In the movement to turn wastewater treatment plants from cost centers to profit centers, grease could play a significant role. 

RPM Sustainable Technologies of Storrs, Conn., is introducing a new process to convert brown grease into biodiesel fuel. A co-byproduct, glycerol, could have even more lucrative applications as a building block for high-end chemicals and other products. 

“Wastewater treatment plants collect a lot of brown grease, either from haulers or through the sewer system,” says Richard Parnas, co-founder of RPM and professor of chemical engineering at the University of Connecticut. 

“Here in Connecticut, most of it is either taken to landfills or incinerated,” he adds. “That’s not a good scenario. We think we can find a better use for it — clean up an environmental issue and provide a new energy source, as well.” 

Grease reaction 

The RPM technology uses a proprietary catalyzed esterification process, which reacts grease with methanol. The fatty acids in grease are converted to biodiesel and water. In later parts of the process, glycerol is produced as a byproduct and can be marketed to produce glycerin or other specialty chemicals, Parnas says. 

The process, while based on technology that converts yellow vegetable-based grease into biofuel, is able to deal with the higher levels of fatty acids in brown grease. “The chemistry (in the process) is a hundred years old,” Parnas points out, “but the reactor we’ve designed gets rid of some of the post-treatment steps that are normally required. 

“For example, the glycerin separation step occurs right in the reactor. Previous attempts at this have resulted in lots of problems. We have put lots of emphasis on the front end of the process to make the back end a lot simpler.” 

The straightforward design of the system is illustrated by a demonstration unit being assembled for the wastewater treatment plant in Torrington, Conn., operated by the Torrington Water Pollution Control Authority. “The whole process can be packaged up in two corrugated steel Connex shipping containers, transported by flatbed truck and unloaded with a forklift,” Parnas explains. 

The Torrington demo unit is scheduled for installation around Thanksgiving, and should be up and running and producing biofuel by next spring. The project is receiving grant money from the state of Connecticut. A number of potential strategic partners are interested in the results, Parnas says. 

Interested markets 

RPM foresees a broad market for the grease-to-biofuel technology. “In the United States, as many as 2,500 wastewater plants could support the installation of a full system,” Parnas says. “In the case of smaller plants, a smaller version of the front end of the technology could be installed, with complete systems in operation at larger plants — a sort of hub and spoke setup.” 

He says the technology represents a potential 30 percent increase in biodiesel supply in the U.S., with uses including onsite generators or boilers and fleet vehicles. The fuel could also be sold at market rates. A class III operator who works with RPM, John Zaczynski, is helping RPM understand the best way to integrate their technology into plant operation. 

Parnas estimates that for small to mid-sized wastewater plants, the payback on a grease-to-biodiesel system would be around three to five years; with larger plants, the payback could be as little as two years, he says. 

“What we envision is cleaning up an environmental problem, creating a renewable source of energy, and changing the financial picture of wastewater treatment plants,” Parnas says. “Instead of just being a water factory, plants can transition into being energy factories, and (through the sale of recovered products) ultimately into a money factory.” 

What revolutionary ways can the clean-water treatment industry make money? Post a comment below.