LCA) of buildings using wood revealed that the embodied GHG is one third to half of the life-cycle-related GHG emissions of buildings in general [3]. The biogenic carbon content is often, however, not considered or declared.

The goal of this conference article is to do a comparative LCA-based carbon footprint of wood
products in a multi-residential lightweight wood structure, and based on LCA-approaches of
practitioners in 16 countries participating in the IEA EBC Annex 72. Three biogenic CO2 accounting
approaches were reported by the participants. The 0/0 method considers neither fixation nor releases of
biogenic carbon. The -1/+1 method, prescribed by EN 15804+A2 [4], accounts for the fixation of
biogenic carbon in the production stage and its release in the end-of-life (EoL) independent of the EoL
treatment. Some countries apply a -1/0 or close to 0 in the case of recycling or landfill at the end of life:
recycling and landfills are considered a permanent sink of biogenic carbon, and no or not all biogenic
carbon is modelled as an emission at the end of life. Timber from certified forests has negative CO2
emissions in the production stage (assuming that trees are replanted in certified forests), to distinguish
it from non-certified forests. More details on the approaches and the results at the building level are
found in the Annex 72 report [5] . This article presents the assumption on the permanence of carbon
storage from the participants and the results of their assessments on four wood products.

**2. Method**

The object of assessment, the PAL6 multi-residential building was constructed in 2016 in Quebec City, Canada. Its lightweight softwood structure is made of (in mass) 52% concrete 25 MPa, 27% softwood beams, and other wood-based products, 7.6% fire-resistant gypsum panels and 4.6% regular gypsum panels. Laminated wood flooring is not included in the product comparison. In total, around 1500 metric tons of wood were used, with a volumetric breakdown into 1896 m³ softwood beams, 116 m³ plywood,
102 m³ oriented strand board (OSB) panel, 32 m³ fibreboard, and 0.1 m³ laminated wood flooring. The laminated wood flooring was not included in the product comparison.

This study compared the carbon footprint accounting methods from 16 countries for the same building, according to the prevailing method between September 2020 and January 2021. Each national team applied the reference study period (RSP), life cycle modules covered, modelling rules, the geographical scope of inventory data as well as the LCA database according to its specific national method. The building specification and methodological choices from the participants are found in [2]. In this paper, the results are normalized in kg CO₂ equivalent per kg of wood products. The results are not adjusted for the service life, but presented in increasing order of service life. Each participant indicated the LCA phases considered and the LCA methodology (0/0, -1/+1, -1/+1*)

## 3. Results

### 3.1. Survey of national methods

Every country considered the initial embodied impacts of the product phase (A1-A3) (Table 1). Many countries also included the construction process (A4-A5), the replacement (B4), and the end-of-life (module C). The benefits and loads beyond the system boundary (module D) were considered by a few countries only. For France, D was reported separately in the Annex 72 spreadsheet but subtracted from C in the tool as it is used in France. Stages B6, B7, and D were not analyzed. The reference study period (RSP) at the time of this assessment is 50 years for Australia, Austria, Brazil, Czechia, Germany, Portugal, Spain, Sweden, and the United States, 60 years for Belgium, Canada, Norway, Switzerland. 90 years for New Zealand, and 100 years for France.

