Unicharm turned used diapers back into new ones with ozone-sterilized pulp

Japan ages, and its incinerators fill with diapers. The environment ministry expects used diapers to grow from around 4% of general waste in fiscal 2015 to roughly 7% by fiscal 2030. Wet, soiled absorbent waste burns badly — it wastes fuel and emits extra greenhouse gases — and because it is contaminated, recyclers had written it off. The market behind it keeps shifting toward care: by 2022 Japan's baby-diaper market was ¥144.1 billion, up just 0.4%, while adult diapers reached ¥115 billion, up 4.2%.

Unicharm, Japan's top diaper maker, began developing horizontal recycling — used diapers back into the same value of material — in 2010. The obstacle was never machines but hygiene. After testing approaches, the company landed on ozone processing: in 2019 it announced a technique that sterilizes at low concentration in a short time and yields recycled pulp of the same quality as unused pulp, a world first for diaper recycling. Shredding and washing separate pulp, superabsorbent polymer and plastic; ozone kills, deodorizes and bleaches what remains.

The loop closes through collection design, not chemistry. Unicharm built the RefF project around partners: Kagoshima's Shibushi City and Osaki Town — pioneers of waste separation — set out dedicated diaper collection boxes and bags so residents sort at source. By March 2025 the company had recycling processes for every material in the product: pulp into new diapers, polymer into cat-litter sand, plastic into the collection bags and boxes themselves. About 6.32 million used diapers had been recycled by the end of November 2025.

The output now sells twice. In February 2025 Unicharm and Sumitomo Realty & Development put toilet paper containing the recycled pulp into the property firm's large office buildings, starting in Tokyo's Mita district — a visible credential for Sumitomo's DBJ Green Building certifications. Unicharm launched adult diapers with recycled pulp in 2022 and baby diapers in parts of Japan in 2024, targets 20 participating municipalities by 2035, and in December 2025 began work on a 'dry cleaning' process with Kagawa's Fujii Clean to cut the water the loop consumes.

Hygiene was the blocker, so they engineered the sterilizer

Ozone processing cracked the one problem that made dirty absorbent waste unusable: guaranteed sterilization, deodorization and bleaching in one step.

Diaper-to-diaper quality (not downcycling) means the recycled pulp competes with virgin fiber on performance, so demand does not depend on goodwill.

Collection is co-designed with municipalities and landlords, converting separated waste from a cost into feedstock.

Closing every material loop — pulp, polymer, plastic — lets the same collection network fund several products.

Being the incumbent diaper maker, Unicharm captures the value at both ends: it sells the diaper and buys back its own material.

When a material is called unrecyclable because it is dirty, the missing technology is sanitation, not sorting. Solve hygiene, then co-design collection with whoever holds the waste.

The Sumitomo Realty toilet-paper installations in Tokyo office buildings began in February 2025, a visible credential for the landlord's green certifications. Recycled-pulp diapers reached baby products in some regions in 2024, the October 2025 ESG plan targets 20 participating municipalities by 2035, and a December 2025 'dry cleaning' partnership with Fujii Clean aims to strip water from the process. Oji Paper's retreat from baby diapers keeps adult care — and its waste — growing.