The substitution effect of wood products could compensate for Finland’s greenhouse gas emissions

​When we use wood products to displace other materials and avoid their fossil emissions, we speak of a substitution effect. Finland already boasts significant substitution effects, but they can be further increased by utilising forest industry side streams more extensively as raw material for products.

Elias Hurmekoski, a postdoctoral researcher at the Department of Forest Sciences of the University of Helsinki, leads a project focusing on substitution processes related to wood products and their climate impact. “Of all the climate impacts related to wood consumption, substitution effects may be the most abstract, since they refer to the fossil emissions avoided through the use of wood. We’ve known about substitution effects for 30 years or more, and there have been many attempts to calculate them. However, major gaps in information remain in the field.”

“In this project, we adopt a multidisciplinary approach, because we’re interested in both the fossil emissions avoided and market operations. We focus on preparing calculations and analysing the underlying assumptions, but the project also provides a more detailed estimate of the size of substitution effects.”

Substitution effects can be increased

“When calculating substitution effects, the essential data concerns the products that wood is expected to displace. There are thousands of potential products and thousands of purposes of use. We also have a host of products with the potential to be substituted by wood. It’s impossible to examine all the combinations, so we need to make a number of rough assumptions.”

Product portfolios can help to significantly increase substitution effects. Wood construction is a good example of this, and from a climate perspective, it is still one of the smartest ways to use wood.

“It can be challenging to calculate the substitution effect if you focus on a single product group. For example, if you examine a stand marked for final felling or a single tree, for example, part of it is log wood, while the rest is treated as pulpwood and other fractions. This makes it essential to analyse the use of side streams. They are currently used for pulp, energy production and chip boards, among other things. However, to maximise the substitution effect of wood, we should increasingly steer these side streams to products and postpone their use as energy until the end of their life-cycle.

Substitution benefits from textiles

“Textiles are a very interesting pulp-based product group. Their manufacture offers the potential for large substitution benefits. If the end use of pulp shifts from graphic paper to the textile business, this would be a very positive change for the climate. Wood-based products also offer many other benefits apart from climate aspects. Talking about textiles, the cultivation of cotton, for example, involves freshwater consumption and pesticide use, which pulp-based products do not.”

According to Hurmekoski, the packaging materials and chemicals used to displace plastic are other pulp- and side stream-based products that could generate greater average substitution benefits – greater efficiency from the same volume of wood, if you like.

“Wood has been used throughout the history of humankind, and forest use is bound to continue. It may change a little, and the forest sector will probably look different in 2050. What the changes will be like is an interesting question,” says Elias Hurmekoski, postdoctoral researcher at the University of Helsinki.

Elisa Hurmekoski, postdoctoral researcher at the University of Helsinki

The potential of wood consumption in the mitigation of climate change

As for the overall climate impact of forests and wood consumption, Hurmekoski emphasises the need to distinguish between the present state and the potential of climate change mitigation.

“Analyses carried out from these different perspectives can result in completely opposite conclusions. If you add up the carbon sink of forests, the substitution effects and the carbon storage of wood products, the sum is more or less equal to Finland’s current greenhouse gas emissions. In a sense, this leads to the conclusion that our forest sector compensates for Finnish emissions in practice.”

“This is in itself a valid interpretation, but if we’re discussing the potential to curb climate change, we must examine changes from the present state. This means balancing the development of carbon sinks and the fossil greenhouse gas emissions that are successfully avoided. For additional felling to be justifiable from a climate perspective in the short term, average substitution effects should nearly quadruple from the present. This does not exclude climate benefits in the long term – over a few decades or a century – since the replanted forest gradually sequesters carbon from the atmosphere.

“A key consideration is that substitution effects can be increased by making changes to the product portfolio, irrespective of the felling volumes,” Hurmekoski says.

Key concepts

When a forest acts as a carbon sink, it stores more carbon dioxide than it releases into the atmosphere. In other words, carbon sinks track changes in the carbon storage of forests.

Substitution effects mean the fossil greenhouse gas emissions that have been avoided. For example, the use of wood products in construction displaces products with higher emissions, such as concrete or steel.

The carbon storage effect of wood products results from wood being made into products. Carbon remains sequestered in the products throughout their life-cycle. Carbon may remain in wooden constructions for up to several decades but is released from paper in a few years. The carbon storage effect is comparable to a sink if the volume of wood annually stored in products is greater than the volume released.

This article, written by Armi Purhonen, was published in Metsä Group’s Viesti magazine issue 1/2021.
Image: Seppo Samuli

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