Large Field Trial Shows Miscanthus Could Meet US Biofuels Goals With Less Land
31 July 2008
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| In field trials in Illinois, researchers grew Miscanthus x giganteus and switchgrass in adjoining plots. Click to enlarge. Credit: University of Illinois |
Researchers at the University of Illinois have concluded that the perennial grass Miscanthus×giganteus could produce enough ethanol to offset 20% of current US gasoline use, while requiring 9.3% of current agricultural acreage. By contrast, using corn or switchgrass to produce the same amount would require 25% of current US cropland.
The findings come from side-by-side trials of Miscanthus and switchgrass established for the first time along a latitudinal gradient in Illinois. The results of the trials appear this month in the journal Global Change Biology.
Over 3 years of trials, Miscanthus×giganteus achieved average annual conversion efficiencies into harvestable biomass of 1.0% (30 t ha-1) and a maximum of 2.0% (61 t ha-1), with minimal agricultural inputs. The regionally adapted switchgrass variety Cave-in-Rock achieved somewhat lower yields, averaging 10 t ha-1. Given that there has been little attempt to improve the agronomy and genetics of these grasses compared with the major grain crops, these efficiencies are the minimum of what may be achieved. At this 1.0% efficiency, 12 million hectares, or 9.3% of current US cropland, would be sufficient to provide 133 × 109 L of ethanol, enough to offset one-fifth of the current US gasoline use. In contrast, maize grain from the same area of land would only provide 49 × 109 L, while requiring much higher nitrogen and fossil energy inputs in its cultivation.
In 2007, University of Illinois researchers presented the first direct comparisons of the biomass productivity of the two C4 perennial grasses switchgrass (Panicum virgatum) and Miscanthus. Results given at Plant Biology and Botany 2007 showed that Miscanthus is more than twice as productive as switchgrass. Its efficiency of conversion of sunlight into biomass is amongst the highest ever recorded. (Earlier post.)
(C4 refers to the type of photosynthesis used by the plant: in C4 photosynthesis, the CO2 is first incorporated into a four-carbon compound, as compared to the more common C3 photosynthesis and its three-carbon compound. Among their differences, C4 plants photosynthesize faster than C3 plants under high light intensity and high temperatures, and have better water use efficiency. Corn is also a C4 plant.)
The Miscanthus/switchgrass field trials study was led by U. of I. crop sciences professor Stephen P. Long. Long is the deputy director of the BP-sponsored Energy Biosciences Institute, a multi-year, multi-institutional initiative aimed at finding low-carbon or carbon-neutral alternatives to petroleum-based fuels. He also is the editor of Global Change Biology.
What we’ve found with Miscanthus is that the amount of biomass generated each year would allow us to produce about 2 1/2 times the amount of ethanol we can produce per acre of corn.
—Stephen Long
In trials across Illinois, switchgrass produced only about as much ethanol feedstock per acre as corn, Long said. The yields for switchgrass were equal to the best yields that had been obtained elsewhere with switchgrass, Long said. The Miscanthus proved to be at least twice as productive as switchgrass. Miscanthus is also tolerant of poor soil quality.
Miscanthus begins producing green leaves about six weeks earlier than corn in the growing season and stays green until late October in Illinois while corn leaves wither at the end of August. The growing season for switchgrass is comparable to that of Miscanthus, but it is not nearly as efficient at converting sunlight to biomass as Miscanthus, Frank Dohleman, a graduate student and co-author on the study, found.
One of the criticisms of using any biomass as a biofuel source is it has been claimed that plants are not very efficient—about 0.1 percent efficiency of conversion of sunlight into biomass. What we show here is on average Miscanthus is in fact about 1 percent efficient, so about 1 percent of sunlight ends up as biomass.
Keep in mind that when we consider our energy use, a few hours of solar energy falling on the earth are equal to all the energy that people use over a whole year, so you don’t really need that high an efficiency to be able to capture that in plant material and make use of it as a biofuel source.
—Stephen Long
Because Miscanthus is a perennial grass, it also accumulates much more carbon in the soil than an annual crop such as corn or soybeans.
