Harnessing energy from sewage is not a new concept for the thousands of wastewater treatment plants that exist throughout the world. Many of these facilities are creating electricity from the biogas they generate in anaerobic digesters. But one plant in Fountain Valley, Calif., is taking wastewater treatment one step further.

The Orange County Sanitation District (OCSD) is able to take some of the methane produced through the anaerobic digestion process to not only create electricity to power its operations, but also to produce hydrogen. The hydrogen is made available to vehicles at a fueling station located at the facility.

This pilot project to use fuel-cell technology for on-site electricity and hydrogen generation is now in the second year of a three-year testing phase. FuelCell Energy, Danbury, Conn.; Air Products, Lehigh Valley, Pa.; and the National Fuel Cell Research Center at the University of California, Irvine, are participating in the project with support from California Air Resources Board, South Coast Air Quality Management District, the U.S. Department of Energy and the Southern California Gas Co., Los Angeles.

Jeff Brown, OCSD senior engineer, says, “It has been a continuing area of importance [for OSCD] to always look at new, more efficient and environmentally friendly ways of doing things,” which is why the treatment plant was interested in the project. He adds, “Fuel cells as a power generation technology are by far the most environmentally friendly way of doing it. There’s essentially no emissions. You can’t get cleaner than a fuel cell.”

OCSD still generates some of its electricity from digester-gas-powered engines, which do produce emissions. “There are still emissions from those engines, and we are subject to the same air-quality regulations anyone else has,” Brown says.

The opportunity to reduce emissions and support hydrogen-powered vehicles with the project made it ideal for OCSD. “It incorporates a lot of firsts in the world for the way things are done, and it’s a way to continue with our mandate from our board of directors to be as environmentally friendly in our operations as we can be,” says Brown.

FuelCell Energy’s technology is being used at OCSD. The company’s Direct FuelCell (DFC) power plant provides renewable hydrogen for vehicle fueling and what it calls “ultra-clean” electricity for the facility.

Air Products Inc. operates the on-site hydrogen fueling station.

Tony Leo of FuelCell Energy says of the project, “The fact that we have a carbonate fuel cell running on wastewater treatment gas is not that unique. We are doing that a lot in California. The unique thing about it is it is the first field demonstration of the hydrogen export concept.”

The DFC is currently only producing 300 kilowatts of electricity, or about 5 percent of the facility’s electricity needs. Brown says it’s a demonstration of a technology that could be easily sized up. The system wasn’t intended to replace the engines OCSD currently use just yet.

“First, we wanted to make sure the technology worked, and so far the plant is meeting or exceeding the efficiency standards that were planned for,” says Brown.

There are many possibilities as to how OCSD could use the fuel cell in the future. One possibility is a public/private partnership where OCSD would use the electricity, and the OEMs producing fuel-cell vehicles would have access to the hydrogen.

According to Brown, fuel-cell vehicles are expected to be introduced to the public in 2015. Convenient access to hydrogen-fueling stations is a big hurdle to vehicle deployment.

“There is going to have to be the infrastructure put in place that will allow people to easily get the fuel they need,” says Brown. Hydrogen is also costly to transport, which makes being able to use the fuel on site advantageous. “So this distributed hydrogen-generation concept could be a major component in developing the infrastructure that is going to be needed for the hydrogen-fueled vehicles,” he explains.

The fuel cell at OCSD produces enough hydrogen to fuel 100 vehicles per day. In addition to electricity and hydrogen, the fuel cell also can produce heat, taking cogeneration to the next level. Since this system can produce three types of energy—electricity, hydrogen and heat—the term “tri-generation” has been coined to describe the system. The system can be adjusted to produce varying amounts of each product.

FuelCell Energy has been able to capitalize on the biogas produced at wastewater treatment and food processing plants. The methane these facilities produce is flared off, used to power engines or, as in the case of the OCSD, put into a fuel cell.

The Process
Most fuel cells work by electrochemically reacting hydrogen and oxygen to make water. Leo likens fuel cells to batteries. A battery makes electricity from a reaction of two chemicals inside it. A fuel cell works the same way, only the reacting chemicals are continually being pumped into it. Because fuel cells use a chemical process and not a burning process, they do not produce the same harmful emissions or particulates of a combustion process, according to Leo. He says the levels of particulates and nitrogen oxide produced from a fuel cell are so low they are “almost immeasurable.”

Air Products handles the hydrogen purification and dispensing end of the system. Leo thinks OCSD has shown that hydrogen can be produced and dispensed locally, saving on delivery costs and the environmental concerns of building a large hydrogen plant.

“We’ve demonstrated that the concept works,” says Leo. He sees the potential of biogas as a source for fuel cells. In California alone, FuelCell Energy is generating about 17 megawatts of electricity from its fuel cells.

“We see a significant near-term market in wastewater treatment plants and food and beverage processing,” says Leo. “We see an even bigger, longer-term market in agricultural waste. We have actually configured our products to be ready to operate on those fuels, so it is a really important market segment for us.”

The author is managing editor of Renewable Energy from Waste magazine and can be contacted at [email protected].