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. Plants use the carbon 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. ‘During the lifetime of biobased building materials like these, there is therefore less CO₂ in the air,’ explains Arjen van Kampen, a project lead and coordinator construction materials at Wageningen Food & Biobased Research (WFBR).

And that is valuable as we move towards more biobased construction, 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 Martien van den Oever, researcher at WFBR. He and his colleagues therefore worked on a calculation method to quantify precisely that gain in time.

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 Kampen. ‘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. ‘And it would give biobased materials a fairer chance 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 biogenic carbon a material stores and the longer it remains stored, the greater the positive 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, to be fair, fossil materials primarily emit CO₂ and have not recently absorbed it from the atmosphere.’ Crude oil also contains carbon, of course, but that carbon is millions of years old. ‘With fossil resources, the biggest impact can be achieved just by leaving them alone,’ adds Van Kampen.

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, the homes were comparable, but were built using different types of materials.

The environmental impact of biobased homes was between 18 and 35 per cent lower. This did not even include biogenic carbon storage, which turned out to yield an additional 10 to 25 per cent in environmental benefit. 

The difference between biobased and conventional materials is actually even larger than is apparent at first glance. The environmental impact of all the reference homes is largely determined by standard elements such as installations. Many of the construction activities, which also generate emissions, are the same for all homes. In biobased construction, these standard elements account for up to 54 per cent of the overall environmental impact. The difference between biobased and conventional materials is therefore actually even greater, as the 18 to 35 per cent reduction is achieved with only some of the building materials.

Van den Oever and his colleague did not stop at these calculations. They also helped to add 13 biobased materials to the database by providing lifecycle analyses for them. ‘We believe in these materials,’ explains Van Kampen, ‘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. ‘A fairer valuation of biobased products can help us make better use of the climate benefits they offer.’