'Nappy Line' (Photographer: Richard on flickr)
Science

CCI and “nappy science gang” set new bottom line for diaper dilemma

by Harry Bligh

Experts from Cardiff Catalysis Institute at Cardiff University’s School of Chemistry are helping parents to explain and prevent the build-up of ammonia in their infants’ reusable nappies.

Only around 5% of parents choose to use reusable nappies on their infants compared to the more popular disposable nappies commonly seen in supermarkets. Reusable nappies can set parents back around £20 each and with 4 or more changes a day, multiple need to be purchased meaning this method is quite an investment.

The problem with disposable nappies, despite seeming more affordable and hygienic, are the environmental and ethical impacts. A single nappy can take around 500 years to fully degrade, and that’s assuming its in open air, often used nappies are buried deep landfill sites.

Parents contacted the ‘Nappy Science Gang’, a citizen science project run by cloth nappy users and scientists, complaining of a strong ammonia smell coming from their children’s nappies. Ammonia is a very basic chemical which is irritant and can cause severe nappy rash. The team found that there was a common mineral build up in the reusable nappies, possible after washing them, called ‘hydroxyapatite’, a crystal compound comprised of calcium and phosphate. It’s likely that this mineral harbours bacteria (found in faecal matter) which then reacts with urine, catalysing the break down of urea and producing ammonia.

The first question was working out where the calcium and phosphate was coming from.

To answer this, the researchers synthesised hard and soft water in the laboratory and mimicked washing cycles that parents would use when washing the nappies. They hoped to decipher how exactly the mineral was formed. They found that calcium was common in hard water (common in southern and eastern areas of England). It could also be found in urine due to the the large quantities of milk in babies’ diets. Phosphate is also present in water but in very small quantities, one theory was that it may be found in detergent.

Their hypothesis was that the hydroxyapatite formed in solution from calcium and phosphates and when the nappy dried, tiny microcrystals stick to the lining of the nappy forming ‘nucleation points’ meaning more crystals of hydroxyapatite will form and build up over time. Now that the mystery behind the formation of ammonia has been solved, the next step is to find a way to wash nappies, stripping them of hydroxyapatite or to avoid the initial build up of the mineral to prevent ammonia formation.

Leading the team from CCI are Dr Jennifer Edwards and Dr Jonathan Bartley who are working with citizens and other scientists in the ‘Nappy Science Gang’ funded by Wellcome Trust and Royal Society of Chemistry. This team have already managed to change the NHS guidelines on the washing of reusable nappies. Alongside Dr Edwards, this research has also been undertaken by BSc student Elliot Rees and assisted by PhD student, Alex Howe.

Dr Edwards hopes to continue with this ground-breaking research and hopes to find the ideal method to wash reusable nappies combining low temperature and low chemical content so that the washing is eco-friendly and the nappies are free from anything harmful. They also hope to look at advancements in the disposable nappy industry, potentially making recycling them more of a reality.

There is possibly a fully funded PhD opportunity from September working with CCI and Dr Edwards, if you are interested in applying contact edwardsjk@cardiff.ac.uk

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