Winthrop’s Deer Island sewage treatment plant. Experts say wastewater’s constant temperatures can be used to generate environmentally friendly heating and cooling. Credit: iStock photo
A potential solution to Boston’s green energy transformation offering major cost savings is flowing through its sewers, sustainability experts say.
So why aren’t more developers diving in?
Wind and solar power might be among the best-known green energy sources, but an increasing number of municipalities around the world are turning to wastewater energy as a heating source for buildings.
Wastewater energy recovery, which encompasses extracting heat from sewage and recycling it to warm buildings in the winter and cool them in the summer to cool buildings, has been deployed in European countries including Germany and Switzerland, Bloomberg reported earlier this year.
In North America, wastewater heat recovery is utilized in Vancouver, Canada, and a Colorado State University campus in Denver as well as Seattle and Washington, D.C.
The state Department of Environmental Protection hosted a Wastewater Energy Recovery Summit to spread the word about the potential of the green energy source in the Bay State.
“There’s a multi-year process that’s been in motion here to move towards figuring out what would be the appropriate regulation and pricing, to take advantage of the thermal opportunity,” said Zeyneb Magavi, co-executive director of Home Energy Efficiency Team (HEET), a Boston-based nonprofit climate solutions incubator. “A thermal market means that wastewater and sewer heat are suddenly assets.”
There is ample energy-producing opportunity in wastewater. The U.S. Department of Energy estimates there is enough energy flowing down the drain each year from toilets, showers, sinks and washing machines to serve more than 30 million American homes.
“It’s the largest untapped renewable energy reservoir,” Magavi said. “There’s no question, and it could not only provide our heating and sometimes cooling, but it could also mitigate the impacts of climate change.”
A development team led by Trinity Financial that’s been chosen to build 686 housing units on Austin Street in Charlestown considered the use of a wastewater heat recovery system as an alternative to fossil-fuel-powered heating and cooling systems. Image courtesy of ICON Architecture
Charlestown Developers Cite Potential Use
The technology uses reversible heat pumps to extract cooling and heating energy from sewer lines and transfer energy to separate water pipes serving homes or commercial buildings. Because of the scale of the systems, the technology primarily has been used in large campus environments such Denver’s National Western Center, a food and agriculture hub that is designed to source 90 percent of its heating and cooling from wastewater.
The local rollout for any wastewater energy recovery at scale appears in its infancy. A Boston Planning & Development Agency presentation during last year’s Wastewater Energy Recovery Summit spotlighted “sanitary sewer, blackwater and seawater heat exchange” on its list of Advanced Energy Feasibility Assessments. The presentation noted that developing policy for waste energy technologies is an agency goal and priority.
Both development proposals submitted to the BPDA – one from Onxy/Dream Austin LLC and the winning proposal from Trinity Financial – for the Austin Street parking lots in Charlestown included wastewater heat recovery systems as potential sustainability strategies.
Representatives with the BPDA did not respond to multiple requests for comment, but other Boston City Hall officials are optimistic about the potential for wastewater heat recovery in future developments.
“We are actively looking at that in Boston. There are some very attractive state [DEP] grants and we are exploring with our water and sewer authority to see if there are physical opportunities for pilot projects,” said Brian Swett, chief climate officer for the city of Boston.
Costs and Utilities’ Cooperation Remain Hurdles
It might seem like a head scratcher as to why wastewater energy recovery isn’t being pursued faster in a city like Boston, with its progressive green energy policies on commercial developments like multifamily housing. It’s not as though the technology is new: The basic district heating component of this dates back to ancient Rome, Magavi noted.
But modern wastewater energy recovery, while offering the potential for immense savings on energy costs, does require a lot of upfront capital investment to build out systems, whether at the property or municipal level. Sources interviewed for this story didn’t provide cost estimates, but the upfront cost along with proof of concept were cited as potential friction points with the development community.
“There are only a couple of products that are available in the market, and they’re all relatively high costs at this point because they’re small companies and not a lot of competition,” said Brian Urlaub, vice president and director of geothermal operations at engineering firm Salas O’Brien. “The other big hurdle is just getting through all the regulation and discussion with the sewer authorities or whoever is in charge [of utilities] to make sure that everybody’s comfortable with it.”
The Boston Water and Sewer Commission did not respond to multiple requests for comment.
But there is optimism that momentum is building for a broader rollout of wastewater energy recovery to bring down monthly energy bills, especially as interest in the green energy source builds around the world.
“Once this works, and once the utilities are satisfied that what they have to produce isn’t infringed upon, you’d be kind of foolish not to do it,” said Joe Savage, a development advocate who worked on the Onxy/Dream Austin proposal for the Austin Street parking lots.
“One of the things we have to do is open up the conversation on what is economic,” HEET’s Magavi said. “It pays back, and the energy cost goes to zero.”
