Harnessing the Power of a Humble Plant

• 

  Duckweed, the world’s smallest flowering plant, makes its home in still or slow-moving water, from the brackish to the fresh. You’ve probably seen it. It is found worldwide, from Siberia to the tropics, and looks like a green carpet resting on the surface of a body of water.

• 

  Duckweed thrives on and renders harmless the same nitrogen and phosphate pollutants—the nasty stuff found in fertilizer run-off and detergents—that treatment plants remove from water. Here, Eric Lam visits a wastewater treatment plant in China where duckweed occurs naturally. One day, such duckweed could be harvested for biofuel and other "green" products. Photo: Courtesy Eric Lam

• 

  Duckweed—so named because (surprise!) ducks love to eat it—grows on ponds like this one at Pinelands Nursery in Columbus, New Jersey, where a Rutgers pilot project aims to demonstrate the wastewater-treatment-to-fuel process. Here the pond is shown in early spring, before the duckweed has begun to bloom.

• 

  With its high starch content, duckweed is harvested and processed to produce ethanol. The plant, high in protein and dietary minerals, is also a feed supplement for chicken, livestock, and farmed fish. In spring 2011, student researchers (l. to r. Ryan Integlia, Jessica Kretch, and Philomena Chu) build a duckweed retaining system from swimming pool noodles. Photo: Courtesy Eric Lam

• 

  While Ryan Integlia and Philomena Chu watch, Jessica Kretch, an undergraduate civil engineering major, uses a canoe to position the retaining system. Unlike algae, with which it is often confused, duckweed multiplies rapidly—it can double in biomass in less than 48 hours—and is easily harvested. Photo: Courtesy Eric Lam

• 

  By June 2011, indigenous duckweed completely covers the pond. Checking on developments is plant biology graduate student and NSF IGERT fellow Philomena Chu, who is comanaging the project. Students are key researchers on the project, which will measure water quality before and after duckweed has been grown on wastewater samples. Photo: Ryan Integlia

• 

  Left to right, students Deepak Khanna, Thomas Maloney, Ryan Integlia, and Jessica Kretch deploy the experimental harvester to skim the duckweed off the surface of the pond and collect it in fabric tubes. The harvest is taken to the nearby Rutgers EcoComplex where samples are preserved at -20˚ Celsius, awaiting arrival of bioethanol production equipment.

• 

  Duckweed grows in a thin layer on the pond’s surface and is easy to collect into the fabric tubes.

• 

  Retrieving samples from the harvester are Eric Lam, right, and Ryan Integlia, who earned his doctorate in electrical and computer engineering from Rutgers in May 2011 and comanaged the pilot project during part of the summer. Photo: Deepak Khanna

• 

  Back at Lam’s lab in Foran Hall on the G.H. Cook Campus, School of Environmental and Biological Sciences undergraduate David Byrnes prepares to remove harvested duckweed from the harvesting sock. At the lab, researchers are developing basic post-harvest procedures for duckweed fermentation. Photo: Courtesy Eric Lam

• 

  In coming months, researchers will place duckweed samples in a fermentation/distillation tank, left, to produce ethanol. Yeast is introduced and reacts with duckweed starch, converting it to sugar, and breaking down the sugar into alcohol. They will use a microsized fuel pump, right, to purify, store, and dispense fuel-grade ethanol.

• 

  Nikolai Borisjuk, a visiting scholar who manages the Rutgers Duckweed Stock Cooperative, is setting up duckweed fermentation protocols at Foran Hall. In a later phase of the project, researchers will gather at the EcoComplex to fuel an "E85 flex-fuel" vehicle—which can run on high-ethanol fuel—with their duckweed-ethanol/gasoline blend.