Researcher Explores Mesquite-to-Ethanol
23 June 2006
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| Texas had 3.8 million acres with moderate to dense mesquite in 1984; that has climbed to 6 million acres. |
A Texas Agricultural Experiment Station researcher is exploring the feasibility of harvesting and using rangeland woody plants, such as mesquite and red berry juniper, as an ethanol feedstock for a distributed bio-energy industry in rural West Central Texas.
The prime area to harvest mesquite is the middle third of the state: a band bordered on the west by a line from Childress to Del Rio and on the east from Decatur to Austin. This mesquite-covered area could provide fuel for about 400 small (5 million gallons per year) ethanol plants, according to Dr. Jim Ansley.
We’ve had so much more interest in this since gas prices went up last summer. That’s going to be a real driving variable. If gas prices continue to go up, I think we could very well see a first generation refinery built in Texas to handle mesquite within five years.
—Jim Ansley
Ansley is working with Pearson BioEnergy in Aberdeen, Mississippi to study the supply, harvest technologies, ethanol conversion rates and ecological effects of mesquite-to-ethanol production.
Pearson is the developer of a combined gasification/Fischer-Tropsch process for the conversion of the mesquite feedstock to a syngas, and then its subsequent conversion to ethanol.
In a trial with Pearson, one oven-dry ton of mesquite wood yielded 214 gallons of ethanol with a conversion efficiency of greater than 98%, according to Ansley.
By comparison, fermenting corn yields about 124 gallons per ton (EERE), and the yield from switchgrass cellulosic ethanol is about 80 gallons per ton (Iogen). (Iogen believes it can increase the switchgrass cellulosic ethanol yield to 100 gallons per ton in the future.)
An acre of the densely populated mesquite standing 10 to 12 feet tall will yield about 8 to 10 tons of wood. A commercial refinery producing 5 million gallons of ethanol per year will require about 30,000 acres to sustain it, assuming a 10% annual harvest and 10 years for regrowth.
The thing that will make this fail is if people think a bigger refinery in the big cities is better. That’s where it will fail. The transport costs to get the feedstock to the refinery will kill you.
—Jim Ansley
Building smaller refineries in the rural regions where the mesquite is located is the key to making this work, Ansley said.
A State Energy Conservation Office grant is supporting the team’s study of different regrowth rates, as well as develop a mechanized system of harvesting mesquite. Working with private cooperators, Ansley has helped design a harvester that is in the patent-pending stages, and hopes to have it ready for a field demonstration on 5 October.
We’re in the process of trying to measure how much energy it takes to harvest mesquite in the field. That’s probably our least researched area. Now that we have this machine constructed, we can start working on that.
—Jim Ansley
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I thought we went to fossil fuels to preserve the forests and trees...
Posted by: Patrick | 23 June 2006 at 10:14 AM
They list a 10% harvest rate and regrowth, which means they'd harvest and replant. There's a difference between slash & burn for the purpose of putting up condos and hotels versus harvest and replanting for the purpose of having a sustainable production of biomass for sustainable liquid fuels.
Posted by: Sid Hoffman | 23 June 2006 at 10:25 AM
I think Americans consume 20 million barrels of oil a day. A few 5 million gallon per year ethanol plants sounds like a drop in the bucket.
Posted by: Joe Rocker | 23 June 2006 at 10:26 AM
I think they mean 400 * 5,000,000 = 2,000,000,000 per year. It's more significative.
Posted by: MH | 23 June 2006 at 10:34 AM
Take 2 billion gallons per year, divide by 42 gallons per barrel, that equals approximately 50 million barrels per year. That is about two and a half days of US consumption. I like the idea, but it is not much.
Posted by: Joe Rocker | 23 June 2006 at 10:52 AM
Joe -
if Americans focussed a little more on how much fuel they consume, then those biofuel capacities will represent a larger share of the market.
What I don't get is why these guys are going to the trouble of full-scale BTL to produce freakin' ethanol. They should directly produce synthetic diesel or gasoline, which have higher energy density. Perhaps with the markets distorted as badly as it is, this is a more profitable route but it makes no sense whatsoever technologically.
A cheaper and more efficient alternative to full F-T is the direct MTG route up to the DME stage. Compress it to ~8 bar and you've got an excellent liquid substitute for diesel.
Posted by: Rafael Seidl | 23 June 2006 at 11:10 AM
That could be interesting, but would prefer butanol over ethanol. Now if they can make something out of cactus, fireants, and grasshoppers,Texas could be the Utopia everyone dreams of.
Mesquite butanol,giant wind farms (already in construction), and solar energy could be the next Texas tea (oil), or the future of Texas energy, if its as good as they say it is.
Posted by: Mark A | 23 June 2006 at 11:16 AM
Mesquite Ethanol ... sounds like something I would marinate my steak in.
Posted by: Neil | 23 June 2006 at 11:31 AM
Let's look at the positive side. This would be about the equivalent of drilling in ANWR, but it is renewable -- improving the carbon situation. It may not be much, but what else are they going to do with that Texas land? In addition, they can put up some wind turbines over the same property and maybe a few solar collectors -- pretty soon you have real energy.
