Posted on 02/23/2009 7:00:01 PM PST by Reaganesque
It sounds almost too good to be true: add a few bugs to food scraps and waste water to generate clean hydrogen fuel. But over the past few years, researchers have been gradually working toward this promising scheme for producing hydrogen.
Now, with the help of an unassuming stainless-steel brush, microbial electrolysis cells (MECs) have taken another step forward. The steel brush can be used to replace the expensive platinum normally employed in the electrolysis cell's cathode, slashing costs by more than 80 percent.
Hydrogen is an appealing, environmentally friendly fuel because burning it creates only water as a waste product. MECs harness the electrons produced by certain bacteria as those bacteria feed on biodegradable material. The bacteria sit on an electrode--the anode--as they metabolize organic matter in an oxygen-devoid chamber. Not being able to react with oxygen, the electrons travel from the anode to the counter-electrode--the cathode--where they combine with protons to form hydrogen.
In late 2007, a team led by Bruce Logan, Kappe professor of environmental engineering at Pennsylvania State University, showed that they could improve the efficiency of this process: by adding a small jolt of electricity (0.25 volts) at the cathode. Until now, however, the researchers have relied on a platinum catalyst on the cathode to make the process fast enough.
"The need to use a precious metal catalyst had been holding back further development of the technique, but now we have found a way to do it without platinum," says Logan.
Compared with platinum, which acts as an effective catalyst when applied in a thin layer to a flat piece of carbon cloth, a simple piece of stainless steel is two-thirds less effective. But when Logan's team increased the surface area of the stainless-steel cathode by arranging the material in the form of a high-density bristle brush, hydrogen production rates increased to values that matched or even exceeded those of the platinum cathode. While the platinum cathode costs around 15 cents, the stainless-steel brush only set the researchers back 3 cents.
Logan hopes that further modifying the chemistry of the brush will improve the results even more. "We now already know more about which types of stainless steel work best," he says. "And we will also want to minimize hydrogen bubbles being trapped between the bristles because this can make recovery of the gas less efficient."
He also emphasizes that high surface area is not everything. A brush made from carbon with an even higher surface area did 14 times worse than the naked steel-brush core, and when the researchers cut the steel brush in half to allow closer spacing of the two electrodes, they got even better results than with the full brush, even though they lost half of the surface area.
Lars Angenent, an associate professor of biological and environmental engineering at Cornell University, says that big challenges remain, and he argues that the effect of electrode spacing is going to be one of the biggest limitations of MEC technology. "I think this work is great, but the next question is, can you scale it up so it's economical?" he says. "In a larger system, moving ions through liquid between cathode and anode is more difficult, so you will produce less hydrogen per unit volume."
Patrick Hallenbeck, a professor of bacteriology at the University of Montreal, in Canada, agrees with Angenent that scaling will be a challenge. However, he is optimistic that with the platinum limitation gone, the outlook for MECs is good: "By showing that platinum can be effectively replaced by stainless steel, Logan's group have removed a critical barrier. These devices were first described only four years ago, and there has been tremendous progress since then. Further developments may very well move MEC devices into the realm of practical application."
I used to have a boxer named scraps but I don’t think he produced hydrogen.
Methane, maybe. ;-)
But but but but but...water vapor is a GREENHOUSE GAS! As soon as this is developed, some greeny lawyers will petition to ban it...
Hydrogen is the most abundant element in the universe. There are vastly easier, cheaper, faster, and more ecomonical ways of getting it than from microbes.
I’m curious how that “small” amount of electricity they have to supply to it compares with the net amount of energy harvested after completing the process and accounting for the real-world percentage of energy you get back burning the hydrogen.
Hope it’s not another fan-powered-windmill powered fan.
They always run into the same problem, it costs more to make the hydrogen than what can be produced by burning it. Reason?
They keep ignoring the universal law of increasing entropy.
>But but but but but...water vapor is a GREENHOUSE GAS! As soon as this is developed, some greeny lawyers will petition to ban it...
You’re probably right.
Contains MUCH more energy that H2.
But I'll bet he produced methane (CH4) in abundance...
No doubt. These global warming "scientists" -pimple faced geeky Jr. High students parroting the idiotic theories of a failed "scientist" who had to become a teacher because he couldn't cut it in the real world- are too stupid to realize that what is LACKING in our atmosphere IS greenhouse gas- WATER VAPOR! Without water vapor there is insufficient snowfall at high altitudes which make the glaciers grow and form the arctic ice pack.
These idiots are too stupid to realize that ice does NOT melt at -50 below, and even if there was a TEN degree "global warming", ice STILL will NOT melt at -40 below.
Ice does however, evaporate at -50 below, and also at -40 below. The rate of evaporation depends on how much humidity there is in the air. Cold dry air vaporizes snow and ice faster than cold but humid air.
So actually we could USE some global warming to produce more water vapor in the atmosphere, and therefore more snowfall. Unfortunately, we are experiencing global COOLING, which has been decreasing water vapor, especially at northern latitudes and higher altitudes where it's needed.
Unfortunately, too many people believe that show is based on some sort of reality.
And now they are running the country.
But it keeps them going. After all if we just burned oil cleanly and cheaply so many fewer professors and big companies would get research dollars.
lol I thought the greenies thought fossil fuels were evil, and hydrogen was going to be the savior of the planet. Now they are going to throw hydrogen under the bus so to speak? So that would leave them with wind and solar. If there was a miracle of innovation and solar or wind were capable of solving the worlds energy needs would the greenies once again have a problem with either of those? One must then wonder, why do the greenies want the human race extinct, including them also? Stranger still is they don’t believe in a God so you’d think they would never want to die.
The Sabatier reaction has H2 and CO2 reacting in the presence of a catalyst to form CH4 and H2O...4H2 + CO2 = CH4 + 2H2O
Then we could distribute the methane and really drive the enviros nuts!
Sure - it’s abundant, but in the wrong form. The energy which has to be invested in converting the abundant form of Hydrogen to pure H is the stumbling block. A lot of effort is going into end-arounds on this problem. I say, right on.
We’ve already hit on the perfect clean energy with hydroelectic. No waste no toxins.
Granted it doesn’t power cars but a huge chunk of our energy needs could be met by more hydro. Unfortunately we’re tearing dams out now to allow fish to swim upstream.
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