Driving on Starch

Roland Piquepaille writes "Using sugar contained in corn or potatoes to build hydrogen-powered fuel cells has already been done. But now, a team of U.S. researchers has developed a new sugar-to-hydrogen technology. Why not put the starch inside the tank of your car? With the help of 13 specific enzymes, 'a car with an approximately 12-gallon tank could hold 27 kilograms (kg) of starch, which is the equivalent of 4 kg of hydrogen. The range would be more than 300 miles, estimates one of the researchers. One kg of starch will produce the same energy output as 1.12 kg (0.38 gallons) of gasoline.' The beauty behind this idea is that no special infrastructure would be needed. Starch could be distributed by your local grocery store."

from the article

[wizardforce]

The abbreviations are: PPP, pentose phosphate pathway; G1P, glucose-1-phosphate; G6P, glucose-6-phosphate; 6PG, 6-phosphogluconate; Ru5P, ribulose-5-phosphate; and Pi, inorganic phosphate. The enzymes are: #1, glucan phosphorylase; #2, phosphoglucomutase; #3, G-6-P dehydrogenase; #4, 6-phosphogluconate dehydrogenase, #5 Phosphoribose isomerase; #6, Ribulose 5-phosphate epimerase; #7, Transaldolase; #8, Transketolase, #9, Triose phosphate isomerase; #10, Aldolase, #11, Phosphoglucose isomerase: #12, Fructose-1, 6-bisphosphatase; and #13, Hydrogenase.
it looks like they built it like this: starch=>glucose [amylase]=>glycolysis=>pyruvate decarboxylation=>TCA cycle and finally liberating the hydrogen from protons and electrons from the TCA. I wonder from this is how they deal with the enzyme's need for cofactors, corrosion, stability of enzymes and side reactions. it looks promising for sure but it looks like they have a lot of work ahead of them. there is also the problem of the starch settling in the tank and thus being unavailable for the reaction unless that is where it happens in that case what about H2 build up? lastly, with the problem of corn shortages being possible for ethanol, what exactly will happen when starch is used instead as it is also taken from food plant sources?

Re:Cue the "hydrogen is not a power source" chorus

[Raptoer]

You're right, it is not a power source. Nothing is a power source if we were to take it to a certain degree, oil based products got their energy from the sun, so does ethanol, and this new system using starch.(the sun gets its energy from the fusion, so I guess you could say that is a power source, but that gets its power from the mass, which gets its power from... well... magic!)

But the real important thing is turning it into a form of energy that we can use. We cannot use the sun's energy directly, we instead use plants (corn/sugar for ethanol, or long dead plants for oil) that changes it into chemical energy that we change into a different chemical energy that is then used for kinetic/thermal energy to drive our cars, which then goes entirely to thermal in the form of friction.

Enough with being pedantic and onto the being practical.

Oil is a power source in the sense that it is readily available stored energy. The difference between it and hydrogen is that hydrogen manufactured through electrolysis is manufactured at a 1:1 ratio of energy put in verses energy removed (under perfect conditions). This starch process allows hydrogen to be produced at a rate much closer to a perfect 0:1 (from our point of view, yes I know energy cannot be created) which is similar to oil.

The question now is, are there enough of these enzymes to go around? Does processing the starch via enzymes leave a byproduct which ends up in our cars? will people be willing to modify their cars to run on hydrogen (a fairly simple process, but try convincing someone of that)? will there be enough starch to go around? In other words, yes it works out chemically, but does it work out practically?

Re:Question

[normuser]

From your comment:

Yeah, someone isnt thinking energy alternatives through again. 1,000 people a day probably visit my grocery store. How are they going to pull 13 gallons of starch each? Where will by store put 13,000 gallons a day. In the cereal aisle?

From TFA:

A car with an approximately 12-gallon tank could hold 27 kilograms (kg) of starch, which is the equivalent of 4 kg of hydrogen. The range would be more than 300 miles

So all of these people drive 300 miles a day?
I see your point regarding the supply of starch to all the people in a givin town, but exagerated statements just make me wonder if you actually RTFA.

Re:Required Post: ER/EI

[wizardforce]

you are correct that you put more energy into a system in this case hydrogen production than you get out but hydrogen is meant to be an energy carrier not a true energy source. it is useful when your battery technology relies on crummy Ni/Cd or lead acid technology. it's useful when you can make more usable power from gasoline once it has been converted into hydrogen and carbon dioxide. it isnt the least bit pathetic as you suggest.

Very impressive.

[Gibbs-Duhem]

Now, I know this probably will never get seen by anyone, but none of the posts so far were appropriate to reply to.

I am actually a bioengineer, and I'm actually working in this field, trying to convert ethanol into hydrogen.

And I can say, this process looks excellent. Finding natural enzymes that do the conversion makes everything enormously easier.

