A team of researchers from Kitakyushu University in Japan has developed a type of concrete capable of replacing up to 40% of sand with shredded layers. As reported in the study published in the journal Scientific reports, the goal is twofold: to demonstrate that nappies can be diverted from landfills and used to help build affordable housing; and to show that concrete, which is responsible for 8% of global greenhouse gas emissions and requires around 50 billion tonnes of sand each year, can be made more sustainable.
As crazy as it sounds, the idea of reusing diapers is not without precedent. In 2022, for example, Welsh company NappiCycle collected more than 100,000 used nappies from British nappies company Pura and used them to pave 1.4 miles of roads in Wales. As Pura’s sustainability manager Matt Moreland explains, nappies have great potential as a material because they’re made of plastic and cellulose fibers, both of which can be used as binders. “Fibers have been used for a very long time in high-quality asphalt,” he says. “Their properties improve the homogenization of the bitumen and the structure of the asphalt laid.”
Asphalt is one thing, but building walls made of layers in a house to live in is another. The idea (and some of the funding) came from an Indonesian renewable energy and waste management consultancy called Awina Sinergi International. The research is still in its infancy, but concrete has already been tested to build a small house in Indonesia. Spanning one story and the size of two parking spaces, the house contains approximately 3,700 pounds of shredded diapers, none of which is visible to the naked eye.
Siswanti Zuraida, who is the study’s lead author and a doctoral student in architectural engineering at Kitakyushu University, explains that she washed and cleaned her own baby’s dirty diapers, left them to dry in the sun for about a month. months, then manually shred them with scissors.
Then the team started experimenting with ratios. More layers meant lower compressive strength, and vice versa. So, after pressure testing various samples, they landed on a recipe: non-structural components could be made by replacing up to 40% of the sand with used layers; structural components such as columns and beams could be made with 10% layers.
In Indonesia, Zuraida then teamed up with a team of local architects and materials engineers to design a prototype house to the country’s building standards. The final design uses metal beams and concrete blocks made from 27% layer waste.
For now, the process is closer to a DIY experience, and for it to work on a larger scale, the team would need to implement a robust collection system that allows people to recycle used diapers and partner with various stakeholders to properly disinfect diapers. , then grind them with appropriate machines. A version of this has already been done in Amsterdam, in 2019: recycling company TerraCycle designed around 200 bins for the municipality to distribute to pharmacies and nurseries in two neighborhoods. Trash cans could be opened by parents with a special app, which also showed the location of the nearest trash can. Similar diaper recycling programs are being developed in Belgium and Italy.
But in the meantime, the experiment is an interesting example for low-income communities to replicate the process. “Our goal is to provide a disposable diaper recycling system with low technology so that people can make their own materials,” Zuraida explains.
If the team achieves their goal, they’ll have another challenge: convincing people that a house made with used diapers isn’t as gross as it looks.