A new filtration system turning manure into drinking water may soon help to improve farming operations across the drought-prone Western United States.
Developed by researchers at the University of Michigan, the McLanahan Nutrient Separation System works with an aerobic digester, which extracts energy and chemicals from the raw manure. The combined system then produces potable water through processes of ultrafiltration, air stripping, and reverse osmosis.
The water is clean enough for cattle to drink, the researchers say.
“Here in Michigan we have a tendency to take water for granted,” lead developer Steve Safferman said in a press statement. “But out West, for example, where drought remains an issue, the accessibility of clean water could make the difference between a farm remaining viable or going out of business.”
The system presently converts manure to water at a two-to-one ratio, with 50 gallons of water produced for every 100 gallons of manure. However, the researchers plan to increase that ratio to 65 gallons of potable water. The typical farming operation using the system would save millions of gallons of water per year.
“If you have 1,000 cows on your operation, they produce about 10 million gallons of manure a year,” Safferman said. “About 90 percent of manure is water but it contains other nutrients, carbons, and pathogens that can have an environmental impact if not properly managed.”
Thus, the water filtration technology provides the ancillary environmental benefit of trapping ammonia “that would otherwise be lost in the atmosphere,” he added.
Jim Wallace, a researcher who earned his doctorate under Safferman, says the process “goes beyond a typical digester." “For example, we’re able to capture a large percentage of the ammonia that would otherwise be lost,” he said in the statement. “Ammonia is a negative from an air quality standpoint.”
After a decade of development, the system will likely be ready for commercial sale by the end of the year.
Yet some municipalities in the dry West have already implemented similar water filtration systems, though without the new ammonia-trapping feature designed by the Michigan team. In California’s Orange County, sewage water is already recycled into clean drinking water using microfiltration and reverse osmosis, in addition to processes exposing the water to ultraviolet light and hydrogen peroxide.
However, don’t expect residents to drink water from sewage, whether produced by humans or industrial farming. Treated water in Orange County is recycled back into the aquifer, where it's filtered naturally through rock and gravel before coming to tap.