Used nappies should be used in housebuilding to save sand, scientists have said.
Up to 8% of the sand in the concrete and mortar used to make a single-storey house could be replaced with shredded used nappies without significantly diminishing their strength, scientists from the University of Kitakyushu, Japan, have found.
The study, published in the journal Scientific Reports, said building regulations could be changed to allow this material to be used, and it would reduce the carbon footprint of the homes as well as finding a use for the otherwise non-recyclable waste.
Disposable nappies are usually composed of wood pulp, cotton, viscose rayon and plastics such as polyester, polyethylene and polypropylene. Because they cannot usually be recycled, the majority are disposed of in landfill or by incineration.
The lead author, Siswanti Zuraida, and colleagues prepared concrete and mortar samples by combining washed, dried, and shredded disposable nappy waste with cement, sand, gravel, and water, curing the samples for 28 days. They then tested six samples containing different proportions of waste to measure how much pressure they could withstand without breaking. They then calculated the maximum proportion of sand that could be replaced with disposable nappies in a range of building materials.
The researchers found concrete made with nappies was as good as conventional materials. They said: “The research also demonstrated that the mechanical properties and microbial content of disposable diaper concrete, in specific compositions, are identical to conventional concrete. Adding 1% diaper to concrete enhances internal curing hydration and produces the most robust, durable material. In addition, a mixture of up to 5% disposable diapers with concrete had the maximum strength at 28 days compared to other percentages.”
The scientists said it was unlikely the use of nappies in the mixture would have any negative effects on health, as sodium chloride could be used to sanitise them.
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It also found that using waste to create homes had more ecological benefits than incinerating it. The study says: “Compared to other waste management methods such as incineration and co-firing, the recycling of disposable diapers as concrete components has more significant benefits regarding carbon emissions and eco-costs. As a result, the study intends to tackle the problem of housing provision by creating building materials from non-degradable waste, which is cost-effective while meeting building standards.”