Floating Aquatic Vegetative Tilling: Can We Put Water-Hyacinths to Good Use?

By now, the issue of nutrients in Florida’s waters is well-recognized. Runoff from urban and agricultural systems and the loss of natural wetlands have combined to raise levels of nutrients, primarily phosphorus and nitrogen, in natural systems. These can lead to blooms of algae and general imbalances of the systems. In estuaries, such as the Indian River Lagoon, algae and other side effects of high-nutrient loads can choke out sea grasses and shellfish. Since estuaries are the cradles of the ocean, this can lead to reduction in healthy hatches, and adversely impacting the health and quantity of fish and other sea creatures in the estuary and beyond. When flowing into the Everglades, even relatively small increases in nutrient levels can cause vegetative imbalances, which disrupt this vital natural system.

Equally well-known are Florida’s issues with exotic invasive species, some of which have been here so long and are so widespread that we might forget that they are in fact not native. A perfect example of this is the ubiquitous water-hyacinth (Eichornia crassipes) (“hyacinths”).

For years, efforts to reduce or eradicate hyacinths have included attempts to gather them and place them on dry land. But their high water content and resulting weight make them difficult to harvest efficiently, and their nutrient content is not high enough to make them attractive fertilizer. Consequently, chemical spraying has emerged as the preferred method of control. But they continue to be present in almost every water body in Florida, and have spread around the world, according to the United Nations Environment Programme (UNEP).

I was honored to be involved in a project where hyacinths could be used in a positive way to help remove nutrients from a Florida stream that flows into Lake Okeechobee, and ultimately, to Florida’s Everglades.

Fisheating Creek is the only remaining free-flowing tributary into Lake Okeechobee. A portion of the Creek flows through a portion of the iconic Blue Head Ranch in Highlands County, which is owned by a client of our firm. The company approached us about a proprietary process for Floating Aquatic Vegetative Tilling (FAVT), which proposed a new design for water treatment using hyacinths. The project at Blue Head Ranch would be the second of its kind in Florida.

FAVT works by diverting flowing, nutrient-impaired water through multiple containment areas where hyacinths have been introduced and where systems are put in place to prevent their escape from the project boundaries.(Florida has such strict controls on the transport of hyacinths that a permit is required.)

The fast and incessant growth of the plant, a tremendous problem in natural systems, is useful as a tool for rapid removal of nutrients, primarily phosphorus, from flowing waters. When a containment area is filled with hyacinths, it is then drained and the plants are allowed to dry, after which they are carefully tilled into the soil.

Where the death and decay of hyacinths in natural systems causes the return of captured nutrients to the water column, tilling them into the soil serves to capture these nutrients in the soil, and research has shown that the nutrients introduced into the soil in this fashion have not returned to water once the water level is raised. (Cory Catts discusses this in his University of Florida master’s thesis titled, “Water Hyacinth Treatment Systems in Agricultural Watersheds: Influence of Biomass Incorporation into Soil on Phosphorus Retention.”)

Essentially, this means the process can be repeated, continuing to remove nutrients. The expense of harvesting and transporting the plants, and the issue of where to place them, is eliminated, and the nutrients captured are actually removed from the natural system.

The project at Blue Head Ranch is being built on about 250 acres of land that had been previously permitted for agricultural uses. Water from Fisheating Creek will be pumped onto bermed uplands divided into compartments which allow for filling and draining. Timing of the filling and emptying of the compartments is determined in part by high- and low-flow periods for the Creek. The project is anticipated to operate for five years, with potential for extension.

No solution to Florida’s water-quality issues is a silver bullet, and addressing them will require an assortment of approaches, including reservoirs, natural and manmade wetlands, changes in both urban and agricultural environments, as well as individual and collective efforts to reduce nutrients at their source.

These efforts will need to be on private as well as public lands, and hopefully will constantly improve over time as we learn more through experimentation. Through this and other projects, the Dean Mead Agribusiness Industry Team is excited to be part of this process to help restore and sustain Florida’s natural systems for the future.

About the Author:
Dennis G. Corrick is a shareholder in the Fort Pierce office of Dean Mead. He practices in the areas of commercial real estate, zoning and land use, and general business law. He has experience in every element of real estate purchase, ownership, governance and sale. In addition, he assists clients in land use and zoning matters, permitting and licensing, and in agreements governing the use of property such as covenants and restrictions, commercial and agricultural leases, easements and licenses. He has extensive experience working with issues unique to agricultural businesses and properties. He is a member of Dean Mead’s Agribusiness and Real Estate Development Industry teams. He may be reached at (772) 464-7700 or dcorrick@www.deanmead.com.