Started a new thread for the Hydrogen/fuel cell discussion.

One of many issues is that currently most of the commercial hydrogen is created from natural gas. Obviously this is still releasing CO2. In order to be carbon neutral, we would need to obtain it through renewable energy. This could be either thermally or electrically split from water.

I have.. a lot of views on it. They put me largely in favor of fuel cells for fixed locations, and electric (battery) for transportation, at least for the near term.

---

Janice

Yeah, hydrogen has its uses, primarily in fixed locations. If you have a source of hydrogen, for instance from using the waste heat from a nuclear fission reactor to crack water, it might make sense to collect it and use it to generate more electricity. Not very cost efficient at the moment, but doable. In my opinion, the hydrogen generated thus would be better used in various industrial processes than to generate electricity. It would be a non-carbon replacement for the natural gas (CH4) cracking frequently used today to produce hydrogen for industrial uses.

For transportation uses, electric vehicles are the winner, hands-down.

Started a new thread for the Hydrogen/fuel cell discussion.

One of many issues is that currently most of the commercial hydrogen is created from natural gas. Obviously this is still releasing CO2. In order to be carbon neutral, we would need to obtain it through renewable energy. This could be either thermally or electrically split from water.

I have.. a lot of views on it. They put me largely in favor of fuel cells for fixed locations, and electric (battery) for transportation, at least for the near term.

If I understand the cracking process correctly (and I could well be wrong), it uses heat and catalysts to convert methane (CH4) to carbon and hydrogen (CH4 + heat -> C + 2H2). No CO2 in the mix. I would imagine that if oxygen were to enter the mix you'd end up with a mix of C, CO, CO2, CH3OH, H2, H2O, etc. Also of note CO2 is less of a greenhouse gas than CH4 (as measured by it's ability to absorb IR radiation). So keeping it out of the atmosphere is a good idea too :).

---

I think you'll find it's a bit more complicated than that ...

the quick wiki on natural gas gives us..

Before natural gas can be used as a fuel, it must undergo processing to remove almost all materials other than methane. The by-products of that processing include ethane, propane, butanes, pentanes, and higher molecular weight hydrocarbons, elemental sulfur, carbon dioxide, water vapor, and sometimes helium and nitrogen.

As far as the methane to hydrogen portion(obviously an additional or different process) would release the C to the atmosphere during the "heat" and combine either with a single or double molecule of oxygen. So CO or CO2 would be an additional byproduct.

A side note, methynol can be used directly into a different design of fuel cells directly. Another technology that I am aware of, but not willing to delve into in this thread. It still might be superior to the internal combustion engine.

But the main point is, if we keep using fossil fuels, including natural gas, we continue to release greenhouse gases that have been trapped for ages, and that is just really bad timing for the situation we are facing.

---

Janice

the quick wiki on natural gas gives us..

Before natural gas can be used as a fuel, it must undergo processing to remove almost all materials other than methane. The by-products of that processing include ethane, propane, butanes, pentanes, and higher molecular weight hydrocarbons, elemental sulfur, carbon dioxide, water vapor, and sometimes helium and nitrogen.

As far as the methane to hydrogen portion(obviously an additional or different process) would release the C to the atmosphere during the "heat" and combine either with a single or double molecule of oxygen. So CO or CO2 would be an additional byproduct.

A side note, methynol can be used directly into a different design of fuel cells directly. Another technology that I am aware of, but not willing to delve into in this thread. It still might be superior to the internal combustion engine.

But the main point is, if we keep using fossil fuels, including natural gas, we continue to release greenhouse gases that have been trapped for ages, and that is just really bad timing for the situation we are facing.

Methanol... (CH3OH) Also known as 'wood alcohol'. Similar in structure to methane (CH4) but quite different in properties (due to the polar nature of the -OH group -- methane is non-polar), just replace one of the -H on the carbon with an -OH.

Re: CH4 cracking into hydrogen and carbon. In addition to the CO2 present as an impurity (alongside lots of others) in natural gas, care needs to be taken to avoid oxidation of the left-over Carbon. As you say, that can lead to additional CO2.

while not an expert in the process I doubt very much they leave carbon pellets behind. I would be very surprised if the process does not leave the carbon "oxidized".

