Upcycling Fukaya green onions into plastic products to support local farmers — Saitama Institute of Technology

Saitama Institute of Technology in Fukaya City, Saitama Prefecture is working on a project to turn green onions into plastic products such as chopstick rests and Reversi (Othello) game sets. Green onions are well known for their warming effect on the body when you have a cold, and they are an especially popular vegetable during the winter season. Fukaya is famous as a major production area for green onions. However, when shipping harvested green onions, farmers are required by packaging standards to cut off the elongated green tops, and there had been no way to make use of the trimmed portions. The Institute hopes to contribute to local revitalization through industry-government-academia collaboration, including efforts to have the upcycled products adopted as gifts in the city's hometown tax donation (furusato nozei) program.

From flowers to fiber, from "toge no kamameshi" to tiles — Turning discards into useful products

If you head down a vegetable field lined road from Okabe Station on the JR Takasaki Line, you will arrive at the campus of Saitama Institute of Technology. The surrounding winter fields produce green onions, broccoli, Chinese cabbage, and other vegetables. Professor Teruhisa Hongo of the Department of Life Science and Green Chemistry, Faculty of Engineering, who specializes in environmental materials chemistry, has devoted his research to the theme of "transforming things that have been thrown away and left unused into something of value."

His previous work includes turning rice husk ash into an adsorbent for volatile organic compounds (VOCs) and making washi paper from lily flower fibers. One of his more intriguing projects started when he noticed that the container of Toge no Kamameshi, Gunma's famous station bento lunch, is made of Mashiko ware fired at over 1,000 degrees Celsius. He developed and published a technique for grinding the lid and body together to create tiles.

As part of that work, a local agricultural machinery industry contact brought him a question in the spring of 2022: "Green onions are always sold after being trimmed, except at direct-sales stands. Could the cut-off parts be reused?" Green onions are shipped to retailers in cardboard boxes to prevent breakage. Because of the standards associated with these boxes, farmers must trim and even up the green tops before packing the onions.

Green onions grow with the white part covered in soil while the green part performs photosynthesis. In the Kanto region, the white part is the preferred part to eat, but without the green section the onion wilts quickly. That contact had already tried "using the trimmed green tops as smoking chips," but the smoked food turned out to be unpleasant, and the idea failed.

When Hongo consulted various people about the problem, he heard comments such as "we get complaints about the smell" when disposing of the trimmings. The cause is the sulfur-containing compounds such as allyl sulfide in the green onion tops, which produce a strong rotting odor.

Processed into pellets — The odor problem solved

With companies at a dead end on reuse, Hongo drew on the knowledge he had accumulated so far and started his own research. First, in the summer of 2022, he ran an experiment to "extract only the cellulose from green onions." If he could obtain cellulose, it could be processed into a wide range of products such as fiber or chemical compounds. Since green onions lack a strong stem like lilies, he judged them unsuitable for papermaking and instead considered whether they could be converted into a raw material for plastics.

Raw green onions are soaked in an alkaline solution to remove hemicellulose and part of the phenolic compound lignin. At this stage, the material still looks like "green onion." After subsequent bleaching and complete lignin removal, it becomes a white fibrous substance that no longer resembles green onion at all. Collecting the loosened fibers yields high-purity cellulose.

The cellulose the researchers extract is returned as composite resin pellets produced by an affiliate of a major electronics manufacturer. The composite resin pellets are brown, have no onion smell, and do not degrade even after long-term storage. Fifty-five percent of the pellets are derived from green onion material, with the remaining 45 percent being polypropylene.

Thanks to the cooperation from a laboratory that studies injection molding within the Institute, the team heated the composite resin pellets to approximately 190 degrees Celsius, poured them into a mold, and produced chopstick rests in the shape of green onions. Color was applied with an airbrush, resulting in a playful "miniature green onion."

Rather than applying color by airbrush, mixing a colorant directly into the pellets allows for a range of other uses. Inspired by the promise of an "odorless and useful" green onion material, the team further processed it into toys, creating a Reversi (Othello) game set. The pieces were made from green onion material, and the board was made from recycled husks from locally grown rice. Rather than the standard black and white, the two sides of the pieces are white and green—and because a colorant was used, they came out as a pleasing, muted shade of green.

This Reversi set caught the attention of Fukaya City, and it is reportedly being considered as a gift item in the city's hometown tax donation program for fiscal year 2026. Mayor Susumu Kojima was also present at the product launch event held in November 2025. There is a Japanese proverb about a duck walking up with an onion on its back—meaning something comes along exactly when needed. In this case, it was the green onion chopstick rests, used when eating a duck-based dish, that "brought along" the toys.

Giving back to farmers — The driving force behind the research

Hongo is originally from Ogose Town in Saitama Prefecture. He just announced a new project in February this year; this will focus on the plum, a specialty product of Ogose, creating black plates from plum pits and activated charcoal from pruned branches. He hopes to continue bringing about more environmentally friendly "change" through upcycling.

Looking back on his research, Hongo's eyes lit up as he said: "Even things that are no longer wanted can keep the economy moving if they can be made profitable. The joy is in bringing materials that are hard to break down into fertilizer through composting back to life." He is currently thinking about whether the large leaves of broccoli—everything but the edible part — can be turned into something useful.

"Farmers do hard work in both the heat of summer and the cold of winter to put food on our tables, yet consumers always look for lower prices. I hope that what comes out of this research can be returned to farming as real profit," he said. One might describe this as research that "praises" (negirau) the farmers who have been "lowballed" (negiru)-a playful pun on the word negi (green onion).