The Risk of Biomass Invasion

Arundo donax, commonly known as giant reed, has tremendous potential as a biomass crop. It also illustrates the emerging issues around the potential for unintended weedy invasions.
By Susanne Retka Schill | March 10, 2008
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Southerners joke that kudzu is the plant that ate the South. Initially introduced as a forage crop and once widely used for erosion control, kudzu has spread throughout the Southeast becoming a major invasive weed problem. Johnsongrass is another infamous perennial grass initially introduced as a forage crop and now considered a noxious weed in 19 states. Some in the scientific community are sounding the alarm that the push for bioenergy crops could have the unintended effect of creating new biomass invaders potentially even more troublesome than kudzu or johnsongrass. The November 2007 commentary published by the Council for Agricultural Science and Technology, "Biofuel Feedstocks: The Risk of Future Invasions," warns that many of the same traits making a particular plant an ideal biomass crop are shared by plants that become invasive. To make it potentially worse, efforts are underway to enhance new biomass crops to produce more biomass, improve their performance in poor soils and growing conditions, and reduce lignin content to make the conversion process more efficient—efforts that could compound the ecological impact if the biomass crops escape cultivation.

The nation has a huge conflict of interest says Jacob Barney, co-author of the CAST report and a post-doctoral scholar in the Department of Plant Science at the University of California-Davis. On the one hand, is the renewable fuels standard just passed in the new Energy Bill, which will rely upon cellulosic feedstocks for the fuels of the future. On the other hand, are the Invasive Species Act and other legislation trying to control invasive species. Sorting out the competing goals will also be a challenge because a weed in one place isn't a weed everywhere. Growing Arundo donax as a biomass crop in California would be unadvised because it's one of the state's worst weeds, Barney says. "Taken to another place it has the potential to be grown safely," he adds. Some people in California raise concerns about switchgrass, the widely touted model biomass feedstock, which is native to the states east of the Rocky Mountains but not to California and the Pacific Northwest. Rice growers are particularly concerned that switchgrass could create problems if it were to get established as a weed in rice fields, Barney says. "Now, we have no evidence to suggest it will, but it is a concern," he says. Studies evaluating switchgrass's potential as an invasive weed are beginning in California. "However, the assessment we conduct here in the Central Valley of California will not be applicable to other regions," he adds.

Indeed, the scientists involved in the CAST report recommend that new biomass crops and even new genotypes be evaluated in every region before being introduced commercially.

The evaluations they recommend include:

› A weed risk assessment of each potential genotype targeted for cultivation within a particular region

› A climate-matching analysis to determine regions of agronomic suitability and identification of regions climatically suited to potential invasions

› Evaluation of cross-hybridization potential with related species to assess the risk of genetic invasion

› Determination of the susceptibility of native and managed ecosystems to biomass feedstock escapes from cultivation

› Multiyear studies in regions susceptible to weedy encroachments to evaluate the interactions between proposed feedstocks and native and agronomic species

› Establishment of management practices to eradicate unwanted stands prior to introduction

Promising Traits
Arundo donax, commonly known as giant reed, is one of those crops being developed as a new energy crop but is considered invasive in some areas. Giant reed originated in India and was carried around the world for use as a windbreak, for construction cane and as the source of reeds for woodwind instruments. Brought to the United States 300 years ago by Spanish missionaries, giant reed looks like bamboo, but actually is a perennial grass that grows 20 to 30 feet tall.

University of South Carolina professor of biology Laslo Marton remembers using the long, strong canes as fishing poles when he was a child in his native Hungary. In central and southern Europe, giant reed was widely used to soak up excess water and nutrients from backyard septic systems, he says. At the University of South Carolina, Marton began studying giant reed for its potential to remove contaminants from the soil. One test plot in South Carolina is being used to study the plant's effectiveness in cleaning up sewage water and diluted sludge. For many sewage sludge disposal projects, accumulations of phosphorus are becoming a problem, he explains. "Arundo has the potential to remove 200 kilograms [485 pounds] of phosphorus per acre per year." Giant reed also removes halogenated organic compounds, such as dioxin and agricultural pesticides, from contaminated soils. "In Arundo, most of these organic pollutants are metabolized, broken down to carbon dioxide or, in the worst case, hydrochloric acid which is neutralized by the soil," he says.

Using giant reed as a biomass feedstock solves one of the major limitations of its use for phyto remediation—what to do with the 20 to 50 dry tons per acre of biomass that's produced.