<table><caption>Table 1: Reference study period (RSP) and life cycle modules (according to CEN TC 350 standards) covered in the country's assessment</caption><thead><tr><th rowspan="3">Country</th><th rowspan="3">Code</th><th rowspan="3">RSP</th><th colspan="16">Life cycle modules covered</th></tr><tr><th colspan="4">Product stage</th><th colspan="8">Use stage</th><th colspan="4">EoL stage</th><th rowspan="2">Benefits</th></tr><tr><th>A1<br/>-<br/>A3</th><th>A4</th><th>A5</th><th>B1</th><th>B2</th><th>B3</th><th>B4</th><th>B5</th><th>B6</th><th>B7</th><th>C1</th><th>C2</th><th>C3</th><th>C4</th></tr></thead><tbody><tr><td>Australia</td><td>AU</td><td>50</td><td>x</td><td>x</td><td>x</td><td></td><td>x</td><td></td><td>x</td><td></td><td></td><td></td><td>x</td><td>x</td><td>x</td><td></td></tr><tr><td>Austria</td><td>AT</td><td>50</td><td>x</td><td>x</td><td>x</td><td></td><td></td><td>x</td><td></td><td>x</td><td></td><td></td><td>x</td><td>x</td><td>x</td><td></td></tr><tr><td>Belgium</td><td>BE</td><td>60</td><td>x</td><td>x</td><td>x</td><td></td><td></td><td>x</td><td></td><td>x</td><td></td><td>x</td><td>x</td><td>x</td><td>x</td><td></td></tr><tr><td>Brazil</td><td>BR</td><td>50</td><td>x</td><td>x</td><td>x</td><td></td><td></td><td>x</td><td></td><td>x</td><td></td><td>x</td><td>x</td><td>x</td><td>x</td><td></td></tr><tr><td>Canada</td><td>CA</td><td>60</td><td>x</td><td>x</td><td>x</td><td></td><td></td><td>x</td><td></td><td>x</td><td></td><td>x</td><td>x</td><td>x</td><td>x</td><td></td></tr><tr><td>Czechia</td><td>CZ</td><td>50</td><td>x</td><td></td><td></td><td></td><td></td><td>x</td><td></td><td>x</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Denmark</td><td>DK</td><td>50</td><td>x</td><td></td><td></td><td></td><td></td><td>x</td><td></td><td>x</td><td></td><td></td><td></td><td>x</td><td>x</td><td></td></tr><tr><td>France</td><td>FR</td><td>100</td><td>x</td><td>x</td><td>x</td><td></td><td></td><td>x</td><td></td><td>x</td><td>x</td><td></td><td>x</td><td>x</td><td>x</td><td>x</td></tr><tr><td>Germany</td><td>DE</td><td>50</td><td>x</td><td></td><td></td><td></td><td>x</td><td></td><td>x</td><td></td><td></td><td></td><td></td><td>x</td><td>x</td><td>x</td></tr><tr><td>New Zealand</td><td>NZ</td><td>90</td><td>x</td><td>x</td><td>x</td><td></td><td>x</td><td></td><td>x</td><td></td><td>x</td><td>x</td><td>x</td><td>x</td><td>x</td><td>x</td></tr><tr><td>Norway</td><td>NO</td><td>60</td><td>x</td><td></td><td></td><td></td><td></td><td>x</td><td></td><td>x</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Portugal</td><td>PT</td><td>50</td><td>x</td><td></td><td></td><td></td><td></td><td>x</td><td>x</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Spain</td><td>ES</td><td>50</td><td>x</td><td></td><td></td><td></td><td></td><td>x</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Sweden</td><td>SE</td><td>50</td><td>x</td><td>x</td><td>x</td><td></td><td>x</td><td></td><td>x</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Switzerland</td><td>CH</td><td>60</td><td>x</td><td></td><td></td><td></td><td></td><td>x</td><td></td><td>x</td><td></td><td>x</td><td>x</td><td>x</td><td>x</td><td></td></tr><tr><td>USA</td><td>US</td><td>50</td><td>x</td><td>x</td><td>x</td><td></td><td>x</td><td></td><td>x</td><td></td><td>x</td><td>x</td><td>x</td><td>x</td><td>x</td><td>x</td></tr></tbody></table>
The LCA approach was attributional with a process based LCA database approach in all cases. Table 2 showed the methods used by the participating countries, with the software, database, carbon content source, and if the GWP of biogenic carbon is recorded separately. While some countries have national databases (e.g., Ökobau.dat) and EPDs in place, most countries use different versions of Ecoinvent adapted to the national tools and context. Spain for example chose to keep the continuity of environmental data over time, instead of a new version of the database and they found the version of the database does not affect significantly their results. The software SimaPro was the most often used software for the calculation and many countries had their own tool.

