AguaCulture ‘proof of concept’ underway on Lake O

Can plants currently considered an invasive nuisance be key to cleaning up Lake Okeechobee?

Can old technology be combined in new ways to make mechanical harvesting of aquatic plants cost-effective?

Can this new concept help reduce the need for chemical herbicides to control aquatic plant growth on Florida waterways?

A proof of concept project underway on Lake O near the Indian Prairie Canal seeks to answer those questions.

The project is a potentially novel approach to remove invasive plants and remove some nutrients from the lake; the company doing this is called AguaCulture.

The project is funded by a grant from Florida Fish and Wildlife Conservation Commission (FWC). The process uses mechanical harvesters to remove invasive plants from the lake, then dumps the plants into a machine that shreds and processes them into a liquid, which is pumped through miles of hose to be spread on nearby pastures.

Nonnative aquatic plants – often introduced by well-meaning gardeners -- have plagued Florida lakes and waterways for decades, clogging navigation channels and crowding out the native plants. FWC’s invasive plant control efforts include the use of chemical herbicides, biological controls and mechanical harvesting.

Fishermen and environmentalists have voiced opposition to the use of chemical herbicides, which they say cause the plant material to fall to the bottom, adding to the muck at the bottom of the lake and contributing to the nutrient excess that fuels algal blooms.

Biological controls have not been successful in controlling some invasives.

Traditional mechanical harvesting removes the plants from the lake, but if the plants are merely stacked up on the shoreline, as they decay, they add nutrient load to the runoff that goes back into the water. And transporting truckloads of plant material to a dump site away from the lake is expensive, especially with high fuel prices.

The AguaCulture process removes the invasive plants, along with the nutrients they contain. Instead of a waste product, the process turns the invasive plants into a beneficial soil amendment that can be spread on pastureland.

The contract with FWC is to clean up water hyacinths, explained AguaCulture champion Mike Elfenbein, conservation chair of the Izaak Walton League Cypress Chapter.

He said they can harvest both the living hyacinths on the surface of the water and also suck up the decaying hyacinths in the water column.

The process starts with mechanical harvesters, which gather hyacinths from a designated area of Lake Okeechobee. The plants are dumped into the device dubbed “The Green Mach 1,” which sits on a barge near the shoreline. “We can put this machine wherever the largest concentration of hyacinths is,” explained Nick Szabo, AguaCulture owner.

From the Green Mach 1, the liquified hyacinths are pumped through a hose to a pasture on the Lazy JP Ranch, about five miles away. Two auxiliary pumps are used along the way to keep the liquid flowing smoothly. The liquid could be pumped as far as 20 miles, Szabo explained.

On the ranch, the liquid flows into a CMA (continuous manure applicator) which has a retractable hose that connects to a tractor. The tractor sprays the liquified hyacinths at the equivalent of about one-eighth inch of rainfall. Because the liquid is absorbed by the earth, there is no runoff. Small pieces of plant material are distributed on top of the pasture -- much like lawn clippings. Those will continue to nourish the pasture as they decompose.

Elfenbein said the initial project will use about 300 acres of pasture on Lazy JP Ranch, but thousands more acres of ranchland are available if the project is expanded.

Hyacinths are about 90% water, Szabo said. He said before they sprayed the liquid on the pasture, they tested it for chemicals and found none.

AguaCulture not only provides an alternative to chemical spraying, it also prevents the accumulation of plant material that falls to the lake bottom year after year with chemical treatments.

Removing the plant material also removes phosphorus and nitrogen from the water. Szabo said they are sending samples to the lab to determine the concentration of nutrients removed.

“If you want to clean up the lake, manage and harvest the plants,” he said.

Federal and state agencies must find ways to reduce the invasive plant populations on lakes and streams and remove the excess nutrient load from the water. AguaCulture is looking for ways to help the agencies solve both problems, Szabo said.

“The health of so many people depends on this lake,” he said.

While one machine isn’t going to solve all the problems, “you’ve got to start somewhere,” he added.

The AguaCulture process is faster than traditional mechanical harvesting,  Elfenbein said. Traditional harvesters can clear about two acres a day, he said. When the Green Mach 1 is up and running, the AguaCulture harvesters can clear 10 acres a day. Stationing additional machines and more harvesters in targeted areas could speed the process.

He said the state has other projects to remove phosphorus from lakes, with a cost of $300 or more per pound of phosphorus removed. By letting the plants clean the water, then removing the plants, AguaCulture could remove phosphorus at half that cost … even less with the economy of scale, he added.

He said Dr. Dan Canfield at the University of Florida has estimated there is about 13,000 metric tons of phosphorus locked in Lake Okeechobee. “In 50 years of talking about it, no one has done anything about it. Our goal is to take that nutrient load out.”

What happens to the nutrient load after it is spread in the pasture? The nutrients leave the watershed in one of two ways, Elfenbein explained. The rancher can grow hay, cut the hay and export it. Or the cattle can eat the grass or hay and when the steers go to market, they take the nutrient load with them.

Florida ranches are “cow/calf” operations. Each year, about half the herd is taken to market. Florida cattle are shipped to the feedlots in the Midwest for finishing because it is less expensive to ship the steers to the grain than to ship the grain to the steers.

Before Lake Okeechobee was diked, in years with heavy rains, the lake swelled its banks and when it receded, it left behind aquatic vegetation that would decay and enrich the soil, Elfenbein said. Taking aquatic vegetation off the lake and redepositing it in the pasture mimics that natural cycle.

Eight generations ago, Brad Pharr’s ancestors at the Lazy JP Ranch harvested and sold native clover, which grew abundantly there. Now there is little clover to be found on the ranch. Szabo is confident the AguaCulture process will improve the soil, allowing the native plants like clover to thrive.

“To me, the bigger picture is we can create a new model for conservation,” said Elfenbein.

The use of water hyacinths and other aquatic plants to clean water has been around for a long time said Mike Graves, AguaCulture president. He said an Okeechobee woman told him she uses water hyacinths to clean the water in her pond, then feeds the hyacinths to the pigs and what the pigs don’t eat, she spreads on the ground and runs over with a mower.

The scale of Lake Okeechobee is the challenge.

“If we can solve this problem on his lake, we can do it any place in Florida,” he said.