Mass timber embodied carbon factors

Author: Tom Place, Clare Perkins and Lucy Caine

Date published

1 December 2021

Price
Free
Back to Previous

Mass timber embodied carbon factors

Blog
Author

Tom Place, Clare Perkins and Lucy Caine

Date published

1 December 2021

Author

Tom Place, Clare Perkins and Lucy Caine

Price

Free

Arup has conducted a review of European manufacturers’ CLT and glulam Environmental Product Declarations (EPDs). The review demonstrates that the currently adopted industry average carbon factors for CLT and glulam have reduced when compared with factors from the Inventory of Carbon and Energy database (ICE database).

The currently adopted factors are 0.437 kgCO2e/kg for CLT and 0.512 kgCO2e/kg for glulam, and are referenced by the IStructE's How to calculate embodied carbon guide1 for mass timber. The new figures recommended are 0.25 kgCO2e/kg and 0.28 kgCO2e/kg for CLT and glulam respectively. This is predominantly due to changes in the recorded energy mix and energy use during production.

This article proposes updating the figures referenced by the IStructE to those based on current European manufacturer EPDs.  

The ICE database mass timber carbon factors referenced by the IStructE in How to calculate embodied carbon, are based on a range of international EPDs in addition to data provided by Wood for Good2 nearly a decade ago. Given UK consumption of mass timber broadly reflects the distribution of its manufacture across Europe, Arup decided to conduct a review of current European manufacturer EPDs, to derive suitable, up-to-date factors for CLT and glulam.

A1 – A3 embodied carbon factors were extracted from eleven CLT manufacturer EPDs and eight glulam manufacturer EPDs. Manufacturer data was included and weighted based on production volumes, reflecting the likelihood of a particular product being supplied and limiting the skewing of data by EPDs representing a smaller portion of the market.

The EPDs utilised in this work are third-party independently verified, and have been undertaken in alignment with the requirements of ISO 14025 and EN 15804.

Figures 1 and 2 show current European production volumes from CLT and glulam manufacturers respectively3.
Figures 3 and 4 show the distribution of A1 – A3 embodied carbon factors (excluding sequestration) for CLT and glulam4, as well as the derived weighted average figure calculated by Arup. Average A1 – A3 embodied carbon factors, weighted by production, are 0.25 kgCO2e/kg and 0.28 kgCO2e/kg for CLT and glulam respectively.  

 

"These new carbon factors for CLT and glulam represent an important progression of the knowledge base. It’s encouraging to see that many of the main CLT and glulam manufacturers have published Environmental Product Declarations (EPDS), which provides the embodied carbon of their products. This new research shows the benefit of more suppliers publishing the embodied carbon of their products, giving a welcome reduction in the embodied carbon of CLT and glulam."
Dr Craig Jones, Circular Ecology

 

Figure 1 CLT annual European production

Figure 2 Glulam annual European production

Figure 3 CLT embodied carbon A1-A3 without sequestration

Figure 4 Glulam embodied carbon A1-A3 without sequestration


 

Figures 5 and 6 below show the mixture of renewable and non-renewable primary energy quoted by each manufacturer (including renewable energy from burning waste wood on-site). The ICE database does not provide an energy breakdown with its carbon factors. However, the Wood for Good (2013) EPDs, which formed part of the ICE database study and represented a 2013 UK industry average, has been used to give an indicative energy mix for the study period. Several observations can be made:

  • Less energy is typically used by each manufacturer to produce 1m3 of mass timber compared to the Wood for Good analysis
  • Less non-renewable energy is typically used by each manufacturer to produce 1m3 of mass timber compared to the Wood for Good analysis
  • The A1-A3 embodied carbon factors correlate to the non-renewable energy component quoted by each manufacturer

Based on industry engagement, primary contributing factors also include varying transport distances during production, the energy mix of the country of manufacture and the utilisation of the factories studied.

It is also useful to compare the new embodied carbon factors derived to the value for conventional sawn and dried softwood timber.

The softwood value given in the ICE database and the IStructE guide is 0.263 kgCO2e/kg – very similar to the new values for CLT and glulam proposed. A review of current EPD data from Europe’s largest sawn and dried softwood timber producers suggests that this value may also warrant reduction, and further work by the industry in this space is suggested.
 

