The tiniest flowering plant could prove well-suited to two very big jobs: cleaning industrial animal pollution and providing clean biofuel.
Able to thrive on nutrients in animal waste, duckweed produces far more starch per acre than corn, say researchers. It could be an alternative to corn-based ethanol biofuel, which is disfavored by environmentalists because of waste generated in farming it.
“Based on our laboratory studies, we can produce five to six times more starch per unit of footage,” said Jay Cheng, a biological engineer at North Carolina State University.
More than a decade ago, Cheng and fellow NC State forestry professor Anne-Marie Stomp wondered whether fast-growing duckweed, commonly seen in shallow ponds, might remediate animal waste. Excrement from the billions of animals raised every year in America’s factory farms has fouled watersheds, especially in the South, and fed oxygen-gobbling algae blooms responsible for rapidly-spreading coastal dead zones.
Duckweed, they discovered, has an appetite for animal waste, quickly converting it to leafy starch that can then be converted into ethanol. The current source for most U.S. ethanol is industrial-scale corn farming, which requires large amounts of toxic pesticides and dead zone-feeding, fuel-intensive fertilizers. When the costs are added up, corn-based ethanol may prove little cleaner than gasoline.
Duckweed could help solve both problems at once.
“We did small-scale tests in the laboratory to convert duckweed starch to ethanol using the same technologies as the fuel industry currently uses in corn,” said Cheng. “With the same technology, we can easily convert it.”
Duckweed consumes nitrogen, phosphorous, calcium and iron, making it a potential source of remediation not only for the lagoons in which farm waste accumulates, but any type of wastewater.
Because duckweed is found in all but the coldest climates, there’s little chance of it causing problems as an invasive species, said Cheng. The researchers have moved from the laboratory to a pilot-scale operation on a commercial farm.
“Now that the concept is proven, we’re trying to scale up, testing harvesting systems and doing some economic analyses,” said Cheng. “The production rate is higher than corn starch, but to do it commercially, the economics will determine if it’s feasible.”