It's no secret that disposable nappies generate huge amounts of plastic waste, with three billion thrown away each year in the UK according to recycling charity Wrap.
So if you're concerned about the environmental impact of your child's nappies, biodegradable ones might seem like an appealing option.
Our survey results show that 35% of parents who buy biodegradable nappies choose them because they think they're better for the environment*. But can you be sure that they're greener than non-biodegradable nappies?
To find out more, we spoke to experts Dr Charlotte Lloyd, Royal Society research fellow at the University of Bristol, and Dr Sarah West, director of the Stockholm Environment Institute at the University of York.
Something that is biodegradable will break down, given the right conditions such as temperature, oxygen and the presence of microorganisms.
There isn't currently a UK standard that nappy manufacturers need to comply with in order to claim their nappies are biodegradable. In 2020, the British Standards Institute introduced a voluntary standard to verify biodegradable plastic claims, but it only applies to products left to break down in the open air, not those disposed of in landfill.
Some of the most popular brands offering biodegradable nappies include Naty and Kit & Kin. But although these nappies may claim to be biodegradable, Dr Lloyd warns that no disposable nappy will be made from 100% biodegradable materials.
'All biodegradable nappies contain some non-biodegradable materials. For example, often the outer layer of the nappy contains polyethylene film, and the sticky tabs will be made from polyurethane.'
According to Dr Lloyd, even nappies made with a high proportion of biodegradable materials will struggle to degrade under landfill conditions.
'Microbes and oxygen are needed to aid the biodegradation process, and landfill sites are actually designed to minimise these factors. To degrade, these materials would need to be composted'.
She adds, 'There needs to be a shift in the waste management of nappies to allow industrial composting. The investment in biodegradable products is somewhat wasted if they end up in landfill.'
It's also worth bearing in mind that biodegradable materials will only break down if they're exposed to the environment.
For example, Kit & Kin recommend placing the used nappy inside a biodegradable nappy sack and placing it outside of the bin liner to maximise the exposure to oxygen.
'If your biodegradable nappy has an outer film of polyethylene and it is rolled up after use, then the biodegradable components will remain 'protected' inside the film layer', Dr Lloyd explains.
'The same is true of biodegradable wipes - they're rendered pointless if rolled up inside a non-biodegradable nappy.'
If biodegradable nappies do degrade, there's a risk that the substances released could harm the environment, says Dr Lloyd.
'There's an assumption that just because a biodegradable nappy may be made from natural materials, it will degrade into natural substances that are non-toxic to the environment. But scientific evidence does not yet support this assumption. There is currently very little research on this subject.'
In addition, Dr West highlights the need to consider the environmental impact of nappies throughout their lifecycle, as there's research to suggest that the production of disposable nappies has an even greater environmental impact than their disposal.
For example, Dr Lloyd says that the biopolymers used in biodegradable nappies can be more energy intensive to produce compared with traditional petroleum-based polymers used in non-biodegradable nappies.
'Do not be fooled into thinking that because you are investing in a biodegradable nappy, you are eliminating your environmental impact,' warns Dr Lloyd.
'However, nappies containing natural fibres that are sustainably grown and harvested are going to be more environmentally friendly than something synthetic. If you can choose this type of nappy, then that is probably heading in the right direction'.
Dr West also emphasises the need to choose nappies made from sustainable materials. 'The absorbent part of disposable nappies is commonly made of wood pulp. Although this is a natural material, if the trees that the pulp is derived from are not managed sustainably, this leads to deforestation'.
In our survey*, 48% of parents said they choose reusable nappies because they're better for the environment.
In Dr West's opinion, the most environmentally friendly choice is reusable nappies. But as well as the extra water and energy required for washing, there are several other factors to consider.
'Reusable nappies made of synthetic fibres can shed microplastics, contributing to pollution. Plant based materials like cotton, bamboo and hemp are considered more environmentally friendly - however it's best to avoid non-organic cotton, as it requires high amounts of fertiliser, pesticide and water to produce'.
'Taking steps such as buying second-hand, using on multiple children, and air-drying wherever possible all help to reduce the environmental impact'.
*Survey of 1,512 parents with children up to 5 years, conducted in March 2020