DESPITE eco-minded chefs dishing up local parsnips and foraged mushrooms, the average American meal travels around 1500 miles from farm to table. In the US, processing, packaging, transporting, storing and preparing fruit and vegetables requires about four times as much energy as growing them in the first place. And around the world, up to a third of fresh food spoils in transit.
The problem is that while the countryside is a great place to grow plants, with ample water, free sunlight and fertiliser from livestock, fewer and fewer people are living there. Over half the world now lives in cities, a proportion that will rise to 70% by 2050. If tomorrow’s urban centres are not to go hungry, they will need to produce much more of the food their dwellers consume.
At MIT in Cambridge, Massachusetts, two groups are tackling the problem from different directions. The CityFarm initiative at MIT’s Media Lab wants to add large vertical farms to existing buildings. Caleb Harper, CityFarm’s founder, envisages retro-fitting office blocks with glazed ‘plant factories’ many stories high but only a few feet deep. The farms would use natural sunlight but also LED lights tuned to emit only the red and blue wavelengths of light that plants need for photosynthesis. The plants would be grown either hydroponically, in shallow troughs of water with minerals added, or aeroponically, suspended in a fine mist of water that delivers all the necessary nutrients. Aeroponic plants require sophisticated pumps and control systems but waste very little water, are less susceptible to diseases, and easier to automate. Internal lifts would move the crops up or down for planting and harvesting.
Mr Harper’s team is currently experimenting with a prototype plant factory in the Media Lab itself. Early results suggest that plants raised there can be harvested in roughly a third of the time of outdoor crops. This has caught the attention of Google, which is considering integrating CityFarm’s aeroponic system into its legendarily hip corporate cafeterias. “I’m really interested in high production, high intensity farming environments,” says Mr Harper. “But if a lot of restaurants and high schools start growing their own foods, I’ll learn how to compete with the razor-thin margins on commercial produce.”
Two recent MIT graduates have an even more radical vision. Jamie Byron and Gabe Blanchet would like to decentralise food production completely. Their company, Grove Labs, has secured venture capital funding to develop an appliance for people simultaneously to raise fish and grow organic vegetables in even the smallest, darkest kitchens. In their aquaponic system, ammonia excreted by trout in a fish tank is broken down by bacteria into natural nitrate fertilisers. The tank water is then pumped to the top of the unit, where it flows past the plants’ roots before being recycled back to the trout. As in the CityFarm, smart sensors and low-power LED lights provide optimum growing conditions. All the user has to do is add fish food – and even that could be automated.
In spite of its many moving (and some swimming) parts, aquaponics has several advantages over hydroponics. The most important is that the Nitrosomonas nitrogen-fixing bacteria out-compete harmful microbes so that the system requires little cleaning. Hydroponic gardens, by contrast, need to be thoroughly sterilised between harvests. Another bonus is that aquaponic farms produce tasty fresh fish to enliven all those greens. Mr Byron and Mr Blanchet plan to sell modular units that will connect to create a nano-farm as small or large as people need, all controlled by a smartphone app.
“We’re inspired by the way Lego stacks together,” says Mr Blanchet. “We see people taking up a whole room or basement and fitting them with these modules. If you do that, you can grow a significant amount of your own food, perhaps 40% or more.”
Whether plants are grown inside or outside, high-rises that are self-sufficient in food are still some way off. Initially, both MIT technologies are focusing on crops that are expensive in supermarkets, small and easy to grow. That means lots of salad, herbs and leafy greens, plus treats like out-of-season strawberries. And although LEDs and digital sensors are becoming more affordable, neither system can compete on cost with traditional agriculture. To keep prices down, Grove Labs’ debut appliance might even skip its cutting-edge fish tank in favour of cheap hydroponics.
“If you’re really going to try to sell tomatoes, you have to compete with the guys with hectares under cultivation in Mexico and California,” says Mr Haper. “That’s where we’re all aiming and no one can do it yet. The technology to compete with conventional methods is still five or ten years away.”
Until indoor farms are ready to feed the world’s cities, then, it seems that only well-heeled geeks will get to taste the fruits of high-tech plant factories. Your correspondent bravely sampled some aquaponically-raised bok choi and found it rich, dark and delicious, with not a hint of trout.