Duckweed "Quacks" Volumes of Potential

From Ethanol Magazine
By Bryan Sims

The drive to develop sustainable nonfood, starch-based ethanol feedstocks and more efficient conversion processes is intensifying as the U.S. attempts to reduce ethanol's carbon footprint by transitioning from corn to cellulosic ethanol. That has prompted researchers at North Carolina State University to take a closer look at plants, such as duckwee, that could be a potential feedstock for ethanol production.
Duckweed has traditionally been studied becuase of its inherently rich protein content at 30% to 35% on a dry-weight basis. the purpose was to explore whether duckweed could be a protein source for animal and human food. A growing interest in sustainable ethanol feedstock development, however, has researchers exploring the plant's starch content.
NCSU researchers Anne-Marie Stomp, associate professor of forestry, Jay Cheng, professor of biological and agricultural engineering, and Mike Yablonski, post-doctoral research associate, are discovering that duckweed can be used to clean up animal waste at industrial hog farms and could be used to make ethanol. They have determined that duckweed grown on swine wastewater can produce fice to six times more starch per acre than corn, according to Stomp, who co-authored the research with Cheng.
The research, funded by the Biofuels Center of North Carolina, was presented at the annual conference of the Institute of Biological Engineering in March in Santa Clara, California.
"The original investigations focused pretty much entirely on the protein side," Stomp says. "At the time all of that work was being done, there was no compelling economic reason to domesticate this plant because we had plenty of other plant protein sources in grains and legumes. Back then, the prices of those grains and legumes were low and the market was fully supplied."
The one challenge that has impeded duckweed's progress in becoming a sustainable, dedicated energy crop for biofuels production or being used as a bioremediator for farm or city wastewater treatement operations is the fact that it wasn't domesticated. "The trick to domesticating duckweed is going to be how much it will cost per ton to grow this stuff," Stomp says, adding that data on ecnomic feasibility will be released later this year. "That number provides a threshold for commercial viability," she adds.
Cheng and Stomp are currently developing a pilot-scale project to further investigate the best way to establish a large-scale system for growing duckweed in animal wastewater, and then harvesting and drying the plant. "We're actually exploiting a lot of existing technology used in the food industry, because duckweed is like a slurry," Stomp says. You can pump it, sieve it and do other things."
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