1. Eliminating Agricultural Waste
How Aquaponics Works
Sweet Water believes in turning wastes into resources, and in reconsidering how we think about waste. “We’re even debating whether we should use the word waste, since there’s no waste in nature,” James Godsil said.
To help understand how aquaponics can take waste out of the agricultural equation, let’s take a look at the process.
“Aquaponics is a biomimicry experiment, meaning an innovation inspired by nature,” Godsil explained. “Aquaponics mimics a wetland, river or stream. Humans strive to create conditions similar to what appears in natural ecosystems where there is a collaboration of life forms who exchange resources with one another.”
For fish and plants to exchange resources in an aquaponic system, a fish tank is built below a bed of vegetables with mechanisms connecting the two sections. Then, given the right conditions of light and heat, beneficial bacteria will also grow in the system.
Fish in the system produce waste in the form of ammonia, Godsil explained, and this ammonia is used by bacteria that turn it into nitrites. These nitrites are then converted into nitrates by another kind of bacteria. Nitrates are what plants like and what function as fertilizer in an aquaponic system. In return, the plants help filter the water to keep it safe for the fish. To facilitate this process, the water is pumped up to the plants and then drains back into the fish tank.
The system basically works as a loop, with the fish producing waste that benefits the plants, and the plants cleaning the water for the fish. The only external inputs are fish food, oxygen and, in the case of indoor systems, artificial light.
Additionally, aquaponics uses about one-tenth of the water used to grow vegetables in the ground, according to Backyard Aquaponics, which Godsil confirmed.
“It makes for the best tasting lettuce any of us have ever had,” Godsil said.
Using Wasted Waste
In an aquaculture system where fish are raised in tanks, farmers have to deal with fish waste, just as any other farm raising large numbers of animals would. Aquaponics largely eliminates this problem, since the plants will use the waste from the fish. Just as livestock manure can be utilized to fertilize soil crops at a typical farm, in urban aquaponics, fish waste can feed plants, too.
At Sweet Water, they even take using waste one step further. Some solid waste does need to be filtered out of the fish tanks, and at Sweet Water they add it to their compost pile, which they have had on site for years.
“We’re making the vision of aquaponics in a city context not a fearful one because people won’t have to worry about fish waste. One of the concerns about aquaculture across the world is ammonia,” Godsil said.
Right now, aquaponics is a growing area for research, too, and many people are experimenting with ways to eliminate even more waste. Some experimenters hope to create soil-based food for the fish (instead of feeding them smaller fish).
“Compost can be given to worm farmers to raise red wiggler worms which can become food for the fish,” Godsil said, demonstrating that when growing food, many activities can be connected. Godsil emphasized that these systems are complex, but are becoming increasingly accessible if people are interested in learning about them.