Switchgrass could be an excellent source of biofuels - if only it were easier to break down its cellulose.
US Govt
Posted on 09/11/2008 7:11:20 PM PDT by neverdem
Switchgrass could be an excellent source of biofuels - if only it were easier to break down its cellulose.
US Govt
A genuine revolution in biofuels is currently hindered by the difficulty of converting the most recalcitrant parts of plants, primarily the cellulose of their fibres, into useful fuel. Two chemists in California now claim that it might be remarkably easy to do just that with little more than a strong acid to break down the cellulose.
Mark Mascal and Edward Nikitin of the University of California, Davis say their new process is the most efficient way yet described for converting cellulose into small, energy-rich organic molecules, using no more than basic textbook chemistry.
"It's surprising that they can do this, and sounds unique," says James Dumesic, a chemical engineer at the University of Wisconsin-Madison, who was not involved with the work. But, he adds, important questions remain about whether it can be scaled-up into a viable way of making biofuels.
Today's biofuels are made by fermentation of plant-derived glucose, typically from maize (corn), rape seed or sugar cane, into ethanol. But this uses only a fraction of the carbon in the plant matter: much of the fibrous material can't be converted to glucose, and goes to waste. That's part of the reason why the 'first-generation' biofuels produced at present have failed to deliver on their promise of cheap and abundant renewable energy.
The challenge for 'second-generation' biofuels is to break down cellulose, a stable and insoluble biopolymer that makes up most of plant fibres, into the glucose molecules from which it is built, so that they too can be transformed into a fuel like ethanol. Most current attempts to do so involve bacteria or other microorganisms genetically engineered to contain cellulose-degrading enzymes. It's costly and still rather inefficient.
Besides, even if the cellulose is turned into glucose, fermenting this to ethanol still wastes one third of the available carbon as carbon dioxide. Mascal and Nikitin say that it would be preferable to avoid fermentation altogether, instead using simple chemistry to degrade cellulose directly into organic compounds with a high energy content that might be used as non-traditional fuels.
Now they have found a way to do it. And the striking thing is that it involves no obscure or complex reagents, but merely a well-known process called acid hydrolysis – splitting chemical bonds using a powerful acid – to chop up the cellulose chains. The research is published in Angewandte Chemie1.
Chop chop The researchers mixed a fine powder of cellulose with lithium chloride in concentrated hydrochloric acid, and heated it up for about 30 hours. They extracted the products of the reaction by dissolving them in an organic solvent, and found that most of the cellulose is transformed into three compounds related to furan, whose molecules have rings of four carbon atoms and one oxygen atom. All of these products can be used as potential sources of fuel.
Mascal says that extracting the products as they form is crucial to prevent them from reacting further to give less useful products. This problem, he says, "is probably what kept researchers from pursuing this approach in the past".
The main product, called 5-(chloromethyl)furfural (CMF), isn't a viable fuel itself: it contains a chlorine atom which needs to be lopped off. But the researchers find this can be done quite easily, either by stirring CMF with ethanol at room temperature or by adding hydrogen using a palladium-based catalyst. The researchers say that both of the two products of these processes have low toxicity, and that the one produced from the reaction with ethanol has an energy content comparable to gasoline and diesel fuel.
This isn't the first attempt to make fuels directly from plant-based carbohydrates by chemical methods. Dumesic and his co-workers, and Conrad Zhang and colleagues at the Pacific Northwest National Laboratory in Richland, Washington, have both shown that fructose and glucose can be converted to other furan compounds23.
But neither of these starts with cellulose, the raw fabric of plants. Moreover, they could be expensive – one uses a costly, exotic solvent, while in the other it is tricky to separate the fuel product.
There are still plenty of hurdles to make the new process work. "These conditions are pretty nasty," says Dumesic. Handling highly corrosive concentrated hydrochloric acid in an industrial process is no easy matter. But Mascal counters that "engineering know-how and materials science have advanced to the point where this is not a critical issue". Dumesic adds that it could be challenging to remove all traces of chlorine from the final product, which is crucial if it is to be used as a fuel.
