This house was built partly from recycled diapers

Meet the house that diapers built.

Researchers have designed and erected a house that has shredded, disposable diapers mixed into its concrete and mortar. A single-story home of about 36 square meters can pack nearly 2 cubic meters of used diapers into its floors, columns and walls, the team reports May 18 in Scientific Reports.

Using recycled diapers as composite building materials would not only shrink landfill waste but also could make such homes more affordable, the team says, a particular need in developing countries like Indonesia where the demand for low-cost housing far outstrips the supply.
Indonesia’s urban population has increased by about 4 percent per year in the last three decades, and more of its people are moving to urban centers. Over two-thirds of Indonesians are expected to live in urban areas by 2025, says environmental engineer Siswanti Zuraida of the University of Kitakyushu in Japan. That population boom is putting a heavy strain on both housing demand and waste management, says Zuraida, who is originally from Indonesia. Used disposable diapers mostly pile up in landfills or get incinerated, adding to a growing waste problem.

The materials used to build a house, meanwhile, particularly those needed to shore up its structural integrity, are often the biggest barrier to making homes affordable. So researchers have previously examined the possibility of using a wide variety of unconventional materials that could also save costs. These materials included many that would otherwise pile up as waste, such as the husks of rice grains or fly ash, the fine residue left over from the combustion of pulverized coal. Disposable diapers, as it happens, contain a lot of potentially useful building material, such as wood pulp, cotton, rayon and plastic.

Zuraida and colleagues assessed how much of the sand, gravel and other traditional building materials used in mortar and concrete could be replaced by diapers — washed, dried, sterilized and shredded — without reducing the strength of the structures. They created six different samples of concrete and mortar by mixing different proportions of diaper material with cement, sand, gravel and water. Crushing the samples in a machine let the researchers test how much weight each could bear.

The team then went on to design — and then build — a small, single-story, two-bedroom, one-bathroom home based on the maximum amount of diaper waste they calculated they could use. Recycled diapers could replace up to 27 percent of the traditional materials used in load-bearing structural components like columns and beams without losing significant strength, the team found. For buildings with more floors, that fraction is somewhat less: A three-story home could use up to 10 percent disposable diapers in its load-bearing structures, the team calculated. As for nonstructural components like wall partitions or garden paving blocks, shredded diapers could replace up to 40 percent of the sand.

Despite the need for more affordable housing, there are significant hitches that stand in the way of adopting diapers or other low-impact nonconventional materials, Zuraida says.

Diapers’ plastic components would have to be separated from the organic fibers, a complicated recycling process currently available only in developed nations. And Indonesia’s building regulations restrict construction materials to concrete, bricks, wood and ceramics — materials that also bear a high cost in terms of carbon emissions.

“Thinking about how to use waste for other purposes is an excellent idea,” says chemist Christof Schröfl of Technische Universität Dresden in Germany. But there may be limits on the ultimate environmental friendliness of repurposing used diapers in buildings, he says, due to the existing challenges of separating and sanitizing diapers in waste. “It’s maybe worthwhile to start thinking about ways to replace single-use diapers” with something less frequently disposed of.