Wearing more protective gear than he needs for gardening, Bill Brower stepped inside a knee-high fence to pluck a few ripe tomatoes from an overgrown vine.
“I encourage people to take a bite,” he said, wearing the hardhat and neon vest that’s required at DC Water’s Blue Plains Advanced Wastewater Treatment Plant.
The cherry tomato tastes as good as it should in late July. Brower explains that it was grown with the help of composted biosolids — organic matter that has been recycled from the sewage of the District of Columbia’s residents.
A sign in the small demonstration garden explains:
“This soil is amended with DC Water Class A biosolids compost — recycling DC’s nutrients back to you,” and, in case passers-by don’t quite get it, it continues, “So, in your own small way, you have made a contribution to helping these plants grow!”
“There’s not enough room on there to say, ‘This is your poop that grows the tomato,’ ” Brower, manager of biosolids operations at DC Water, said with a grin.
The recycled nature of these garden soils might be expected here at Blue Plains, where the water authority treats and “recovers resources” from the sewage and wastewater of more than 2 million DC-area residents. But the same sign — complete with a QR code that can be scanned for more information — can be seen at a growing number of sites that grow food and plants in the city.
“When we deliver to a community garden or school, we want to be really open about what we’re doing,” said Brower, whose contact information is also on the sign.
But, if the lack of angry calls he’s gotten — and the warm reception he continues to get at gardening conferences — is any indication, many DC gardeners have embraced the idea of toilet-to-garden compost.
That response is one that the plant’s staff has been working on for some time as they prepared to bring new technology online that will make a more refined version of the biosolids more widely available as a soil amendment.
At the Rooting DC conference in January, DC master gardener Neil Hoffman interrupted Brower’s presentation to give an unsolicited and hearty endorsement. The biosolids compost he’d worked with at a community garden outperformed others, he said, and didn’t come with unwanted weeds like leaf composts. Not to mention, it was free (for now).
Brower said that 10 years ago — when his boss, Chris Peot, DC Water’s director of resource recovery, first espoused the idea of applying urban biosolids in an urban setting — he might have been booed off the stage at such food-growing conferences.
Now, “people are comfortable with it, and they’ve had great results,” said Brower, who was brought on staff more than two years ago to continue spreading the word among urban gardeners about the full-circle benefits of biosolids.
His wife worked at a farming nonprofit and both she and Brower were well-rooted in the local gardening scene. Not to mention, Brower was an early convert to the idea that biosolids were a resource, not a hazard, that the city could use rather than export.
For decades, DC Water has paid a third party about $12 million each year to truck 18 tractor-trailer loads a day of partially treated biosolids to farmers’ fields, mostly in Virginia. There, the partially treated — or Class B — product was spread for years as free fertilizer for growing animal feed crops and hay. EPA regulations do not allow Class B biosolids to be used on crops for human consumption unless they are composted or there is a lag time before planting, so giving it to farmers was a lot better and cheaper than sending it to landfills.
The plant has been offering the composted biosolids to community gardens for years and ramped up its efforts to do so in light of new technology that would make the biosolids more refined and more approachable for an urban audience.
This last year, the plant added processing steps to further treat the biosolids into a Class A product that can be used without composting to grow food that people eat. This new line of biosolids also has the potential to make, rather than cost, the water authority money.
“We wanted to have a Class A product so it would be more versatile,” Brower said. “We wanted to bring down our costs and make it into a revenue maker, which we hope to do in the coming years.”
This spring, farmers began receiving the Class A biosolids, which have a darker, denser appearance coming off the conveyer belt that removes most of the liquid. Those farmers will be weaned off the free fertilizer soon as DC Water develops new markets for the improved soil amendment.
In the meantime, Brower has continued the public relations campaign for the composted Class B biosolids he calls “a gateway drug” for the more refined product that DC Water is producing but won’t have the permits to distribute until the end of the year. The compost that’s currently available is mixed off-site with wood chips and brought to high temperatures for three weeks to kill unwanted bacteria, making it safe for growing food in the city.
As part of the effort to win over gardeners, Brower delivered the compost to dozens of community and school gardens, as well as nonprofits like Casey Trees over the last two years.
“It’s easy to make friends when you have a really good product that you’re giving away for free,” Brower said. He plans to continue giving the new product to those groups even as he works to build an audience of paying customers in the future.
The biosolids that are now coming out of DC Water’s digesters are “suitable for an urban area” without composting, Brower said. “So, rather than shipping these resources off to Virginia, we want to be utilizing them here.”
Calling the biosolids “resources” rather than “waste,” is part of a broader paradigm shift at these facilities “that I think we have been at the forefront of,” Peot said.
DC Water is the largest facility of its kind and treats enough water to fill a football stadium each day, removing nitrogen and other pollutants before it is released into the Potomac River. But what does it do with the “nutrients” that are removed at several stages from that water?
That’s where “resource recovery” comes in — and the biosolids. Rather than fill a landfill with what shouldn’t go into the river, the industry is looking for a better use.
“The ultimate thing is that we’re trying to limit the amount of nutrients going to the Bay. That is the No. 1 thing,” Brower said.
While the facility has fed some of its waste to methane digesters since its inception in the 1930s, those stomach-like machines are now valued for their energy production — methane-fueled turbines provide one-third of the plant’s power today — and, increasingly, for their byproducts.
The biosolids coming out the back end of the digesters were made more precious last year by a new system that functions like a pressure cooker to remove pathogens from the sludge before it enters the digester, producing Class A biosolids from the digested solids that are left over. The plant was the first in North America to employ Norway’s Cambri system of thermal hydrolysis to this end. If the flurry of attention the machine received at the Water Environment Federation conference is any indication, other plants could soon follow suit.
DC Water is also considering other waste streams for its digesters, such as food scraps from the city or sugar from soda plants, that could speed digestion and keep organic matter out of landfills.
“Our industry is used to dealing with something that’s gross. People don’t want to think about it, so they take it to the landfill, flush it down the pipe or throw it in the river,” Brower said. “We’re trying to change that thinking, to see everything as a resource.”