Microbes turn food waste into energy

When 115,000 tonnes of food waste hit Surrey’s processing facility in British Columbia each year, billions of microbes convert everything from banana peels to leftover pizza into renewable natural gas (RNG). Now, researchers at The University of British Columbia (UBC) have identified a previously unknown bacterium in the Natronincolaceae family that plays a crucial role in this process.

The discovery, published in Nature Microbiology, was led by Dr Ryan Ziels, an associate professor in UBC’s Department of Civil Engineering, who studies how to turn waste into useful resources using biological treatments.

“We were studying microbial energy production in the Surrey Biofuel Facility when we noticed something odd: the microbes that usually consume acetic acid had vanished, yet the methane kept flowing,” Ziels said. “Traditional methods couldn’t identify the organisms doing the heavy lifting.”

To solve the mystery, the team fed microbes nutrients containing a heavier form of carbon. Microbes use carbon to build new proteins — so by tracing the carbon in proteins, the researchers could tell who was doing the work.

“Converting waste to methane is a cooperative process involving multiple interacting microbes,” explained Dr Steven Hallam, a professor in UBC’s Department of Microbiology and Immunology and a co-author on the paper. “This newly identified bacterium is one of the key players making it happen.”

Protein-rich food waste naturally produces ammonia as it breaks down, but too much ammonia can halt methane production and cause acetic acid to build up, turning waste tanks acidic and unproductive. The newly discovered microbes, however, tolerate high ammonia levels that would shut down other methane producers, keeping the system running when it would normally fail.

“Municipal facilities owe a lot to these organisms,” Ziels said. “If acetic acid builds up, tanks have to be dumped and restarted — an expensive, messy process.”

The findings help explain why some digesters sputter while others, like Surrey’s, continue producing energy under challenging conditions. The discovery also suggests that high-ammonia environments may actually benefit these key microbes, offering insights for more efficient designs.

The molecular tagging approach could also detect other elusive microbes. Ziels and his colleagues are now using the same technique to study microbial communities breaking down microplastics in the ocean.

As cities worldwide wrestle with waste management and low-carbon energy transitions, the team believes some of nature’s smallest organisms may hold the keys to our biggest environmental challenges.

“Next time you toss your scraps in the compost bin, remember: you’re not just composting. You’re feeding microscopic powerhouses that help produce cleaner energy,” Ziels said.

The research was conducted in collaboration with FortisBC and Convertus. Researchers at the US Department of Energy’s Joint Genome Institute and Environmental Molecular Sciences Laboratory also contributed to the study.

“We’re delighted to help support British Columbia’s research ecosystem that has the potential for real-world impact. Advancements like this — that deepen our understanding of anaerobic digestion — may have the potential to enable facilities like Surrey Biofuels to produce more renewable natural gas from the same amount of organic waste,” said Jamie King, Director, Innovation and Measurement at FortisBC. “Collaborations between UBC, FortisBC and the Surrey Biofuel Facility continue to strengthen our ability to support lower carbon energy solutions.”

Felizia Crozier, Process Support Engineer at Convertus Group, said, “At our Surrey facility, we strive to maintain a stable microbial community in order to achieve the benefits of RNG as a clean biofuel. If stability is compromised, this has significant financial implications as production schedules must be adjusted and we would have to restart from scratch.”

Image caption: The Surrey Biofuel Facility. Image credit: FortisBC.