Build with biobased materials
Building with biobased materials instead of CO2 intensive materials like concrete reduces CO2 emissions and energy consumption in buildings.
Using biobased materials
The building sector is a significant consumer of raw materials, contributing a substantial share of CO2 emissions worldwide. In the Netherlands, the sector accounts for 40% of all CO2 emissions (1). Simultaneously, the sector faces numerous challenges in terms of new construction, sustainability, and building renovations. It is therefore crucial to explore alternative materials that can help reduce CO2 emissions and support the transition toward a circular economy. Biobased materials offer a promising solution in this regard.
Biobased materials are derived from renewable biomass, sourced from natural resources. Incorporating biobased materials into construction is considered a key step to achieving a fully circular building sector. Currently, their use remains relatively low. For example, in the Dutch construction sector, wood constitutes only 2% of all materials used, while other biobased materials represent a mere 0.1% (2). The global construction industry faces similar challenges, with the adoption of biobased materials progressing at a slow pace (3). Therefore, it is crucial to accelerate and promote the use of biobased materials.
Benefits of biobased materials
The use of biobased materials offers several advantages:
As traditional raw materials become scarcer, biobased materials provide a renewable alternative with shorter delivery times.
CO2 emissions during material production are considerably lower than traditional building materials. When it comes to insulation material, for example, the CO2 emissions for biobased wood fiber is 2.6 kg CO2 per m2, whereas for rockwool it is 5.6 kg CO2 per m2 (4). Furthermore, promoting local production chains reduces the CO2 impact of transportation.
Natural materials also contribute to a healthier indoor climate. This is because biobased construction focuses on ‘vapor-open’ construction versus traditional ‘vapor-closed’ construction. Biobased materials allow humidity to be regulated naturally, as vapor-open construction allows the material to breathe.
Several biobased materials, such as straw and hempcrete, have higher thermal capacity than traditional building materials, meaning they retain heat more effectively.
Biobased materials offer the potential for associated carbon removal, since they act as a temporary CO2 storage, ranging from decades to centuries.
As mentioned earlier, the global use of biobased materials is slowly increasing, but progress remains limited. While timber constructions have seen some acceleration, the adoption of other biobased products lags (5).
One pressing global challenge that biobased materials could help solve is urbanization. The United Nations estimates that by 2050, nearly 70% of the world's population will reside in cities. Rapid urban growth translates into a higher demand for housing and other buildings in urban areas. However, buildings significantly contribute to CO2 emissions, primarily due to the use of concrete and other carbon-intensive materials. To reduce this CO2 impact, the use of biobased materials is crucial. An illustrative example is provided in Figure 1 below.
Figure 1 – The Urban Woods (2)
The Urban Woods is a housing concept in the Netherlands with a support structure composed entirely of wood and other biobased materials. As a result of this design, 102 energy-neutral, climate-adaptive, and nature-inclusive apartments will be constructed (3). Moreover, the building is 85% circular, meaning its components can be almost completely reused. In Figure 2 and 3, the wooden construction is shown next to the final building. In addition to the building itself being constructed in a manner that is completely sustainable, it also serves to inspire people to live more sustainably.
Figure 2 & 3: The Urban Woods, wooden construction and final building (2)
Targeted emissions sources
The use of biobased materials reduces the environmental impact of Scope 3 emissions. Depending on the perspective (building owner, lender, or constructor), the emissions can be categorized within the Scope 3 GHG Protocol. Below is a summary of the targeted emission sources:
Category 1: purchased goods and services:
Biobased materials reduce CO2 emissions during production because these materials are significantly less CO2 intensive compared to traditional building materials. The CO2 emissions associated with producing biobased wood fiber, for example, is 2.6 kg CO2 per m2 and for rockwool it is 5.6 kg CO2 per m2.
Category 4: upstream transportation and distribution:
Opportunities are created for more local production chains, reducing the impact of transporting materials, since shorter distances need to be covered.
Category 13: downstream leased assets:
The use of bio-based materials improves the indoor climate in buildings, often reducing the need for installations. This reduces energy consumption.
In addition to the lower CO2 impact of producing biobased materials compared to their traditional counterparts, biobased materials also offer the potential for an associated carbon removal, acting as a temporary CO2 storage, ranging from decades to centuries.
