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Carbon Dioxide (CO2) as a fuel.
  [vote for,

Absorb CO2 from the atmosphere, then combine it with H2 or Water and get Methane: 2H2+CO2--Ni->CH4+O2 or 2H2O+CO2--?->CH4+2O2. Then burn it, recycling the CO2, or reform it into hydrogen for electrolysis, fuel cell.

Combine : a solar panel, a battery, a CO2 absorber [Ca(OH)2 + a heating element], a tank full of distilled water, a Nickel filled reactor, some gas seperators, and some pumps,

...and you've got an engine that will produce electricity till all the trees die and noone can sleep.

gustable, Jan 31 2003

don't confuse carbon dioxide with its monoxide cousin http://www.nationalcenter.org/NPA334.html
[po, Oct 04 2004, last modified Oct 06 2004]


       If CO2 is declared an undesirable gas, does that mean we will all have to stop breathing out? Or only in California?
DrCurry, Feb 02 2003

       Well, yes, but if you read the small print in the bill, the only person it applies to is your good self, Doctor ......
8th of 7, Feb 02 2003

       if CO2 is so bad, why are victims of panic attacks told to breathe and rebreathe into a paper bag. do we hate them *that* much?
po, Feb 02 2003

       so it cannot be that bad then?
po, Feb 02 2003

       I thought that people who were hyperventillating had too MUCH oxygen in their blood, and that breathing into a paper bag lowered their blood oxygen level. But, not being a doctor, nor even researching this, might make you wonder why you're still reading this.
Overpanic, Jun 18 2003

       They have plenty of oxygen but too little carbon dioxide. Fast breathing like UB describes blows off carbon dioxide more effectively than it takes in oxygen. Low carbon dioxide levels make people feel buzzy and weird. Breathing into a paper bag recycles your own CO2; you breathe it back in. Plus it gives people who are wigging out something to do.   

       But I think I am going to bone this idea. The first step costs more energy than the last provides.
bungston, Jun 18 2003

       Bungston has it right. The combustion of methane and oxygen to produce CO2 and H2O is an exothermic reaction (gives off energy), therefore the combination of CO2 with H2O to produce methane is an endothermic reaction (absorbs energy). You'd have to provide this energy somehow, plus some additional energy to force them together, since the reaction is not spontaneous.   

       Disclaimer: IANAC
Perhaps you could use solar energy to electrolyze water into H2 and O2, and electrolyze high-pressure liquid CO2 into O2 and graphite. Combine the graphite and hydrogen at high pressure and high temperature to form hydrocarbons.

       I think that the energy put into forming the hydrocarbons could be used much more efficiently by powering something directly, instead of going through the conversion process.
Freefall, Jun 18 2003

       //The first step costs more energy than the last provides.// Who cares? Sure, if you're trying to use the energy directly you'd just stick with the solar panels. But the point here is using it as a fuel. Storable energy is much more valuable than available energy for uses such as transportation.   

       Gasoline is used because it's a high energy storage medium that you can take with you. If you're stuck with solar panels, you have to walk on cloudy days. The problem is that we are a) going to run out of fossil fuels and b) probably going to ruin our world first with all of the greenhouse gasses produced by burning fossil fuels.   

       This idea is suggesting the creation of a portable fuel. Sure, it's much less energy dense than gasoline, but more energy dense than hydrogen - the alternative. The other benefit to this over hydrogen is that it is possible that hydrogen is a bit of a greenhouse gas as well.
Worldgineer, Jun 18 2003

       but where do we get the energy to reform the CO2 and water into hydrocarbons in the first place? Why would we want to do anything to reduce the efficiency of our energy conversion? If our goal is to reduce our use of fossil fuels, then feed the original source power back into the grid and reduce the load on existing power stations. My point is that CO2 is already a low-energy-state compound, and that putting energy back into it just so we can store it and burn it later with yet another massive conversion loss is pure foolishness.
Freefall, Jun 18 2003

       Well, the usefullness for this idea assumes we can get to a state where anything you plug in can be powered in a renewable way. The problem is then with everything that can't be plugged in. Batteries work for very low powered applications, but they have a relatively low power density and have toxic componenets. For higher energy applications - take shipping for example - batteries just won't cut it.
Worldgineer, Jun 18 2003


       I always liked the idea of really big sail boats... perhaps even with zeplin style balloons to reduce drag in the water.
madness, Jan 17 2005

       //increased CO2 levels are thought to be the reason for global warming, hence the lawsuits to have industrial production limited//   

       When I went to sleep in the mid 90's global warming was being caused by a hole in the ozone layer, now I wake up to find our that it is CO2 instead. Hmm I wonder what it will be in another 10 years? Maybe like Worldgineer said, it will be hydrogen, since cars and industry will be using it a fuel at that time. While I'm not going to bone this idea, it does sound a lot like perpetual motion.
dlapham, Jan 19 2005

       [dlap] I think the real problem is that you're confusing two global issues.   