<table><caption>Table 2: Method for biogenic carbon, software and database used, as well as the possibility of showing GWP biogenic values (separately from GWP total values).</caption><thead><tr><th rowspan="2">Country code</th><th colspan="3">LCA method</th><th rowspan="2">Software</th><th rowspan="2">Database</th><th rowspan="2">Carbon content source</th><th rowspan="2">Is GWP biogenic separately given?</th></tr><tr><th>0/0</th><th>-1/+1</th><th>-1/+1*</th></tr></thead><tbody><tr><td>AU</td><td></td><td></td><td>x*</td><td>SimaPro 9.0.0.41</td><td>AusLCI database (2016)</td><td>AusLCI database in SimaPro and EPDs Australasia</td><td>Yes</td></tr><tr><td>AT</td><td>x</td><td></td><td></td><td>SimaPro 9.1.0.8</td><td>Ecoinvent v3.5</td><td>n/a</td><td>No</td></tr><tr><td>BE</td><td>x</td><td></td><td></td><td>SimaPro 8.5.0</td><td>Ecoinvent v3.6</td><td>n/a</td><td>No</td></tr><tr><td>BR</td><td>x</td><td></td><td></td><td>SimaPro 9.0</td><td>Ecoinvent v3.4, 3.5, 3.6</td><td>n/a</td><td>No</td></tr><tr><td>CA</td><td></td><td></td><td>x*</td><td>SimaPro 9.1.0.8</td><td>Ecoinvent v3.4</td><td>Ecoinvent</td><td>Yes</td></tr><tr><td>CZ</td><td>x</td><td></td><td></td><td>Excel-based tool/calculation</td><td>Ecoinvent v3.3</td><td>n/a</td><td>No</td></tr><tr><td>DK</td><td></td><td>x</td><td></td><td>LCAbyg 3.2</td><td>Ökobaudat v2016</td><td>EN 16449:2014</td><td>No</td></tr><tr><td>FR</td><td></td><td></td><td>x*,**</td><td>EQUER</td><td>Ecoinvent v3.4</td><td>Ecoinvent</td><td>No</td></tr><tr><td>DE</td><td></td><td>x</td><td></td><td>LEGEP 2018</td><td>Ökobaudat v2018</td><td>EN 16449:2014</td><td>No</td></tr><tr><td>PT</td><td>x</td><td></td><td></td><td>SimaPro 8.4.0</td><td>LCIA database for Portuguese Building Elements and Materials</td><td>EN 16449:2014</td><td>No</td></tr></tbody></table>
<table><tr><td>ES</td><td>x</td><td></td><td>Excel-based tool/calculati on</td><td>Ecoinvent v2.0</td><td>n/a</td><td>No</td></tr><tr><td>SE</td><td>x</td><td></td><td>Byggsektor ns Miljöberäk ningsverkty g (BM), (Swedish Building Sector Environme ntal Calculation Tool) (BM)</td><td>Database embedded in Swedish Building Sector Environme ntal Calculation T ool (BM)</td><td>n/a</td><td>No</td></tr><tr><td>NZ</td><td></td><td>x*</td><td>LCAQuick 3.4.2</td><td>EPDs + Ecoinvent v3.1</td><td>EPDs Australasia</td><td>GWP total (biogenic carbon can be derived)</td></tr><tr><td>NO</td><td></td><td>x</td><td>ZEB tool</td><td>Norwegian EPDs + Ecoinvent 3.1</td><td>EN 16449:2014</td><td>Yes</td></tr><tr><td>CH</td><td>x</td><td></td><td>Excel-based tool/calculati on</td><td>KBOB LCA data DQRv2:20 16</td><td>n/a</td><td>No</td></tr><tr><td>USA</td><td>x</td><td></td><td>Athena IE v5.4</td><td>GaBi v9.2</td><td>n/a</td><td>No</td></tr></table>

## 3.2. Permanence in carbon storage

Table 3 shows end-of-life scenarios based on current national practice for the module C. The participating countries applied different definitions of permanence with respect to landfill (Table 1). The countries assuming a permanent sequestration in landfills are Australia, Canada, France and New Zealand. In Australasia, two values of degradable organic carbon fraction (DOCf) for softwood timber are allowed: NZ applied the lower value of 0.1% while AU applied the higher value of 10% [6, 7], which results in 99.9% and 90% assumed permanent sequestration of biogenic carbon in NZ and AU, respectively. Canada assumes 11% release in landfills and France assumes 8 to 9%, according to the wood type. Wood landfilling is forbidden in most European countries due to its potentially reactive characteristics; it is often incinerated and a proportion is recycled. When wood is landfilled at the EoL, the assumptions taken when modelling landfilling wood and other biobased materials must be reported transparently, in particular whether biogenic carbon stored in landfills is considered permanently sequestered and if so under which conditions and for which time horizon.

<footnote>* Wood sent to recycling and landfill gets a value ">0" but <<1".</footnote>