Mascal and Nikitin admit that they have not yet fine-tuned their process, nor figured out whether it can be scaled up for industrial use or applied to raw plant biomass. "We are currently planning to scale up first to a 50-litre reactor," says Mascal. "If that proves successful, we will begin to think bigger."
References
Mascal, M. & Nikitin, E. B. Direct, High-Yield Conversion of Cellulose into Biofuel Angew. Chem. Int. Ed. (2008); advance online publication 1 August 2008 (doi: 10.1002/anie.200801594).
Chheda, J. N., Roman-Leshkov, Y. & Dumesic, J. A. Green Chem. 9, 342-350 (2007).
Zhao, H. et al. Science 316, 1597-1600 (2007).
Now if they could only make fuel out of Desert Broom!
Because of this I guess.
“These conditions are pretty nasty,” says Dumesic. Handling highly corrosive concentrated hydrochloric acid in an industrial process is no easy matter. But Mascal counters that “engineering know-how and materials science have advanced to the point where this is not a critical issue”. Dumesic adds that it could be challenging to remove all traces of chlorine from the final product, which is crucial if it is to be used as a fuel.
Nitrocellulose is made into gun powder, should work.
Thirty years ago I saw a report of an experiment where hydrolysis of cellulose was accomplished very rapidly with concentrated warm sulfuric acid. The lab was somewhere in the British isles.
bmflr
Very interesting and encouraging. I think cellulosic feedstocks make a lot of sense, but according to process folks I’ve talked with, they’re incompatible with today’s biorefineries, especially on the front-end. Granted the plants could be modified and new ones built, but it’s an issue. But on the other hand, todays ethanol plants are located in corn producing areas, and cellulosic plants should be located near where the switchgrass or whatever is grown.
I was four when I first heard the announcement of the perfect ‘acid’; nothing could withstand its solvent properties; alas, it remains a commercial failure as no one has found a way to package it and put it to use.
Cheez---somebody needs to tell these guys that this isn't the eighteenth century. The chemical industry handles "concentrated hydrochloric acid" in multi-ton quantities on a daily basis. Yeah, it's corrosive, and yes, "we have the technology".
let me guess 10 yrs out with good grant money
It has been. What these guys are doing differently is continuously extracting the product as it is formed, thus shifting the reaction equilibrium.
"“These conditions are pretty nasty,” says Dumesic. Handling highly corrosive concentrated hydrochloric acid in an industrial process is no easy matter. But Mascal counters that “engineering know-how and materials science have advanced to the point where this is not a critical issue”. Dumesic adds that it could be challenging to remove all traces of chlorine from the final product, which is crucial if it is to be used as a fuel."
No, none of this is particularly problematic. The chemical industry knows how to do this stuff. They do more complicated and difficult things on a daily basis.
It seems to me that a sustainable fuel source is aborted Democrat fetuses. There is always a supply and they could be mashed up and fermented which should yield burnable fuel. What could be better than a Prius running on the owner’s aborted fetus? Now there is a true environmentalist!!!
Detailed Study on Spread of H.I.V. in U.S.
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Nitric acid...
Nitro cellulose = gun grass?
Chop it up fine, blow it into the cylinders, and diesel it?
If it works for grass, maybe it will also work for ‘grass’, giving the Hippies a use for their seeds?
I think that oil from ALGAE is going to be the best way to capture solar energy for transportation. Algae were the primary source of the fossil petroleum that we use today.
One pathway extracts raw algal oil from the dried algae, and processes it into biodiesel that is very similar to other plant oils.
The other pathway uses algae that produce a “green crude” - it is literally green in color - that can be fed directly into the petroleum refineries in use today.
In either case, the productivity of algae per acre is far higher than any land-based crop, and the requirement for fresh water is almost eliminated - most strains of algae grow in sea water, brackish water, or even sewage.
Innerestin’
thanks neverdem.
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