Making Gas from Prairie Grasses
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All Things Considered, December 7, 2006 · The idea of burning grass to fuel your car or heat your home might seem a bit odd. But call grass a “biofuel” and suddenly it sounds plausible.
Scientists are struggling to make biofuels cheap enough to compete with fossil fuels such as oil and coal. Growing anxiety over how fossil fuels warm the Earth’s climate has quickened the pace of research.
Grass can be turned into a liquid fuel or burned in a power plant to make electricity. But it’s an expensive process. Corn is the biofuel of choice instead. But ecologist David Tilman at the University of Minnesota says he’s found a way to make prairie grasses more attractive than corn.
“We actually get more energy from an acre of land growing prairie grasses [and] mixtures of prairie grasses and converting them into ethanol or into synthetic gas and diesel than you would by growing corn and soybeans and converting them into ethanol or biodiesel,” he says.
Tilman’s team grew plots mixing 16 types of prairie grasses, including lupine, turkey foot, blazing star, and prairie clover. The plots with the most varieties produced the most biomass and produced more potential energy than corn and soybeans.
And the multigrass plots did something else. Like all plants, grasses capture and use carbon dioxide from the air. When a plant or a plant-fuel is burned, the CO2 goes back into the air. That’s not good if you’re worried about climate change.
But Tilman’s prairie grasses bury much of that CO2 in the soil and in their deep, permanent roots. So a good deal of the CO2 stays in the ground after the harvest.
“We have discovered a way to make biofuels that by the time the whole life cycle is done and they are combusted, there is less carbon dioxide in the atmosphere than there had been before,” Tilman says.
The cycle starts again after harvest, with new grass growing from the same roots.
Writing in the journal Science, Tilman calls this “carbon-negative” biofuel. It’s just the opposite of biofuels from corn and soybeans, which are “carbon-positive. ” They produce more CO2 than they absorb because it takes more fossil fuel to make them. You need fossil fuel to run farm equipment, to make fertilizer, to make electricity to run fermentation tanks. Prairie grasses need much less help to grow.
“They’re adapted to the region,” says Tilman. “They grow with almost no input. We don’t apply any pesticides. We don’t need to use fertilizer. We don’t irrigate them. They grow on nutrient poor soils and they are very efficient at converting the resources we do give them into energy.”
But converting prairie grass into a useable fuel isn’t easy. Robert Jackson, an ecologist at Duke University who’s studied biofuels, says Tilman’s findings are encouraging. But the marketplace still rules.
“Right now biomass is more expensive than traditional fossil fuels and many other renewables,” says Jackson, “and the only way to change that is some sort of carbon tax or carbon-trading mechanism. When we pay for carbon, then we change the price structure for carbon.”
The Department of Energy says it costs about five times more to make fuel from grasses than it does to make it from corn. But Jackson notes that prairie grasses do have advantages that could help them compete. Unlike corn, for example, they grow happily on poor, sandy soils. At some point, good places to grow corn will get scarce. That’s when grasses may start to look a lot greener.
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View Image by
All Things Considered, December 7, 2006 · The idea of burning grass to fuel your car or heat your home might seem a bit odd. But call grass a “biofuel” and suddenly it sounds plausible.
Scientists are struggling to make biofuels cheap enough to compete with fossil fuels such as oil and coal. Growing anxiety over how fossil fuels warm the Earth’s climate has quickened the pace of research.
Grass can be turned into a liquid fuel or burned in a power plant to make electricity. But it’s an expensive process. Corn is the biofuel of choice instead. But ecologist David Tilman at the University of Minnesota says he’s found a way to make prairie grasses more attractive than corn.
“We actually get more energy from an acre of land growing prairie grasses [and] mixtures of prairie grasses and converting them into ethanol or into synthetic gas and diesel than you would by growing corn and soybeans and converting them into ethanol or biodiesel,” he says.
Tilman’s team grew plots mixing 16 types of prairie grasses, including lupine, turkey foot, blazing star, and prairie clover. The plots with the most varieties produced the most biomass and produced more potential energy than corn and soybeans.
And the multigrass plots did something else. Like all plants, grasses capture and use carbon dioxide from the air. When a plant or a plant-fuel is burned, the CO2 goes back into the air. That’s not good if you’re worried about climate change.
But Tilman’s prairie grasses bury much of that CO2 in the soil and in their deep, permanent roots. So a good deal of the CO2 stays in the ground after the harvest.
“We have discovered a way to make biofuels that by the time the whole life cycle is done and they are combusted, there is less carbon dioxide in the atmosphere than there had been before,” Tilman says.
The cycle starts again after harvest, with new grass growing from the same roots.
Writing in the journal Science, Tilman calls this “carbon-negative” biofuel. It’s just the opposite of biofuels from corn and soybeans, which are “carbon-positive. ” They produce more CO2 than they absorb because it takes more fossil fuel to make them. You need fossil fuel to run farm equipment, to make fertilizer, to make electricity to run fermentation tanks. Prairie grasses need much less help to grow.
