Carbon accounting, embodied carbon and UK grown timber

At Buckland Timber, we love working with local timber. We take great care to source from sustainably managed woodland and forests, as close to our manufacturing facility as possible to reduce carbon cost but also ensure quality standards are met.

Many of our projects are created using locally grown, UK sourced timber, but we also use imported beams for some projects too. We do both as they complement each other well and provide a range of services to our customers.

We’re sometimes asked what the difference is between using UK sourced timber and in-house manufacturing versus using imported beams. There are a few reasons why you might choose one over the other; type of wood, suitability, cost, the timescale for completion etc.

One of the reasons can be the sustainability of construction materials. Sustainable building is essentially producing as little CO₂ as possible, and customers sometimes seek low embodied carbon suppliers and manufacturers.

What is low embodied carbon?

Simply put, low embodied carbon is the amount of carbon dioxide or greenhouse gas emissions associated with the manufacture and use of a product or service. For construction products and projects, this means the CO₂ or GHG (greenhouse gas) emission associated with extraction, manufacturing, transporting, installing, maintaining and disposing of construction materials and products.

This can be quite complex to work out, particularly with certain building materials. Trees for example used for building material, sequester atmospheric carbon dioxide while they grow. This might outweigh the emissions produced during manufacture, so it’s not as simple as it might seem calculating the overall emissions!

We’re always interested however in learning more about what low-embodied carbon actually means and how we can help inform our customers, so we wanted to explore whether there is a carbon difference between imported and home-sourced timber.

Wood being transported by Devon Oak

Comparing locally grown to imported timber

To see how the carbon footprint would compare if a customer were to use German-imported glulam instead of locally sourced timber, we took a closer look at a recent project of ours using local larch.

There were inevitable differences in the timber harvesting, milling and processing efficiencies of glulam production between Devon and Germany. For example – at Buckland we use manual presses rather than hydraulic ones, which makes it difficult to compare the felling, drying and manufacturing processes like for like.

To get around this complexity and variability, the main accounting tool for construction products – Environmental Performance Declarations (EPDs), uses one common figure for the production of sawn boards and the lamination process*.  This means that, as far as official carbon accounting is concerned, the carbon cost of a UK and German beam is the same.

So far, not helpful, but there is a great analysis for glulam produced by Wood for Good which breaks down all the elements of the life cycle. The biggest measurable difference from this between home-grown and imported beams is the carbon dioxide produced during transportation.

The carbon impact of transporting glulam

With this in mind, we decided to look at the impact of transporting glulam rather than the entire lifecycle carbon cost.

Using values based on the UK Government 2021 greenhouse gas conversion factors for company reporting we were able to estimate that the transport impact associated with using locally sourced timber contributes over 10x less CO₂ to the atmosphere than if we were to import the same material from Germany.

That is a massive saving for the planet and certainly not something to be overlooked for those conscious of making a more sustainable choice.  For this particular project, using imported and home-grown worked out like this:

 German manufacturer to site = 1017km

0.000107 kgCO₂e**/kg/km x 1017 = 0.11kg CO₂e/kg

Buckland to site = 129km

0.000107 kgCO₂e/kg/km x 129 = 0.01kg CO₂e/kg or

For the 23m3 of larch in this project, the carbon cost of transport if imported would have been 1,240kg of CO₂ but was reduced to 113 kg of CO2 – a saving of 1,127kgs of CO₂

Much as we are proud of our local heritage, this does not mean we advise always choosing locally grown timber; as we said at the beginning there are many reasons why imported timber may be most suitable for your project.

What we can confirm though, is by specifying local timber in your projects, design, and planning, you can be assured your project will have a more positive environmental impact than the same material being imported.

If you would like to talk this through with one of our team for one of your projects do get in touch.

*In a future post we may look at EPDs and why we have not gone down this route to date as well as timber species options and the circular economy of using UK grown timber.

**the “e” in these figures and other carbon accounting figures means “equivalent”.  The notation says it is an estimate that reflects the complexity and inherent variability in these calculations.