Mie grad students make biofuel from unwanted fruit


Graduate students at Mie University have produced biofuel from the region’s tangerines, saying the technique provides a use for unwanted fruit. They believe it could be promoted as a locally sourced form of renewable energy.

The researchers at the university’s Graduate School of Bioresources fermented rotten and unsold fruit, and plan to market the technique in the next two or three years.

The southern part of Mie Prefecture is a major center of cultivation for mandarin oranges.

JA Mie Nanki, which represents the Japan Agricultural Cooperatives group in the prefecture, says around 150 tons of harvest is thrown away every year in Mihama, where the group is based, and neighboring Kumano. Two-thirds end up being incinerated, which costs about ¥2.5 million.

The researchers produced about 20 milliliters of biobutanol from 3 kg of tangerine waste by adding bacteria and letting the mixture ferment for about 10 days.

Last September, the team proved that the product was viable as a fuel when they tested it in an 80-cm radio-controlled vehicle as a replacement for gasoline.

In the past, researchers have produced ethanol from squeezed mandarin orange extract. But butanol is more efficient than ethanol as its properties are similar to gasoline.

However, technology used in the fermentation process remains undeveloped, and therefore the use of mandarin biofuel is not widespread yet.

Mie University has now founded a startup to support continued work in the area.

“If we were to start mass-produce the biofuel, we would need to invest a lot in building a transport infrastructure or even filling stations,” said Junji Yoshii, president of the startup and an assistant professor at Mie University. “At this point we are thinking about producing the mandarin energy for local consumption only.”

The researchers believe one use for the biobutanol could be to fuel agricultural equipment and to heat greenhouses.

However, the process produces waste that itself needs to be disposed of. The team is now considering ways to address that.

“The high sugar content of fruit means it is energy-efficient,” Yoshii said, adding that in the future the group will attempt to produce biofuel from other fermented fruit, including discarded apples.

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