“They’re adapted to the region,” says Tilman. “They grow with almost no input. We don’t apply any pesticides. We don’t need to use fertilizer. We don’t irrigate them. They grow on nutrient poor soils and they are very efficient at converting the resources we do give them into energy.”
But converting prairie grass into a useable fuel isn’t easy. Robert Jackson, an ecologist at Duke University who’s studied biofuels, says Tilman’s findings are encouraging. But the marketplace still rules.
“Right now biomass is more expensive than traditional fossil fuels and many other renewables,” says Jackson, “and the only way to change that is some sort of carbon tax or carbon-trading mechanism. When we pay for carbon, then we change the price structure for carbon.”
The Department of Energy says it costs about five times more to make fuel from grasses than it does to make it from corn. But Jackson notes that prairie grasses do have advantages that could help them compete. Unlike corn, for example, they grow happily on poor, sandy soils. At some point, good places to grow corn will get scarce. That’s when grasses may start to look a lot greener.
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Replies
And they call it Grassoline.
Nancy said to keep off the grass or was it just say no! I can't remember.
"Biomass" is not the same as fuel, much less biodiesel or ethanol. To convert prarie grass biomass to ethanol requires cellulose ethanol technology that lots of people have developed to some degree but none have as yet commercialized to fuel ethanol production. The reasons are many.
Dunno of any way to convert prarie grass to biodiesel as you need vegetable oil as the starting point and these grasses don't produce much grain yield to get the oil from.
And as far as burning the grasses for fuel- the most efficient means to obtain energy from them- it's only worthwhile if you can dry them substantially in place and you don't have to transport the dried grasses very far. Otherwise, a good portion of the energy you produce goes into transporting the "fuel", since it's at such a low energy density per unit volume.
There's no technological fix to this problem. People should stop holding out for one and get on with the real solution. We simply need to use energy more wisely. There's lots of advice here on how to do that effectively in your own home.
It's an interesting idea.
The one "trick" of it, is in the prairie grasses. They tend to grow, and grow well, based on local conditions. That's not necessarily consistent grown, though. Makes bailing p/g a bit problematic. Industrial processes are, generally, not made more effecient with irregular raw material supply. (Getting folk to go run out with the hay cutter and thene the bailer, in dribbles and drabs is tough sledding, too.)
I was surprised to not see Bahia or Dallis grass on the list--they are perennial (NPI) banes of the cotton growers, and as common as Johnson grass. Of course, both grow in a less-than "lush" sort of way (more "mangy" to pick a convenient illustritive word).
Can't be all that difficult .. Cows do it all the time . ;-)
Cows do it all the time
<G>
Sheep will shear even closer--both "nitrogen fix" in the, ah, "output," too (less ideal for fuels). They are less concerned about making bales, too (you don't bale wet grass, neither do you want short bales--catch-22). Ruminants don't "have to make hay while the sun shines."Occupational hazard of my occupation not being around (sorry Bubba)
Heard a cool one the other day too: combine the cows with chickens- but only after the cows have left the field for a couple of days. The chickens eat the fly larvae out of the "leavings", cutting down on the flies as well as feeding the chickens. Cycle the right animals in the right sequence across the land and you can apparently actually get a "crop" of meat, milk etc. off the land while leaving it richer in both biomass and fertility, while you neither till nor sow nor use any chemicals. Last I checked, meat and milk were worth more than fuel ; ) Mind you, you'd need a fair bit of effort on the part of the farmer- and there's winter to consider too. But it makes a lot more sense to me to use arable land to feed people than to feed cars.
Cycle the right animals in the right sequence across the land and you can apparently actually get a "crop" of meat, milk etc. off the land
Hmm, wonder how many chickens per beeve? Gets complicated kinda quick--if it's, oh, a dozen birds per beeve, that does not sound like so many. That is, until you start running 50 or 100 head. Herding 12000 chickens gets more than middling complicated.
Only other part that monkey-wrenches a schem like that is that dairy "production" and beef "production" have only a limited overlap, with geography and climeat big factors in that.
Doesn't mean it won't work, it will work nicely, actually. FLW ciphered out that an 'average' family only needs about 2 areable acres for self sufficiency, largely by such 'cyclical' ag practices. The trick of that, though, is that then every family not only must want to, but must also be skilled in animal husbandry. As with so many things, there are those good at Ag; and there are those who are hopeless.Occupational hazard of my occupation not being around (sorry Bubba)
I'm a dyed-in-the-wool DIYer, but I'm very happy to pay a farmer to grow my food for me. Just wish the economics of farming were a bit more favourable to the farmer!
Check this out:
<http://www.iowadnr.com/energy/renewable/switchgrass.html>
In southern Iowa, it's been in testing for years. My brother made out like a bandit when there was a push to seed acres to switchgrass, he sold semi-loads of cleaned seed for something like $15/pound.
I believe the jury is out on it's feasibility...and something that may help is this technology <http://www.newswise.com/articles/view/525043/>
Rip
rez,
This was covered recently on NPR, a complete discussion explaining the full benefits which includes dramatically lowering the amount of carbon in the atmosphere with it's attending benefits for global warming..
