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Researchers Caution on Potential of Energy Crops as Invasive Species

A research plot of Miscanthus.

A University of Arkansas researcher and his colleagues are calling for caution in developing dedicated energy crops, citing the possibility of some of those biofuel crops becoming invasive species.

Robert N. Wiedenmann, professor of entomology, and his colleagues S. Raghu, Roger C. Anderson, Curt C. Daehler, Adam S. Davis, Dan Simberloff and Richard N. Mack put forth their argument for ecological studies of biofuel crops in the policy forum in the 22 September issue of Science.

Most of the traits that are touted as great for biofuel crops—no known pests or diseases, rapid growth, high water-use efficiency—are red flags for invasion biologists. We want to start a dialog and approach the question of biofuels systematically.

—Robert N. Wiedenmann

The authors of the article in Science call for an examination of potential invasiveness as crops are examined for their biofuel potential and before putting such crops into large-scale production.

Seemingly benign crops that have become invasive species have already occurred in the United States. Wiedenmann and his colleagues cite the case of Sorghum halepense, otherwise known as Johnson grass. Johnson grass was introduced as a forage grass and now has become an invasive weed in many states, causing up to $30 million annually in losses for cotton and soybean crops in just three states.

One proposed biofuel crop, Miscanthus, can grow up to eight feet in six weeks. Wiedenmann describes it as “Johnson grass on steroids.”

Plants like these, particularly grasses, have great potential from an energy standpoint, but the benefits need to be balanced with the costs.

—Prof. Wiedenmann

Although invasive species are traditionally thought of as introduced species, a native species also can become invasive through alterations to the environment, Wiedenmann said. One example: the removal of oak and chestnut trees along much of the east coast has led to sugar maples becoming invasive in some areas.

Invasive species alter ecosystems in ways that can cause both ecological and economic harm. Since 1999, the U.S. government has had an invasive species council, which develops invasive species management plans.

Researchers investigating the potential for biofuels tend to be engineering or agricultural specialists who are looking at maximizing energetic conversion or crop size. Wiedenmann and his colleagues want to see ecologists at the table with engineering and agricultural researchers addressing the potential for invasiveness.


  • Adding Biofuels to the Invasive Species Fire?”; S. Raghu, R. C. Anderson, C. C. Daehler, A. S. Davis, R. N. Wiedenmann, D. Simberloff, R. N. Mack; Science 22 September 2006: Vol. 313. no. 5794, p. 1742 DOI: 10.1126/science.1129313



How about kudzu? That stuff grows so fast you could practically use it for a continuous feed. The plant goes in one end, cellulosic ethanol/butanol out the other...

allen Z

Again, it is an exotic invasive species. Along with Chinese Tallow (aka Florida Aspen and Popcorn tree), they are invasive species to the US that have biomass fuel potential. The Chinese Tallow (Sapium sebiferum), in fact, can produce ~500 gallons SVO per acre.

Chinese tallow:
(search Sapium sebiferum)


allen Z

Kudzu also causes crop damage. On the other hand, if the biomass production is complemented with some sort of management that also halts the spread (and mitigates damage), then this might be a viable scheme; Dido for Chinese Tallow. The vine has spread throughout the South, and might have jumped up in the Northwest.



How feasible is it to - genetically, if necessary - ensure that a plant species is sterile?

If it's possible for an energy crop, can the EROEI stay good enough?



I was making a half-joke. Kudzu is already so established in the South that making getting rid of the stuff profitable could be a good thing.

FYI co2

i don't think you can rely on ANY sort of management to keep seeds from becoming airborne/transplanted by bird/animal


As far as envasive its already all over the south this brings up an interesting point make a test plant where this is already a problem. dont bring the kuduk to the plant but bring the plant to the kudzu worst case
you get rid of the Kudzu which can grow a foot a day in its growing season


The US government is part owner of the terminator gene, something developed to make genetically engineered plants that produce sterile seeds. The problem with it is that if that genetic code crosses into wild plants via pollen, it would be a huge calamity. Transgenic crops are already polluting organic farms causing millions of dollars of loss because it cannot be sold as organic food.


In recent years I've seen canola growing as roadside weed. This could be both good and bad for adjoining fields; as a legume it improves soil nitrogen for the following crop. However if it is a herbicide resistant self sowing variety it might become difficult to grow any other crop. This shows that some fuel crops will grow on land unsuitable for food provided they can be kept separate.