Marton is enthusiastic about Arundo's potential as a biomass crop. "This is a plant which gives you high biomass, has very low maintenance and very high resistance to environmental factors and biological pests," he says. "No known herbivore eats it. The literature says Indian elephants eat it, but it very seldom happens that there are free Indian elephants roaming around the United States." The plant has high energy content at 8,000 British thermal units per dry pound, and the cellulose is easily separated from the lignin so it can be digested with enzymes and converted to liquid fuel. Arundo stands stay productive for decades and can be eradicated by cutting and spraying the young shoots. "It's a crop for the future," he says.

Texas and California have areas where Arundo has become a significant weed problem, he admits. "Texas and California were human mistakes, which gave it a bad reputation as a potentially invasive plant," he says. In both places, giant reed was planted along streams and irrigation canals to stop soil erosion. In flooding conditions, the canes and roots were dislodged and carried by the water to colonize new areas. When kept away from running water, Marton argues, the plant doesn't spread. "How could [Arundo] be invasive when there are no seeds, its rhizomes aren't running, and the major problem in planting required developing a special technology to plant it?" he asks. A sterile plant with no pollen and no seeds, Arundo has been limited to small commercial plantings worldwide because the roots must be dug up, split apart and hand planted. Marton developed a micro propagation technology which uses embryonic stem cells. The cultures of stem cells can be stored in a Petri dish, and when needed, treated with hormones to begin developing tiny propagules. Those are planted in greenhouse flats and tended until ready for transplanting with conventional tree or tobacco transplanting equipment.

South Carolina Targets
South Carolina economic developer Joseph James is working to transform Marton's work into an economic opportunity for South Carolina farmers. James helped form the South Carolina Biomass Council and chairs the feedstock committee, which is looking at a variety of feedstocks for the Southeast. "When you get out of the Midwest where you have these huge industrial-sized farms, you have multiple small farms and multiple ownerships," he says. "You might need 50,000 acres of biocrops to supply a cellulosic ethanol operation. If so, you might have to have 300 to 500 farmers involved. The challenge becomes coordinating the crops that they grow, and the harvesting and shipping. That tends to put pressure on having the most productive biocrops in terms of tons per acre."

James hopes to recruit farmers around South Carolina to plant Arundo this spring. With one eye on the invasive species concerns being raised, they intend to keep plantings on dryland fields with tilled borders to keep the planting contained, James says. "We would love to have federal funding to help us do that," he adds. "There are plenty of grants to get switchgrass projects going, but executive order 13112 essentially prohibits the use of federal funds when you have any crop that has invasive potential unless the secretary that heads the agency deems the plant acceptable." James has become quite frustrated in his attempts to get federal agencies such as the Agricultural Research Service and the Invasive Species Council to study the crop. "The leadership of the U.S. DOE and the USDA need to get moving on tests, growing a number of acres of these kinds of crops under controlled situations to get comfortable with them," he says.

James sees great potential in Arundo crops for South Carolina farmers. He has sent samples to Iogen Corp., a Canadian ethanol producer, which has conducted preliminary tests and finds it promising for the company's cellulosic ethanol program. The state's paper industry is quite interested in using Arundo as a pulp source because the cane's long fibers make particularly high quality paper, he says. A paper plant recently outbid a utility that wanted to cofire Arundo with coal using the limited Arundo supplies now available, he says. Another company is testing Arundo as a biomass source to complement wood in its production of fuel pellets for the European market.

Other State, International Projects
There are other Arundo projects under development, says Michael Birch, managing director of Orapa Ltd., based in Athens, Tenn. He is working with the South Carolinans to license and commercialize the patented propagation and planting technology. A project in Florida is looking at planting 20,000 to 40,000 acres of Arundo for a biomass power plant using gasification technology, he says. A six-year evaluation of Arundo in Florida didn't find invasive tendencies in any stand, he says. However, Florida did add some safeguards. "Soon after the assessment Florida issued a new set of rules," Birch says. "You have to apply and get approval for growing dedicated energy crops." Progress Energy Florida, a utility company, signed an agreement in mid-2006 to purchase electricity from the proposed 130 megawatt biomass power plant in central Florida using a variety of Arundo trademarked as E-grass. The original agreement was with Biomass Investment Group Inc., which has since become part of the Innovative Energy Group with main offices in Dubai, United Arab Emirates.

Birch has also been involved in discussions with oil and chemical companies in Texas that are interested in exploring Arundo's potential for phyto remediation of contaminated soils. Several Central American countries are developing Arundo projects to grow biomass for power, many of which have high electrical energy costs due to a lack of local energy sources. Other projects are underway in Europe and Australia. Birch expects to be making further announcements this spring on other projects in development.

Susanne Retka Schill is an Ethanol Producer Magazine staff writer. Reach her at or (701) 738-4962.