It is simple, we need to leave fossils in the ground. split from water is the only CLEAN way to do it, either by heat or electrolysis.

Besides, the hydrogen comes out more pure, extending the life of fuel cells.

---

Janice

Started a new thread for the Hydrogen/fuel cell discussion.

One of many issues is that currently most of the commercial hydrogen is created from natural gas. Obviously this is still releasing CO2. In order to be carbon neutral, we would need to obtain it through renewable energy. This could be either thermally or electrically split from water.

I have.. a lot of views on it. They put me largely in favor of fuel cells for fixed locations, and electric (battery) for transportation, at least for the near term.

If I understand the cracking process correctly (and I could well be wrong), it uses heat and catalysts to convert methane (CH4) to carbon and hydrogen (CH4 + heat -> C + 2H2). No CO2 in the mix. I would imagine that if oxygen were to enter the mix you'd end up with a mix of C, CO, CO2, CH3OH, H2, H2O, etc. Also of note CO2 is less of a greenhouse gas than CH4 (as measured by it's ability to absorb IR radiation). So keeping it out of the atmosphere is a good idea too :).

It is fine that you wish to keep methane (CH4) out of the atmosphere. In keeping with that desire, I hope that you refrain from eating meat or dairy from certain animals -- specifically from cows.

In some parts of California, for instance, the cattle are so numerous in ranching operations that the methane (a natural byproduct of the cow's method of digestion, plus decomposition of their manure) that these cattle emit far and above exceeds methane emitted from all other sources in these areas.

From page 6 of http://animalscience.ucdavis.edu/extension/Factsheets/wmgt/ucce-dmms-4.pdf

Methane gas, a key component in the global
warming issue, is produced by both enteric feed
fermentation in ruminating animals and by the
anaerobic digestion of their manure. Estimates
vary as to the contribution of cattle-related
methane to total global greenhouse gases (2, 7,
10). Human activities which contribute to
atmospheric methane concentrations are rice
agriculture (110 Tg/yr; 27%), ruminant animals
(80 Tg/yr; 20%), biomass burning (55 Tg/yr;
14%), coal mining (50 Tg/yr; 12%), oil and
natural gas (45 Tg/yr; 11%), landfills (35 Tg/yr;
9%), and animal wastes (28 Tg/yr; 7%). Animal
waste includes ruminants and nonruminants.
Estimated contribution of U.S. animal waste to
global methane emissions is 4.2 Tg/yr or 14.8%
of the global livestock waste emissions. That
translates into less than 1% of the methane
emissions from human activities are a result of
U.S. livestock waste. It is estimated that U.S.
dairy cattle wastes are responsible for 30% (0.8
Tg/yr) of U.S. emissions or less than 0.3% of
global methane emissions.

That kinda puts things in perspective. Avoid rice too, rice being the BIG culprit planet-wide in methane emissions (over one quarter of the planet-wide total), as well as everything else on this list.

Think about it. Dairy cattle are responsible for 30% of the total methane emissions in the USA... 0.8 Tg/yr. That is 800 million kilograms of methane per year. From just dairy cattle in the USA. And the 800 million kg of methane per year is less than 0.3% of the total yearly emissions of methane worldwide.

CO2 isn't the only GHG problem we have.

Methane occurs. I have no problems with using that for fuel. When processing "natural gas" as in from the ground, it is being pumped up, not being taken from dairy farms.

The emissions from dairy farms is an issue, but not the largest. Most natural
gas is of fossil fuel origins, and genuinely better left in the ground.

Cracking natural gas for hydrogen gas is not helpful, it moves the problem.
In natural gas I (and most people) are referring to the fossilized natural gas.

http://en.wikipedia.org/wiki/Natural_gas_processing this has a small flow chart of the process. But I think it is fair to call it "messy".

The use of dairy/pig/chicken farm waste is a good subject for another thread. That is not how hydrogen gas is made now. Methane is a useful fuel for another thread.

---

Janice

Another facet to the methane problem. Methane, while a much more potent GHG than CO2, is much less of a problem.

Why? Because methane, in our current atmosphere, breaks down rather quickly due to the oxygen. While it is much more potent than CO2, it is in our atmosphere for a much shorter time than CO2.

