Why does timber have a negative carbon footprint?

There is a material revolution happening in the construction industry and it’s having a major positive impact on the environment. By swapping cement and steel for timber, the notoriously polluting construction sector could not only avoid greenhouse gas emissions but actually make their projects carbon negative. This is because timber acts as a natural carbon sink – storing the CO2 that’s taken from the air by the trees that are harvested and used to create timber.

How does it work?

Mother Nature is quite clever really. Indeed, our planet has natural mechanisms in place to help keep carbon dioxide at optimum levels.

As a natural product, wood is designed to help keep the balance in check using photosynthesis, which takes carbon from the atmosphere and converts it into wood, which is mostly carbon based atoms.

During this process, as only sunlight and water are required to fuel it, CO2 is absorbed and broken down so that oxygen is released back into the atmosphere whilst the carbon remains in the wood.

In this manner, wood effectively acts as a carbon sponge and that’s why forests play such a vital role in the global carbon cycle – now more than ever as we pump increasing amounts of CO2 in the atmosphere.

Thanks in no small part to the intervention of the FSC®, some forests are protected, resilient, and capable of producing large volumes of timber sustainably. This means that construction projects built primarily using materials derived from these forests might have a minimal or even negative carbon footprint.

Using buildings as carbon stores

The construction industry is responsible for 39% of all carbon emissions worldwide so something truly needs to be done to help them change their ways. There are many things they could be doing to help cut down their carbon footprint, but using wood-based materials in their projects is a great place to start.

The largest potential, of course, lies in external walls (timber cladding), floors, and roofing, which, together with the frame and insulation. can significantly reduce the carbon footprint of a building if built with timber. Huge amounts of carbon can potentially be stored in a building over the course of its life as long as it is well-maintained.

What’s more, any wooden parts of the buildings that are no longer used can also be easily recycled into other products such as furniture, toys, etc – keeping the carbon locked away as the wood enjoys a new lease of life.

How Sustainable is Wood Used For Timber?

When a tree is turned into timber, it is not left to rot. This means that the sequestered carbon is stored for as long as the timber is used. 1kg of dried timber contains around 0.5kg of carbon. Thus every kg of timber used in construction represents 1.8kg of absorbed CO2e.

A small amount of this carbon is let back into the atmosphere during production and processing. During these processes, although more CO2e is released, it still usually is not more than the amount sequestered, giving a negative net embodied carbon for the timber you use.

End of Life and Disposal

The latest figures from 2011 show that only 60% of timber used for construction in the UK is either reused or recycled at the end of its life. The rest ends up in the landfill, which is not quite so eco-friendly. This is a lot less than other construction materials, though it is expected to increase because of the UK landfill tax escalator.

However, timber cannot be recycled easily in the traditional sense of the word  – which works to reprocess materials into a brand new product with the same characteristics. Nevertheless, it can be recycled into slightly lower grade products, such as animal bedding and wood particleboard.

Timber which has been taken to the landfill, on the other hand, will slowly decompose. As it does it gives off methane, an extremely powerful greenhouse gas. A small amount of this can be stored and used in energy production, but most of it will be released into the atmosphere.

However, it is good to note that around 96% of the carbon stored in the timber is not converted into methane and released. Instead it moves into the soil as the wood decays and remains there, potentially locked away for thousands of years.

Other Indicators for Sustainability in Construction

Standards such as BS EN 15804 look at and consider any additional indicators which can be used to measure sustainability in construction. These include:

• Depletion of the ozone layer
• Energy, water and resource use
• Land and water pollution and acidification
• Eutrophication

The Environmental Product Declarations (EPD) data does not see any consistent environmental concerns for timber when looking at these indicators. The only area where sustainability does fall a little is in water use, which is usually high for timber because of the amount of rainwater needed to grow a tree. Though as it is rainwater and not treated water which is used, the impact is fairly low.

The Global Carbon Cycle

Forests play a huge role in the world’s carbon cycle and are key in our fight against climate change. They are major and essential carbon sinks, absorbing CO2 from the atmosphere and storing it safely, helping to lower levels in the atmosphere. By increasing the forest area of the planet and using timber sourced from responsibly managed forests, you can invest in a method of carbon capture which is proven to help our planet. It is a strategy which can reduce the effects of our past carbon emissions, working towards a greener, safer future.

Choose Sustainable Timber With FSC

At EcoChoice, we know the value of sustainable timber, both for what it can bring to your project and what it can do for our planet. If you would like to learn more about this eco-friendly construction material, feel free to get in touch with our team today! We can also match your needs to the right timber species, ensuring your project has exactly what it needs to be a sustainable success.

Looking ahead

An increased use of timber is perhaps one of the most logical ways that the construction sector can help to stabilise an increasingly unstable climate. But there needs to be a major change if we have any hope of really making an impact.

If business is to continue as usual, for example, then just 0.5% of new buildings will be built with timber by 2050. If mass timber manufacturing increases, however, then studies have suggested that as much as 90% of timber construction is conceivable. This would result in a world where 700 millions tonnes of carbon are stored per year.

There are currently 11,000 million tons of carbon being emitted per year, so this would only offset a percentage of the damage being done. However, if the construction sector, one of the world’s most notoriously polluting, can set a precedent by making a more considered move into a more sustainable future then it’s only surely a matter of time before the rest of the world follows suit.