The firework explodes, the sky empties and part of the party comes back down. Pieces of the casing may end up in fields, rivers or on banks, where someone will have to collect them. In Japan they tried to eliminate at least this step: a fireworks company and a research team from Ryukoku University have developed a water-soluble and biodegradable resin-based shelldesigned to dissolve after falling to the ground or into water.
The project comes from Shiga prefecture, overlooking Lake Biwa, the largest lake in Japan. Here the Kakinoki Fireworks Industry organizes numerous fireworks displays and the problem can be seen quite clearly the next morning: the casings of aerial bombs, traditionally made with kraft paper, can fall onto the banks and remain in the environment for a long time before degrading. From that post-show rubbish began a years-long collaboration with Takahiko Nakaoki, professor of applied chemistry at Ryukoku University.
After the rain the fragments disappeared within a few days
The research began in 2018 and it was not enough to take a soluble plastic and give it the shape of a sphere. The casing must withstand handling, transportation and throwing, then properly rupture upon explosion. The group then worked on the resin composition and additives, looking for a material that was resistant enough during preparation and vulnerable enough to water after use. The Nakaoki laboratory also recounts much less poetic difficulties: during processing the viscous resin tended to stick to the machinery.
The most interesting test came in March 2025, on the university’s Seta campus. After the launch, researchers followed the fragments left on the ground. After the rain, most of the pieces were dissolved within three or four days; the university reports that they had subsequently disappeared completely. In water the process begins even more quickly.
The project has since left the lab. According to Ryukoku University, Kakinoki Fireworks will begin commercial-scale production and sales in late 2025. The new enclosures have already been used on Lake Tōya, Hokkaido, and at some government-related events. Launches are also planned for 2026 in the areas of Nagahama, Hikone, Higashiōmi, Kusatsu and Osaka. On April 23, after a public presentation of the research, some of the new fires were launched off the port of Nagahama.
The problem remained on the ground while the fires rose into the sky
Kakinoki had already been working on the material weight of fireworks displays for some time. On its website the company presents a previous generation of “eco-fireworks” designed to reduce by up to a fifteenth the amount of residue that falls to the ground after launch. The new shell addresses a different piece of the same problem: what remains of the structure that contains the charge before the explosion.
President Hiroyuki Kakinoki now aims to grow this production significantly. For 2026 the company plans to build around 20 thousand fires and would like half of them to use solutions considered more ecological. It is an objective declared by the company, therefore it should be read as such, rather than as a result already achieved.
Then there is an important boundary. The new material it reduces the waste associated with the packaging and does not transform a fireworks display into an activity with no environmental impact. What remains is the combustion, emissions and other residues produced by the fires. And the data on the degradation of the new shell comes for now from tests conducted as part of the collaboration between university and business; are not presented as a peer-reviewed scientific study.
The target, however, is very concrete. Just look at a shore after a big show to understand why Kakinoki started working there: the fire lasts a few seconds, its casing decidedly longer. With these new shells, at least that part of the evening could finally have a more show-like length.
