The convenience of disposable nappies, or diapers, comes at a shocking environmental cost. Every year, 8.5 million tonnes of absorbent hygienic products (AHP), which include disposable diapers, end up in Europe’s landfills or incinerators. AHP makes up around 3 to 4% of household waste.
In response, scientists have developed an innovative system to convert previously non-recyclable used nappies, sanitary pads and adult incontinence products into high-value new materials.
AHP are mainly made from cellulose, plastics and superabsorbent polymers. These valuable materials are in demand for many products, from packaging and bottle caps to organic fertiliser and new AHP, such as absorbent mats for medical treatment.
The nappy conversion system was successfully tested at a full-scale demonstration plant in Treviso, Italy. The fully automated process separated used nappies and other AHP into their component parts.
The first stage opens up the products and sterilises them using steam in a rotating vessel called an autoclave. The sterilised waste is then gently dried. In the final stage, mechanical and optical separators turn the waste into components ready for recycling.
The project demonstrated the pre-treatment of up to 1 500 tonnes of AHP waste every year. It converted the recovered cellulose-based materials into sugars that were then used to make biodegradable and compostable bioplastics.
By-products were used to produce biogas and high-quality compost for soil improvement and regeneration.
As the separate collection of AHP waste was central to the success of this model, the project also developed smart bins for dedicated municipal nappy collection.
An accompanying phone app located and opened the nearest bin, which otherwise remained locked to keep the nappies and smells inside. A trial of 12 bins in two densely populated districts in Amsterdam was a success, as were other trials in Paris and Verona.