• Jiji


A silver lining is beginning to emerge in efforts to deal with pumice stones from an undersea volcanic eruption, which have become a headache for many areas in Japan, as a number of ideas to utilize the troublesome debris are now taking shape.

A large amount of pumice stones from the eruption of an underwater volcano at the Ogasawara Islands in the Pacific has drifted onto the coasts of Okinawa Prefecture and other areas, dealing a blow to the fishing and tourism industries in the affected regions.

In Okinawa, pumice stones have piled up in a range of locations, including at fishing ports.

Rather than disposing of the stones, which would be a costly operation, ways to utilize them are being sought, although this is not easy due to their high salt content and brittle nature.

A team of researchers from the Kanagawa Institute of Industrial Science and Technology has successfully carried out an experiment to convert the surfaces of the pumice stones into crystals of zeolite, a material often used as an adsorbent.

Yosuke Ono, researcher at the institute in Kanagawa Prefecture said that it may be possible to improve the quality of seawater by floating the stones on the ocean. They “can also possibly be used to treat radioactive water” although the participation of companies would be necessary to make this commercially viable, he added.

Meanwhile, Hiroshi Miyade, 45, has started to use pumice stones he collected from a beach to improve the soil in his coffee fields on the island of Tokunoshima in Kagoshima Prefecture after washing the salt off the stones.

“The stones are expected to improve drainage,” the coffee farmer said, adding that he is also considering using the pumice stones, which are great insulators, as a material for the walls of his coffee-bean roasting house.

Masakazu Soma, 72, from the village of Yomitan in Okinawa, is using ground pumice stones in glaze for “tsuboya-yaki” traditional pottery. The ground stones were “more fitting than I had imagined,” the veteran potter said, noting that they gave a deep reddish brown color to his works.

Soma named the new coating material using the pumice stones “magma glaze” because they come from a volcanic eruption.

“For the past 300 years, Okinawa pottery has used local materials such as coral and husk,” he said. “Now, the annoying pumice stones can be utilized in the craft world.”

The Okinawa Prefectural Government has received about 50 proposals from companies and others about how to use the stones effectively, including utilizing them as a material for road pavements and artificial reefs. The prefecture is set to assess the feasibility of the ideas.

“This is a good example of waste being recycled into resources after being given new value from innovative ideas,” said Misuzu Asari, associate professor at Kyoto University graduate school.

“Human wisdom is limitless, so the way we look at waste could change if we stop for a little while and think, instead of simply regarding it as waste,” Asari said.

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