Hotaeoi research, Prof. Ishii's explanation - related technologies and historical background (1990s)

Hotaeoi research, Prof. Ishii's explanation - related technologies and historical background (1990s)

In the 1990s, water pollution and eutrophication were social issues in Japan. In Lake Biwa and Kasumigaura, the influx of nitrogen and phosphorus caused the formation of blue-green algae, and the treatment of domestic and industrial wastewater was urgently needed. Against this backdrop, Professor Takeshi Ishii of Okayama University of Science turned his attention to reevaluating the white mallow, which had been considered a "harmful grass" because of its excessive reproductive power.

This plant has the property of efficiently absorbing nitrogen and phosphorus in water, and there was a possibility that it could be used as a purification plant. The first related technology is the "floating water purification system. By floating water hyacinths on the surface of the water, they absorb nutrients from their roots, preventing eutrophication. In addition, the "Planting Mat System" was studied as a system that can efficiently treat a wide area of water by fixing plants to nets or raft-like platforms. These are part of bioremediation using aquatic plants.

Professor Ishii also explored the possibility of using water hyacinth as a biomass resource, rather than just a purification material. Mouse experiments have confirmed that the stems and leaves that thrive in large quantities can be dried, crushed, and used as animal feed. Furthermore, by applying fermentation technology, we succeeded in producing a prototype of "hotei-aoi shochu," a Japanese distilled spirit that produces alcohol. This was a pioneering experiment that led to the current bioethanol research, in which cellulose and hemicellulose are saccharified and fermented to produce ethanol. In addition, a way to reuse the material as agricultural fertilizer by applying composting technology was also considered.

At the time, the Kyoto Protocol (COP3 in 1997) had led to a global agreement to prevent global warming, and the effective use of biomass was expected as part of the new energy policy. Professor Ishii's research redefined the concept of non-native waterweeds, which had been considered a nuisance, as a resource that could be applied in a variety of ways, including water quality improvement, energy, food, and fertilizer. This embodied the concept of a recycling-oriented society that began to emerge in the 1990s, and could be considered a forerunner of later biomass utilization technology and regional recycling-oriented energy policies.