Concrete incorporating up to 10% waste disposable nappies is strong enough to build ‘low cost’ three-storey homes in Indonesia, with significant environmental implications for developing countries, the latest research reveals
They say construction is a dirty job, but no one ever suggested using old disposable nappies as part of the building process … until now.
In a brave example of ‘bottom-up’ thinking, researchers from the University of Kitakyushu in Japan have developed a low carbon concrete that uses shredded waste infant undergarments as a replacement for sand in the mix.
The study, published in the journal Scientific Reports, was funded by Japan's Ministry of Education, Culture, Sports, and Science and Technology, and Indonesian renewable energy and waste management consultancy Awina Sinergi International.
It set out to tackle the twin problems of unsustainable nappy waste in developing countries, where the majority is disposed of in landfill or by incineration due to a lack of access to diaper recycling technology, and a chronic shortage of decent quality affordable housing.
Tests revealed that concrete with up to 10% of the fine aggregates replaced by shredded used nappies could achieve a compressive strength of 20-25MPa, appropriate for a three-storey house, according to building standards in Indonesia. Furthermore, replacing 10-19% of sand with waste nappies was suitable to build a two-storey house, and replacing 19-27% was suitable to build a single-storey house.
Non-structural components of up to 10Mpa could be made using up to 40% disposable diapers.
Researchers said recycling disposable diapers in concrete components has significant benefits regarding carbon emissions. However, specific calculations of embodied/whole life carbon savings were not part of the research.
Scientists prepared concrete and mortar samples by combining washed, dried, and shredded disposable nappy waste with cement, sand, gravel, and water, and then cured the samples for 28 days.
Samples containing different proportions of waste were tested to measure the compressive strength and calculate the maximum proportion of sand that could be replaced with disposable nappies in a range of building materials.
Local architects in Indonesia helped design and build a full-scale prototype low-cost home using the material with a floorplan of 36m2.
The project identified several barriers to scaling up the technology. Stakeholders involved in waste treatment, including municipal waste authorities, would be needed to collect diaper waste from households, wash and sanitise it. The small-scale manual production process in the lab would need to be scaled up using industrial machines to shred the waste.
Researchers used a conventional chemical admixture to clean dirty nappies, but according to the study’s lead author Siswanti Zuraida, further R&D involving researchers in other fields is required to identify the best ways to guarantee cleanliness.
‘Dirt and health issues have become our concern to ensure acceptance in a society where people may refuse to use the materials as a part of their home,’ Zuraida told RIBAJ. ‘In addition, existing building rules and regulations [in Indonesia] are limited to conventional building materials, so the role for the government in regulating these innovative materials needs to be opened up.’
Although the research remains at an ‘infant’ stage, Zuraida hopes to find an investor to provide further funding to take the product to the next stage of development.