<footnote>** Differentiation between certified (-1) and non-certified (0) forests</footnote>
<table><caption>**Table 3.** Shares of solid wood recycled, incinerated, landfilled in the countries' assessments for module C of EoL assessment (n/a means not available because EoL is not considered in the national methods)</caption><thead><tr><th rowspan="2"></th><th>Wood recycled</th><th>Wood incinerated</th><th>Wood landfilled</th><th>Permanent sequestration in landfill assumed</th></tr><tr><th>%</th><th>%</th><th>%</th><th>Yes/No</th></tr></thead><tbody><tr><td>AU</td><td>40</td><td>5</td><td>55</td><td>Yes</td></tr><tr><td>AT</td><td>75</td><td>25</td><td></td><td>No</td></tr><tr><td>BE</td><td>75</td><td>25</td><td></td><td>No</td></tr><tr><td>BR</td><td></td><td>100</td><td></td><td>No</td></tr><tr><td>CA</td><td>60</td><td></td><td>40</td><td>Yes</td></tr><tr><td>CZ</td><td>n/a</td><td>n/a</td><td>n/a</td><td>n/a</td></tr><tr><td>DK</td><td></td><td>100</td><td></td><td>No</td></tr><tr><td>FR</td><td></td><td>100</td><td></td><td>Yes</td></tr><tr><td>DE</td><td></td><td>100</td><td></td><td>No</td></tr><tr><td>ES</td><td>10</td><td>80</td><td>10</td><td>Yes</td></tr><tr><td>NO</td><td></td><td>100</td><td></td><td>No</td></tr><tr><td>PT</td><td>n/a</td><td>n/a</td><td>n/a</td><td>n/a</td></tr><tr><td>NZ</td><td>15</td><td>10</td><td>75</td><td>Yes</td></tr><tr><td>SE</td><td></td><td>100</td><td></td><td>No</td></tr><tr><td>CH</td><td>50</td><td>50</td><td></td><td>No</td></tr><tr><td>US</td><td>n/a</td><td>n/a</td><td>n/a</td><td>n/a</td></tr></tbody></table>

### 3.3 Wood products assessment

Figures 1 to 4 show the results, according to the three types of methodology to assess a building with biogenic content (Appendix table A1 to A4). The countries that applied a 0/0 method did not account biogenic carbon (Austria, Belgium, Brazil, Czech Republic, Portugal, Spain, and Sweden). All countries applying -1/+1 apply a GWP on biogenic CO₂ (Denmark, Germany, Norway). According to this approach, carbon dioxide capture (during biomass growth) is characterized by a factor of "-1 kg CO₂eq/kg CO₂". When this carbon is released in the form of CO₂, the emission is characterized by a factor of "+1 kg CO₂eq./kg CO₂". If the wood or fibre is recycled at the end of its life or reused by another system, a factor of "+1 kg CO₂eq./kg CO₂" is applied to the biogenic carbon content of the material. Australia, Canada, France and New Zealand applied a -1/+1* methods, which consider a fraction of carbon was permanently as just discussed in 3.1.
For the softwood beams, the assessments from Canada and New Zealand show a net negative biogenic CO₂ balance considering phases A1-A3, A4-A5, and C1-C4. When considering plywood, OSB and fibreboard, only New Zealand shows a negative balance kg CO₂-eq per kg of wood for plywood and OSB. The more wood is processed, the more variable were the wood products GHG emissions among the different countries, which is due to variations in the wood transformation processes. Plywood, oriented strand board (OSB), and fiberboard generally had a greater impact of kg CO₂-eq/kg wood products, than the softwood beams.

The negative emission should be accounted only if permanent carbon storage is secured at the end of life. The carbon storage at the EoL can be secured by a legally binding commitment to not release the biogenic carbon in timber products to the atmosphere. However, in this assessment, the legal binding commitment was not checked. More concertation is needed about the procedure for monitoring and legally binding negative emission, before guideline. This could be achieved by incineration in wood heat and power plants equipped with carbon capture and storage (CCS), reuse/recycling (the legally binding commitment must be transferred to the new owner of the timber products). A legally binding commitment may be an entry in the land register. Module D is about potentially avoided emissions (based on counterfactual scenarios). While negative emissions were reported, there is no negative emission (withdrawal of CO₂ from the atmosphere) and shall not count on the negative side of zero net GHG emissions.

<figure><img src="image_6.png" /><figcaption>**Figure 1.** Greenhouse gas emissions in kg CO₂-eq per kg softwood beams as assessed by the different countries and grouped according to the 0/0 and -1/+1 approaches</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>**Figure 2.** Greenhouse gas emissions in kg CO₂-eq per kg plywood as assessed in the different countries and grouped according to the 0/0 and -1/+1 approaches</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>**Figure 3.** Greenhouse gas emissions in kg CO₂-eq per kg of oriented strand board (OSB) as assessed in the different countries and grouped according to the 0/0 and -1/+1 approaches</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>**Figure 4.** Greenhouse gas emissions in kg CO₂-eq per kg fibreboard as assessed in the different countries and grouped according to the 0/0 and -1/+1 approaches.</figcaption></figure>

