Reduce, reuse, recycle: Turning wastewater into energy

Reduce, reuse, recycle: Turning wastewater into energy
The False Creek Energy Centre in Vancouver, B.C., has an exterior look much like a museum. The stacks are topped with LED lights. (Photo courtesy of Vancouver’s Neighborhood Energy Utility)

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The mantra “reduce, reuse, recycle” has become the buzz phrase of the 21st century. And while its applications may vary, the tenets also apply in the wastewater industry, where municipalities and private contractors alike are beginning to address the equation “waste + technology = energy.” 

While there are many steps in between — including the issues of public perception, licenses and permits, massive building projects, huge costs and possible political battles — the benefits appear obvious. What could be better, some believe, than taking an unlimited resource (sewage) and turning it into an essential, and often costly, end product (thermal energy)? 

The road to reuse

The False Creek Energy Centre in Vancouver, B.C., is the first application of localized sewer heat recovery in North America — and the only one to use untreated sewage. For about two years, the plant has provided hot water and heating for the Neighborhood Energy Utility (NEU) in Vancouver, a city of about 650,000. 

The $30 million False Creek Energy Centre services a portion of the city seeing significant new building development — about 2.7 million square feet, which is expected to grow to about 7 million square feet. 

The plant supplies 100 percent of the heating and hot water demand — 70 percent from sewage heat recovery and 30 percent from natural gas boilers, according to Chris Baber, Vancouver’s NEU manager. 

“It’s been operating quite reliably,” Baber says, adding that the sewage heat recovery system produces 50 percent less greenhouse gas emissions, compared to conventional energy sources. 

“Our primary objective was to reduce carbon pollution,” says Baber. “The program has strong sustainability objectives attached to it, and it has to appeal to people with different types of values (including energy efficiency and energy security).” 

The city’s NEU initially also looked at biomass as an alternative, renewable heat source, but investigation and public input led them to the sewage heat recovery route. Currently, only three sewer heat recovery systems worldwide recover heat from untreated sewage — one in Tokyo, Japan, and two in Oslo, Norway. 

Baber admits the system was “very abstract to people” in the development stage, but while concerns were initially raised by the public over potential odors and water contamination, the city was able to overcome the concerns and move forward. Now that the neighborhood association has seen and toured the ultra-modern plant (which has an extremely modern architectural, almost museum-like, façade), Baber says they are “super appreciative.” 

“Implementing a new technology requires a great deal of public participation,” says Baber. “The public’s perceptions are not always based on technological facts. If you don’t have sufficient material to present when you go public, people’s imaginations are left to fill the gaps.” 

So, ultimately, one of the hurdles was to explain to the public how, exactly, untreated sewage is turned into energy to heat a home or business. 

In essence, heat pumps transfer thermal energy from warm sewage to a higher temperature range effective for heating and hot water. Similar in concept to geo-exchange systems, sewage heat recovery is more efficient and cost-effective — especially because the raw sewage has a higher temperature than ground-source heat, thereby requiring less energy to upgrade. 

“One of the things that surprised us is how warm the sewage is,” says Baber. “There’s a huge amount of waste heat that is present in the sewage; it forms the potential for the technology.” 

Accessing sewer lines is less invasive and less cost intensive than drilling for geothermal heat, and it utilizes a continuous supply of waste heat. A distribution pipe system runs beneath the streets, delivering thermal energy in the form of heated water from False Creek to the buildings. Insulated pipes reduce energy loss through distribution. False Creek uses about 30 gallons of wastewater per second, reaping 3.2 megawatts of capacity.

Metro support is strong

Metro Vancouver handles utility services for 24 local authorities in British Columbia and has made sustainability a key part of its operating and planning philosophy. “We’ve got some energy recovery goals and projects,” says Genevieve Tokgoz, project engineer for Metro Vancouver. It’s part of becoming a “zero-waste” region. Metro Vancouver’s website notes, “We commit to recover energy, nutrients, water or other usable materials from liquid waste and return water to the environment in a manner that protects public health and the environment.” 

Tokgoz says, “We’ve received a number of requests from municipalities who are interested in extracting heat from sewers.” Metro Vancouver is currently taking a long-term look at the issue and is involved in conducting pre-feasibility studies. 

“We want to send a message to anybody ready and interested … to let them know that Metro is keen to support making that happen,” says Tokgoz. “It’s sort of the way things are going; district energy projects can really reduce carbon footprints.” 

Recycled water to power generation 

The City of Santa Rosa, Calif., has taken a novel, but somewhat similar, approach to sewer heat recovery to create energy. In 2003, the Geysers Recharge Project began pumping 11 million gallons per day of highly treated wastewater from the Laguna Wastewater Treatment Plant to the Geysers Steamfields, which are the world’s largest geothermal fields, according to Mike Sherman, geysers operation and maintenance coordinator for the city. The reclaimed water is used by Calpine, North America’s leading geothermal power producer, for steam production. 

According to Sherman, the delivery is currently 12.62 mgd, generating enough “green” electricity for 100,000 households in Sonoma and other North Bay counties. 

Once the recycled water is released from the project’s terminal tank, gravity carries it through Calpine’s pipeline to the steamfields, where it is injected into the ground — thus extending the life of the steamfields and allowing the generation of electricity to remain at its current level. 

The Geysers Recharge Project has been lauded worldwide as a weather-independent component of its reuse system. The city’s Geyser Expansion Project built on this success, and has the potential to increase water delivery to the steamfields up to 15.9 mgd, or as much as an additional 936 million gallons per year to meet future growth and demand. 

According to information on the city’s website, each 100 megawatts of capacity at the Geysers eliminates the need to burn approximately one million barrels of oil per year — reducing that carbon footprint so important to many businesses and municipalities in the 21st century. 

“Our relationship with Calpine is a win-win. It works really well,” says Sherman. “You have to sometimes think outside the box and look at the different resources you have in your community.” 

Could projects like those in Santa Rosa and Vancouver be replicated elsewhere? The topic is certainly under study in many places. 

After years of study, engineers at Oregon State University have learned that with enhanced performance of microbial fuel cells — technology that changes chemical energy into electrical energy — in wastewater can be used as a source to produce electricity at a volume 10 to 50 times higher than many other approaches. And other companies are researching how to refine wastewater into a base to create biofuel. 

Baber notes that for a system similar to False Creek to operate, “You need economies of scale. You need a thermal energy grid; you need to interconnect buildings. That’s been a challenge … getting those grids established.” And, of course, you need up-front capital. 

Still, Baber believes this technology will continue to be explored and interest will grow. “Look across North America — district energy is really undergoing a renaissance,” he says. “Not all these systems will use heat from sewage, but the basic district energy approach is becoming much more common and popular.”



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