Here's the deal. Ethanol has slightly more energy than straight sugar, because the fermentation adds energy to the system. That added energy is negligible in comparison to the total energy. However, you lose a butt-load of energy because you have to heat the sugar up in order to ferment it, deal with transportation costs for the crops, and if you're using it as an additive (instead of reforming 20-25% ethanol in water directly), distill it to 100%, which uses a ridiculous amount of energy (10 times more to get it from 95-100 than from 20-95). However, the plus side is that ethanol is a pretty high energy density liquid, about 85% that of gasoline, and much higher energy density than compressed hydrogen gas. So, with an ethanol+water mixture, you end up getting 6 H2 out of every one etOH molecule. Pretty durn good. (if you think I'm an idiot because I have more hydrogen coming out than are on an ethanol molecule, look up steam reforming instead of making yourself look like a fool)

However, at the end of the day, it's extremely questionable whether or not ethanol itself is net energy positive, because of all the energy that goes into producing it (even though the liquid itself increases in energy density). Sugar, however, is less refined, and so less energy goes into making it. The idea is this -- if the net energy is negative, then you're still using more fossil fuels than you save. But if sugar is energy positive, then you can use 1kg of sugar to produce 2kg of sugar, and use that to make 4kg of sugar, and so on.

Sure, you have to pay attention to the problems of rising food costs. But starch? Don't worry about it, it'll be more efficient than gasoline, and it'll be more efficient than ethanol. You're talking a 3x fold improvement on efficiency right off the bat because it's a fuel cell instead of an I.C.E. Now, your sugar production has to be net energy positive, so multiply that factor (guess would be around 2-3) times the 3x fold efficiency improvement in the fuel cell and you're using 6-9 times less energy to produce the same amount of work. The economy will figure out the rest -- hell, you can get starch out of all sorts of crop waste way more easily than you can get ethanol out of them.

Re:Question

[Anonymous Coward]

The question is - how many gas stations are there and how many grocery stores are there.

Right now, the US consumes about 9.3M barrels (390M gallons) of gasoline [doe.gov] per day. That's per capita, annual consumption of about 468 gallons (3000 pounds) per year. By comparison, in 2004, US consumers bought 192 pounds of grains [usda.gov] per person.

You're not going to "fill up" your car at the grocery store the way grocery stores exist now.

Re:Roland the Plogger again

[Animats]

Read the research web site [vt.edu], not the press release or the Roland the Plogger misinterpretation. This research involves several approaches of cracking cellulose from agricultural waste down to something more useful. Starches and cellulose are both glucose chains.

The back end of the process is supposed to be a scheme for getting hydrogen from sugar. Their goal is C5H10O5 + 7 H2O --> 12 H2 + 6 CO2, driven by some synthetic enzymes. But they're vague on how far they've actually progressed in this direction. The web site references published papers for the cellulose research, but not for the hydrogen-from-sugar scheme.

"Diesel", the word you're looking for is "Diesel"

[Joce640k]

Diesel engines are available now, get *way* better mileage then gasoline engines, are absolutely prefect for SUV-sized vehicles whose owners are convinced they might need to tow something or go off-road, and we know how to make it with almost zero-sum CO2 emissions from human waste.

Most people wouldn't even notice the difference between gas/diesel SUVs unless you told them.

So:

a) Which part of that isn't "win"?

b) Which part doesn't make "starch" or "ethanol" look like a silly idea?

Re:Very impressive.

[Gibbs-Duhem]

You're right! The reason is actually extremely subtle. I was talking about enthalpies of reaction. The gibbs free energy (i.e. the important one), however, goes down. All values are kJ/mol. Enthalpy is the relevant free energy when pressure is constant, but your reactor doesn't allow heat flow (i.e. entropy is constant). Gibbs is the relevant free energy when pressure is constant, and your temperature is constant. Not really sure which is applicable to the fermentation itself, but certainly after temperature is equilibrated (which has to happen sooner or later), the ethanol will have less energy per mole than the sugar.

6CO2 + 10H2O -> C6H12O6 + 4H2O (\Delta G = +2830, \Delta H = +2540) (photosynthesis)

C6H12O6 + 4H2O -> 2CO2 + 2 etOH + 4H2O (\Delta G = -210, \Delta H = +20) (fermentation)

2CO2 + 2 etOH + 4H2O -> 6CO2 + 10H2 (\Delta G = -330, \Delta H = -140) (reforming)

Neat. I hadn't really noticed that before, since I only really deal with the reforming step. Thanks for pointing that out.

Re:Question

[Rei]

Not only is the infrastructure already there, but it should scale nicely, too. As the article notes, running a starch/hydrogen car is three times more efficient than an ethanol/IC system. So, if you could replace a third of our current needs with corn ethanol, you could replace all of our needs with starch/hydrogen. The reason is pretty simple. You lose energy in brewing ethanol (the source is still the corn starch), and then you burn the ethanol at ~30% efficiency. With starch/hydrogen, you skip that step, lose a little in the hydrogen generation, then use the hydrogen at ~70% efficiency in a fuel cell. Plus, since the car is really electric, your car automatically can use the benefits of a hybrid (regenerative braking, no wasted energy while stopped, etc)

I'm really fond of this idea. It's a lot more realistic than the aluminum one.