Students at the University of Nevada – Reno develop a novel technology for drying biosolids and turning it into a high-quality fuel


The University of Nevada — Reno has a business opportunity for a wastewater plant looking for an efficient and creative solution to one of its major expenses. Its chemical engineering students have come up with a new process for drying biosolids so that it can be converted to fuel. Their idea has been proven in the field and is ready for a commercial-scale pilot project.

“We started in 2006 looking at converting solid waste to energy,” says Chuck Coronella, Ph.D. and associate professor of chemical engineering, who led the project. “Wastewater biosolids is a good candidate because it’s uniform and you can find it everywhere.”

The students’ work received funding from the California Energy Commission and the U.S. Department of Energy. “We’ve applied for a patent on our novel fluidized bed dryer,” says Coronella. “One of the uses is likely to be the production of power.”

 

Proven concept

The fluidized bed dryer operates at the very low temperatures of 120 to 150 degrees F. Rather than use a fuel like biogas or natural gas, it runs off waste heat from a boiler or cogeneration unit. “What comes out is a very dry powder, typically around 5 to 8 percent moisture content,” says Coronella.

Dewatered biosolids, about 80 percent water, is fed into the fluidized bed. Air is injected through the material and the bed, made of an inert material like sand, creating a vigorously bubbling mixture.

“Because it’s bubbling, the biosolids heats up rapidly and breaks apart,” says Coronella. “The smaller fragments dry quickly because they have much more surface area. As they dry, they break up faster and faster until the fragments are so small that, like dust, they are carried up by the airflow and can be captured in filters.”

The students’ design was built in the university lab and put into operation at the Truckee Meadows Water Reclamation Facility in Reno. After some kinks were worked out, it processed 20 pounds of wet bio-solids per hour to produce three pounds of dried powder. “It was impressive from a technology development perspective,” says Coronella.

He worked with three chemical engineering students — undergraduates Chris Moore and Cody Niggemyer and graduate student Mike Matheus. Their demonstration project ran for as long as seven hours at a time over nearly four months in the summer of 2010. “We did several tests exploring the behavior of the process,” Coronella says. “Things like temperature and time and other parameters we can manipulate, to see how those affected performance.” The next step for the R&D project is to produce fuel pellets from the powder. The fuel has a BTU value similar to dried wood.

 

From the lab

“It is an environmentally friendly and economical solution,” says Michael Birdsell, director of intellectual property marketing for the university’s Technology Transfer Office, who sees “significant opportunity” for commercialization from the students’ work.

His office is charged with finding partners and markets for technology developed by faculty and students doing research on campus. For example, UNR has recently licensed an enhanced method for removing arsenic from drinking water to EaglePicher Corporation.

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“The U.S. generates the equivalent of 8 million tons of dry biosolids a year,” he says. “The cost of disposal is roughly $2 billion annually and is one of the primary costs for wastewater treatment plants.”

He estimates that a fluidized bed dryer would cost about $2 million and could pay for itself in 10 years. “We’re looking for a waste-water plant partner that can offer investment and support for a commercial-scale pilot project,” says Birdsell. He is also seeking grants, investors, and other ways to fund the commercialization and is talking to engineering firms, equipment companies and startup environmental companies that may be interested in moving the process into practical application.

“Converting waste to energy is rich with opportunities,” says Coronella. “There are much better ways for us to think about waste. It can be a valuable resource.”

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