Posted by: JMartin | 23 June 2006 at 12:32 PM
My gut-reaction guess is that they are indeed tailoring their output towards ethanol in order to capture the $0.50 per gallon tax credit which the Federal government currently provides for ethanol fuel. With gasoline futures trading at around $2.10 per gallon, that credit represents a 25% price distortion on a volumetric basis, or a 17% distortion on an energy basis. If synthetic gasoline were in fact somewhat more efficient to produce and distribute than ethanol, that difference would be lost to the distortions created by the tax credit unless the difference exceeded 17% -- a big number.
Frankly, we should extend the current tax credit to all renewably-derived liquid fuels, ideally on an energy-content basis -- biodiesel would get a higher credit than BTL synthetic gasoline, which would get a higher credit than ethanol. Keep the ethanol credit at $0.50 per gallon if you have to please the farm lobby, and gear the credits for other fuels to higher figures from there. Slowly ramp up petroleum taxes to help pay for these credits, and plan for the eventual day when the credit will be phased out and replaced with a standard motor fuel tax -- eventually, if enough biofuel is used, the government will need the tax revenue for all its traditional purposes. By then, renewable fuels will hopefully be competitive enough to sustain a reasonable tax. Continue to tax petroleum-derived products at a higher rate to account for the greater external costs associated with their use.
Focusing on means instead of ends usually results in sub-optimal outcomes. Making the choice between synthetic gasoline and ethanol a tax-credit neutral one would allow the fuel with better technical qualities to emerge on the market.
If you want to extend this discussion, consider extending some amount of tax credit to GTL or CTL fuels which have some quantifiable benefits, even if they are not carbon-neutral. Such synthetic fuels might be low-sulfur, might have higher octane or cetane numbers (allowing for higher compression and better mileage engines), might promote "energy independence," or might have other benefits. If they have such benefits, and if those benefits are not reflected in their ordinary market price, then a tax (credit) policy should be used to price them in.
Electric technologies are important, but any incentive scheme for them would have to take a considerably different shape than a liquid fuel policy.
Posted by: NBK-Boston | 23 June 2006 at 12:32 PM
Texas could just take parts of their Rio Grande valley, and make solar electric/algae oil-biomass production facilities. That may do the trick.
Posted by: allen zheng | 23 June 2006 at 04:28 PM
Federal land, and surface areas of reservoirs inside the US along he Rio allow for cheap land. Federal, state, and local govt could team up with colleges/universities and energy/tech-biotech groups for collaboration, research, development, production and revenue.
Posted by: allen zheng | 23 June 2006 at 04:31 PM
Rafael and NBK,
It looks like you guys are right, the logic for using G-F/T to produce ethanol, appears to be the lobbyist driven legislation. Note that according to my information, ethanol gets the $0.50/gal subsidy, while biodiesel and TDP/TCP diesel (Sec. 1346 on page 1445) gets $1.00/gal. With a good lobbyist, I'd imagine that one could get a $1.00/gal subsidy for renewable diesel produced via G-F/T, similar to TDP/TCP.
As NBK mentions we need better energy legislation. Good luck with that, though. This is the best congress that lobbyist money can buy. If they won't even put the country before self-interest when it comes to homeland security money, well, then energy legislation has no chance, has it?
Joe Rocker's right about the scale: insignificant really. And that is before factoring in the energy and labor required to collect and transport the wood. Algae is a better solution, for one thing, it has a yield that is about 30 times better than other green plants. Algae can also be grown on sewage (free water and fertilizer), which would have byproducts such as clean water and fertilizer. Harvesting would consist of a pump and a separator (probably a dissolved air flotation unit). In other words, you'd have a fully automatic system, with minimum labor requirements.
Posted by: An Engineer | 23 June 2006 at 05:22 PM
Engineer has a great application, and we will probably see it employed as energy becomes more efficient. The problem with Allen's proposal is that the Rio is running out of water now, due to the growth of cities and other uses. The pecan growers in Texas are losing old growth trees because the water table continues to drop.
Posted by: JMartin | 24 June 2006 at 09:14 AM
Along the Rio. This means floatable facilities on barges that are anchored, and can sit on dry ground. They can alos be built on high and dry ground More advanced facilities/production methods can use much less water than the simple racetrack pool designs. The point is to use Federal/State land, and not buy it form private holders, lessening/eliminating the possibility of NIMBY and holdouts. Concentrator dishes and arrays can make economical use of expensive, high efficency (35 to >50%) photovoltaic cells. High efficency/pressure/ temperature solar-themal concentrator heat engine (Sterling and other) ops. can do the job for peak power demand too.
Posted by: allen zheng | 24 June 2006 at 11:25 AM
I have been resurching making ethanol from the mesquite bean. Lots of them fall every year and they have a pretty high sugar content.
Have any expiriments been done to see how much ethanol these beans can produce.
Posted by: Kelly Perry | 13 November 2007 at 03:17 PM