It’s a view again not shared by Licciardello, however, who claims that his own start-up’s natural gas production from duckweed can already easily compete with natural gas garnered via fracking.
Once up to speed, Biomass Alternative Power will process about a million sq. ft. of duckweed per day says Licciardello. But he remains undecided about whether his greenhouse lagoons will be filled with wastewater or whether the company will fertilize their ponds with phosphorous, nitrogen and potash.
However, revenue streams from processing wastewater treatment for counties and municipalities could arguably aid fledgling duckweed bioenergy start-ups’ bottom lines.
Duckweed in Argentina
There may even be room for more socially-conscious entities, such as Argentina’s Mamagrande, a Buenos Aires-based biotech concern that has a stated goal of “regenerating ecosystems” by using duckweed to cleanup wastewater. It may also eventually ferment the duckweed’s starch into lactic acid to manufacture biodegradable plastic and/or bioethanol.
Funded with only several hundred thousand dollars, Mamagrande currently is working with a 4 hectare (9.88 acre) pilot plant in the small Argentinean town of Totoras.
Eduardo Mercovich, one of Mamagrande’s co-founders, says the initial cost of the duckweed needed to get such projects going is almost negligible. That’s in part because, as he notes, usually within a month’s time, the plant can grow to cover a hectare (2.47 acres) of a lagoon’s surface area.
“In our pilot plant,” said Mercovich, “we should have ten fresh wet tons of duckweed per day; or about a quarter ton of starch per day; half of which would produce 100 liters of ethanol daily.”
Mercovich says that once Mamagrande’s duckweed process is proven in Argentina, its technology will be made publicly available. He notes that in both Brazil and Argentina, ethanol is currently made from either corn or sugar cane. But unlike cane or corn, as Mercovich points out, duckweed needs less energy to process.
Bioengineering Starch for Ethanol
If future duckweed bioenergy entrepreneurs can find some sort of revenue-generating synchronicity with global municipalities interested in cleaning up wastewater — either to be reused as graywater for agricultural irrigation or for drinking water — then duckweed may find a viable bioenergy conversion niche. And as Stomp points out, it also compares favorably with corn, as it is likely easier to isolate starch from duckweed.
After over 15 years of duckweed research in the laboratory, Stomp explains that she and Cheng proved that once loaded into a fermentation vessel, more than 95 percent of its starch could be converted into ethanol.
“By growing duckweed on wastewater from hog production,” said Stomp, “we harvested duckweed biomass at the rate of 20 grams of dry weight per sq. meter a day, which is equivalent to 54,000 kg of dry weight on 2.5 acres a year.”
Stomp notes that if this 54,000 kg of dry weight duckweed were only 50 percent starch then it would yield something like 27,000 kg of starch for every 2.5 acres, or roughly four times the starch that could be expected from 2.5 acres of corn.
Stomp, however, says that by using enzymatic degradation of corn stover, the traditionally unused portion of a corn plant for ethanol conversion itself, then that “drastically” increases dry weight biomass that can harvested from an acre of corn.
But with bioengineering, duckweed would likely still have an edge on corn.
“You could probably trick this plant into accumulating starch to as much as 75 percent; [roughly] the same starch percentage as corn,” said Stomp.
Lead image: Duckweed via Shutterstock