Who needs dirt when you’ve got fish?
If you guessed soil, pat yourself on the back with a clean hand.
If you doubt that’s the right answer, consider a new greenhouse operation called WeFeedUs at Route 641 and McAllister Church Road, about 2 miles west of Carlisle.
Here’s the inside dirt: there is no inside dirt.
Some 5,000 plants are growing inside the 6,000-square-foot WeFeedUs facility, yet there’s not a speck of soil.
The plants are growing via an innovative, sustainable method known as “aquaponics,” a combination of aquaculture (producing fish) and hydroponics (growing plants in nutrient-rich water instead of soil).
Waste from fish tanks is used to add nutrients to water, which is then used to supply moisture and nutrition for about 20 types of edibles, which are grown year round.
Both the fish (tilapia) and edibles (mostly lettuce and herbs) are Pa. Preferred products that are sold locally, including to the Messiah College dining hall and local restaurants.
It’s a fascinating process and so common-sensical that you wonder why more of our food isn’t grown this way.
“There’s no soil in the whole greenhouse,” says Mike Andrus, who co-founded WeFeedUs with John New earlier this year. “There’s no pesticides, no herbicides and no drains either. We don’t have to dump anything. Everything gets used. It’s a closed loop.”
Four 50-gallon fish tanks are at the beginning of the loop.
Each holds about 800 baby Nile tilapia (“fingerlings”). These come from a non-GMO hatchery for now, but Andrus says plans are to breed the fish on site.
Waste from the tanks is filtered and separated into holding tanks – solids one way, liquid another.
Bacteria converts ammonia in the liquid waste into water that’s rich in nitrates. That’s perfect for fertilizing plants.
Baby plants, meanwhile, are started from seeds in rock wool, which is a spongy, light-weight fiber made out of minerals.
Once the seedlings are up, they go into holes spaced a few inches apart in long boxes that look a lot like fluorescent light fixtures without the bulbs.
The boxes are mounted horizontally on waist-high tables, and each box has a tube that feeds the nitrate-rich water into one end and out the other.
After the plants mature to a size where you’d normally see them sold at garden centers, they go into holes on inch-thick foam boards.
Andrus lifts up a board growing Romaine lettuce to show the humongous root system happily growing underneath.
What usually fakes out dirt gardeners at this point is how plants can possibly grow sitting in water.
In the garden, after all, plant roots rot in even temporarily soggy soil.
The explanation is that it’s not the water that kills the plant roots. It’s the lack of oxygen resulting when excess water pushes out the tiny air pockets that should be in the soil.
In other words, soggy soil kills plants by suffocating them.
In hydroponics and aquaponics, roots get the oxygen they need either directly from the air (i.e. when the roots are partially exposed with water constantly moving over them) or from oxygen that’s pumped into the water in the tanks.
Besides raft tanks, the WeFeedUs greenhouse has two, long, 4-foot-wide, on-the-ground rows of an apparently “normal” vegetable and herb garden.
Look closer, though, and you see the beds are filled with light-weight, chunks of expanded shale – in other words, rocks, not soil. Nitrate-rich water from the solid fish waste is piped through the root zones of these beds with the rocks serving mainly as a way to hold the plants upright.
A third growing method is ready to start up along one of the greenhouse walls involving vertical PVC tubes with holes drilled in them.
Andrus says these will be filled with perlite (another super-light mineral often used in potting mixes), planted with herbs and grown with water percolating down through the insides of the tubes.
It’s about as space-saving a way to grow as possible.
Andrus says the basic idea of aquaponics is an old one, dating back at least 5,000 years when South American Indians dug fish ponds and grew floating plants on top because the two benefited one another.
Andrus came across the concept while helping an algae-byproducts company look for ways to use algae. With fish farming on the upswing, he realized that algae could become a growing food source.
Growing algae is on the drawing board at WeFeedUs as well, which will replace the need to buy fish food and make the whole place almost fully sustainable.
Beyond that, Andrus says the operation fits into the grow-local/eat-local movement, it produces food organically, and it does so with little to no non-renewable input.
Water use is very low, for example, because the only loss is evaporation, lighting is low-power LED, and heat for winter growing will come from solar hot water.
“We want to be off the grid,” says Andrus.
Even the rain water coming off the greenhouses is collected for watering outdoor tomatoes and a 38-box, raised-bed community garden the company makes available at no charge to area residents.
Next up is a cafe planned for the adjacent Mountain Lakes Market, which New and Andrus also own.
And beyond that is taking WeFeedUs to the world. “Our real goal,” says Andrus, ” is to be able to replicate this around the world to cost-effectively feed people.”
A good rundown on the basics of aquaponics is available through Colorado State University’s Extension office.