Duckweed: Environmental Star

Duckweed, the world’s smallest flowering plant, may blossom into the next big thing for earth’s environment. Working to make that happen are plant biologist Eric Lam, an expert on the small but plentiful pond denizen, and his Rutgers team.

A Green Fuel Solution?

Eric Lam first came across duckweed as a graduate student at the University of California–Berkeley in the 1980s. Using this simple plant, he studied how chloroplasts capture light energy.

Lam, a professor of plant biology in the Department of Plant Biology and Pathology in the School of Environmental and Biological Sciences, joined the Rutgers faculty in 1989. In the following decades he advanced the study of chromatin and programmed cell death in plants, knowledge that could help develop crops that better survive diseases and environmental stressors. For his work, he received the prestigious 2011 Alexander von Humboldt Research Award in the category of molecular biology.

In the midst of this research, three years ago, a great conversation brought his attention back to tiny duckweed.

“Todd Michael [then an assistant professor at Rutgers’ Waksman Institute of Microbiology and working on a team to sequence the duckweed genome] discussed with me duckweed’s potential as an attractive biofuel crop,” recalls Lam.

The diminutive plant, which grows quickly on the surfaces of ponds from Siberia to the tropics, helps purify wastewater because it thrives on nitrogen and phosphates, pollutants found in such common products as fertilizers and detergents. It also has a high starch content, a key attribute for a potential biofuel.

“The prospect of coupling wastewater remediation with biomass production made so much sense that I picked up this research again after 30 years,” Lam says.

What’s So Great about Duckweed

What has Eric Lam and other Rutgers researchers so excited?

Scientists view duckweed as
• A natural wastewater treatment option. The plant feeds on nitrogen and phosphate organic pollutants, the very stuff treatment plants aim to remove from wastewater.
• The world’s “greenest” feedstock. Fast growing, high in protein and dietary minerals, and easily harvested, the plant is cultivated as a feed supplement for chicken, livestock, and farmed fish, especially in developing countries.
• An inexpensive, earth-friendly source of the biofuel ethanol. Unlike corn, duckweed requires minimal human-made energy to grow and it doesn’t deplete the world’s food supply.
• A cleaner fuel. While duckweed-produced ethanol, like other plant-based fuels, releases some carbon dioxide into the atmosphere, the plant also absorbs CO2 as it grows.

Test Run: Wastewater Treatment to Ethanol

After much preparation in the spring of 2011, Lam launched a pilot project to demonstrate how duckweed treats wastewater and is simultaneously harvested as a biomass for producing ethanol. To help run the wastewater-treatment-to-fuel demonstration project, Lam enlisted the assistance of graduate students Philomena Chu and Thomas Maloney, recent graduate Ryan Integlia, and undergraduates David Byrnes, Deepak Khanna, and Jessica Kretch.

"We want to create a working pipeline from wastewater to fuel. That’s key to catching the interest of commercial world and government agencies to this renewable fuel," Lam says.

  • Closeup of duckweed
    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.

  • Eric Lam
    Harnessing the Power of a Humble Plant

    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

  • Sunset
    Harnessing the Power of a Humble Plant

    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.

  • Students build retaining system from pool noodles
    Harnessing the Power of a Humble Plant

    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

  • Positioning the retaining system on pond
    Harnessing the Power of a Humble Plant

    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

  • Student with duckweed thriving on the pond
    Harnessing the Power of a Humble Plant

    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

  • Experimental duckweed harvester is deployed
    Harnessing the Power of a Humble Plant

    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 harvester vacuums duckweed from pond surface
    Harnessing the Power of a Humble Plant

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

  • Collecting samples from duckweed harvester
    Harnessing the Power of a Humble Plant

    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

  • Student in lab with harvested duckweed
    Harnessing the Power of a Humble Plant

    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

  • efuel
    Harnessing the Power of a Humble Plant

    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.

  • Nozzle
    Harnessing the Power of a Humble Plant

    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.

  • Closeup of duckweed
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  • Eric Lam
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  • Sunset
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  • Students build retaining system from pool noodles
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  • Positioning the retaining system on pond
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  • Student with duckweed thriving on the pond
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  • Experimental duckweed harvester is deployed
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  • Duckweed harvester vacuums duckweed from pond surface
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  • Collecting samples from duckweed harvester
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  • Student in lab with harvested duckweed
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  • efuel
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  • Nozzle
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