The write stuff: Scallop shells recycled as chalk

The Yomiuri Shimbun

BIBAI, Hokkaido--A Kawasaki-based company has been chalking up success--literally--by turning scallop shells destined for the garbage heap into high-quality chalk that has brightened classroom blackboards in Japan and South Korea.

Nihon Rikagaku Industry Co. developed the chalk by mixing fine powder from crushed scallop shells with calcium carbonate, a conventional chalk material. The chalk has won over schoolteachers and other users for its brilliant colors and ease of use, and has helped recycle scallop shells, disposal of which was once a major problem for scallop farmers.

About 30 workers at the company's factory in Bibai, a major scallop production center, churn out about 150,000 sticks of chalk a day, using about 2.7 million scallop shells annually.

Factory head Kazuhito Nishikawa, the brains behind the chalk's first practical application in 2005, said development of the scallop blend was not considered a long-term project.

"In the initial stage of development, we planned to give up if we didn't succeed in a year," Nishikawa said.

Nihon Rikagaku, like most chalk manufacturers, previously made chalk solely from calcium carbonate, which comes from limestone.

Nishikawa hit on the idea of using scallop shell powder after receiving an overture in 2004 from the Hokkaido Research Organization, a Hokkaido government-run body for regional industrial promotion, for a joint research program on recycling fishery shells.

Scallop shells are rich in calcium carbonate. But sea alga and gunk that builds up on the shell surface must be removed before the shells can begin their chalky transformation.

"Removing the gunk by hand was very costly, so we decided to do it using a burner instead," he said.

Nishikawa, 56, subsequently invented a method of pounding the shells into minute particles just a few micrometers across. A micrometer is one-thousandth of a millimeter.

Finding the optimum ratio of shell powder and calcium carbonate also gave Nishikawa a few sleepless nights.

An early 6-to-4 mix of shell powder and calcium carbonate was too fragile and crumbled when used for writing. So Nishikawa reduced the shell powder to just 10 percent of the mix, a blend that ultimately produced chalk that was easy to write with.

"At that ratio, crystals in the shell powder act as a cement holding the chalk together," Nishikawa said.

Schoolteachers and others have praised the new chalk for how smoothly it writes, he said.

When chalk sticks become too short to hold easily, they offer yet another use, according to Nishikawa--burying them in a flower bed can improve soil quality as calcium carbonate has alkalization properties.

The chalk has impressed some teachers so much that they have taught about the manufacturing and recycling processes in their environmental conservation classes, he said.

Scallop shells are an abundant resource. About 3.13 million tons of fishery products, including fish innards and shells, were discarded in 2008, according to the Agriculture, Forestry and Fisheries Ministry. About 380,000 tons--half of that amount being scallop shells--were thrown away in Hokkaido in fiscal 2008, a Hokkaido government official said.

Most scallop shells were discarded until about a decade ago. These days, more than 99 percent are recycled for soil improvement and other uses.

In March 2007, the Hokkaido government designated Nihon Rikagaku's chalk as a "Hokkaido recycling-oriented brand good," a recognition that generated considerable publicity. The company recently started exporting its chalk to South Korea and acquired a patent for it with the Hokkaido Research Organization.

Nishikawa, however, is not resting on his laurels.

"These days, even popular recycled goods can get pulled off the market if customer preferences change. We'll keep improving the quality of our chalk," he said.