But what does it break down into? Yes, you guessed it. CO2 (plus water).

CH4 + 2 O2 ---> 2 H2O + CO2

Ok, that information published by University of California, Davis, that I linked to and quoted in my previous post lists a total of 403 Tg/yr of methane emitted due to human activity. How much CO2 is this, per year, once all the methane is broken down?

Roughly, the mass of a carbon atom is 12 amu, and the mass of a hydrogen atom is 1 amu (I am dropping all the decimal places in atomic masses in these figures, and rounding off to the nearest whole numbers).

This means that of the 403 Tg/year of methane emitted, 12/16th of it, or 0.75 of it is carbon. That is 302.25 Tg/yr of carbon.

The mass of a carbon atom is 12 amu, and the mass of an oxygen atom is 16 amu. So this equates to a ratio of CO2 to C of 12+16+16 / 12 or 44/12.

302.25 Tg/yr of carbon * 44/12 is 1108.25 Tg/yr of CO2.

That is, the 403 Tg/yr of methane, once it has completely broken down, yields 1108.25 Tg/yr of CO2.

That is 1108250 million kg/yr of CO2 or roughly 1.1 x 10^12 kg/yr of CO2.

For ease of comparison, converting to Gt (giga tons (metric)) yields 1.1 Gt/yr.

Per the IPCC report of 2007, total human caused CO2 emission was 26.4 Gt/yr.

As you can see, the total CO2 from the breakdown of the methane emitted per year due to human activity is a significant fraction (~ 4.2%) of the total CO2 emitted due to human activity per year.

Something to think about next time you eat that steak or that bowl of rice.

Edit: granted this is a bit off-topic for this thread on hydrogen. However, methane was mentioned as a source for hydrogen, and I think it fair to demonstrate that methane is its own can of worms, and is better, as you say, left alone, Soft^Spirit.

methane is a good discussion. But it is not related to hydrogen other than chemical links. Please feel free to start a thread, and I may see you there Kong.

---

Janice

methane is a good discussion. But it is not related to hydrogen other than chemical links. Please feel free to start a thread, and I may see you there Kong.

I just might, Soft^Spirit. Back to hydrogen.

the quick wiki on natural gas gives us..

Before natural gas can be used as a fuel, it must undergo processing to remove almost all materials other than methane. The by-products of that processing include ethane, propane, butanes, pentanes, and higher molecular weight hydrocarbons, elemental sulfur, carbon dioxide, water vapor, and sometimes helium and nitrogen.

As far as the methane to hydrogen portion(obviously an additional or different process) would release the C to the atmosphere during the "heat" and combine either with a single or double molecule of oxygen. So CO or CO2 would be an additional byproduct.

Not so fast, if C were released to the atmosphere then what's to stop the H2 also being released? When cracking CH4, the C is precipitated (it becomes a solid). On reading the article I linked on catalytic cracking, one of the issues with that process is the accumulation of carbon on the surface of the catalyst leading to a gradual decline in efficiency.

On the numbers from MajorKong (and apologies for extending the atmospheric CH4 discussion a little), as one mole of one gas occupies the same volume as one mole of another gas (provided temperature and pressure are the same for the two different gases), it means that 403 Tg of CH4 occupies the same volume as 1108 Tg of CO2. CH4 is roughly 20 times as absorbent of IR as CO2 by volume, thus 403 Tg CH4 is approximately equivalent to 22,160 Tg CO2. Of course CO2 remains in the atmosphere for about 200 years compared to CH4's about 16, making it in the long term about 1/12 as significant a GHG.

BTW the primary sink for atmospheric methane is the reaction CH4 + OH -> CH3 + H2O. One would typically expect 2 CH3s to bond to form ethane (C2H6). CH4 + 2 O2 -> CO2 + 2 H2O is the outcome of burning CH4, not atmospheric decomposition.

Back to hydrogen ...

---

I think you'll find it's a bit more complicated than that ...

when they "crack" natural gas(fossilized to remain on topic) to make hydrogen,
the given is there. They are releasing H2.