It seems to me that situation with energy crops follows pity way of GM EV-1 – it was put into production before battery technology matured enough to support commercialization. Food to fuel technology, such as corn or canola to ethanol or diesel, is severely limited and, to be honest, uneconomical and unsustainable in long run. Cellulosic ethanol technology is not yet mature enough to support economical production of fuel from cellulosic feedstock. When, and if, it will mature, we will have enough time to organize cultivation of cellulosic crops before huge amount of agricultural and forestry waste streams will be utilized in full.

Personally I do not believe that specialized cultivation of energy crops will ever take place. Amount of organic wastes ready to fuel conversion is so huge, that governments will have to limit it production in order to prevent unemployment problems in oil/petrochemical industry. Naturally, this could happened no closer then in 20 years, and that is another reason not to rush immature technology into full-scale production.


Andrey: "Personally I do not believe that specialized cultivation of energy crops will ever take place".
What about brazil?


I think it is better to develope battery technology for EV and build a couple of nuclear breeder reactor. And launch the radioactive crap into space.


I have read that switchgrass at one time covered much of the central US. Does anyone know enough about entomology to know if it would be considered invasive today?

As far as using only electricity is concerned, recall that only 2/3 of petroleum is consumed in transportation - to really address oil use, bio products of some sort must be used to provide the atoms for that other 1/3 of oil use. Biomass is the only renewable source of carbon atoms - at least until CO2 from the atmosphere can be used as easily.



It is not an obvious question. And I do not pretend to nail it. But take into consideration:

Currently US produces more corn ethanol then Brazil produces sugar cane ethanol. Yet for US it is about 4% of gasoline consumption, and for Brazil it is more then 50% consumption. Both sugar cane and corn plantations used for ethanol production are excess lands already cleared, irrigated, fertilized, populated, and integrated to transportational grid for sugar and food/feed production, but succumbed because of chronic market overproduction. In fact, both cultures are WASTE to fuel production technology.

Take also into account that sugar cane is native to S. America species, and have 5-10 higher yield then N. American corn. It is also very labor intensive.

All in mind, you can barely hope then even heavily subsidized corn ethanol will ever exceed 5% oxygenate gasoline requirements without being heavily subsidized on taxpayers behalf.

P.S.: cellulosic ethanol is totally different matter.

Harvey D.

USA and Canada may have enough land to become self-sufficient with home made liquid bio-fuels for an extended period. However, can the earth produce enough liquid bio-fuel for 10+ billions vehicles and food for 10+ billions people?

Sooner or latter, the world will have to reduce its reliance on polluting liquid fuels. The common sense liquid fuel replacement is clean electricity.

High efficiency, high power/energy, light weight, on-board Energy Storage Units (ESU)will be around, at a reasonable price, within a few years.

Producing the clean sustaininable electricty required for 200+ million vehicles from wind, sun, hydro and up-to-date nuclear plants is not a major challenge. The resources used for the Irak war could have financed most of it.

With an average of 2000 hours of sunshine per year, cars and trucks equipped with thin roof mounted, automatic high efficiency folding/sliding sun panels, could collect (free) a very high percentage of the energy required for the daily use while driving and/or parked outside.


I agree, with the $500B spent on war, we could have built a heck of a lot of solar thermal, PV, wind turbines, ethanol and biodiesel plants and tell OPEC to keep their oil..forever.


Not unless we step up efficency in major ways

2000 hrs * 1000 watts per sq meter say 4 sq meters
@ 20% efficency = 1600 Kwh which is pretty optimistic if you ask me factoring in losses in charging your pack and that your pack has limited capacity and once it is full more sunshine does not help you any.

So if we managed to get that much and our electric vehicle used 370 Wh/mile (toyota rav4 EV) we could go just 4300 miles off solar power.

at best with the asumptions given and/or implied


Take the number of cars times the amout of power they ues per mile times the number of miles driven per yr.

assume 200 million rav 4 ev's

(200x10^6)*15000 mi per yr * 370 Wh/ mi = watt hrs / yr= 1.11 penta watt hrs (1.11 * 10^15) +/- as I didn't check if that is the power that needs to be generated, more likely that is the power required from your wall outlet before transmission losses.

