Kao Corp. (TYO:4452) and Kyoto University are getting to work to establish a carbonization recycling system for used disposable diapers.
Over 2 million tons of used diapers are disposed of as waste in Japan every year, largely by way of incineration. Estimates are that they account for 4–6 percent of all incinerated waste in the country. And given the moisture-absorbing nature of diapers, their disposal has been known to result in decreased processing efficiency in incinerator facilities. Against this backdrop, the expected aging of Japan’s population – and related increase in disposable diaper use – brings with it not only hopes for the establishment of effective recycling technologies but also numerous issues.
Two major issues in all this are (1) the storage, collection and transportation of used diapers; and (2) the technological matter of separating the diapers’ constituent materials. With regard to the first of these matters, the fact that used diapers contain excreta means that their weight is 2–4 times that of an unused product. And not only is this an issue of bulk; they also require frequent collection on the pure basis of hygiene. As for the second major issue, recycling demands the separation of items into their constituent components – and with diapers being made up of pulp, polyethylene, polypropylene, superabsorbent polymer and more, there are real technical difficulties in separating these materials.
Looking to overcome these issues, Kao and Kyoto University aim to develop equipment for the carbonization of used disposable diapers prior to their collection. A key point of emphasis in this is that the equipment be capable of rapid, efficient carbonization while also requiring relatively low energy input by utilizing low-temperature reaction. This technology would allow for the weight and volume of used diapers to be reduced while also achieving sterilization and deodorization.
Existing carbonization equipment involves processing at approximately 600 degrees Celsius. However, the equipment to be developed by Kao and Kyoto University is aimed at lowering this temperature requirement. Moreover, the carbonization of CO2 planned here would see the carbon within these used diapers immobilized – so the expectation is that carbon emissions will be reduced compared to the process of incineration.
It is envisioned that the carbonized used diapers will then be converted into carbon materials for use in industrial applications – including tire filler and electronic materials – or as activated carbon for air and water purification.
Plans are to have the system put in place in Japanese society during or shortly after 2025, with expectations then being to branch out with this overseas to the likes of Southeast Asia.