Miscanthus is a sterile hybrid, and must be propagated by planting rhizomes. Mechanization allows the team to plant about 15 acres a day. In Europe, where Miscanthus has been grown for more than a decade, patented farm equipment can plant about 50 acres of Miscanthus rhizomes a day, Long said.
Once established, Miscanthus returns annually without need for replanting. If harvested in December or January, after nutrients have returned to the soil, it requires little fertilizer.
Keep in mind that this Miscanthus is completely unimproved, so if we were to do the sorts of things that we’ve managed to do with corn, where we’ve increased its yield threefold over the last 50 years, then it’s not unreal to think that we could use even less than 10 percent of the available agricultural land. And if you can actually grow it on non-cropland that would be even better.
Resources
Emily A. Heaton, Frank G. Dohleman, Stephen P. Long (2008) Meeting US biofuel goals with less land: the potential of Miscanthus. Global Change Biology doi: 10.1111/j.1365-2486.2008.01662.x
I'm stil not comfortable with converting it to ethanol. The distillation away from the fermentation water takes a huge amount of energy that today comes largely from coal.
It would presumably make a good feedstock for more efficient processes like Choren/Fischer-Tropsch etc.
Posted by: clett | 31 July 2008 at 06:28 AM
No it doesn't. The energy would come largely from the lignin within the grass, which cannot be easily converted into ethanol.
Posted by: Bryan | 31 July 2008 at 07:01 AM
Good point concerning the energy required to create ethenol.
With more ethenol production occuring all the time, what are the prospects of using a portion of the ethenol created to generate power on-site so these refineries are off-grid?
Posted by: Rod | 31 July 2008 at 07:07 AM
20% of US gasoline use, with 9.3% of current ag land used..... so 100% of US gasoline with 46.5% of current ag land used? This is very impressive - and they haven't even done any significant hybridization or genetic modifications yet on miscanthus gigantus. VIVA MISCANTHUS!
Posted by: ejj | 31 July 2008 at 08:01 AM
Forget about distillation, its a dinosaur technology, and will be replaced in 2nd generation biofuel plants with more advanced membrane and pervaporation technologies which require minimal energy.
Posted by: MeanandGreen | 31 July 2008 at 08:01 AM
In any case, get on with it; Exxon just made another record profit and I'm tired of being screwed by the global economy and our corporate government in Washington.
Posted by: Lad | 31 July 2008 at 09:20 AM
So flex fuel is coming back?
I was just getting used to the elimination
of the ICE engine and heavy cars.
But what of air quality? This has still got to
pollute.
Posted by: BobT | 31 July 2008 at 09:45 AM
There is a crucial point that continually gets glossed over. The current "demand" for transportation fuels is not what we actually NEED....by about a factor of eight. It's what we "demand" while using very inefficient and wasteful technology. Using PHEVs and bio-methane the "demand" could be reduced from the current 143 billion gallons of gasoline (16 quads) to 17 billion gallons of gasoline equivalent ( 2 quads)...a fraction of the energy, and totally eliminating the need for fossil derived gasoline, while making alternative sources of end use energy such as Miscanthus all the more viable.
Posted by: bud | 31 July 2008 at 09:50 AM
Bio methane? What ice tech takes methane ?
Posted by: bobt | 31 July 2008 at 10:57 AM
What ice tech takes methane ?There are hundreds of thousands of compressed natural gas vehicles already operating around the world today.
Posted by: Paul F. Dietz | 31 July 2008 at 11:17 AM
It seems that about 100% of the liquid fuel required could be produced with about 50% of all USA croplands.
Would the remaining croplands (about 50%) be enough to overfeed 350 million people or should many (about 35%) of us diet (i.e. reduce food intake from 4000 calories/day to 2000 clories/day) to make sure that our gas guzzlers have enough agro-fuel?
This may be an acceptable side benefit but many may not be able to afford to buy 2000 calories/day and may be too thin to work.
Using good croplands to feed our gas guzzlers may not be a very good idea.
