[USA] Can the algae in Lake Okeechobee be extracted and turned into biofuel? An experiment conducted near the Moore Haven lock in July indicates this could be a possibility.
Dr. Martin Page, project manager, with the U.S. Army Corps of Engineers said the 2018 WRDA provided the corps with some funding for research into Harmful Algal Blooms (HABs). This system pulls algae out of the water and then puts the clean water back into the lake.
“Even if you get the algae out of the water, you need to do something with it,” he continued. The project is trying to extract value from what would otherwise be considered a contaminant.
Compared to the past few years, there has been relatively little algae in the lake this summer.
“The algae levels have been a little low relative to what we were planning for,” said Dr. Page. He added that despite the low levels of algae, they were able to collect a great deal of data during the three-week experiment.
The process collects “whatever is in the water.” During the three-week experiment, that meant a mixture of algae and cyanobacteria (sometimes called blue green algae).
At the pilot scale, the technologies work with the each other. Dr. Page said they hope to conduct a longer demonstration next summer that will include taking the equipment out on the lake on barges.
The algae extraction process is one the stakeholders can consider, not just for Lake Okeechobee, the Caloosahatchee River and St. Lucie River but also for lakes and rivers all over the country. The increase in blue green algal blooms is a problem across the country, he said.
The goal is to take something that is considered potential hazardous and turn it into a resource.
Using the process to treat the whole lake would be a “really big ask,” he said. There are physical limits to the process. But they could treat water at the inflows and outflows. Equipment on barges could be used to treat high concentrations of algae in the middle of the lake.
Algae collected during the experiment were sent to the Pacific Northwest National Labs, which is part of the U.S. Department of Energy, to be converted into fuel.
“Algae are like little solar cells which contain energy,” he said. Instead of treating it like a waste product, this process treats algae as a resource.
A high temperature and pressure will be used to turn the algae into a biomass which can be converted into fuel. This process also destroys any toxins that might be in the biomass.
While the process of extracting algae and turning it into fuel will not pay for itself, it could offset the cost of the process. At some point, biomass produced from algae might even be used to fuel the process.
“We’ve been developing a process to harvest intact algae cells, and in so doing we can remove the key nutrients that fuel harmful algal blooms, such as nitrogen and phosphorus,” said Dan Levy of AECOM, an engineering company that specializes in algae removal. Mr. Levy is co-investigator on the project.
Mr. Levy said the pilot program has allowed them to treat 100 gallons per minute. He said they believe they can scale that up to treat 100 million gallons a day.
During the experiment, the process collected a mix of algae and cyanobacteria, making use of “whatever was in the water.” Algae recovered from natural waters tends to be higher in protein than algae grown in a lab, he said. The process that converts algae to biofuel works better with “wild algae” than with algae grown in a lab.
David Pinelli, senior scientist for AECOM, explained that they pump the water from the lake into large tanks. The water flows from the tanks through a container where “billions and billions” of microscopic air bubbles attach to the solids in the water and float the mass to the surface. The algae and cyanobacteria in the water column rise to the top of the tank. The algae is scraped off the surface of the water by a skimmer, and goes down a chute into a cannister. A pipe on the side of the treatment container allows the clear water to flow out into another container. The clear water is treated a second time with an ozone process that eliminates toxins, should any be present.
During the three-week test period, no toxins were found in the lake water at Moore Haven.
“We put green water in, get sparkling water out and then put it through a second product to polish the water to make it even cleaner,” he said.
Mr. Pinelli said the process means equipment that requires only a small footprint of space can handle a large volume of water.
The water that comes out of the process is crystal clear, and while it is free of algae, cynobacteria and toxins, the process does not remove nutrients such as phosphorus from the water.
“We can get some co-precipitation of phosphorus when the process removes the biosolids, but the process will not remove all phosphorus,” Mr. Pinelli said. “The goal is to capture intact biomass.”
Mr. Levy said they want to harvest cyanobacteria before it becomes a toxic bloom. “We want to do this ahead of the chaos,” he said. “We don’t want to get to the point that we have toxic algae in someone’s yard.”
The algae removal project is the second of three projects funded by the Corps. The first project was the Franklin Lock project. The third experiment will involve using a peroxide based algacide to kill algal blooms in small enclosed areas such as marinas.
Linda Nelson of the U.S. Army Corps of Engineers said they planned to conduct a test at the Pahokee marina, but the algal bloom there disappeared before they could conduct the test. They still plan to conduct the test there if an algal bloom forms there again.
Photo: A pilot project conducted over three weeks in July near the Alvin Ward Park in Moore Haven removed water from Lake Okeechobee, separated the algae from the water and returned clean water to the lake. (Immokalee Bulletin/Katrina Elsken)
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