EVERETT, Wash. — Growing Power’s Will Allen described the tools he uses to make urban agriculture work:
“I couldn’t farm without composting,” he said. For his farms to yield at least $5 a square foot, he depends on intensive production.
He grows crops year-round by piling compost in all four corners of a greenhouse to use the heat it produces.
The compost is built around three carbon sources: wood chips, cardboard and straw or hay. Allen doesn’t use leaves from the city because too much other debris is scooped up.
Spent grain from Milwaukee’s breweries adds the nitrogen, and he collects food waste from grocery stores and processors.
Walmart has the best program in the country for handling waste, he said. “It hires companies as consultants and haulers. You will not find a plastic bag or anything in their waste.”
When the compost is finished, he inoculates it with worms.
The key to sustainability is the seven varieties of redworms Allen raises.
“These are our livestock,” he said.
Not only do they eat their own body weight daily, they destroy E. coli bacteria from animal waste. Layering the worms with other compost keeps them fed.
Whenever he seeds a crop, he covers it with the vermicompost. He has learned, though, that drip irrigation doesn’t provide enough water for the material.
He makes tea from the worm castings to spray on the crops. He also sells the castings for $4 a pound.
By developing a research lab in a greenhouse, Allen has fine-tuned system components to produce two food products: crops and fish.
Tilapia has become a popular food fish, but most tilapia comes from China, he said. “Ours taste a lot better.”
Pond-raised fish cannot be used in the production system because they bring in contaminants that can kill all the fish. Growing Power received a grant to train people to raise the fingerlings.
Aquaponics poses unique challenges, including maintaining water temperature. Tilapia, a Nile River fish, needs warmer water than lake perch, which bring a higher price.
“But tilapia are a great starter fish,” he said. “It’s hard to kill ’em.”
Still, the fish need to be monitored closely, because they are sensitive to changes. “Sometimes you have minutes, not hours, to correct a problem.”
In the greenhouse laboratory, Growing Power has devised a 10,000-gallon mechanical system that would cost $50,000 to buy, “but we built it for less than $5,000.”
It can be made with materials accessible in all communities, Allen said, and communities in Kenya, Uganda and Ghana are using the systems.
“We can train more people than universities with their small labs and small programs,” he said. “We’re a business, not just a laboratory.”