Sometimes an interesting observation can lead to a valuable scientific avenue. For researchers in BiOrbic Bioeconomy SFI Research Centre at NUI Galway, it has led them to mine valuable fatty acids from food waste.

In a previous project, the researchers had been looking at how to use anaerobic digestion (a process that uses microbes to digest organic material) to break down food waste into short chain organic acids that can be used to produce biogas. But something else was being produced along with the short chain organic acid in the anaerobic digester too, explains Dr Corine Nzeteu, a post-doctoral researcher at NUI Galway Department of Microbiology.

“In that project, we were looking at sustainable ways to divert food waste from landfill and instead use it for fuel. We were experimenting with food waste in the anaerobic digester, and we could see that a medium-chain fatty acid called caproic acid was accumulating in the digester.”
Dr Corine Nzeteu

This observation led to Dr Nzeteu and colleagues looking more closely at caproic acid, and how it might be produced from waste. “Caproic acid has very wide industrial application, such as natural antimicrobial in animal feeds and as a precursor chemical for biofuels and biodegradable plastic,” she explains. “At the moment it is mainly produced through chemical synthesis using fossil fuel, or it may be extracted from palm or coconut oils but the yield from those oils is very low.” 

To look for a more sustainable source of caproic acid, Dr Nzeteu Is looking to create the right environment in the anaerobic digester to create the chains of fatty acids from food waste. “We are trying to make caproic acid the primary output from anaerobic digestion of food waste or grass,” she says. “We are now optimising that process to manipulate the chemistry in the digester, so that caproic acid is made in larger quantities.”

The researchers are now talking to industry and collaborating with colleagues at Queen’s University Belfast to bring the findings to the next steps. That includes extracting the fatty acids from the digester mix, developing a pilot-scale process and integrating into industrial processes. 

Ultimately, Dr Nzeteu hopes the approach will offer a more sustainable approach to sourcing caproic acid, adding value and new uses to grass and waste food.