Whether baked or mashed, or turned into tater tots and French fries, Americans love potatoes.
But few know, perhaps outside of Idaho farmers, that to clean, peel and slice them before reaching market requires millions of gallons of water. That water must in turn be treated and disposed of as wastewater because it contains organic matter, silt and sand.
While traditionally thought of as an ecological problem, it appears wastewater may now have an unexpected environmental benefit.
Researchers from Idaho National Laboratory believe they’ve uncovered a way to use potato wastewater as a means to capture a special bacterium that could be used to recycle high-tech devices, industrial catalysts and other sources of rare earth elements.
As reported on the website of the Idaho National Laboratory:
An INL research team has developed an environmentally friendly way to recycle rare earth elements using a bacterium called Gluconobacter oxydans. When provided with nutrients, Gluconobacter produces organic acids that dissolve the metallic elements from the surrounding material and pull them into solution—a process called “bioleaching.”
Previously, INL researchers Vicki Thompson and David Reed conducted an economic analysis of their bioleaching process and found that the glucose used to feed the microbes was the biggest expense, accounting for 44% of the total cost.
In their most recent study, Thompson, Reed and INL senior scientist Yoshiko Fujita compared the performance and cost of glucose to alternative nutrient sources, namely potato wastewater and corn stover—the leaves, stems and cobs left over after corn is harvested.
Reed and his colleagues fed the bacteria the three different nutrient sources and measured how well the resulting mixture recovered rare earth elements from fluid catalytic cracking catalyst—a substance used by petroleum refineries. Potato waste performed almost as well as glucose, while corn stover was slightly less effective.
The researchers then looked at the costs of building and operating an industrial-scale rare earth element recycling process using each nutrient source. They found that using corn was more cost-effective than potatoes, but not by much. In the end, both corn stover and potato wastewater are cheap nutrient sources for the bacterium to grow on, with the added benefit of reducing waste.
To read the full story on the Idaho National Laboratory website, click here.