As for pollution reduction, the results so far look "very promising," said Ted Atwood, Baltimore's energy office director.

His office is involved in the experiment HY-TEK is running at the city's Back River Wastewater Treatment Plant, where bioreactors are bathed in colored light. The project, which kicked off last year, is funded with a $250,000 grant from the federal energy department and about $850,000 in donated equipment and services from U.S. companies enthused about the idea.

HY-TEK has four bioreactors at the plant. That's enough to take in about one-eighth of the flue gas emitted by the electricity-generating engines there, which run on biogas made by waste digesters on site, Atwood said.

The flue gas is injected into the bottom of the bioreactors. As the gas works its way up, the algae breaks nitrogen dioxide into its components and consumes the bad stuff — wiping out the pollutant, HY-TEK says. The algae also eliminates about 85 percent of the carbon dioxide.

That's with 10-foot-tall bioreactors. HY-TEK is about to replace them with a 20-foot-tall design. Mroz said he's confident the extra space will reduce the carbon dioxide to zero.

Atwood said Baltimore decided to try the project after staffers reviewed the plan and thought it compared well with the competition.

"We felt they were doing more to maximize the growth of the algae," he said. "They had better economic potential than some of the others … we knew were out there."

Biofuel to pollution

What got Mroz and French interested in algae five years ago was alternative fuel. French, who pilots ultralight planes, wanted to develop biofuel for that aircraft. But when they looked into it, Mroz said, "we had an epiphany."

"It takes two tons of CO¿ to produce one ton of algae," he said. "We said, 'What are we doing fuel for? This stuff needs to be used in the mitigation of greenhouse gases.'"

They formed HY-TEK Bio in 2009 and teamed up with researchers at the University of Maryland Center for Environmental Science, who narrowed down tens of thousands of algae strains in an effort to find ones best suited for the company's purposes.

The winner happened to come from Back River in Baltimore County, right beside the wastewater treatment plant.

"It had never been isolated before, so we got to name it," Mroz said. "That was pretty neat."

(It's now called HTB1, for HY-TEK Bio strain 1. That's the sort of name algae gets.)

One of the company's cost-saving measures is making bioreactors from Mylar strengthened with Kevlar mesh, cheaper than alternatives like acrylic plastic or fiberglass. And they're modulating their colored LED lights — turning them on and off — in a way that they say increases algae growth and decreases energy use.

Next up: skipping fertilizer as food for the algae and extracting nutrients from chicken manure instead. A 16-ounce bottle of Miracle-Gro costs $2 in bulk, Mroz said, compared with less than a penny for the same amount of nutrients from the manure.

Mroz said the company is in talks to construct its algae systems for a small power plant expected to be built in Maryland and a local waste-to-energy operation. HY-TEK is on track to start selling algae products next year, he said.

Mroz said he's also talking to people outside the energy industry about other applications for the bioreactors, such as cleaning air in subways and offices.

For now, though, his company manages on a shoestring budget. None of its 12 workers — the co-founders included — is getting paid. Mroz's Dayton home doubles as headquarters. He and French won grants to cover much of the research, but they've each contributed thousands of dollars.

They keep pushing on, enthused about the possibilities and the level of interest. Mroz said hundreds have visited the Baltimore pilot site, including a group from China.

Kathy Magruder, executive director of the Maryland Clean Energy Center in Annapolis, connected HY-TEK with the University of Maryland and a program that helped fund that research. She said she's glad the company has managed to "navigate the Valley of Death so far" in the tough world of translating intriguing technology into a revenue stream.

"What they're doing is validating their technology works," Magruder said. "They're showing us what's possible."