History of Utilization of Leftover Sweet Potatoes in Nishiaoshi Town, Kumamoto Prefecture (2000s-2020s)

History of Utilization of Leftover Sweet Potatoes in Nishiaoshi Town, Kumamoto Prefecture (2000s-2020s)

### 2000s: Start of research and establishment of infrastructure
In 2004, the Kyushu-Okinawa Agricultural Research Center, based in Nishiaoshi Town, Kumamoto Prefecture, began research on a zero-emission system for utilizing sweet potato residue. In this project, technology to extract polyphenols from shochu dregs and a method to use sweet potato leaf stalks as livestock feed were developed. With the cooperation of Kirishima Shuzo, we installed a mini-plant at their factory and conducted demonstration tests. At this stage, research was conducted with the aim of effectively utilizing the thousands of tons of leftover material produced annually.

### 2010s: Commercialization and Expansion of Scope of Utilization
In the 2010s, the research results moved into the commercialization stage: In 2012, polyphenols extracted from shochu dregs were commercialized as a food additive and cosmetic ingredient, with annual sales exceeding 1 billion yen. Furthermore, livestock feed using sweet potato leaves and stems has been widely adopted by livestock farmers in Kumamoto Prefecture, and a supply system of over 8,000 tons per year has been established.

In addition, biomass power generation technology was introduced in 2017, and a biogas generation plant installed in Ugi City began supplying regional circulating energy. The plant processes 1,200 tons of residual waste annually and has achieved results that supply enough electricity for approximately 500 households. These efforts contributed to the reduction of environmental impact and the development of local industry.

### 2020s: Further Technological Innovation and International Expansion
In the 2020s, the technology was further advanced, and the efficiency of polyphenol extraction from shochu dregs was improved by 50%, making it possible to extract 15 mg of polyphenols from 1 liter of shochu dregs, accelerating market development in Japan and abroad. In addition, the utilization rate of sweet potato residue has increased from 75% in the 2010s to 85%, attracting attention as a model case of a regional recycling-oriented society.

### Challenges and Future Prospects
Although challenges such as a temporary decline in shochu consumption due to the pandemic occurred in the 2020s, Kirishima Shuzo and the agricultural cooperative are focusing on developing export markets and new product development. Further technological innovation and international collaboration will be promoted with the goal of increasing the overall utilization rate of sweet potato residues to over 90%.

This initiative not only supports the sustainability of the region centered on Nishiaoshi Town in Kumamoto Prefecture, but is also attracting attention both domestically and internationally as a model case for building a recycling-oriented society nationwide.