A great potential for harmonization of the LCA methods is apparent from the comparative assessment of a multi-residential wooden building from the method applied in 16 countries. The full life cycle approach is needed to assess the impact of wood products if the -1/+1 and -1/+1* approaches are applied. The minimum stages to include are A1-A3, B4, and corresponding C1-C4. The mass balance of biogenic carbon must be checked: the amount of biogenic CO₂ fixed (withdrawn) in wood material manufacture must match with the amount of biogenic CO₂ released. The carbon content of 1 m³ of wood products is calculated by multiply the kg carbon/kg wood and the molecular weight ratio of CO₂/C [8]. This calculation does not consider the service life. As different lengths of service life were used, the mass value can be further normalized. However, there is not a consensus yet on the use of the mass balance approach in the environmental product declaration [9]. The main difference between the -1/+1 and the -1/+1* assessments was due to different interpretations of the potential effect of landfilling and recycling wood at the end-of-life. The LCA must specify if landfilled biogenic carbon is considered permanently sequestered and the applied timeframe. Studies have been done extensively in Australia and there is one study in the USA[2]. The value reported by the countries should be supported by experimental data and there is a need for standardized testing procedure on carbon storage.

There are three stakeholders' groups what are willing to participate in guidance of LCA of biogenic carbon: (a) those developing or selecting/specifying “standards”, (b) the consultants that provide building/project level GWP / embodied carbon emission figures on design-materials-specs- options to designers and/or owners, (c) the wood industry that want to promote the wood products in construction. Moreover, the methodology and results must connect to those performing the carbon balance at a larger scale to mitigate the anthropogenic carbon and its impact on the climate. The presented options for dealing with wood and/or bio-based products in LCAs make it clear that transparency and traceability are crucial to reducing uncertainty in decision-making. Thus, the influence of LCA outcomes on building design and material choices is growing. It is therefore urgent to consider the precision and accuracy of LCA outcomes. There is a great need for assessment results that are based on scientifically recognized and correctly used methods. In particular, with respect to a performance-based approach to the assessment of design options, the conception of funding programs or the development of legal
requirements, the results must be reliable and credible. Discussions between LCA experts and those in charge of national greenhouse gas inventories of harvested wood would contribute to improving the harmonization of the LCA method to account for biogenic carbon. Approaches that are scientifically consensus-driven and have already been harmonized via standards are preferable.

## 4. Conclusion

The comparative life cycle assessment of a multi-residential wood lightweight structure revealed three approaches used by the practitioner of LCA in considering biogenic carbon (0/0, -1/+1, -1/+1*). The end-of-life scenarios (incineration, landfill, recycling) and different perceptions of the permanence of biogenic carbon landfilled cause variations in the assessment of the same building. New Zealand, using the -1/+1* methodology, reported a negative carbon balance for the softwood and the plywood, while Canada reported a negative balance of biogenic carbon for the softwood beams. There was more variability among countries for the plywood, OSB, and fibreboard, compared to the softwood beams. The input and output flows of biogenic carbon must be balanced to ensure a proper assessment of climate change impacts of biogenic CO₂. Future guidance on the LCA of biogenic carbon must consider the wood industry, LCA analyst doing an assessment at the building and project level, as well as the standard and climate experts.

## References

[1] IPCC, "Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change," Cambridge, U.K., 2021.

[2] C. M. Ouellet-Plamondon et al., "Carbon footprint assessment of a wood multi-residential building considering biogenic carbon," *Journal of Cleaner Production*, p. 136834, 2023/03/17/ 2023, doi: https://doi.org/10.1016/j.jclepro.2023.136834.

[3] C. E. Andersen, F. N. Rasmussen, G. Habert, and H. Birgisdóttir, "Embodied GHG Emissions of Wooden Buildings—Challenges of Biogenic Carbon Accounting in Current LCA Methods," (in English), *Frontiers in Built Environment*, Review vol. 7, no. 120, 2021-August-31 2021, doi: 10.3389/fbuil.2021.7.29096.

[4] EN 15804:2012+A2:2019, European Committee for Standardization (CEN), 2019.

