Life Cycle Assessment of the Closed-Loop Recycling of Used Disposable Diapers

In Japan, approximately 23.5 billion paper diapers are produced annually (total of diapers for infants and adults produced in 2018). The majority of used paper diapers are disposed of through incineration; in certain regions, some paper diapers are recycled, mostly by open-loop recycling or thermal recycling. To date, several methods of recycling used paper diapers have been proposed and developed, but these methods are considered to have different types and amounts of recycled materials and different environmental performances. In this study, a new technology was developed for the closed-loop recycling of used paper diapers, and the use of the recycled pulp and superabsorbent polymer (SAP) as materials for paper diapers was evaluated via the environmental impact using the life cycle assessment (LCA) method, using data obtained from experimental facilities for recycling. The results between the comparison of the new method with the landfill and incineration processes demonstrate a greenhouse gas reduction of 47% and 39%, respectively. The results also show that such recycling is expected to reduce land-use occupation and water consumption, closely related to the pulp, main raw material of paper diapers.