YAWATAHAMA, Japan >> Shikoku Electric Power Co., researchers from Tokyo University of Agriculture and Technology, and other organizations have begun tests to explore the possibility of “microbial power generation” in mikan (mandarin orange) orchards in Yawatahama and Ikata in Ehime prefecture.

Making use of microorganisms that emit electrons and generate hydrogen ions when decomposing organic matter in soil, the team’s “microbial fuel cell” stores the small electric charges for later use. This fiscal year, the team plans to examine how climate and seasons affect the generation of power. Next fiscal year, they plan to use the power generated for “smart agriculture,” to remotely monitor data such as field temperatures.

The university began researching microbial power generation in 2019. According to assistant professor Keisuke Matsumura, the understanding that microorganisms emit electrons was established about 100 years ago, but because the amount of electricity generated is small, research into its practical application never gained traction.

In recent years, however, as technologies such as microbial fuel cells have been developed, universities and other institutions have already been conducting similar tests in rice paddies.

Tokyo University of Agriculture and Technology has developed its own energy storage device, making it possible to output relatively large amounts of electricity for short periods of time. This allowed researchers to use the generated power to wirelessly transmit data.

Using microorganisms to generate power does not require cultivating them to increase their numbers, and on-site soil can be used. Devices can be buried in the soil to generate power using just the nutrients found there.

The technology is expected to help mikan farmers, many of whom are aging. If temperature and other conditions can be monitored remotely, the technology could reduce the demands on farmers to patrol their orchards, which are often on steep slopes.

In early September, Matsumura and his team buried a device about 30 centimeters (nearly a foot) underground in a mikan orchard in Yawatahama and began measuring the voltage. The orchard, located at an altitude of about 200 meters (about 656 feet), is managed by a company affiliated with Shikoku Electric Power.

“Although it doesn’t output that much power, we want to make use of the small amount of energy in the soil around us for agriculture,” Matsumura said. “We also want to determine how power generation changes depending on the quality of the soil, and show others that microbial power generation is useful.”

Hiroyuki Mishima, head of Shikoku Electric Power’s New Business Planning Department, agreed.

“We would like to make use of this system to solve local problems,” Mishima said. “Thanks to its simple structure, it may be possible to provide it at a low cost.”