Posted by: HarveyD | 31 July 2008 at 12:56 PM
@bobt
A couple of points re: bio-methane.
Diesel engines run on up to 60-70% methane without modifying the engine. Both spark ignition and diesel run on methane by modifying the engines or with factory CNG engines.
There is no reason to assume that it is necessary to use any cropland in order to produce the 15 quads of bio-methane required to run the U.S. economy. Although it would be much more beneficial to convert, say, 20 million acres of corn ethanol land (the land required to produce the current 8 billion gallons) and put it into Miscanthus, hybrid sorghum or better yet wetlands...which is what alot of it started out as.
The 8 billion gallons of ethanol represent .6 quads of energy of which .16 is net energy, after the inputs are subtracted. Twenty million acres of hybrid sorghum or cattails from the wetlands would yield 2.4 quads of energy as bio-methane, 15 times as much energy.
If the cornfields were converted back into wetlands there would be other environmental benefits of course in terms of erosion, nitrate runoff, soil carbon loss, wildlife habitat, etc.
Posted by: bud | 31 July 2008 at 02:00 PM
"It is frequently asserted that plants convert only 0.1% of solar energy into biomass, therefore requiring unacceptable amounts of land for production of fuel feedstocks. The C4 perennial grass Miscanthus×giganteus has proved a promising biomass crop in Europe, while switchgrass (Panicum virgatum) has been tested at several locations in N. America. Here, replicated side-by-side trials of these two crops were established for the first time along a latitudinal gradient in Illinois. Over 3 years of trials, Miscanthus×giganteus achieved average annual conversion efficiencies into harvestable biomass of 1.0% (30 t ha−1) and a maximum of 2.0% (61 t ha−1), with minimal agricultural inputs. The regionally adapted switchgrass variety Cave-in-Rock achieved somewhat lower yields, averaging 10 t ha−1. Given that there has been little attempt to improve the agronomy and genetics of these grasses compared with the major grain crops, these efficiencies are the minimum of what may be achieved. At this 1.0% efficiency, 12 million hectares, or 9.3% of current US cropland, would be sufficient to provide 133 × 109 L of ethanol, enough to offset one-fifth of the current US gasoline use. In contrast, maize grain from the same area of land would only provide 49 × 109 L, while requiring much higher nitrogen and fossil energy inputs in its cultivation."
So 133/49 = 2.7 times the fuel yield (though no mention of the animal feed co-product from maize) "with minimal agricultural inputs". Plus the lignin would provide heating fuel. Hence much lower field-to-wheel GHG emissions than gasoline.
These field test results strengthen the case for building fuel alcohol plants now as a path to a low GHG future when cellulose alcohol becomes cost effective.
Displace 20% of current gasoline use from 9.3% of current cropland; say 15% of US oil consumption.
Update trade policy to enable import of sugar cane ethanol from other American countries; say 10%.
Displace 1/3 of 70%, say 23% of oil with LNG/CNG for trucks & buses from T.Boone Pickens wind plan.
Displace at least 20% of current fuel consumption by downsizing and efficiency through Feebates and CAFE.
Plus DOE estimates that off-peak electricity from existing generating capacity could provide 40% of current vehicle miles in PHEVs (eventually).
15% + 10% + 23% + 20% + up to 40% = 108%
There are other options to explore like extending Pickens plan North developing untapped HEP resources in Canada to provide load-following peak power. If Pickens wind farms displace all the NG from electricity generation, new Canadian HEP would displace coal, reducing GHG emissions or enabling CBTL with CCS for aviation grade synthetic fuel.
Then there is still biogas from manure & sewage for CHP or BioGTL; BTL from forestry waste etc.
There is no silver bullet, but by combining options it seems like we could build up alternatives to eliminate US imports from OPEC, reducing the external costs of oil to US taxpayers.
Posted by: Polly | 31 July 2008 at 03:08 PM
"Using good croplands to feed our gas guzzlers may not be a very good idea."
the Miscanthus does not require prime arable land. primarily scrub or marginal land is sufficient. fertiliser, water inputs are similarly modest.
