New greenhouse means savings for Cocoa Beach
New system will repurpose sludge from sewer plant
There is something new under the sun, after all, at least in this surfing mecca--sludge.
Cocoa Beach’s sun-dried sludge now cooks in a 100-foot-long greenhouse at the city’s sewer plant off Minutemen Causeway, Local 6 news partner Florida Today reports.
The dried-up brown stuff could one day fertilize farms, possibly local yards, or even provide fodder for fuel.
Those aspirations may take a while, city officials say, but their sun-baked dark brown sludge already is providing a green way for the city to save plenty of green.
“Even if it doesn’t work out as a fertilizer, we’re greatly reducing what we take to the landfill,” said Darby Blanchard, the city’s water reclamation director.
Cocoa Beach once spent upward of $70,000 a year to haul off sludge to a landfill. But the $270,000 sludge greenhouse — one of only a few of its kind in Florida — will save money or possibly even make money in the long run, city officials say.
The greenhouse is made by Nexus Greenhouse Systems, based in Colorado.
The new process dries out sludge much more than previously, to 75 percent or more solids, rather than the 15 percent or so obtained previously by a belt-press.
And the sun delivers most of the energy to dry the sludge, rather than the electricity used to power the older machines.
Last year, Cocoa Beach generated about 2,800 wet tons of sludge. The city had to pay about $70,000 to dispose of the waste at Brevard County’s main landfill west of Cocoa, Blanchard said.
The city hauled off four or five truckloads a week, he said. Now, because of the much dryer sludge, the city only expects a few truckloads monthly.
And the sludge may soon find greener pastures. It’s expected to be clean enough to fertilize farms, possibly even yards. The city would first have to conduct tests to prove to state regulators that the sludge meets environmental standards.
The sludge-drying process is straightforward. To get it to the greenhouse, a conveyor belt pulls the sludge into a dump truck, which drops the gritty stuff along the greenhouse’s concrete floor. The city ultimately plans to automate that step, so the conveyor belt carries the sludge all the way to the greenhouse.
On a recent day, a tractor tilled the sludge along the concrete greenhouse concrete floor. But in December, that step of the process also will be automated, by two $150,000 small automated electric cars. They turn, spread and aerate the sludge to speed up drying.
A weather station atop the structure senses humidity and triggers the greenhouse roof vents to close automatically to prevent rain from coming in. It reopens when rain chances are slim.
The sludge takes two-to-four weeks to dry before it can be hauled off.
The Okeechobee Utility Authority installed a similar greenhouse system in early 2008, and the concept has been catching on in Europe.
The Okeechobee utility formerly spread its sludge on land surrounding the sewer plant, but opted for the greenhouse system when state and county rules restricted the practice.
“It kind of forced us to either go to the landfill or go to a different method,” said John Hayford, the utility’s executive director.
Hurricanes were among his main concerns, but the greenhouse has held up well through storms so far. Cocoa Beach’s greenhouse is built to withstand 160 mph winds, Blanchard said.
Like Okeechobee, Cocoa Beach hopes there will be interest in the sludge as fertilizer. They also could spread it on the city’s nearby golf course.
“It’s not going to be a high-nitrogen fertilizer,” Blanchard said.
To protect the Indian River Lagoon, the state in 2009 adopted stricter limits on the nitrogen levels the city’s plant can produce.
Cocoa Beach’s sludge greenhouse is part of about $22 million in upgrades to the city’s sewer system. That includes a $15 million new sewer plant and $2.4 million well to store reclaimed water to be pumped up later for sprinkling on lawns.
The city also plans $4 million in fixes to old, cracked clay pipes and manholes, starting next year.
Cocoa Beach entered an administrative order with the state in 2008, setting a compliance schedule for meeting new nitrogen and phosphorus limits and major plant upgrades.
Upgrades are expected to be finished by Jan. 1, but so far the new plant has exceeded the city’s expectations in terms of reducing nitrogen.
The plant churns out reclaimed water with 1.8 milligrams per liter of nitrogen, compared with the old plant’s 7 to 12 milligrams.
Sludge has potential as a fuel source in power plants and cement kilns, or it can be heated in a process that creates a synthetic gas that could be used to operate portions of the sewer plant.