Shortage
Global urbanization is increasing the demand for affordable housing. Sustainable houses constructed using a mix of recycled plastic and sawdust may be part of the solution to the housing shortage. DTU helped test the plastic-based building material.
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The company was founded in 2018 and was heavily inspired by the tiny house movement.
“The most sustainable square metres are the ones you don’t build,” says Morten Bove and continues: “We insist on creating small houses. If someone asks, ‘Can we get one that’s 100 m2?’, we say no, because that’s not the way to go.”
The 3D printer’s ‘ink’ consists of a mixture of recycled plastic and sawdust. The insulation for the walls, ceiling, and floors is made of wood wool from wood waste. This recipe enables WOHN to reduce the carbon footprint by 90 per cent compared to a house of the same size built with conventional materials.
“Every time we produce a new 20 m2 house, we’re recycling four tonnes of plastic waste and saving 15 tonnes of CO2 compared to traditional construction work,” says Morten Bove.
The most sustainable square metres are the ones you don’t build.
The first homes are scheduled to be ready in early 2023, and several municipalities and private landlords are queuing up to have them delivered to use as student and holiday homes.
According to Morten Bove, the flexibility of the houses is key, as they can be moved around and placed as needed. Thus, they can be used in a forest kindergarten for a few years and then as refugee housing somewhere else later. “This could be an alternative to the incredibly expensive prefabricated buildings that municipalities rent in huge quantities for long periods of time.”
The UK is also interested in the company, as the public sector is struggling to deliver on its promises of building the many planned affordable homes. WOHN is also in talks with the authorities in Kenya to deliver modules to be used for schools and housing, among other things.
Morten Bove sees great potential in introducing their solution to developing countries where plastic waste is a huge problem and people live in terrible conditions:
“Imagine if you could create a system where people collect plastic waste from the streets, hand it in at a waste station, and receive a voucher. When they have enough vouchers, they can use them to buy a house. One that they have collected the raw materials for themselves. Imagine that!”
The makeup of the composite ‘ink’ used in the printer will vary depending on the local conditions—after all, it doesn’t make sense to transport Danish plastic waste and wood offcuts across the globe.
For example, Kenya has a big mango production, so it would make sense to use the fibres from the many tonnes of mango skins and stones left over from fruit processing for the construction of the houses there. In countries like India and the Philippines, coconut shells would be an obvious choice.
WOHN’s long-term plan is to construct apartment buildings.
“We won’t save the world by building holiday homes. The big impact comes when we stack the homes on top of each other in two, three, four layers. We can do this by creating a kind of super structure, in which we insert the housing modules,” says Morten Bove.
Because WOHN is using an untested material for a design that no one has used before, the plans have changed many times along the way. In fact, the experience gained by the team along the way has led to changes in pretty much everything from the original concept: production design, composite material, and print design.
“That annoying saying of building the plane while flying it is kind of true for us,” says Morten Bove.
From rural to urban
According to the UN, 55 per cent of the world’s population lived in urban areas in 2018.
If the current trend continues, that number will rise to 68 per cent by 2050.
This corresponds to more than 200,000 people moving into the city every day.
Urbanization has a major impact on population density.
When the population density of an area increases, house prices also increase, if the housing supply doesn’t keep up.
At DTU Construct, Senior Researcher Yang Zhang helped calculate whether homes made using the plastic-based building material are sufficiently durable. Her research area is recycled plastic. A higher degree of recycling will have a significant positive impact on the environment, in part because 7 per cent of the world’s petrol consumption is used in plastic production.
“It’s a trendy topic,” she says with a smile, while also emphasizing that recycling plastic is challenging, because plastic is made up of long molecular chains that break and shorten every time it is heated up and made into something new. This affects the strength of the material.
According to Yang Zhang, it is possible to compensate for these changes by adding virgin (new) materials or additives, like WOHN does with wood fibres. DTU’s testing of WOHN’s building materials and construction methods will prove that they meet the relevant standards.
“If the concept is exported to another country where the composite material is made with a different additive, new testing will need to be done,” Yang Zhang explains.
Yang Zhang Associate Professor Phone: +45 45254892 yazh@dtu.dk