Current generating capacity of USA ~ 1,000,000 mega watt hrs

1000 Giga watt hrs (great scott!)
1 * 10^12

So not only do we have an order of magnitude difference between capacity and would be use that is TOTAL generating capacity not clean generating capacity.

No mater what happens I'm all for clean technology, but realize that the effort required to do so is not trivial.



"3.10  Why not put solar panels directly on the car's roof?

Nice idea! But not very practical. After a full sunny day, you will have gathered only enough energy to go a whopping 1/2 mile! It would take 1 month parked in a sunny spot to fully charge the battery."

Quote from FAQ on plug in conversion site above.


Talk about invasive species is typical ecolo-nonsense. What are we humans supposed to do, curl up and die?

For dinosaurs, mammals were an invasive species. So were flowering plants for ferns. This is called evolution. Do it or die.

Final point: burning fossil instead of biofuels will endanger far more native plants because of climate change.

EM, in Canada (95% untouched by man, 80% dramatically changed by arctic warming)


Talk about invasive species is typical ecolo-nonsense. What are we humans supposed to do, curl up and die?

Nonsense is making up ridiculous strawman arguments -- like saying any critical reasoning about a given issue is tantamount to murdering the entire human race.

Hey - has anyone seen "Freedom Fighter"?

Rafael Seidl

Rexis -

when you send things up into space, there is a high risk of a lauch failure. Many satellites contain small amounts of radioactive material to keep the electronics warm and power them via thermocouples. The material is well-packaged to prevent burning up on re-entry when the satellite de-orbits. Sometimes a little plutonium goes missing...I'm sure Osama would love to get his hands on it. See section 10 here:


Ergo: sending large quantitities of highly radioactive material into space is a non-starter. If there is a decision to return to nuclear power to reduce dependence on foreign oil and/or GHG emissions, the waste will have to be stored underground. Reprocessing can stretch the uranium reserves and reduce the volume of waste, at the expense of higher levels of radioactivity of isotopes with longer half-lives. Besides, the Yucca Mountain repository is still on hold.

Better to go for biofuel crops. Avoiding invasion of areas reserved for food crops is a legal and economic objective, so adding ecologists to your team makes sense if you want to limit your future liability. Neutering the seeds is one option.

Harvey D.


Our previous all electric house used an average of 55 KWh/day. Our present all electric better built and equipped home uses only 32 KWh/day. The net realized saving of 23 KWh/day could power a Toyota PHEV Prius about 23 x 4 = 92 Km/day (or about 33 580 Km/year) without drawing a single extra KWh from the power grid or a single drop of liquid fuel.

This is not an impossible thing to do. Most of us (living in all or mostly electric houses) can find ways to reduce power consumption enough to power a mid-size PHEV without significant impact on the total power consumption. No extra zillions tetrawatts are required.

If you roll out, slide out or unfold your 4 square meter solar panels, you may easily double the area to 8 square meters x 6 hours X 1000 watts x 20% = 12 Kwh/day. while your car is parked at the work place or the shopping center. That is enough to drive a PHEV Prius for about 48 Km/day.

The idea is not to find ways to consume more energy but to reduce wastes and inefficiencies.


Agreed. That is a sarcastic way of handling waste of dumping them elsewhere.

That should be the way to go. Energy efficiency. Not find more energy to waste but learn how to save energy.


I would agree that the best energy dollar spent is what rmi.org calls "negawatts"..that is the dollar not spent on energy through conserving.
Most people are so used to energy being readily available that they don't think about it until they get their monthly bill. Then, they forget about it until the next bill arrives in the mail.


RJ - You have a mistake in your math. You got 10^15 watt-hours per year, so you need to divide by about 10^4 hours per year to get about 10^11 watts continuous power generation to run a national fleet of efficient electric cars. Current power generation you have as 10^12, so this would only increase U.S. power generation requirements by 10%. (Note, I didn't check that your data was correct, just the math.)


I think that the total amount of electrical energy consumed per year in the U.S. is 13.7 quads which is 4 X 10^12 KWH which requires a generating capacity of 450 GW

The 10^15 wh/year would require a generating capacity of
127 GW.

Therefore, power generation would need to increase by 28%

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