The necessary path to decarbonisation
Bio-based materials will have to be used more extensively if the environmental damage caused by the construction sector, a major emitter of greenhouse gases, is to be limited. But there is still a long way to go.
The growing climate crisis and soaring energy costs are causing us to reinvent the common materials and methodologies in our sector that are more sustainable, more local and CO2-negative. If there is a positive side to this situation, it is that Belgians are becoming more aware than ever of the need to insulate their homes given the sky-high energy costs. After all, as is often said, the cheapest energy is that which is not consumed.
In this respect, bio-based materials should be at the forefront of any decision to build or renovate.
But what exactly are they? They are materials that are derived from renewable organic matter (also known as biomass) of plant or animal origin. Wood (timber and related products) is the main bio-based material, but it is far from being the only one. Others include hemp, rapeseed, flax, straw, cork, cellulose wadding, miscanthus (a plant originating from Asia, also known as Chinese reed), meadow grass, etc.
The use of bio-based materials means more sustainable and environmentally friendly housing. The construction sector is responsible for 9% of greenhouse gas emissions worldwide. The European Green Deal calls for these emissions to be reduced by at least 55% by 2030, compared to 1990 levels. In short, if the sector wants to reach this target it will have no choice but to use bio-based materials. It is worth pointing out that they are already an obligation in the Netherlands and in France, where the “Climate and Resilience” law, passed at the end of July, will require bio-based materials to be used in at least 25% of major renovations and public buildings from 2030 onwards.
These low-carbon materials are mainly used in the field of thermal and acoustic insulation. Hemp is also used in the formulation of lightweight concrete.
For the sake of completeness, it should be noted that alongside bio-based materials there are also geo-based materials derived from mineral resources that require little processing before use (dry stone, raw earth, etc.), and eco-materials that have a low environmental and energy impact in terms of their composition from manufacture to the end of their life cycle.
Bio-based materials are derived from biomass, which is renewable by its very nature, but they can also be derived from recycling. They offer three major advantages. Firstly, they are able to capture CO2 from the atmosphere and store it throughout the life of the building. Secondly, their transformation and manufacture require little energy. For example, the amount of grey energy required to use straw for insulation is 140 to 180 times lower than that used to produce expanded glass, rock wool or extruded polystyrene.
Thirdly, bio-based materials have very good hygrometric and thermal qualities with excellent indoor air quality because the most demanding VOC (volatile organic compound) emission thresholds are far from being reached. In short, using bio-based materials is not only environmentally friendly but also good for your health.
The disadvantages are that these materials are sensitive to humidity. They must therefore be used in the context of dry processes with highly advanced prefabrication. Furthermore, in order to improve their performance, some bio-based materials contain related products and additives. Examples include binders (polyesters) for their cohesion and durability, fire retardants, etc.
However, they are still not yet used in Belgium to any great extent. Since we know that wood (used in structures or insulation panels) is the most highly used bio-based material, but that only 7.7% of new homes were built from wood in Belgium in 2020, we are better able to measure the progress that remains to be made. The figures provided by Houtifobois confirm this stark delay: in 2011, the proportion of timber houses reached 6.59% of the total number of building permits authorised for a residential building with a single dwelling (24,298). Nine years later (in 2020), the figure was 7.71% (for 24,035 permits granted). This stagnation is striking and calls for some urgent raising of awareness.
Bio-based insulation represents only 5% of the insulation market. The most frequently used material is wood fibre (50%). There is a glimmer of hope, however: the dynamic of these insulators on the market is very strong, with annual growth rates of more than 10% over the last few years. The current crisis is sure to reinforce their use, as will current and future legislative constraints.
According to a French study (IFPEB and Carbone 4), if the carbon neutrality objectives for the entire construction sector are to be met, the volumes of wood products will have to increase by 60% between now and 2030 and be multiplied by 2.5 by 2050, compared to 2015 levels.
The biggest problem with bio-based materials is that they are still being used far too little. As a result, the players involved in this market are small in scale. Expertise is scarce and the level of industrialisation is very low, which implies obvious additional costs. This problem will only be solved by a significant increase in demand.
However, we can conclude on a positive note: the bio-based sector allows the use of local resources. And Belgium has enough of them. So why wait?
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