[5] T. O. Alexander Passer, Nicolas Alaux, Thomas Lützkendorf, Martin Rock, Bernadette Soust-Verdaguer, Antonio Garcfa Martfnez, Marcella RM Saade, Rolf Frischknecht, Endrit Hoxha, Zsuzsa Szalay, Benedek Kiss, Lisa Wastiels, Alexander Hollberg, Aoife Houlihan Wiberg, Sebastien Lasvaux, Alina Galimshina, Guillaume Haberth, Rafael Horn, Roberta Di Bari, Katrin Lenz, Carmen Llatas, Juan Carlos Gomez de Cozar, Jakub Veselka, Harpa Birgisdottir, Maria Balouktsi, Daniel Plazza, Michael Ortmann, Deepshi Kaushal, Dave Dowdell, Jarred Butler, Claudiane Ouellet-Plamondon, Bruno Peuportier, Theres Reisinger, "EA EBC Annex 72: Assessing Life Cycle Related Environmental Impacts Caused by Buildings: Guidelines for design decision-makers: Energy in Buildings and Communities Technology Collaboration Programme," Uster, Switzerland 2023.

[6] Wood Solutions, "Environmental Product Declaration Softwood Timber" Forest and Wood Products Australia Limited, Australia, 2020.

[7] Australian Government, "National Greenhouse Accounts Factors – August 2016," Department of Environment, Canberra, ACT, Australia, 2016.

[8] Tallwood Design Institute, "Cross-Laminated Timber Info Sheets" University of Oregon Corvallis, Oregon, 2019 [Online]. Available: https://tallwoodinstitute.org/wp-content/uploads/2022/05/Info-Sheets_Final_200616.pdf

[9] H. Hauan and C. Donath. "ECO Platform Statement on Mass Balance Approach (MBA) from Dec 12, 2023." ECO Platform. https://www.eco-platform.org/position-statements.html (accessed 3 janvier 2024, 2024).
Appendix

<table><caption>Table A1: Total greenhouse gas (GHG) emissions for the softwood (kg CO₂-eq / kg)</caption><thead><tr><th>Label</th><th>Method</th><th>Country</th><th>A1-A3</th><th>A4-A5</th><th>C1-C4</th><th>D</th><th>Total (without D)</th></tr></thead><tbody><tr><td>AT (0/0)</td><td>0/0</td><td>AT</td><td>0.061</td><td>0.017</td><td>0.021</td><td>0.000</td><td>0.099</td></tr><tr><td>BE (0/0)</td><td>0/0</td><td>BE</td><td>0.111</td><td>0.016</td><td>0.018</td><td>0.000</td><td>0.146</td></tr><tr><td>BR (0/0)</td><td>0/0</td><td>BR</td><td>0.064</td><td>0.000</td><td>0.015</td><td>0.000</td><td>0.079</td></tr><tr><td>CH (0/0)</td><td>0/0</td><td>CH</td><td>0.133</td><td>0.000</td><td>0.010</td><td>0.000</td><td>0.143</td></tr><tr><td>CZ (0/0)</td><td>0/0</td><td>CZ</td><td>0.171</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.171</td></tr><tr><td>PT (0/0)</td><td>0/0</td><td>PT</td><td>0.085</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.085</td></tr><tr><td>SE (0/0)</td><td>0/0</td><td>SE</td><td>0.094</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.094</td></tr><tr><td>DE (-1/+1)</td><td>-1/+1</td><td>DE</td><td>-1.516</td><td>0.000</td><td>1.645</td><td>-0.739</td><td>0.129</td></tr><tr><td>DK (-1/+1)</td><td>-1/+1</td><td>DK</td><td>-1.469</td><td>0.000</td><td>1.596</td><td>0.000</td><td>0.127</td></tr><tr><td>ES (-1/+1)</td><td>-1/+1</td><td>ES</td><td>-1.354</td><td>0.000</td><td>1.472</td><td>0.000</td><td>0.118</td></tr><tr><td>NO (-1/+1)</td><td>-1/+1</td><td>NO</td><td>-1.723</td><td>0.000</td><td>1.884</td><td>-0.464</td><td>0.161</td></tr><tr><td>AU (-1/+1*)</td><td>-1/+1*</td><td>AU</td><td>-1.490</td><td>0.012</td><td>1.899</td><td>0.000</td><td>0.421</td></tr><tr><td>CA (-1/+1*)</td><td>-1/+1*</td><td>CA</td><td>-1.000</td><td>-0.055</td><td>0.813</td><td>0.000</td><td>-0.242</td></tr><tr><td>FR (-1/+1*)</td><td>-1/+1*</td><td>FR</td><td>-1.360</td><td>-0.059</td><td>1.478</td><td>-0.058</td><td>0.058</td></tr><tr><td>NZ (-1/+1*)</td><td>-1/+1*</td><td>NZ</td><td>-1.147</td><td>0.118</td><td>0.611</td><td>-0.287</td><td>-0.419</td></tr></tbody></table>

