Smoldering-hot idea nabs 3MT top prize

Civil and Environmental Engineering PhD candidate Taryn Fournie is researching the ability to extract metals and nutrients from sewage sludge, which can then be repurposed for agriculture or new products.

We are flushing away a chance at a more sustainable future – but Taryn Fournie has a plan.

The Civil and Environmental Engineering PhD Candidate has proposed a process whereby valuable metals like cobalt and zinc and nutrients like phosphorus are recovered from sewage sludge created by wastewater treatment plants from human waste.

“I know what you’re thinking, it sounds pretty gross that I’m trying to extract nutrients from your poop,” said Fournie.

Her recovery process uses a flameless form of burning called smoldering to treat the sludge. (Think what you’d see in the bottom of a fire pit when all the flames have died off.) It could be a cheaper, more energy-efficient and sustainable alternative to current processes.

The idea earned Fournie the top spot at Western’s Three-Minute Competition last month.

She will represent the university at the 3MT Ontario 2020 provincial competition at the University of Windsor. Scheduled for this week, the event is on hold as a result of the COVID-19.

Currently, sewage sludge is reduced via an incineration method before being shipped to the landfill. The energy-intensive process involves drying to reduce volume as sludge is about 75 per cent moisture.

She estimated 95 per cent of London’s sludge is sent to the landfill.

“We are running out of room,” she said.

Fournie’s idea involves using lower smoldering temperatures (500-600 degrees F versus up to 1,000 degrees F with incineration). Elements and metals are not lost through emissions in her process, with almost full retentions of the metals present among the ash.

“The ash that remains is less than 5 per cent of the initial mass of the sewage sludge, which makes it much easier to recover the metals and nutrients,” she said, adding her research is now determining what benefits can be extracted from the ash, including uses in agriculture or new products.

“If we find ash has lower availability of metals, it may be beneficial to be used where there are a lot of farming communities,” said Fournie, adding smoldering is also a potential option for developing countries.

She also sees a more sustainable future around her idea, saving pressure on the planet by further mining and extraction.

“Looking at phosphorus alone, we currently get most of our elemental phosphorus as mined phosphate rock,” she said. “At the current rate we are mining phosphate, reserves are expected to be depleted in the next few decades. The same is true for several other elements, as well. So how will we obtain these materials once reserves are depleted?”

While perhaps odd for a researcher to say, Fournie is enjoying the idea of not knowing what many come from her work and where it may lead her – which is the exciting part.

“There are so many different and changing aspects to it all the time. That is really exciting,” Fournie said. “I don’t feel that I’m just doing the same thing every day and challenges are intriguing for me.

“There is always something to be done because there are always new contaminants that can create issues. Can we change the process the treat the contaminants? How does it work and thermally breakdown? Taking that understanding and adapting the smoldering process to treat it, that’s pretty cool.”