To determine the full GHG impact of biobased materials, the net removal needs to be assessed against the full lifecycle emissions and compared against its storage permanence.
Additionally, it is essential to consider the recyclability of the material, as some biobased materials currently have shorter lifespans. When recycling becomes challenging, the stored CO2 is unfortunately released back into the atmosphere.
Table 1 below shows the extent to which each material can store CO2. For wood, an average has been taken from various tree species.
Table 1: CO2 storage of biobased materials (4)
ton CO2/1000 kg (two weeks)
In addition to the climate impacts of using the biobased materials described above, there are also financial benefits.
Due to the scarcity of materials, the construction process can sometimes take longer than planned. Because biobased materials are renewable, delivery times can be shorter, which helps speed up the construction process.
Biobased materials in buildings provide a better indoor climate, which can possibly result in the need for a reduced number of installations in a building. Besides bringing environmental benefits, this can also reduce construction costs.
Using bio-based materials creates opportunities for more local production chains. Besides being financially advantageous for local farmers, this also reduces transportation costs of the materials by shortening transport distance.
Biobased materials are often seasonal, so they are not always available year-round, which can sometimes slow down the process.
Biobased materials currently tend to be more expensive than non-biobased materials because they are offered on a much smaller scale. For example, the biobased insulation material flax fiber has an average price of around EUR 18 per m2, compared to rock wool, which is around EUR 11.
Impact beyond climate and business
In addition to climate and business-related benefits, building with biobased materials can often also have a positive effect on building users and/or residents. As mentioned in the Urban Woods example, the goal of the architects was also to inspire residents to make more sustainable choices. With biobased materials, sustainability becomes visible, which can positively affect people’s mindsets and behaviors.
Unfortunately, building with biobased materials is not black and white when it comes to the CO2 impact. It is therefore important to apply nuances and consider possible side effects. First, land use may increase with the use of biobased materials. An example is deforestation, because natural materials are used. In addition, agricultural land is scarce, with food production often taking precedence over the production of material. Fortunately, biobased materials can also be made from waste streams. It is therefore essential to have insight into the entire value chain of biobased materials, which is still quite complicated. On the one hand, it is better to buy wood from Europe, for example, as the FSC certification is often more reliable within Europe. On the other hand, the climate in the Tropics, for example, lends itself better to the tree growth, making the wood stronger and sometimes more suitable for construction. Therefore, it is still better to use residual material, biobased or non-biobased, than it is to buy new biobased materials.
Key parameters to consider
The use of biobased materials is still, for the most part, an early-stage innovation. When it comes to building with wood as a construction material, the industry is already a step ahead.
Technical constraints or pre-requisites:
Conflicting issues sometimes arise when building with biobased materials, like wood. One example is that acoustic solutions are sometimes difficult to achieve by today's standards with a wooden construction. This often results in adding another layer of concrete or other material to the structure to create more mass, which creates additional CO2 emissions. If a wood floor is laid in a building, one solution may be to fill the hollow space under the floor with recycled rubble, which benefits acoustics.
One of the bigger barriers to using biobased materials is the concern about whether these materials can meet fire safety requirements (6). This concern is sometimes addressed by adding an extra layer of protection or chemical additives, which increases the environmental impact. Research is underway to find (environmentally friendly) alternatives to meet fire safety requirements. For large-scale research into this, it is important that parties join forces to remove barriers and increase the use of bio-based materials in the building sector. This increase will eventually build confidence that bio-based materials can indeed meet fire safety standards.
Another technical challenge regarding building with wood as a structural material is stability. Often, wooden structures still require a concrete core to provide reinforcement. To overcome this, a wooden stability system can be moved to the facade of the building.
Implementation and operations tips
To increasingly implement the use of bio-based materials in buildings, it is important that they are included as a starting point in the program of requirements. If they are only included at a later stage, they could be difficult to manage and may conflict with the building schedule or budget. However, if they are included in the designs early on, the process can be better equipped to make it work.
It is thus essential to work with companies that have substantive knowledge of building with biobased materials, while also being aware of the nuances and potential side effects. In the end, it remains an early-stage innovation, and it is important to continue developing this area to truly achieve decarbonization.