From ancient times to modern-day, some places manage water and excreta in a smart way. Recently, I visited one — the Biocycle Farm in Eugene, Oregon.
Flush the toilet in this town, and here’s a surprise: your contribution may be transformed into an eco-friendly building material — poplar trees. This climate-friendly practice recycles nutrients, keeps local rivers clean and could one day spark a new economy.
At first glance, the bathrooms in Eugene and Springfield, Oregon, appear the same as in any other American town. The difference comes after the flush. Sewer pipes connect toilets to the wastewater treatment plant. It’s run by the Metropolitan Wastewater Management Commission (MWMC), a partnership between these neighboring cities and Lane county.
At the plant, the solids (mainly poop and toilet paper) separate from the liquids (dirty water) and both are cleaned. These solids enter a giant tank, like a mechanical stomach, where they’re digested by bacteria. At night, powerful pumps swoosh the processed slurry a few miles down the road to another facility for further treatment.
Over the next few years, this facility converts the partially processed poop into biosolids — human-derived compost.
From the toilets to the trees
Elegant poplar trees line the biosolids facility property, like tall sentinels, separating it from train tracks and an RV lot.
Each day, 200,000 gallons of nutrient-packed slurry flows into the plant. The sludge comes in runny, like a melted charcoal milkshake, but it ends up as moist and crumbly compost.
The first stage of treatment happens in lagoons. The six-acre lakes waft an anaerobic, creek-bottom smell into the air. Here, millions of gallons of slurry decompose for several years. Once the process is complete, a dredge crawls across the lagoon, sucking up the bottom layer.
The dredged goop is thickened with a polymer then squeezed-dry in a machine. The resulting biosolids are piled in long rows, waiting for the summer to be sun-dried.
Much of the biosolids will fertilizer fields of grass-seeds. And about a third of the material grows poplar trees, at the Biocycle Farm.
Biosolids: Trash or treasure?
Back when people dumped used car oil on the ground after an oil change, wastewater treatment plants dumped semi-treated poop anywhere convenient. Now, this sludgy material is regulated to prevent it from polluting. Still, many view it as a waste product.
Millions of tons of biosolids are dumped into landfills across the US, where they release methane, a potent greenhouse gas. Other places burn biosolids, which uses lots of fossil fuels to power the process.
Todd Miller and MWMC have a better idea.
“They’re really valuable nutrients [in biosolids] and we shouldn’t be throwing these things away,” he says. Miller is the Environmental Services Supervisor at the wastewater agency.
Poplars are unique and well-suited for a biosolids farm. “They absorb tremendous amounts of nutrients,” says Miller, “and they’ll take as much water as you throw at them.” These trees are irrigated with recycled water from the treatment plant.
This variety of poplar grows like a racehorse — up to 15 feet per year. Not strong enough for structural timber, it can replace other wood products, such as pulp, wood chips, plywood, or decorative boards like window frames.
Miller dreams of creating a local economy built around these trees. It's a work-in-progress, as he looks for stable relationships with local mills and woodworkers. For the next harvest, he’d like to partner with an affordable housing developer. Then, the wood could benefit housing needs of the community.
Heart of the community at City Hall
In the dappled light, under the canopy of poplars, you're surrounded by tiny bits of everyone in town. The nutrients that passed through each person are here, growing something new. A bit of magic. If someone sought the heart of the community, could this be it? A living, respiring reminder of how we are all connected.
Across town from the poplar farm, the finished product is on public display. The wood decorates the City Council Chambers at Springfield City Hall. Thin, horizontal boards cover the back wall. The wood is pale yellow, specked with rusty-colored knots. It shines a natural beauty among the room’s routine decor.
Here, the local government supports turning waste into something useful. This wood has come full circle.
Notes:
- Barry Mays and Cory Boswell. Crop Manual for Hybrid Poplar at the Metropolitan Wastewater Management Commission Biocycle Farm. Jan. 16, 2008.
- Website. About the Biocycle Poplar Farm
- T. Miller. Personal communication. May, 2024.