The double wonder of worms

Montreal, November 9, 2016 — In North America, a whopping 30 to 40 per cent of our residential waste is organic — biodegradable garbage that could be composted but often isn’t. 

With governments like Quebec’s looking to ban organic waste from landfills by 2020, we need to act fast to reduce the amount of food scraps we’re throwing out. 

A study recently published in Waste Management by researchers from Concordia’s Faculty of Arts and Science shows that one method of composting is potentially more efficient than others. The catch? There are worms involved. 

The study’s lead author, Louise Hénault-Ethier, carried out her research while pursuing a master’s from what is now Concordia’s Individualized program. She experimented with different methods of vermicomposting to see whether they could break down bacteria enough for public consumption. 

“Centralized composting, which is one of the fastest growing industrial composting methods, has strict governmental guidelines, requiring thermal sanitation to prevent the survival of harmful bacteria,” she says.

That process requires heating up the compost to 55 degrees Celsius over a period of three days. 

“But in our case, you can’t do that or you’ll kill all the worms! We wanted to see if it was possible to do vermicomposting without the heat while still getting rid of harmful bacteria.”

Hénault-Ethier worked with Concordia chemistry professor Yves Gélinas and biology professor Vincent Martin to examine the impact of vermicomposting on E. coli, a bacteria often found in fecal matter that can easily make its way into composted material. 

They devised three experiments to monitor the presence of E. coli, testing whether the size of the batch of compost, the amount of naturally occurring soil microbes and the rate at which the compost was fed would affect the survival of the pathogen. 

Time and again, the worms worked their magic and eventually produced compost that was bacteria free. It just took a little more time to get there.  

"We found that the compost batches take on average 18 to 21 days to fully degrade the E. coli to levels well below the legal limit,” explains Gélinas, who worked closely with Hénault-Ethier to examine how the chemicals present in the compost materials would affect the bacteria’s presence.

“While that's slower than traditional composting methods, it’s not a prohibitive amount of time."

‘Upcycling waste’

For Hénault-Ethier, who was recently named head of scientific projects for the David Suzuki Foundation, it’s the added benefits of vermicomposting that are most important.

"The soil it produces may lead to higher plant yields when used as a fertilizer, and — even more surprising — the red wigglers themselves could then be reused as feed for other animals on the food chain,” she says.

This is what's called “upcycling” — generating something more valuable than the initial waste product.

Although the idea of using invertebrates as animal feed may seem a little strange, it’s actually a proven method for potentially replacing the resource-intensive soybeans or fish meal traditionally used. 

"This study proves that upcycling technologies like vermicomposting can be more widely developed for commercial use,” says Hénault-Ethier. As a past environmental coordinator for Concordia, she spearheaded a large-scale worm-farming project in which 15 tons of the university’s waste were composted per year.

“By expanding the timeline from three days to a mere three weeks, we can potentially create a product that provides nutrient-rich feed to both plants and animals. It's a win-win situation."

The results show that vermicomposting is a promising method in the sanitation of organic waste, which would allow for producing proteins for animal feed.

That said, while the E. coli inactivation observed in the current study is promising, Hénault-Ethier cautions that further research on a more diverse array of pathogens is still required before vermicomposting can start on a massive scale.

Partners in research: This study was funded in part by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Fonds de recherche du Québec – Nature et technologies.