Our pee could help bring back seagrass
A crystallized version of human urine could revitalize seagrasses, which provide food, habitat, and shelter in their ecosystems.
Urine contains two key ingredients in plant fertilizers: phosphorus and nitrogen. Even better, wastewater treatment facilities already process this abundant resource and create byproducts that would otherwise be sent to the landfill.
In its crystallized form, this byproduct is called struvite. Scientists applied the material applied to seagrass in a recent study.
“Struvite occurs during the wastewater treatment process because magnesium, ammonia, and phosphate are all readily available to form the crystal byproduct,” says Conor MacDonnell, who carried out the study as a PhD student in the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) department of soil, water, and ecosystem sciences.
“The result is a relatively insoluble, sustainable compound found in wastewater treatment plants.”
That relative insolubility led MacDonnell, now works a postdoctoral associate studying seagrass restoration, to team up with Gdańsk University of Technology student Franciszek Bydalek and UF/IFAS faculty members Patrick Inglett and Todd Osborne to investigate whether struvite could fertilize seagrass.
“Coastal ecosystems are dependent upon seagrasses,” Inglett says. “As they diminish, it leads to problems like declining water quality and marine life dying off or migrating to other areas.”
To add to the challenges, current methods of seagrass restoration are relatively expensive and unsuccessful compared to other coastal ecosystems. The study points to nutrient-related issues and competition with algae as reasons behind these difficulties.
In the study, scientists grew three types of plots of seagrass in a simulated setting at the University of Florida’s Whitney Laboratory for Marine Bioscience. One type received an application of struvite, another received a common controlled-release fertilizer, and the last received no fertilizer. Two experiments took place to test different dosages of fertilizer.
“From the two experiments, we found struvite performed better than the controlled-release fertilizer in seagrass growth,” MacDonnell says. “Struvite seems to provide a slower, more consistent release of nutrients to the seagrass.”
The advantages of using struvite in these efforts, extend into environmental sustainability, the researchers say.
“Struvite is potentially a win-win for the environment,” Inglett says. “It is removed from wastewater, so it lessens the impact on downstream ecosystems, and it doesn’t over-fertilize when used for restoration.”
Those downstream effects were the subject of a previous study from another then-PhD student in the same department. John Hallas worked with faculty members at the UF/IFAS North Florida Research and Education Center, Cheryl Mackowiak and Ann Wilkie, to investigate the outputs of water treatment facilities near the Quincy-based center.
“Recovering the struvite from wastewater treatment plants is an effective diversion of these useful nutrients for plant growth, rather than allowing them to enter the landfill,” Mackowiak says.
“It also results in a more useful biosolids product, making the wastewater treatment process more sustainable,” Wilkie adds.
MacDonnell explains that struvite’s sourcing also adds to its sustainability credentials over more traditional fertilizers. Mining phosphorus, for example, depletes that finite natural resource and degrades the land.
The potential research on struvite is just beginning, MacDonnell predicts. He has continued studying seagrass restoration and his current role includes working with Osborne as a postdoctoral associate. This work, he says, may include more struvite studies in the future.
“While using struvite in aquatic systems appears very promising, there aren’t many studies of it in marine restoration projects,” he says, “especially in combination with other restoration techniques.”
The study appears in the journal Science of the Total Environment.
Source: University of Florida
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