Up to 8% of the volume of concrete and mortar to make a basic house could be replaced by recycled disposable diapers, according to a new study. The unlikely material could aid the quest for more affordable housing in low- and middle-income countries.
The high cost of building materials is a major barrier to affordable housing in these rapidly urbanizing parts of the world. Meanwhile, population growth means an increase in demand for disposable diapers—and a corresponding waste management conundrum.
Today, used disposable diapers are mostly landfilled or burned. But their materials—various plastics combined with plant fibers such as wood pulp, cotton, and viscose rayon—could be put to better use, the researchers argue.
“Despite its cleanness issues, it is possible to utilize diapers as part of building materials or other valuable things,” says study team member Siswanti Zuraida, a graduate student in civil engineering at Kitakyushu University in Japan.
Zuraida and her colleagues mixed up half a dozen samples of concrete and mortar containing various proportions of washed, dried, and shredded disposable diapers. Then they tested the compressive strength of the samples and calculated how much of the sand in concrete or mortar could be replaced with diapers in different building materials without compromising their function.
The study is part of a growing body of research investigating the possibility of recycling various types of products into low-cost and low-carbon building materials.
Diaper waste can replace 10% of the sand in concrete for structural columns and beams in a 3-story house; 27% of the sand in concrete for columns and beams in a 1-story house; 40% of the sand in mortar for partition walls; and 9% of the sand in mortar for floors and garden paving while still complying with Indonesian building standards, the researchers report in the journal Scientific Reports.
The findings are consistent with those of other studies of diapers as building materials, says Zuraida. The surprisingly-extensive-to-outsiders evidence base on the topic “encourage[d] me to apply their findings on a macro scale, which is to build the actual housing by using the diapers as part of building components,” she says.
Zuraida and her colleagues constructed a prototype 36-square-meter house using their diaper-infused concrete. They were able to incorporate 1.73 cubic meters of diaper waste into the structure, representing just under 8% of the total volume of concrete and mortar used.
“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,” the researchers write.
But scaling up the strategy won’t be easy. It will require changing building regulations to allow the use of recycled diapers as a building material, as well as overcoming the ick factor of living in a dwelling made from dirty (even if subsequently cleaned and sanitized) diapers. Systems for collecting and processing diaper waste will also need to be developed. There are a few companies that recycle used diapers—mostly in wealthier countries—but the technology would need to be refined and rolled out much more extensively.
Zuraida and her colleagues used chemicals to sanitize the diapers used in their study. “For further development, we are still looking for the best ways to solve this cleanliness issue by involving other researchers in relevant fields,” she reports.
Source: Zuraida S. et al. “Application of non-degradable waste as building material for low-cost housing.” Scientific Reports 2023.
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