<table><caption>Table A2: Total GHG for plywood (kg CO₂-eq / kg)</caption><thead><tr><th>Label</th><th>Method</th><th>Country</th><th>A1-A3</th><th>A4-A5</th><th>C1-C4</th><th>D</th><th>Total without D</th></tr></thead><tbody><tr><td>AT (0/0)</td><td>0/0</td><td>AT</td><td>0.662</td><td>0.016</td><td>0.041</td><td>0.000</td><td>0.718</td></tr><tr><td>BE (0/0)</td><td>0/0</td><td>BE</td><td>0.613</td><td>0.016</td><td>0.095</td><td>0.000</td><td>0.724</td></tr><tr><td>BR (0/0)</td><td>0/0</td><td>BR</td><td>0.834</td><td>0.000</td><td>0.015</td><td>0.000</td><td>0.849</td></tr><tr><td>CH (0/0)</td><td>0/0</td><td>CH</td><td>1.060</td><td>0.000</td><td>0.111</td><td>0.000</td><td>1.171</td></tr><tr><td>CZ (0/0)</td><td>0/0</td><td>CZ</td><td>0.685</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.685</td></tr><tr><td>PT (0/0)</td><td>0/0</td><td>PT</td><td>0.628</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.628</td></tr><tr><td>SE (0/0)</td><td>0/0</td><td>SE</td><td>0.204</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.204</td></tr><tr><td>DE (-1/+1)</td><td>-1/+1</td><td>DE</td><td>-1.016</td><td>0.000</td><td>1.512</td><td>-0.698</td><td>0.496</td></tr><tr><td>DK (-1/+1)</td><td>-1/+1</td><td>DK</td><td>-1.352</td><td>0.000</td><td>1.663</td><td>0.000</td><td>0.310</td></tr><tr><td>ES (-1/+1)</td><td>-1/+1</td><td>ES</td><td>-1.232</td><td>0.000</td><td>1.472</td><td>0.000</td><td>0.240</td></tr><tr><td>NO (-1/+1)</td><td>-1/+1</td><td>NO</td><td>-1.301</td><td>0.043</td><td>2.023</td><td>-0.085</td><td>0.766</td></tr><tr><td>AU (-1/+1*)</td><td>-1/+1*</td><td>AU</td><td>-0.530</td><td>0.012</td><td>1.540</td><td>0.000</td><td>1.022</td></tr><tr><td>CA (-1/+1*)</td><td>-1/+1*</td><td>CA</td><td>0.391</td><td>0.042</td><td>0.074</td><td>0.000</td><td>0.506</td></tr><tr><td>FR (-1/+1*)</td><td>-1/+1*</td><td>FR</td><td>-1.405</td><td>-0.062</td><td>1.478</td><td>-0.036</td><td>0.011</td></tr><tr><td>NZ (-1/+1*)</td><td>-1/+1*</td><td>NZ</td><td>-0.537</td><td>0.207</td><td>0.176</td><td>-0.013</td><td>-0.154</td></tr></tbody></table>
<table><caption>Table A3: Total GHG for oriented strand boards (OSB) (kg CO₂-eq / kg)</caption><thead><tr><th>Label</th><th>Method</th><th>Country</th><th>A1-A3</th><th>A4-A5</th><th>C1-C4</th><th>D</th><th>Total without D</th></tr></thead><tbody><tr><td>AT (0/0)</td><td>0/0</td><td>AT</td><td>0.465</td><td>0.016</td><td>0.054</td><td>0.000</td><td>0.535</td></tr><tr><td>BE (0/0)</td><td>0/0</td><td>BE</td><td>0.445</td><td>0.016</td><td>0.210</td><td>0.000</td><td>0.671</td></tr><tr><td>BR (0/0)</td><td>0/0</td><td>BR</td><td>0.464</td><td>0.000</td><td>0.015</td><td>0.000</td><td>0.479</td></tr><tr><td>CH (0/0)</td><td>0/0</td><td>CH</td><td>0.487</td><td>0.000</td><td>0.127</td><td>0.000</td><td>0.614</td></tr><tr><td>CZ (0/0)</td><td>0/0</td><td>CZ</td><td>0.024</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.024</td></tr><tr><td>PT (0/0)</td><td>0/0</td><td>PT</td><td>0.472</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.472</td></tr><tr><td>SE (0/0)</td><td>0/0</td><td>SE</td><td>0.167</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.167</td></tr><tr><td>AU (-1/+1)</td><td>-1/+1</td><td>AU</td><td>-1.050</td><td>0.012</td><td>2.017</td><td>0.000</td><td>0.979</td></tr><tr><td>CA (-1/+1)</td><td>-1/+1</td><td>CA</td><td>0.378</td><td>0.209</td><td>0.074</td><td>0.000</td><td>0.661</td></tr><tr><td>DE (-1/+1)</td><td>-1/+1</td><td>DE</td><td>-0.968</td><td>0.000</td><td>1.629</td><td>-0.755</td><td>0.661</td></tr><tr><td>DK (-1/+1)</td><td>-1/+1</td><td>DK</td><td>-0.942</td><td>0.000</td><td>1.628</td><td>0.000</td><td>0.687</td></tr><tr><td>ES (-1/+1)</td><td>-1/+1</td><td>ES</td><td>-1.232</td><td>0.000</td><td>1.472</td><td>0.000</td><td>0.240</td></tr><tr><td>FR (-1/+1)</td><td>-1/+1</td><td>FR</td><td>-1.116</td><td>-0.047</td><td>1.478</td><td>-0.180</td><td>0.315</td></tr><tr><td>NO (-1/+1)</td><td>-1/+1</td><td>NO</td><td>-1.167</td><td>0.151</td><td>1.740</td><td>-0.081</td><td>0.724</td></tr><tr><td>NZ (-1/+1)</td><td>-1/+1</td><td>NZ</td><td>-0.419</td><td>0.216</td><td>0.173</td><td>-0.010</td><td>-0.030</td></tr></tbody></table>

