Estimated read time: 3 minutes
The smooth concrete floor of Remy Wines in Dayton, Oregon, has a special ingredient, one that helped make its construction carbon-neutral — processed poop.
This product started out as biosolids from a wastewater treatment plant. But instead of being used as fertilizer or dumped into a landfill — the fate of most biosolids — it was transformed by microbes and scorching heat into a type of biochar. This process zapped pollutants in the sludge and bound up carbon, a benefit for the climate. The end result, it turns out, is a unique and useful product.
When John Mead was hired to design an eco-friendly concrete floor for Remy Wines' new 5,000-square-foot warehouse, he turned to this carbon-negative product — called OurCarbon. He was looking for a secure way to offset the carbon emissions from the rest of the construction. Mead knew carbon offsets from places like tree plantings are at risk of burning up in a forest fire. But when they’re embedded in concrete, “the carbon is not going anywhere,” says Mead.
OurCarbon is a stable product that will not break down to release greenhouse gases. Eco-conscious contractors like Mead can add it into the cement mix as a carbon ‘inset.’
The reinvention of waste
Even though biosolids are full of nutrients, they are often viewed as waste products. They can contain undesirable chemicals and heavy metals. In 2022, the state of Maine banned their use as fertilizer. Sometimes it’s too costly to transport them to farms. Landfilling is not a good option either, because it wastes nutrients and creates methane, a potent greenhouse gas. That’s why the company Bioforcetech created a way to reduce the weight and volume of biosolids to one-tenth the original amount, while using no extra power.
Their system dries out wet biosolids with heat from bacteria, instead of natural gas. Then, the dried slurry goes through a process called pyrolysis. This happens in an ultra hot chamber — temperatures of around 1200 degrees F (700 degrees C) — without oxygen. The system creates few emissions, and in the end, any pharmaceuticals, microplastics and ‘forever chemicals’ called PFAS are obliterated, and heavy metals are bound up in the product.
The material that comes out the other end of the system looks like what you might find on a black-sand beach. “It’s not really a biosolid,” says Garrett Benisch, the Director of Design Development at Bioforcetech. It’s not a classic biochar either – it has more ash and less carbon than wood-based biochars, he says. This new product can be used to store carbon, and qualifies for carbon offsets in buildings, like at Remy Wines.
“When we divert from the landfill we have a monstrous change in avoided emissions from methane,” says Benisch. It’s like taking up to seven cars off the road for a year per ton of OurCarbon.
From concrete to fashion
It turns out the jet-black OurCarbon can also be used to replace black ink. The black ink color used in everything from t-shirts to key boards is called carbon black, and it comes from fossil fuels. The production of standard black ink color produces tons of CO₂, Benisch points out. OurCarbon makes black ink that’s just as good. So far, it’s been used to color shirts, furniture, digital print ink, and foam in shoes.
Back at Remy Wines, Mead used OurCarbon to replace some of the sand in the cement mix. He’s happy with the results, yet this won’t be a solution to offset carbon emissions from the cement industry as a whole. There will never be enough of the product, he says, even if all the biosolids in the country were converted. For now, Mead believes it’s good to use this product, because it brings attention to the need to decarbonize cement and find secure sources of carbon offsets.
Interest in these systems is spreading. So far, Bioforcetech has installed 18 systems to dry biosolids with bacteria and three are producing OurCarbon, with more on the way.
And the win for Benisch is happening: “I’m most interested in changing business as usual,” he says, “as well as fixing this carbon and using it.”
Laura Allen is a writer and educator based in Oregon. She co-founded Greywater Action, where she teaches people how to transform their homes to reuse water. She authored the books, The Water Wise Home: How to Conserve, Capture and Reuse Water in Your Home and Landscape, and Greywater, Green Landscape. Her article, For a better brick, just add poop, won the Gold Award in Children’s Science News from the AAAS Kavli Science Journalism Awards (2023). Her favorite pastimes include gardening, hiking, reading and visiting eco-toilets.