Figure 5 CLT primary energy use of production (A1-A3)


Figure 6 Glulam primary energy use of production (A1-A3)

Conclusion

It was found that current European mass timber EPDs give lower carbon values than those derived previously by the ICE database. The EPD data utilised in this study is more recent than data utilised for the existing carbon factors and covers approximately 85% of the volume of CLT and 50% of the volume of glulam produced in Europe. Our recommendation is that new weighted average values are adopted for CLT and glulam structures being constructed across Europe, including in the UK.

In addition, the following further work is proposed:

  • Development of up-to-date embodied carbon factors for European sawn and dried softwood, hardwood, plywood, oriented strand board and laminated veneer lumber
  • Development of timber factors for other global regions
  • Refinement of assumptions around transport routes via road and sea, to capture the increasing influence of stage A4 as earlier production stage factors reduce
  • Further review of lifecycle stages B – D to understand the current whole lifecycle carbon factors for mass timber products

The authors of How to calculate embodied carbon have confirmed that these figures will be included in the next revision of the guide, due for publication in Spring 2022.
 

References


[1] The Institution of Structural Engineers (2020). How to calculate embodied carbon

[2] Jones, C. and Hammon, G. (2019). ICE (Inventory of Carbon & Energy) Database Version 3.0. Circular Ecology and University of Bath. Available at: https://circularecology.com/embodied-carbon-footprint-database.html

[3] Production Volumes
Construction.co.uk. Moelven Laminated Timber Structures
Holzkurier. Expresslieferung in den Norden
Rubner Holzbau. Our strategy. Wood experts
Setra. Långshyttan - Setra's new wood industry hub
Splitkon. Massivtre fra Splitkon
Timber Online. Eight new CLT production sites by 2023
Timber Online. Over 3 million m3 for the first time – record years for glulam
Timber Online. The biggest CLT producers in Central Europe
Versowood. Puureferenssit. References

[4] Environmental Product Declarations
CLT EPDs: EPD-BBS-20190021-IBB1-EN, EPD­HAS­20210172­IBD1­EN, EPD-KLH-20190027-ICA1-EN, EPD-SHL-20180035-IBG1-EN, EPD-SLH-20200098-IBC1-DE, NEPD-2042-902-NO, S-P-01408, S-P-02033.
Glulam EPDs: EPD-BBS-20190164-IBA1-EN, EPD­HAS­20210171­IBD1­EN, EPD-RUB-20180058-IBB1-EN, EPD-SHL-20120017-IBG1-EN, NEPD-1662-655-EN, NEPD-456-318-EN.

Wood for Good life cycle assessments
Wood for Good. Glued Laminated Timber
Wood for Good. Cross Laminated Timber
Manufacturers were contacted directly where production volumes and/or EPDs were unavailable online. All references accessed November 2021.

[5] Codes and Standards
BS EN ISO 14025:2010 Environmental labels and declarations – Type III environmental declarations – Principles and procedures London: BSI, 2010
BS EN 15804:2019 Sustainability of construction works. Environmental product declarations. Core rules for the product category of construction products. London: BSI, 2019.
 

Related Resources & Events

Conference
<h4>Using steel in changing times</h4>

Using steel in changing times

Attend this e-conference to learn how to use steel in an effective and sustainable way in changing times.

Date ‐ 22 November 2022
Location ‐ Online
Price ‐ £45 - £275 + VAT
Course
Historic timber structures

Historic timber structures: assessment and reuse

This course introduces timber as an engineering material, with a focus on its use in historic structures. It covers non-destructive techniques for condition assessment and strategies for the reuse of heritage structures.

Date ‐ 18 November 2022
Location ‐ Online
Price ‐ £265 - £395 + VAT
Course
<h4>Timber: design through worked examples</h4>

Timber: design through worked examples

This advanced practical workshop will teach complex timber engineering through worked examples. It encourages problem-solving through teaching tools and group discussion.