Posted by: eric | 31 July 2008 at 03:18 PM
Both Switchgrass and Miscanthus are only about 40% cellulose.
Hemp, on the other hand, is about 70%.
But illegal to grow, unfortunately.
Posted by: Jim | 31 July 2008 at 03:37 PM
I didn't catch any mention of whether the farm tractors were ethanol powered or whether nitrogen was added to the soil. One good thing about ethanol is that phosphorous and potassium in theory can be recycled back to the soil but again this requires mechanical effort.
This 1% solar capture versus say 15% for photovoltaics has to be weighed up against up capital cost, alternative land use and energy storage density ie liquid fuel vs battery. Maybe some strange combination is optimal such as PV-battery tractors on-farm and outside the farm ethanol is used as a range extender in PHEVs.
Posted by: Aussie | 31 July 2008 at 03:45 PM
The correction we have to make next time we subsidize a biofuel is to require that the farm use land that has been unfarmed for 10 years or more to prevent more food price rises like the corn fiasco.
Posted by: fred | 31 July 2008 at 05:47 PM
There are more than 8 million NG vehicles on the planet and only about 150k of them are in the U.S. Most of those are fleet cars and trucks. Biomass to methane by gasification is a very efficient conversion method and the fuel is delivered to your home garage by pipe. No tankers, refineries nor delivery trucks.
Posted by: sjc | 01 August 2008 at 01:50 AM
Once upon a time before electricity or the ICE, there were horses and city gas plants to provide for gas lights. The good old days before refineries.
Posted by: Kit P | 01 August 2008 at 07:17 AM
Fred,
Biofuels didn't drive up food prices. Energy prices, particularly natural gas, and its effect on fertilizer prices, drove them up.
That being said, the biofuels push certainly didn't help, but really only affected corn in North America. All the other shortages (rice, etc.) are due to energy prices.
Posted by: Jim | 01 August 2008 at 07:21 AM
Jim
A recent study shows that corn ethanal is indeed higlhy responsibpe fo increasing food price, even if people don't eat corn directly there is a domino effect, corn being too expensive to feed animal they start to use other cereals and the whole things is affected.
Corn ethanol is an aberraion, economically, energetically and environmentally as well, period we have to walk away from it asap.
Miscanthus is promising but there is still the problem of carrying all this bimass from the field to the procession plan, and it is hard nut to crack. Remember that a 1 million ton ethanol a year process plan would require a truck every 6 minutes round the clock every single day. Possible but hard to manage and requires a lot of fuel...
Posted by: Treehugger | 01 August 2008 at 08:43 AM
Miscanthus is certainly a much better source for biofuels than corn, but once an industry for using it becomes established, it will be very difficult to limit its cultivation to marginal lands. It will displace production of other crops and raise food prices, simply because there will be more profit to farmers in raising miscanthus in place of other crops.
Posted by: Roger Arnold | 01 August 2008 at 12:47 PM
Posted by: Reality Czech | 01 August 2008 at 01:29 PM
Say something enough and people will accept it as fact. Corn ethanal played a minor role in rise of food prices. But like everything else political it doesn't matter if it is true are not lets just keep insisting it is so and people will believe.
But I am no fan of corn ethanol simply because it sucks. So many better choices out there that will hopefully quickly phase out corn ethanol with something that produces many more gallons of ethanol per acre.
Posted by: omegaman66 | 02 August 2008 at 06:46 AM
If their claim is true one potentially produce 1,800 TWh of biogas.
The US needs about 4000 TWh of electricity per year, therefore 9.3% agricultural acreage can essentially produce over 25% of the US electricity demand with flexible combined cycle power plants (60% effciency). )
(12 Mio hectares = 120'000 km2 at 1% conversion efficiency and 1500 hours of sunhours per year that's 1,800 TWh of biogas. )
Since combined gas power plants are more efficient than IC engines in cars and can very effictively be combined with wind farms, the overall efficiency per area is much higher if biogas is produced, than if this area would only be used to produce ethanol.
However, this scenario will require plug-in hybrids to become popular.
Posted by: gaspower | 02 August 2008 at 09:39 AM