<table><caption>Table A4: Total GHG for fibreboards (kg CO₂-eq / kg)</caption><thead><tr><th>Label</th><th>Method</th><th>Country</th><th>A1-A3</th><th>A4-A5</th><th>C1-C4</th><th>D</th><th>Total without D</th></tr></thead><tbody><tr><td>AT (0/0)</td><td>0/0</td><td>AT</td><td>0.922</td><td>0.016</td><td>0.231</td><td>0.000</td><td>1.168</td></tr><tr><td>BE (0/0)</td><td>0/0</td><td>BE</td><td>0.371</td><td>0.016</td><td>0.210</td><td>0.000</td><td>0.597</td></tr><tr><td>BR (0/0)</td><td>0/0</td><td>BR</td><td>0.210</td><td>0.000</td><td>0.015</td><td>0.000</td><td>0.225</td></tr><tr><td>CH (0/0)</td><td>0/0</td><td>CH</td><td>0.910</td><td>0.000</td><td>0.126</td><td>0.000</td><td>1.036</td></tr><tr><td>CZ (0/0)</td><td>0/0</td><td>CZ</td><td>1.010</td><td>0.000</td><td>0.000</td><td>0.000</td><td>1.010</td></tr><tr><td>PT (0/0)</td><td>0/0</td><td>PT</td><td>0.167</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.167</td></tr><tr><td>SE (0/0)</td><td>0/0</td><td>SE</td><td>0.298</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.298</td></tr><tr><td>AU (-1/+1)</td><td>-1/+1</td><td>AU</td><td>-0.700</td><td>0.012</td><td>1.902</td><td>0.000</td><td>1.214</td></tr><tr><td>CA (-1/+1)</td><td>-1/+1</td><td>CA</td><td>1.219</td><td>0.083</td><td>0.074</td><td>0.000</td><td>1.375</td></tr><tr><td>DE (-1/+1)</td><td>-1/+1</td><td>DE</td><td>-0.946</td><td>0.000</td><td>1.473</td><td>-0.469</td><td>0.526</td></tr><tr><td>DK (-1/+1)</td><td>-1/+1</td><td>DK</td><td>-0.917</td><td>0.000</td><td>1.478</td><td>0.000</td><td>0.561</td></tr><tr><td>ES (-1/+1)</td><td>-1/+1</td><td>ES</td><td>-1.232</td><td>0.000</td><td>1.472</td><td>0.000</td><td>0.240</td></tr><tr><td>FR (-1/+1)</td><td>-1/+1</td><td>FR</td><td>-0.210</td><td>-0.002</td><td>1.478</td><td>-0.633</td><td>1.266</td></tr><tr><td>NO (-1/+1)</td><td>-1/+1</td><td>NO</td><td>-1.109</td><td>0.146</td><td>1.796</td><td>-0.405</td><td>0.834</td></tr><tr><td>NZ (-1/+1)</td><td>-1/+1</td><td>NZ</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.000</td></tr></tbody></table>