In March, five Western Michigan University students won a $15,000 Wege Prize—a national sustainability award—for their aquaponics system. Aquaponics is a circular system of growing food where wastewater from farmed fish fertilizes plants; the plants then take that water and purify it for the fish to use again.
Next spring the students are putting their plan into action to build Local Loop Farms in Paw Paw. Once the farm is built, the team estimates it will be able to raise more than 19,000 heads of lettuce, almost 1,000 pounds of fish, and more than a ton of fish food every week.
How does it work? Aquaponics basically turns fish pee into plant food. The water in the fish tank goes into a filter where two types of bacteria convert the ammonia in the fish waste into nitrates. You might recognize that word “nitrate.” It’s the nutrient you’ll find in pretty much any plant fertilizer.
That water then goes through a PVC pipe with square holes cut in the top—where plants sit with their roots dipping down into the water. Those plants take up those nitrates, leaving only clean water that pours back into the fish tank.
There are a few reasons environmentalists love aquaponics. The system does a lot of the work for you – constantly watering and fertilizing the plants all on its own. There’s also no need for herbicides or tractors powered by fossil fuels. Because it’s a circular system, the Local Loop team says aquaponics actually uses water 90 percent more efficiently than traditional agriculture.
“It makes our food system so much better and so much more sustainable and we’re not polluting our air and water and land with all these synthetic chemicals that we’ve made. We’re just copying nature," says Max Hornick, one of the five Western students who will run the aquaponics system at Local Loop Farms.
But Local Loop is so much more than just aquaponics. Hornick says their model aims to actually make fish food and heat the fish tanks—which no system has done before. It’s more sustainable and could save money too.
“You know about 50 percent of annual aquaculture costs are feed related and that’s only increasing as our ocean fishery stocks decline. Because the majority of fish feeds are based on fish-meal which generally comes from wild-caught ocean fish. And so as our fishery stocks decline we’re not having as much of that available, and obviously if we’re depleting our fishery stocks that much, that’s not very sustainable either.”
Instead of buying regular fish food, the team will raise spirulina algae and marbled crayfish—both of which are easy to raise. They’re also trying out black soldier flies—which can compost food waste in about as little as three days. Unlike Michigan’s black flies, Hornick says these guys don’t bite because they don’t have mouths.
“They do all their eating in their larval stage. So that’s when they’re taking our food waste and composting it—they do all their eating then. They get into their pupal stage when they’re dormant and going through metamorphosis and then after that they are only alive as adults for a very short while. And their only task during that time is basically, reproduce—that’s our job. So they don’t even have mouths at that point because they’re not doing any more eating.”
Hornick says the team will also turn manure from the farm in Paw Paw into heat for the fish tank. It uses little microorganisms in a method called aerobic composting.
“During basically their digestive process, these organisms create this super-heated air and water vapor that we, then in the system, would be recapturing. The temperature in the aerobic composting can get to like 170 degrees potentially. The reason you can put animal manure in it is it gets so hot that it’s killing off any of the pathogens that you might have in there,” says Hornick.
Hornick says the plan for Local Loop Farms isn’t fool-proof yet. They still have to see if the black soldier flies, algae, and crayfish will be adequate food for the farm-raised yellow perch. But Hornick says even if that doesn’t work out, the farm will still help to keep about 28 tons of table scraps out of the landfill every week.
“You know, waste is food," Hornick says. "In nature, waste is food for something else. So if we can find a way to kind of emulate nature on that, that’ll be invaluable to creating a more sustainable culture.”
The Western team plans to begin construction on the large-scale aquaponics farm sometime in spring of 2016.