As any new parent can attest, babies go through a lot of diapers. But instead of simply tossing the soiled diapers in the trash, a team of engineers has proposed an innovative way to repurpose them.
Researchers at Japan’s University of Kitakyushu cleaned and shredded dirty diapers to build a small, structurally sound house, they reported in a new paper published last week in the journal Scientific Reports. Their 387-square-foot prototype home keeps roughly 60 cubic feet of diapers out of landfills, which is equal to about 200 diapers, per New Scientist’s Alex Wilkins.
Recycling dirty diapers into building materials could help solve several problems at once, the team argues. Diapers are a leading source of plastic waste around the globe, and they take a long time to decompose. In the United States alone, people threw away 3.3 million tons of disposable diapers in 2018, according to the latest statistics available from the Environmental Protection Agency. Meanwhile, mining sand—which is a key ingredient of concrete and other building materials—is expensive and harmful to the environment; experts are also forecasting an upcoming sand shortage. On top of that, low- and middle-income communities need more affordable housing options.
To test their ambitious idea, researchers first collected dirty diapers, then washed, sterilized, dried and shredded them. Next, they mixed the diaper bits in different ratios with gravel, water, sand and cement to create concrete and mortar. After letting the samples cure for 28 days, the engineers tested them to see how much pressure they could withstand. From those results, they calculated how much sand they could replace with diaper shreds and still meet Indonesian building codes.
For a three-story home, they found diaper shreds could replace up to 10 percent of sand in concrete used for supporting beams and columns; in a single-story house, that proportion increased to 27 percent. In mortar between concrete bricks, diapers could replace up to 40 percent of sand for the construction of non-load bearing partition walls and up to 9 percent for use in garden paving and floors.
And for a complete, single-story, 387-square-foot home, crews could replace 8 percent of the total sand in the concrete and mortar with diaper shreds, the researchers found.
To check their calculations, the engineers constructed a small concrete house using those specifications. While their proof-of-concept home demonstrates their idea is feasible, the concept is far from ready for prime time. For one, they haven’t yet figured out a process for safely collecting and processing large amounts of dirty diapers. The researchers also want to test the insulating and sound-proofing abilities of the newly developed building materials to see if they’re actually a good fit for human dwellings.
“Unfortunately, at this scale, the research has not yet involved waste management and other stakeholders,” says study co-author Siswanti Zuraida, an engineer at the University of Kitakyushu, to Gizmodo’s Lauren Leffer.
Researchers around the world are already testing a variety of swaps to make concrete more environmentally friendly and keep various items out of landfills, including vehicle tires, plastic bottles, disposable coffee cups, construction debris and biochar, a type of carbon-sequestering material made from burned agricultural and forestry waste. Researchers have also tried using dirty diapers to pave roads.
As for whether soiled diapers will ever catch on in construction, some researchers are skeptical. Rackel San Nicolas, an engineer at the University of Melbourne who was not involved in the study, tells the Australian Broadcasting Corporation’s Nick Kilvert she would “never use it in concrete, that’s for sure.”