       1. Hole in the ozone. Chemicals like chlorofluorocarbons (CFCs) float up to our upper atmosphere and react with ozone, breaking it down. The problem with that is that when it goes, we won't be protected from the sun.   

       2. Global warming. Chemicals like carbon dioxide help reflect heat that should excape from the earth and acts like glass in a greenhouse ("the greenhouse effect"), letting light from the sun in but keeping heat from radiating back out. The problem with this is that the global temperature is rising, which will create all kinds of mischief from climate change to raising the ocean levels.   

       You're not the only one to mix them up, but please don't assume because you don't understand the science that it's wrong. No scientist in the 90's thought the ozone hole caused global warming - it was just you. If you have a theory about Hydrogen causing global warming, I'd be happy to hear it.
Worldgineer, Jan 19 2005

       Hi you all!   

       I read the 'warm' discussion above, and I have learned a couple of things, and would like to put a couple of questions too (which usually happens when you get waylaid by science or engineering).   

       1) Okay, the upper performance limit for 'fuel' production is within the 38-40% range in plants' chloroplasts and algae. No everyday life automobile engine beats 20% aftermaths -I am told (later corrected: diesel machines can achieve 40% yield). Plants and algae they take up CO2 + solar energy, then convert them into 'biological fuel' (for example, 'sugars', which are half-alcochol, half-hydrocarbon compunds -all of this in a nutshell, of course). That used to happen millions of years ago, and continues to happen today. Reduction of those compounds (by replacing -OH alcoholic groups with -H), which renders hydrocarbons, is the only fossil yield we will ever get from the past.   

       2) Now for the 'Apollo 13' movie scheme: they needed to recycle CO2 into O2 at no cost. They came up with an adsorbing material -can't remember the catalytic metal- and NaOH. So CO2 was trapped there, while O2 was released. Generalization: No matter which oxidation state you start at (CO2 is 'completely reduced'): as long as your global yield / energetic performance is positive, you've got a recycling reactor. In fact, even living cells use a fast 'energy-wasting' step at the start of the glycolitic pathway. All your cells can use glucose . Adenosine Triphosphate (ATP) activates Glucose by adding a Phosphate group onto it. This rises the whole molecule free energy, and renders ADP (Adenosine Diphosphate, to be recycled elsewhere) + Phospho-glucose. The rest of of the glucolytic pathway is energy-releasing (a higher number of ATP molecules are released than are taken up; the overall balance is positive). If necessary, glucose can also be completely 'burnt' (oxydized) into plain CO2 + H2O, which we breathe out -some of you already pointed this out -no details here, because glycolysis is a bit more complex than that.   

       So, learnt, take-home message, overall performance matters the most. Hehehe, isn't it ironic Platinum (Pt) is the best AND most expensive catalyst for H2 reactions? Even more expensive than pure gold (symbol, Au). As if nature was sending a 'dead end' warning on those research lines.   

       Questions: 1) Why do people keep on trying to figure out low-to-affordable cost fuels? If the exhaust is CO2-rich (or any other greenhouse gas, GHG-rich) then research on those areas is interesting, but far from profitable (can't see the octane index for CH4 -methane- because it is sooooo low at the bottom of the table). AND, you still get the greenhouse effect out of the whole thing!   

       2) On the other hand, I must tell the truth in whole, so please forgive my biological background again: all animals can be considered as 'automobiles'. They take up fuel (food), and oxidize (burn) the compounds to the fullest extent, if needed -> CO2 + H2O (+ 'reducing power', not to be covered here). Energy production takes place in mitochondria (subcellular organelles in our cells which can be looked at as efficient, ATP-producing power plants). ATP is kown as the 'energy coin for living beings'. Figure out what the performance is? You're right: close to the 40% threshold. Sounds like a joke, only it's true: thermodynamics tells us we are automobiles running on either fat or sugar fuel!!!! (fatty acids are hydrocarbons just about 3 times longer than octane plus a -COOH cap; sugar can be described as semi-alcohol fuel under 'aerobic' cycle).   

       (Written after a bit of wikiwalking:) I guess "ready-made" fuels should follow the sugar-like rule. That is, we already have ethanol-fueled cars, out of fermentation processes which occur in nature. But a 2-carbon-atom alcohol (CH3-CH2-OH, or C2H6O) is poorer than octane: CH3-(CH2)6-CH3 = C8H18). Glucose is C6H12O6. Might as well do as it can be readily converted in vivo into glycerin = 1,2,3-propane-triol (directly used as biodiesel)
mayihave, Jul 27 2007


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