Something like two tons of carbon per acre were not introduced into the atmosphere, on top of that there is a plot in England whereby such techniques were used for the past 150 years with no reduction in biomass produced! Tiny traces of phosperous are consumed but in such small degree that 150 years of constant production hasn't reduced output to any measurable degree!
The advocate didn't suggest taking any productive land out of production, thus no reduction in food stuff. He suggested land already in set aside programs be allowed to be harvested in the fall after wildlife has moved on.
the potential for as much as 16% of our energy needs being met with no loss in crop land and a cleaner enviornment..
If land adjacent to rivers and lakes were provided with say a 300 yard buffer water polution of run off of nitrates and phospereous, would be cleaned up dramatically..
I see this as a win win solution!
If land adjacent to rivers and lakes were provided with say a 300 yard buffer water polution of run off of nitrates and phospereous, would be cleaned up dramatically..
That's a very interesting idea in many ways.
The 'trick' of it would be in how "absorbant" that 900' was, of course.
The proportions would make it tough to get done, too--that's an acre every 50' of river (or, really every 25' both banks). Hundred miles of river is 528,000 feet, or 21,120 acres for just the 100 miles.
Using biomass to control ag chemicals (organic and inorganic) is a hugely elegant scheme. It can/could be tough on the farmer though, "giving up" those very productive acres. Can be done, just tough. Toughest sledding, though, would be getting munis to evern pretend to get into compliance. The cities want the waterfront, and somebody else to keep it clean; but not enough to cede the properties to that purpose.
Whoa, just carried that mental thought through--300 yards would convert most of NE New Orleans back into greensward between the river and Lake Ponchatrain (might be a tad hard on UNO and some other historical sites . . . ) Man, you do not want the cajuns (or the UNOers) mad at you . . . Occupational hazard of my occupation not being around (sorry Bubba)
CapnMac,
I agree that removing productive land from a farmer is not going to be an easy sell. The fact that he could harvest it and sell the biomass might soften the impact a bit however this is certainly one area where the federal government could provide a solution..
If there were some support program for the farmer so that he wouldn't lose on a deal like this there would be some cost to the taxpayer, sure but the gains would offset the losses..
There is a stretch below the Mississippi Delta called the dead zone.. it's where once rich fishing , shrimp, and other marine life lived.. however with the nitrogen/ phosphereous/ and other farm chemicals run off it has not only killed all fishing etc. but is quickly killing more and more fishing in the gulf..
Is the potential gains from fishing going to offset the costs of such a government program? I'd certainly hope so.. (I don't know though) I do know that Germany found out that it could rapidly clean up some of it's polluted rivers once it stopped dumping in them..
As to the Cajuns or UNO's ???? `I thought many Cajuns were fishermen so would they still be angery if they were given back fishing grounds in exchange?
>"They're adapted to the region," says Tilman. "They grow with almost no input. We don't >apply any pesticides. We don't need to use fertilizer. We don't irrigate them. They grow >on nutrient poor soils and they are very efficient at converting the resources we do give >them into energy."
Years ago, we converted the fescue in a corner of our hayfields to prairie tall grass.
The seed was hard to establish and the field looked awful for the first few years. Then we overseeded, did a springtime burn, and it really started to take off.
Once established, prairie grass is a gorgeous, low maintenance plant. Maintenance consists of burning it every couple of years, and possibly mowing once or twice per seasaon. This is to keep saplings from invading and turning the prairie into woodland.
Alternate fuels aside, for anyone with some acreage, prairie grass is worth considering to improve the beauty of your property, benefit wildlife, and reduce your mowing chores.
There is a process for making bio-fuel by heating in a closed system called Fast Pyrolysis. There is a guy in the area that has a system on a trailer that can "cook" the waste products from agriculture and forestry. It produces a bio-oil along with charcoal, and gases which is used to power the system. I don't have a link, so can't post it. This one is a similar system for wood waste.http://dynamotive.com/This one on all kinds of renewable energy.http://www.canren.gc.ca/default_en.asp
People have been doing pyrolysis forever. Some of them even tart it up in high heels and call it "thermal depolymerization" or similar horsesh*t.
Yes, you get a bit of oil when you pyrolyze biomass, but it's a relatively small yield compared to the mass fed. Most of what you get is fuel gas mixed with steam, and char. The char you get isn't typically useful as "charcoal" unless you start with the right stuff and do the pyrolysis in a way that doesn't yield much oil. In fact, most of the pyrolyzers who are after oil burn the char to get the energy to carry out the pyrolysis, since pyrolysis process consumes rather than produces energy. Typically, pyrolysis is a way to burn most of the fuel to operate a process to produce a small fraction of the fuel in liquid form. Far better to simply burn the fuel directly- no energy wasted that way.
Where pyrolysis is worth considering is typically where you have a large volume of a low-grade "fuel"- something typically considered a waste product- far away from anybody who needs the energy. The problem is that the economics of pyrolysis are usually based around using a waste product to produce this "fuel". The trouble is, as soon as you're using a waste to feed a process, it often becomes a commodity!