From Volume I of the 2023 #thisispearl digital magazine

When Ruriko Sakaguchi of the Sakaguchi pearl farm on Ago Bay in Shima City, Mie Prefecture, Japan, found out about the pearl compost initiative, she recognized that this way of processing pearl oyster meat could forever change the cultured pearl industry. Oftentimes, pearl oyster meat that is not eaten or deposited underground in fields as fertilizer is discarded into the sea, adversely affecting water quality around farms.

“Until now, rotting shell meat had to be buried around fruit trees to serve as a fertilizer,” observes Sakaguchi about past uses of pearl oyster meat from farms. “Composting body meat reduces our work.”

Composting transforms the body meat of akoya pearl oysters, a frequently unused by-product of pearl farming, into an odorless, organic substance used as fertilizer. Oyster compost is the brainchild of the Katada Pearl Farmers Association of Mie Prefecture in Shima City, the Pearl Promotion Society of Japan, and the Fisheries Agency of Japan. Together, these organizations created the initiative in 2019 to reduce pearl farming by-product waste and improve water quality around farms.

Process & Goals

Pearl meat compost is produced by mixing three ingredients—oyster meat, rice bran, and rice husk—in an insulated, wooden container; upwards of four months later, the fermented compost is ready for use.

Compost is produced once a year, in winter, immediately following pearl harvests. Though there is an initial investment for the composting equipment, and preparation of materials is time consuming, farmers realize its importance to efficiently eliminate waste. Unwanted oyster meat that is discarded in the sea can cause nutrient loads that deteriorate water quality. Pearl meat composting reduces this excess organic matter, allowing the waters and marine ecosystems of pearl farms to thrive.

According to Sahoko Shimizu of the Mie Prefecture Agriculture, Forestry and Fisheries office, the pearl composting initiative meets three Sustainable Development Goals (SDGs) outlined by the United Nations: SDG 12, Responsible Consumption and Production; SDG 14, Life Below Water; and SDG 17, Partnerships for the Goals. [SDGs are a set of 17 goals with the overarching objectives of ending poverty and income inequality, protecting the planet, and ensuring that people all over the world live in communities in good health, just living conditions, and prosperity.]

Through composting, pearl farmers can produce pearls and use all by-products responsibly and sustainably, which speaks to SDG 12. Pearl composting allows life below water to thrive, which nods to SDG 14. Finally, the success of the project depends on the cooperation of the pearl farmers of Mie Prefecture, members of the Japan Pearl Promotion Society, and the Fisheries Agency of Japan to achieve a common goal (SDG 17)—the development of technology that sustainably utilizes pearl oyster meat.

“The pearl compost initiative is an effort to fulfill our ‘responsibility to produce goal,’” notes Shimizu. “This means being responsible for your consumption and product choices.”

Promoting Purchases

Yuichi Nakamura, CEO of PJ Nakamura and vice chairman of the Mie Prefecture Pearl Promotion Council, has been overseeing promotion of the initiative since its inception. He encourages pearl farmers all over Japan to adopt the initiative. To date, 254 pearl farmers from Mie Prefecture, 241 pearl farmers in the Ehime Prefecture, and 116 in Kyushu (mainly Nagasaki Prefecture) are participating.

“We wanted to produce something light, odorless, easy to transport, and used by anyone,” Nakamura explains.

Once production grows large enough, the compost will be available for purchase to a wider audience. Over time the project is expected to become self-sustaining through sales.

In the last two years, Nakamura has talked to local governments and jewelry industry members at fairs in Japan. More promotional plans include sharing the initiative with the Japan Pearl Exporter’s Association and Japan Export and Trade Organization as well as exhibiting at the Hong Kong International Jewellery show in March.

Ethical consumers who find themselves drawn to responsibly farmed Japanese akoya pearls may also want to use this unconsumed, sustainable farming by-product to grow vegetables and flowers in their own backyards.

“Oyster meat could be used as a fertilizer in our own fields,” says Sakaguchi. “Pearl oyster meat composting will help communicate the environmental efforts of the pearl industry as