Date ‐ 5 October 2022
Location ‐ Online
Price ‐ £265 - £395 + VAT
Course
A bridge over a dry river bed

Net-zero structural design

A new course designed to enable you to design structures with net zero emissions. Delivered as a series of interactive online sessions across five weeks.

Date ‐ 22 September 2022
Location ‐ Online
Price ‐ £485 - £715 + VAT
Conference
A Bastwick Street Conference underway

Annual academic conference 2022

A conference dedicated to best practices in integrating climate emergency teaching into academic curricula, and professionalism and ethics in both academic environments and workplaces.

Date ‐ 15 September 2022
Location ‐ The Institution of Structural Engineers
Price ‐ Free
Course
<h4>Fire engineering - An introduction for structural engineers</h4>

Fire engineering - An introduction for structural engineers

CPD course covering fire engineering, concrete, steel, timber structures and structural design

Date ‐ 7 September 2022
Location ‐ Lecture Theatre M, University of Surrey, Guildford, GU2 7XH
Price ‐ £175
Course
<h4>Modern solutions for repairing, strengthening and waterproofing concrete</h4>

Modern solutions for repairing, strengthening and waterproofing concrete

This sponsored seminar by Mapei will focus on the principles and practices of Structural Below Ground Waterproofing, and it will cover many aspects of waterproofing, including best practices for good QA and monitoring of workmanship on site.

Date ‐ 6 September 2022
Location ‐ The Institution of Structural Engineers
Price ‐ Free
Course
<h4>Structural engineering with bamboo</h4>

Structural engineering with bamboo

This course will equip attendees with practical knowledge about structural design with bamboo stems (culms). The course considers aspects of concept design, detailed design and durability by design.

Date ‐ 13 July 2022
Location ‐ Online
Price ‐ £265 - £395 + VAT
Lecture
<h4>IStructE SA technical talk 6</h4>

IStructE SA technical talk 6

Part 2: “Practical insights, with focus on research done in Africa, quantifying embodied carbon values and the use of these in the design of structures going forward.” by Alex Strachan, Fiona Carr, Omorinola Akeredolu-Ale, Suvarna Maharaj and Tessa Brunette.

Date ‐ 6 July 2022
Price ‐ Free
Conference
<h4>Using concrete in a changing environment e-conference</h4>

Using concrete in a changing environment e-conference

This inaugural e-conference is dedicated to helping structural engineers understand how to assess, strengthen and reuse existing concrete structures to extend their life and reduce the impact the built environment profession has on the environment.

Date ‐ 5 July 2022
Location ‐ Online
Price ‐ £45 - £275 + VAT
Course
wood and timber connection

Eurocode 5: connections and advanced topics in timber design

This course introduces advanced topics in timber design to Eurocode 5, including fasteners and connectors.

Date ‐ 30 June 2022
Location ‐ Online
Price ‐ £265 - £395 + VAT
Lecture
Concrete structure

fib: What's happening? 2022

This annual update provides an overview of the ongoing work from two fib commissions.

Date ‐ 30 June 2022
Location ‐ Online
Price ‐ Free
The Structural Engineer
Blue abstract blocks

Climate action two years on: are we on the right track?

Could do better, concludes Mike Cook in a ‘report card’ on the industry’s response to the climate emergency, as he urges engineers to embrace the paradigm shift required to decarbonise.

Date ‐ 1 June 2022
Author ‐ Mike Cook
Price ‐ £0
The Structural Engineer
Full scale shear wall test

Optimising the structural design of modular housing by combining timber and lightweight steel framin

Smail Kechidi describes his research into cold-formed steel-framed shear walls sheathed in timber, which won the Institution’s Research into Practice essay competition in 2021.

Date ‐ 3 May 2022
Author ‐ Smail Kechidi
Price ‐ £9
The Structural Engineer
Modern methods of construction can enhance quality and safety while reducing material use. Cadence building, Kings Cross

How to achieve a SCORS A rating using current materials and technology

Muiris Moynihan takes structural engineers through a series of actions they could take to lower the embodied carbon of projects to a SCORS A rating.

Date ‐ 3 May 2022
Author ‐ Muiris Moynihan
Price ‐ £0