Adding a buzz of electricity to fermenting food waste can accelerate the breakdown of organic matter and generate greater quantities of useful byproducts that are highly-prized by industry.
This turbocharged fermentation process, described in a recent study, could reduce the amount that gets loaded onto landfills each year, instead transforming more of this waste into genuinely useful products.
The new study builds on previous work by the research team to analyze the value of food waste, and how it could be mined for multiple different uses ranging from biodiesel production to making car tyres. That previous work also looked at how food waste could be mined for something called ‘platform chemicals’, which are the focus of this new research.
These chemicals include ingredients like ethanol and acetone that are used as critical building blocks to make a variety of products, in industries ranging from pharmaceuticals to agriculture and packaging.
Writing in the Journal of Environmental Chemical Engineering, the researchers introduce the key players that convert food waste into these useful platform chemicals as byproducts: microbes. Specifically, they selected two species of Clostridium bacteria for study: C. bijerinckii, and C. carboxidivorans. They supplied these bacteria with a diet of sour cream and ice cream waste because they are rich in organic matter for the bacteria, and then tested their behavior under different experimental conditions.
In one set of experiments, the researchers tested the bacteria in a conventional fermentation container, where they were incubated with the food waste at high temperatures. In another, they tested the microbes at room temperature in an electrofermentation unit fitted with a conductor that transmits an electrical current through to zap the bacteria-infused food waste slurry.
The researchers also looked at how well the bacteria did at producing platform chemicals alone, compared to when the two were paired up.
Their experiments revealed that when the two bacteria species worked together, they produced much higher yields of platform chemicals from the food waste, compared to when they worked alone. The researchers think this is due to a useful synergy between the two species that they chose. The one bacteria species is known for dissembling food waste partly into carbon dioxide, which the other then uses as food, assimilating this building block to make a range of byproducts in turn.
The higher yields were especially notable in the electrofermentation tanks, where working together the two bacteria species produced greater yields than they could alone, of acetone, ethanol, and butanol—products that are crucial for making everything from cleaning products to cosmetics and paints.
The benefit of the electricity is that it seems to supercharge the process, increasing the bacterias’ metabolism, and so increasing the rate at which they break up food waste and generate byproducts.
The study also found that voltage matters, showing, surprisingly, that a slightly lower voltage prompted larger yields from the bacteria, compared to a higher voltage. Interestingly, they say, this suggests electrofermentation provides opportunities to fine-tune the production of platform chemicals, via different voltages and a combination of bacterial strains.
Platform chemicals are big business, and since chemicals including acetone, butanol and ethanol are often sourced from oil and gas, making them from food waste provides a creative way to reduce their impact and that of their associated industries.
Meanwhile, repurposing food waste into something innately valuable reduces its own strain on the environment, especially considering the huge 11% of global greenhouse gas emissions that food waste annually generates.
“We’re making use of waste that a contractor charges businesses to take to a landfill, where it produces methane gas,” says the study’s lead author Saba Beenish, a research scientist in food, agricultural and biological engineering at Ohio State University. “We are creating an industry from another industry’s waste.”
Next, the team says they will be turning their attention to another mountainous source of food waste: coffee grounds.
Saba et. al. “Biomanufacturing of early platform chemicals from industrial processing food waste using mono- and co-culture electrofermentation.” Journal of Environmental Chemical Engineering. 2025.
Image: © Anthropocene Magazine
