Mr. Miyashita: So, I decided to visit a plant factory in Saitama’s Chichibu City. While talking with the factory owner, I encountered the key phrase “low-potassium vegetables.” That factory did not produce “low-potassium lettuce” due to the difficulties of doing so. Thus, then and there, I made up my mind to produce low-potassium lettuce.

HORIBA: I admire your determination.

Mr. Miyashita: I have been told that people suffering from kidney disease who are treated with dialysis are unable to eat fresh vegetables containing large quantities of potassium. So, I felt it was my mission to produce low-potassium lettuce for the 300,000 such kidney patients in Japan. And in order to develop a comfortable work environment for ourselves, I designed cultivation shelves and built the equipment and facilities required for the factory on my own.

HORIBA: You might not have been able to do that without your skills and experience in manufacturing.

Mr. Miyashita: For the circulation facilities including the nutrient solution circulation systems and air conditioning systems, I asked expert manufacturers to do those designs because I couldn’t do myself. In this way, I was able to set up the plant factory five years ago, at the age of 63.

HORIBA: Taking up a difficult challenge at that age is truly amazing.

Mr. Miyashita: In fields, sunlight and soil nutrients are required to grow vegetables. That my plant factory does not do so gives me something of a guilty conscience, so to compensate, I installed a solar power generation system on the roof to generate some of the electricity used in the factory.

HORIBA: You have told us about some of the advantages of vegetable cultivation in a plant factory—such as being free of insect damage, which also eliminates the need to use agrichemicals, as well as ensuring a stable supply of products and therefore avoiding price fluctuations, in addition to providing a good work environment. Are there any other features?

Mr. Miyashita: Harvested vegetables last longer because they have fewer bacteria. Vegetables grown in fields are said to contain approximately 100,000 bacteria. By contrast, lettuce made in our factory has less than 300 bacteria. Therefore, factory-grown lettuce is less perishable than field-grown lettuce and lasts a very long time in the refrigerator. It can also be eaten without washing.

HORIBA: What are you most committed to with respect to producing lettuce?

Mr. Miyashita: The most important thing is to produce low-potassium lettuce. I am very committed to establishing a procedure for reducing the amount of potassium contained in lettuce. While two-thirds of the human body is water, lettuce is 95% water. Since water accounts for such a large percentage of lettuce, we use water filtered through a material made of fine ceramics and activated charcoal.