Building against climate change
One of the current climate objectives is the reduction of our CO2 emissions. But can we also extract CO2 from the atmosphere at the same time? This is possible at high costs and in limited scale through machines currently being developed. However, there is still no machine as cheap and efficient as the tree. We learn early in school that trees convert CO2 into glucose or wood under the influence of sunlight. As trees die and decay, some CO2 is released again. When we burn wood and use it to generate electricity and heat up our homes, the stored CO2 is further released. The disposing of paper or wooden utensils also reverses CO2 absorption. However, if we make building materials out of it, we can capture the stored CO2 for dozens, perhaps hundreds of years! In other words: by building with wood, CO2 is actually extracted from the atmosphere. In contrast to, for example, costly storage under the North Sea (CCS), this form of CO2 storage actually creates value in the form of buildings. The construction sector can thus play an active role in the fight against climate change. That is certainly true now that the Netherlands is on the eve of a huge housing challenge; one million houses have to be built in the Netherlands in the next 20 years. In addition, a large part of the existing homes must be made energy efficient. Both assignments act as a powerful driver for the transition to a bio-based economy.
The emission of nitrogen over the entire chain is also many times lower in biobased building than in the traditional building process. Together with, among other things, shrinking livestock and lowering the maximum speed, biobased building is therefore an important part of the answer to the current nitrogen crisis.
The construction sector is responsible for an important part of global CO2 emissions. But the global pressure on natural resources is also high: 40% is used in construction. In the Netherlands, that amounts to 250 million tonnes of raw materials per year for infrastructure, residential and non-residential construction. There is now a shortage of raw materials, in particular "angular" sand. In addition, the construction sector is overheated and qualified personnel are scarce. As a result, prices are rising. Change in the construction sector is therefore also necessary in order to realize the required housing. Building with wood offers an alternative whereby the total production capacity can be increased. Pre-fabrication and simple assembly also increase construction speed.
Solid wood construction
For almost all building parts there are biobased alternatives such as wood wool and cellulose for insulation and hemp fiber and flax in biocomposite elements. But especially the use of solid wood as a material for the body; the walls, floors, stairs and roofs, has a lot of potential. Fast-growing wood can be glued crosswise to large sheets in different thicknesses under the name cross-layer wood (KLH) or "cross-laminated timber" (CLT). Of these, large structural elements can be prefabricated in an industrial manner in the desired shape and provided with recesses for, for example, windows and pipes by means of CNC milling. These elements are then assembled "dry" at the construction site. This construction method is still in its infancy in the Netherlands, but application in Austria and Germany, for example, shows the possibilities for construction speed, construction costs and working conditions for construction workers.
In addition, solid wood construction has a tactile quality and promotes a pleasant indoor climate. By making solid wooden elements modular, they can easily be replaced or adjusted, which increases the flexibility of use. When a CLT building is no longer adequate, it can be dismantled relatively easily and the modular elements can be reused in a new building. If the elements no longer meet the requirements, they can be recycled into low-grade wood products such as veneer, chipboard and insulation material.
Where do we get all that wood? The Netherlands has a total of 365,000 hectares of forest, more than half of which has been laid out as production forest for, among other things, firewood and logs with which mine aisles were propped up. 225,000 hectares of Dutch forests are now protected nature areas. The remaining 140,000 hectares of forest can be used for the sustainable production of wood, as is often the case in Scandinavia. This means that trees are harvested in a limited and selective way and replaced by young specimens of the same or different species. This yields an average wood harvest of 8m3 per hectare per year, with poplars even up to 15m3 per hectare per year. Converted to an annual production of 1.12 million m3 of wood. By diversifying the size and type of forest plantations, ecological, landscape and recreational added value is also created in the often monotonous (coniferous) forests. This also benefits soil life that suffers from nitrogen emissions from traffic, the bio-industry and (conventional) construction.
An average of 50 m3 of wood is required for the construction of a home. That means that we can make 22,400 homes from Dutch wood every year and need 45 years for the realization of 1 million "home-grown" homes. If we want to speed up production, or if we want to use the available wood for other purposes, we can import wood or plant more forests. Higher demand for wood therefore does not lead to clearing, but to more and better forests! Adding value to forestry is also an impetus for parts of the Netherlands that suffer from poor soil quality, low spatial quality and / or a declining agricultural economy. And maybe we can even live in the new forests. Building with wood could therefore make the Netherlands more beautiful!
If not now then when
How do we get the transition to biobased material use started? After all, we are used to buildings made of concrete, stone and steel in the Netherlands, and wood still seems to have to prove itself here. A number of example projects must therefore be realized quickly. Preferably entire neighborhoods, so that the economies of scale of prefabrication will count. And the construction chain gets the chance to organize itself in the Netherlands. Governments can play an important role in this by making construction sites available under the condition that biobased materials are used for building.
The demand for biobased material use in construction will also increase if the price of traditional materials such as cement rises. The shortage of traditional raw materials will help, as well as the announced CO2 tax. And possibly storing CO2 in a building may even become a revenue model!
ir. Marco Vermeulen, ir. Bram Willemse, ir. Joost van der Waal, Msc. M.Arch. Bertus van Woerden, ir. Joyce Langezaal, BSc. Jasper Veldhuis, MSc. Joshua Ho, MSc. Francisco Monsalve
in cooperation with
Arup Structural Engineering Pavillion
Lüning Structural Engineering Stairs
Derix Laminated Timber CLT
BLC de Kruijff Structural steel elements
Brabantse Populieren Vereniging Trees
Blok Timmeratelier Traditional
Towards a sustainable, economically resilient and more beautiful Dutch-Belgian delta region.