How biobased materials slow down climate change

Everyone learns at school that plants absorb carbon dioxide from the air and then release oxygen back into it. This gives plants carbon that they process to make stems, leaves, branches and trunks. The planet’s forests therefore store a vast quantity of carbon. This is what scientists refer to as biogenic carbon storage.

These trunks and branches, as well as fibre from plants such as flax and bamboo, are increasingly being used to manufacture building materials — not just beams and planks but also panels, cladding or even entire prefabricated elements. The carbon also remains sequestered in all these applications. ‘Less CO₂ is therefore released into the air during the lifetime of biobased building materials like these,’ explains Martien van den Oever, a researcher at Wageningen Food & Biobased Research (WFBR).

That is valuable despite the fact that the carbon will eventually end up back in the atmosphere. ‘It gives us longer to develop solutions that can reduce emissions, or methods for removing carbon from the air,’ explains Van den Oever. He and his colleagues have therefore worked on a calculation method for precisely quantifying that benefit.

Anyone wanting to build in the Netherlands generally requires an environmental and planning permit. One part of that is an environmental performance calculation that lets contractors and architects demonstrate the impact of the building materials they would like to use. For a calculation like that, they need data about the materials. What is the lifespan of the material? How environmentally friendly is the production? Can it be easily reused? That information is held in the National Environmental Database (NMD) – or at least, that is the idea.

Demonstrating the low environmental impact of biobased building materials is not always straightforward. ‘Many biobased materials are relatively new,’ says Van den Oever. ‘They’ve often been developed by smaller companies that weren’t particularly focussed on making their environmental impact visible.’ On top of that, the effects of biogenic carbon storage are not yet included in the NMD’s calculation methods, which gives a misleading picture. Conventional materials can then seem to be equivalent to biobased alternatives, whereas in reality they release more carbon dioxide into the atmosphere.

Having a reliable method for calculating carbon storage, so that it can be included in environmental impact calculations, would make things clearer. ‘It would lead to faster acceptance of biobased materials in construction,’ adds Van den Oever. That is why the NMD asked Van den Oever and his colleagues to develop a new valuation formula.

The WFBR researchers were not the first to try to quantify biogenic carbon storage. ‘But the existing formulas were often too complex for use in a policy context,’ explains Van den Oever, ‘even though they were based on solid scientific work. We’ve turned them into a single formula that can be incorporated more easily into environmental calculations.’

This is roughly how the new formula works. The amount of carbon in the biobased building material and the length of time it stays stored are compared against the impact that the same amount of carbon would have had if it had been in the atmosphere during that period. The more carbon a material stores and the longer it holds on to it, the greater the impact. The construction materials used in terraced houses or office buildings can sometimes last for 75 years or more, so the biobased materials are keeping carbon out of the atmosphere for a significant time.

‘The formula works for all materials,’ says Van den Oever emphatically. ‘Both biobased and fossil. Although it should be said that fossil materials primarily emit CO₂ that hasn’t recently been absorbed from the atmosphere.’ Crude oil also contains carbon, of course, but it is millions of years old. Furthermore, that carbon is often released during production processes. ‘With fossil resources, the biggest impact can be achieved just by leaving them alone.’

Biobased materials can therefore have a lower impact on the environment than fossil-based ones, for example. But how big is the difference? To show this, researchers compared the environmental impact of biobased and conventional buildings. They calculated environmental performance figures for three types of reference homes — a terraced house, a semi-detached house and a flat — for variants built with conventional materials and ones that made maximum use of biobased alternatives. In other words, it was exactly the same house or flat but built using different materials each time.

The environmental impact of biobased homes was between 18 and 35 per cent lower. This did not even include biogenic effects, which turned out to yield an additional 10 to 25 per cent in environmental benefit. Biobased materials are not only less harmful to the environment individually, they also offer other indirect benefits in conjunction. ‘In biobased construction, foundations can be lighter because the materials used weigh less than concrete, for example,’ explains Van den Oever. That makes a difference too in the fuel needed for transport.

The difference between biobased and conventional materials is actually even larger than is apparent at first glance. The environmental impact figures for all the reference homes are largely determined by standard items such as electricity. Much of the construction work, which also generates emissions, is also the same for all homes. In the biobased construction work, these standard items account for up to 54 per cent of the overall environmental impact. Compare that against a semi-detached house built on concrete foundations, where the standard elements account for 23 per cent of the impact and the materials therefore account for 77 per cent of the environmental impact.

Van den Oever and his colleague did not stop at these calculations. They were also able to add 13 biobased materials to the database by providing lifecycle analyses for them. ‘We believe in these materials,’ explains Van den Oever, ‘but confidence alone isn’t enough. Policymakers, architects and contractors need reliable data and values for making decisions.’

The mitigating effect of biogenic carbon storage gives the world more time to shift towards climate-neutral practices. ‘It’s not meant as a way of passing the buck — it’s a way of creating space to take action.’ This gives innovations in biobased materials — both in construction and elsewhere — a better chance of making an impact. ‘Fairer evaluations of biobased products can help us make better use of the climate benefits they offer.’