Wood, flax, elephant grass and other plant-based raw materials are gaining ground in construction. And not without reason: biobased building materials can play an important role in the fight against climate change. But how sustainable are these materials really? And how do they compare to traditional building materials such as concrete and plastic?
These questions were central to a recent study by Wageningen University & Research (WUR), conducted in collaboration with IA Bouwkunde, Agrodome, Centrum Hout and the Stichting Nationale MilieuDatabase (NMD). The results are clear: building with biobased materials leads to a significant reduction in the environmental impact of homes — by an average of 18 to 33 percent compared to conventional construction methods.
Homes as a measuring instrument
In order to make a fair comparison, WUR analysed three reference houses: a terraced house, a semi-detached house and an apartment. For each type of house, the environmental impact was compared when using biobased materials (such as timber frame construction and Cross Laminated Timber) versus conventional materials (such as concrete and sand-lime brick). The entire life cycle of materials was considered: from production and transport to processing, use and end of life.
The outcome was consistent: biobased building materials structurally score better on the so-called environmental performance (MPG). This is partly due to the intrinsically lower emissions during production, but also due to practical advantages. “Biobased materials are lighter, which means that the foundation, for example, does not have to be as heavy,” explains project leader Martien van den Oever (WUR). “That translates into additional environmental benefits.”
The role of biogenic carbon storage
An important part of the research concerned the so-called biogenic carbon: the CO₂ that is captured during the growth of plants and (temporarily) stored in the end product. If flax or wood is processed into a building material, this carbon can sometimes be stored for decades — up to 75 years or longer. This effect is not included in many environmental accounts, while in practice it does contribute to emission reduction.
“This temporary storage is not a long-term solution,” Van den Oever qualifies. “But it gives us valuable time to develop structural solutions for climate change.”
Hidden in the database
A major problem is that many biobased building materials are simply still missing from the National Environmental Database (NMD). Without inclusion, architects and project developers cannot include these materials in their MPG calculations, which are increasingly used as an award criterion for construction projects.
“Many biobased products are developed by smaller parties, in relatively small quantities,” says Van den Oever. “They logically focus on production and sales, but mapping the environmental impact often lags behind.”
That is why WUR also worked on LCAs (life cycle analyses) for thirteen biobased products that were not yet included in the NMD. A uniform calculation method was also developed to correctly include CO₂ storage.
Conflicting regulations
Where the Netherlands goes relatively far in including multiple environmental impact categories in the MPG calculation, a crucial factor is missing: biogenic carbon storage. This is not recognised in the current calculations, despite the fact that it can temporarily make an important contribution to emission reduction.
To change this, WUR is working on a proposal for a valuation formula that includes CO₂ storage in a uniform manner in the calculation of environmental performance. The proposed time horizon is 100 years — the same as what is common in LCAs on climate impact.
“It is remarkable that the Netherlands includes less certain categories, but disregards something measurable such as CO₂ storage,” says Van den Oever.
Source: WUR
