Present status and future outlook of plant factories in Japan

Abstract

Plant factories for the steady production of high-quality vegetables year round, and which can be divided into solar and artificial-light types, have recently been expanding in Japan as trigged by a report by a collaboration study group in 2009 and the Great East Japan Earthquake in 2011. Common solar-type plant factories with mulch-span roofs are often difficult to construct in the northern areas of Japan, especially along the Japan Sea coast, because of limited sunshine duration and heavy winter snowfall, while artificial light-type factories are more promising in this region although high running costs due to electricity bills for irradiating plants and cooling the room often hinder the promotion of such facilities. The use of LEDs has recently increased in artificial light-type plant factories, but fluorescent lights are still predominant for economic reasons. Generally only small plants can be grown commercially in artificial light-type factories and the light intensity reaching the lower leaves decreases continuously as the stem of the plant elongates, deteriorating light use efficiency. Flexible organic electroluminescent devices able to cover the whole plant when irradiation is required and that can easily be applied/removed like a plastic film are expected to be introduced in both types of plant factories.