Several by-products derived from wastewater have long been turned into many useful commodities such as fertilizers. Researchers and engineers are starting to discover more ways to effectively transform wastewater into more lucrative resources. One important study is focused on turning fatty wastes including oil and grease into a reliable supply of renewable energy.
Environmental engineer Bappi Chowdhury and his colleagues from the University of Alberta discovered that using conductive materials on wastewater creates an improved feedstock which increases biomethane production by up to 70 percent. This is achieved from a mixture of fat, oil and grease and ordinary food waste in an anaerobic digester.
Fatty wastes are very difficult to break down. They clog sewer systems and can form barriers that reduce microbial digestion. These fats contain long carbon chains that naturally degrade into methane, a gas that is about 30 times more potent than carbon dioxide as a heat-trapping gas. Chowdhury is hoping that his fat processing method could recapture that biomethane for more productive uses.
Their findings could help municipalities who are struggling with clogged sewer lines, industrial agricultural facilities dealing with animal waste or governments hoping to reduce climate impacts.
“It could solve a lot of problems. It’s sustainable, renewable energy, because as long as there are people, there will be food waste,” says Chowdhury.
Although conductive materials like activated carbon have long been used in wastewater treatment, it has only been in the past decade that it has been utilised for stimulating biomethane production.
Granular activated carbon is usually applied to wastewater to remove the smell and taste of the treated water, but it has also proven to be the most effective conductive material for Chowdhury’s study.
Bipro Dhar, an assistant professor of environmental engineering from the same university, believes that activated carbon can also function as a hub for microbes to further enhance their biochemical processes.
“It can change how microbes interact,” said Dhar, who supervised Chowdhury’s research. “It can significantly enhance how fast we can degrade those organics and produce biomethane.”
They looked into adding more food waste to improve yields. The ideal proportion they found was for 70 percent food waste, which they sourced from the HUB Mall on campus, and 30 percent fat, oil and grease from GHD Canada, an Ontario-based industry partner. When the granular activated carbon was added, they reduced the time of decomposition from 20 to 25 days to just seven.
Another benefit for using granular activated carbon is that the microbes that naturally break down lipids and fats grow right on the conductive materials. This produces a wider range of organisms in the digester, which makes decomposition more efficient than it would be on its own.
“There was more enrichment of micro-organisms,” Chowdhury said. “There are so many microbes attached to the surface, it creates more balance.”
The implications of this study on fatty wastes are huge. A large city like Edmonton may turn to agricultural waste or restaurant waste to improve its organic waste treatment. Farms could switch from disposing of wastes and opt to generate power and heat on site. Developing countries could generate more electricity from waste.
Since anaerobic digesters can work at a variety of scales without a significant retrofit, it’s a solution that could potentially be implemented globally.
If you are a municipality in Ontario and in need of a biosolids management solution, please feel free to contact us at 1 (877) 479-1388.