Used baby diapers once headed to the landfill could now have a more environmentally friendly second life.
Researchers from the University of Kitakyushu in Japan published a paper (pdf) on May 18 that found diapers can partially replace sand in the mortar and concrete composites used to construct buildings, without compromising their structural integrity.
A proof of concept building was constructed in Indonesia, where diapers were washed with sodium chloride, dried, and then shredded before being added to composite mixtures.
The study, published in the peer-reviewed open-access journal Scientific Reports, concluded that up to 8% of the sand used in concrete blocks could be replaced with diapers when building a single-story house in Indonesia, without diminishing its strength.
Lead researcher Siswanti Zuraida, a native Indonesian, used diapers from her own children as well as collecting them from local sources.
Finding locally sourced materials, the study says, is key to creating low-cost housing. The researchers believe disposable diapers, which are non-degradable, could become a cheap and accessible building material and reduce their environmental impact.
Disposable diaper waste, by the digits
300,000: Number of diapers that enter a landfill every 60 seconds, according to a 2020 report from the Bio-based and Biodegradable Industries Association
248.5 billion: Barrels of crude oil used to make disposable diapers each year
167 billion: Number of disposable diapers made each year globally
38.4 billion: Tons of solid waste generated each year from diapers worldwide
6 billion: Estimated number of diapers Indonesia throws out each year
5.75: Kilograms of diapers used to make up 10% of a concrete mix tested in the experiment
1.73: Cubic meters of diaper waste used in the house, which made up about 8% of the composite material volume
Diapers could also be a solution to an imminent sand shortage
Sand is the second-most consumed resource in the world, behind water, and the most-extracted solid material on Earth. An estimated 50 billion metric tons of the material is used each year. Despite its abundance, the world is actually on the brink of a sand shortage because of the critical role it plays in building infrastructure.
Not all sand is created equal. Desert sand is too smooth for construction and considered more or less useless—the sought-after type of sand lies in riverbeds, lakes, and other bodies of water. As a result, many of these environments have been mined and stripped of the resource, enacting massive ecological damage. Indonesia has already lost entire islands in its archipelago due to the plundering of sand pirates.
Scientists at Leiden University in the Netherlands predict that global demand for sand will jump 45% by 2060, fueled by growing populations and economic development in Asia and Africa. Sand prices have continued to go up, causing ripple effects along global supply chains, as the resource has grown more scarce.
Bringing other unconventional building materials into the circular economy
Diapers aren’t the only item scientists are looking to as an alternative construction material. Natural materials like rice husks, banana leaves, and even mycelium, the root-like structure of fungi, have been explored as building materials. Denim has been found to be effective for home insulation. Glass waste, which is almost never recycled into new glass products, has also been identified as a potential building material alternative.
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