Lemna's African Adventures

Chase’s reply: “Why would you travel to a Third World country like that?”

“That guy had a tremendous sense of humor,” Ngo recalls, laughing. “I guess I learned a little bit from him.”

Ngo came to the U of M in 1970 with plans to become a sculptor and painter. “I had to go to engineering school—otherwise, the [Vietnamese] government wouldn’t send me out,” Ngo recalls. “They wouldn’t send somebody out to do studio art.” Still, Ngo found a way to study both at the U.

During the mid-’70s, waste management and pollution were hot topics among Ngo’s classmates in the water resources engineering classes at the university. He and other grad students began looking at ways to use aquatic plants to “naturally” filter out harmful chemicals and organic particles out of water, making it drinkable or reusable.

Ngo, University of Wisconsin adjunct microbiology professor Dr. Warren Poole, and microbiology student Del Hogan invented a wastewater treatment process that uses duckweed, tiny green plants (the Latin name is lemnacae) found floating in freshwater lakes and reservoirs around the world. Duckweed naturally absorbs ammonia; it’s also a high-protein food for waterfowl and other animals. It can be harvested and pelletized for feed, or composted for farmland.

“You grow duckweed on the wastewater, and then you feed the duckweed to animals,” says Poldi Gerard, Lemna’s vice president (she’s also Ngo’s wife). “It’s as high in protein as soybeans,” and could be used to feed livestock.

Ngo and Hogan patented their water cleansing idea and started a company in 1983. They called it Lemna, after the Latin genus name for one of the most common types of duckweed.

In the ’80s, the United Nations Food and Agriculture Organization commissioned Lemna to do a study about a combination of waste treatment and biomass production for animal feed. The UN wanted to find out whether Lemna’s duckweed-based water treatment system could work in developing countries. “We demonstrated that it was technically viable for this technology application in Africa,” Ngo recalls. “But unfortunately, we could not find funding for this technology application in Africa.”

After building several water treatment systems across the United States, Gerard says, “we could never get an economically viable amount of duckweed in one place.” Duckweed could be harvested from holding ponds, but transporting it to the rest of the world would prove too expensive. “In most places now, it’s composted,” Gerard laments. “It does have an ultimate reuse, but it’s not saving the planet.”

Lemna’s best-known project that incorporates duckweed is a water treatment facility it completed near Devil’s Lake, North Dakota, in 1990. The project can be described as both a cost-effective way to clean water and a large-scale environmental artwork. A series of holding ponds and serpentine channels spread over 50 acres looks something like a huge hieroglyph; the design is best viewed from the sky. The project’s design won international recognition and awards, and it brought Lemna some fame in engineering circles for a time.

But like its namesake plant, Lemna is low profile. Even so, it’s getting to be just as widespread worldwide.