THE DETAILS: On hydroponic farms, plants actually live in beds of gravel that are periodically flooded with a water-nutrient mixture to keep the plants fed. "It's all indoors, where the environment is completely controlled," says Ryan Ehst, owner of Butter Valley Harvest. "We control the nutrients in the water and the air temperature, 24/7. This takes away a lot of the normal worries that an outdoor field grower has, and allows us to grow very efficiently year-round."
Because everything is indoors, there are very few pest problems, thus there’s no need for the synthetic pesticides or fertilizers that can pollute groundwater or run off into nearby waterways. As such, the Butter Valley Harvest farm operates on the same principles as organic farming. An added bonus is that hydroponic farms like Ehst's use 80 to 90 percent less water than soil-based farms, even though the entire farm is based on water. Ehst says all the water that circulates underneath the plants is continuously recirculated. The only water lost is what’s taken up by the crops.
Hydroponic farming has proved to be so efficient, both in terms of space and water use, that the United Nations Development Program has set up small hydroponic farms in several developing countries as a local food source for residents. Officials have hailed it as an increasingly viable way to grow local food year-round, and perhaps the future of farming.
WHAT IT MEANS: Hydroponic farming may be a way to provide fresh, healthy, local produce that is much more sustainable than shipping heads of lettuce from California or South America to the northern U.S. all winter, for example. Yet some agriculture experts aren't so sure it's the best antidote to our heavily chemical-dependent way of growing food. Jeff Moyer, farm director of The Rodale Institute, which is a leader in the organic-farming movement, based in Kutztown, Pennsylvania, takes issue with hydroponic farming. He says it's a completely artificial way to grow plants, and says it assumes that the only nutrients people need from food are the ones that farmers add to the water. "History often proves that the science of biology always leads to safer, more secure, and, certainly, more sustainable food systems than do systems based on technology," says Moyer. And there's an interaction between plants and soil that can't be replicated when you take soil out of the mix. Which could mean that the soil contains stuff we don't know about, that's nevertheless important to our health. "If the nutrients aren’t in the growing medium, they can’t make their way to us, either through direct consumption of plants or through the animals that eat those plants," he adds.
There have been few comparative studies on the nutritional value of hydroponic produce, but tests in Holland and Australia suggest that hydroponic tomatoes actually contain more nutrients than field-grown tomatoes. Studies in the U.S. have found no difference in nutrient levels between the two farming techniques. But Moyer says the antioxidant level of hydroponic produce may be lower because the plants are subjected to less stress, so they don’t develop natural defenses against pests and microorganisms the way they would on a soil-based farm.
Then there's energy use. Growing plants in a controlled environment requires a lot of energy—to heat greenhouses and circulate the water, for example. Butter Valley Harvest uses renewable geothermal electricity and hasn't installed grow lights in its greenhouses, but not all hydroponic farming operations are so progressive.
Should you buy food grown via hydroponics? Maybe. Hydroponics are a good way to get fresh, local food out of season, but it's unlikely that the growing method will take the place of soil-based farming completely. Opt for soil-grown produce when it's in season, but try out hydroponic produce from a local grower next time you crave a salad in the dead of winter. First, though, find out as much as you can about the farm where it was grown. Ask how much and what types of energy are used, and how close the farm is to you. The U.S. Department of Agriculture hasn't yet agreed to certify hydroponic produce as organic, so ask if the producers are using pesticides in their greenhouses. Hopefully, it’ll turn out that your best source of fresh, organically raised tomatoes next winter is a greenhouse just down the road.
And remember that if you just have to have an out-of-season edible, you can always look for an organic version. Studies suggest that more of a food's carbon footprint comes from how it's produced than from its transportation to the market. And organic agriculture not only uses far fewer fossil fuels than growing with agrichemcials, it also captures and stores the greenhouse gas carbon dioxide in the soil. Read about the benefits of organic food at the Rodale Institute's Demand Organic site.
Or you could just wait till the season comes around and the produce you crave is available closer to home. After all, don't fresh tomatoes taste so much sweeter when you haven't had once since last summer?