Researchers including those from the University of Tokyo have successfully grown large tomatoes and cherry tomatoes, both rich in nutrients, in tightly controlled environments where the light source was energy-efficient LEDs. Such methods were often limited by the types or sizes of plants that could thrive in such conditions. This feasibility study demonstrates the researchers' method is suitable for urban environments, potentially even in space, and can offer food security in the face of climate change or extreme weather conditions.
Pizza, pasta, soup, salad, the tomato really is a versatile and delicious food crop. Its delicious and nutritious nature comes with a cost though; it has a very high demand for light, as well as water. While tomatoes grow well in some parts of the world, there are many regions where the local climate is not ideally suited to them, and with climate change exacerbating weather and the environment, having a way to improve yields or enable cultivation at all have long been sought. Greenhouses are the main method for creating a controlled environment suitable for growing crops, including tomatoes, but they have drawbacks and still rely on natural sunlight, which can be a limiting factor in some areas. If you've ever bought greenhouse-grown tomato soup in Iceland for example, you may have realized this all too well.
There has been some research and even agricultural use of artificial light plant factories (ALPFs), which are exactly what they sound like: fully controlled environments tailored to specific crops to maximize yields without compromising on other factors. These have a proven track record but require a lot of power to operate due in part to the lighting they require. A logical step is to use energy-efficient LED lights, which has been successful for certain crops such as leafy greens, but nothing more substantial. Spinach and lettuce are nice, but they're no slice of pizza. Realizing this limitation, Associate Professor Wataru Yamori from the Graduate School of Agricultural and Life Sciences at the University of Tokyo and his team decided to refine this concept to make it bear fruit.
"Plant factories are resilient to climate extremes such as droughts, floods and heat waves that increasingly disrupt traditional farming. They can be built in deserts, cities, or one day even in space. By bringing production closer to consumption, they help reduce both climate risk and food transport needs," said Yamori. "For many years, people assumed that crops with relatively long cultivation periods that require high light intensity, such as large-fruited tomatoes, could not thrive under LEDs. Our earlier work proved that cherry tomatoes, and even edamame, could be grown in such systems. Testing large tomatoes was the next logical challenge, pushing the boundaries of what plant factories can do."
The team did more than just change a few lightbulbs out for LEDs though. They firstly fit an enclosed factory space with the standard materials necessary for growing tomatoes, but introduced different lighting setups, both using high-efficiency LEDs, depending on which variety of tomatoes they were growing. Over the course of a year, they lit large-fruited tomato plants from above, coaxing them to grow straight upwards as you'd expect. But the second setup involved lighting smaller cherry tomato plants from either above or from the sides, in such a way that they grew upwards in an S-shape series of bends.
The larger tomato plants grew well but didn't quite match the yields or sugar content when compared with greenhouse-grown plants, though they did have more vitamin C. As for the cherry tomatoes, these exceeded expectations, with similar yields to greenhouses but significantly higher quality. In addition, the S-shaped plants fruited sooner, further increasing yields.
"Our study demonstrates that large-fruited tomatoes, once considered too difficult to grow under artificial lighting, can be stably cultivated in a fully-enclosed LED plant factory. This marks a turning point as LED factories, usually thought suitable only for leafy greens, can also support demanding fruiting vegetables like tomatoes," said Yamori. "At present, greenhouse-grown tomatoes still tend to be larger and sweeter. But LED-grown tomatoes offer improved consistency. They maintain stable quality year-round and are often richer in nutrients like vitamin C. With continued improvements, we expect factory tomatoes to match, or even surpass, greenhouse ones in taste."
Of course, anyone who's ever tried (and especially those who failed) to grow demanding crops like tomatoes knows all too well that there are many factors to control in order to cultivate them.
"Perhaps the biggest hurdle was optimizing the light environment. Large tomatoes need plenty of energy for both growth and ripening, and it wasn't clear whether LEDs could provide enough. But balancing light, temperature, humidity and nutrients in a closed space required a great deal of trial and error," said Yamori. "LED-grown tomatoes are likely to appear first in regions where traditional farming is difficult, or where transport costs are high. They also fit well with the idea of 'local production for local consumption,' something that could be harvested in the city and eaten fresh, without long supply chains. Costs are still a little higher, but as the technology spreads and renewable energy is integrated, prices will become more affordable."
It may still take a while before your local salad bar grows its own crops, but the possibilities extend even beyond that.
"Vertical tomato farms in skyscrapers are not science fiction anymore. Pilot projects exist around the world, though mostly for leafy greens," said Yamori. "With our results, it's realistic to imagine tomatoes being grown in skyscrapers within 10 to 20 years, and even in experimental systems for growing fresh produce on the moon or Mars."
