Sweet success found using molasses to clean up toxic landfills

A sugary ingredient for cookies and breakfast dishes is now being used to clean up some of the country’s most difficult, toxic chemical contaminations. At the former Gloucester Landfill in Ontario, federal government staff have been injecting sticky, sweet molasses into contaminated aquifers to remediate the site — and sweetest of all, it seems to be working. 

The site east of Ottawa is a tough one. One environmental manager for Public Services and Procurement Canada, Darragh Kilroy, called the Gloucester Landfill “the most complex site that we have.” For more than a decade, the landfill was the final destination for bottles filled with dangerous chemicals from federal government laboratories in Ottawa — which would be buried in trenches and blown up with explosives. Cleaning the site has been a decades-long task since its closure. Back in 1988, researchers from the National Water Research Institute published a study showing groundwater beneath the Gloucester Landfill was being contaminated as the chemicals seeped out.

The government has tried all the usual strategies to clean the landfill. In the 80s, contaminated soil and waste was hauled to facilities specializing in hazardous waste. In the 90s, they began treatment by pumping contaminated water from a number of deep wells to a treatment facility, then re-injecting the treated water below ground. 

The techniques available to clean and monitor the extent of the contamination have developed since then. So, recently, Public Services and Procurement Canada, on behalf of Transport Canada, decided to take a different approach: it hired a company to try out the molasses cleanup technique at the tricky site, a representative of the agency explained. Molasses seemed promising since projects from Hawai’i (treating explosives-contaminated soil) to South Korea (remediating contaminated harbour sediments) were already showing potential. A successful trial run of the molasses for cleanup in 2013 in Gloucester, Ont., has since led to full-scale molasses injections to the exact location of the contamination several times a year starting in 2019. 

"A lot of people expect that to decontaminate a site, you need to use a chemical to destroy the contamination. So when they find out that nature has a solution for that, they're surprised," said Jean-François Dion, a senior environmental specialist involved in the project, in a press release by the government. Public Services and Procurement Canada declined to make any researchers available for an interview, but Transport Canada responded to questions in an emailed statement.

These kinds of “bioremediation” projects use naturally-occurring processes to clean up environmental pollution. While some strategies may sound unconventional, they’re not entirely new: nitrogen-rich fertilizers were used extensively to speed up the rates of oil biodegradation after the Exxon Valdez spill in Alaska in 1989, and more recently, sunflowers have been found to remove heavy metals from soil, making once-contaminated land farmable again.

“Bioremediation is a recognized and effective remediation method under the right conditions,” a Transport Canada representative told the National Observer in an email, adding the Gloucester Landfill is currently the only Transport Canada site using this specific approach, after identifying it as a more effective option for meeting site goals. 

Molasses works to clean contamination because it’s so high in carbohydrates. It introduces excess organic carbon for microbes to eat, and helps them grow when injected into the aquifers where they can break down the chemicals. A stabilizer is added to prevent contaminants from moving into new areas, and sensors guide the team to the right places as they drill down into the earth. Molasses isn’t the only food-related tool that can work; in 2022, lactate — a milk by-product — replaced molasses to improve effectiveness in harder-to-reach areas

Just how well molasses actually works, though, is being studied by other scientists around the world, including in Brazil and the United States, given there is no shortage of contaminated lands on which to experiment, and molasses is a relatively cheap source of carbon, compared to other substances. In Yukon, a PhD project tested out molasses for mine remediation in 2018. In Hawaii, where researcher Roger Babcock and his team have found success using molasses to soils contaminated with explosives on a military base, the contaminants have gotten so deep and into such hard-to-reach places that this might be one of the only ways to fix it.

“For that particular problem, there aren't necessarily other solutions [or] ways to attack the problem,” Babcock said. “It’s kind of what you might call an in-situ method, which means you do the remediation in the ground without taking the water out, as opposed to a pump-and-treat, where you pull the water out, treat it, and then possibly put it back as clean. It is desirable, if you can clean it up in place without doing all the pumping.”

In Canada, there are thousands of known chemical contaminations listed on a public Federal Contaminated Sites Inventory, which various agencies have been struggling to remediate. Hungry, tiny microbes who could do the job for them with the help of a bit of breakfast syrup is an attractive proposition.

“The search for natural or biological methods always has a lot of interest,” Babcock said. “Bacteria work for free. Just give them some food, and they'll do the work.”