All other components are either impurities or polutants. Unless you have specific information that leads you to believe the carbon is released in solid form, and which form, the assumption is that it would be released to the atmosphere as either CO or CO2, or other greenhouse gas.

Again, a BAD idea.

Why it is a bad idea is more than covered in other threads.

---

Janice

when they "crack" natural gas(fossilized to remain on topic) to make hydrogen,
the given is there. They are releasing H2.

All other components are either impurities or polutants. Unless you have specific information that leads you to believe the carbon is released in solid form, and which form, the assumption is that it would be released to the atmosphere as either CO or CO2, or other greenhouse gas.

Again, a BAD idea.

Why it is a bad idea is more than covered in other threads.

Natural gas, as you've noted is predominantly methane, and it's the methane in natural gas that is cracked. I think the article I linked (here the link again) on catalytic cracking describes the process of cracking reasonably well. If there were free oxygen in the cracking chamber, it would react with the CH4 and form CO2 + H2O. If there were any atmospheric venting from the chamber H2 would have to be released. So I think we can safely assume that little to no venting takes place. Thus C must precipitate, most likely at a sot like substance.

---

I think you'll find it's a bit more complicated than that ...

when they "crack" natural gas(fossilized to remain on topic) to make hydrogen,
the given is there. They are releasing H2.

All other components are either impurities or polutants. Unless you have specific information that leads you to believe the carbon is released in solid form, and which form, the assumption is that it would be released to the atmosphere as either CO or CO2, or other greenhouse gas.

Again, a BAD idea.

Why it is a bad idea is more than covered in other threads.

Natural gas, as you've noted is predominantly methane, and it's the methane in natural gas that is cracked. I think the article I linked (here the link again) on catalytic cracking describes the process of cracking reasonably well. If there were free oxygen in the cracking chamber, it would react with the CH4 and form CO2 + H2O. If there were any atmospheric venting from the chamber H2 would have to be released. So I think we can safely assume that little to no venting takes place. Thus C must precipitate, most likely at a sot like substance.

According to that article, the first paragraph describes commercial hydrogen extraction. As is. It mentions the carbon being released to CO or CO2.

Again, regardless of what the natural gas, coal, and petroleum people would like to tell us, fossil fuels are what we are trying to move away from.

Commercial production of hydrogen remains a dirty business, with the exception
of extracting hydrogen from water. Unfortunately the dirtiest methods are the most commercially favored. As long as they do not have to clean up their own mess.

Do keep in mind, the hydrogen in tanks, or any other form is merely a way to store and transport potential energy. It takes net energy to produce, and that is where clean and green alternatives become vital. generating hydrogen is one of many ways to store energy until it is needed.

---

Janice

when they "crack" natural gas(fossilized to remain on topic) to make hydrogen,
the given is there. They are releasing H2.

All other components are either impurities or polutants. Unless you have specific information that leads you to believe the carbon is released in solid form, and which form, the assumption is that it would be released to the atmosphere as either CO or CO2, or other greenhouse gas.

Again, a BAD idea.

Why it is a bad idea is more than covered in other threads.

Natural gas, as you've noted is predominantly methane, and it's the methane in natural gas that is cracked. I think the article I linked (here the link again) on catalytic cracking describes the process of cracking reasonably well. If there were free oxygen in the cracking chamber, it would react with the CH4 and form CO2 + H2O. If there were any atmospheric venting from the chamber H2 would have to be released. So I think we can safely assume that little to no venting takes place. Thus C must precipitate, most likely at a sot like substance.

According to that article, the first paragraph describes commercial hydrogen extraction. As is. It mentions the carbon being released to CO or CO2.

Again, regardless of what the natural gas, coal, and petroleum people would like to tell us, fossil fuels are what we are trying to move away from.

Commercial production of hydrogen remains a dirty business, with the exception
of extracting hydrogen from water. Unfortunately the dirtiest methods are the most commercially favored. As long as they do not have to clean up their own mess.

Do keep in mind, the hydrogen in tanks, or any other form is merely a way to store and transport potential energy. It takes net energy to produce, and that is where clean and green alternatives become vital. generating hydrogen is one of many ways to store energy until it is needed.

The points you raise here, Soft^Spirit, are spot-on. As far as Bobby's 'article' goes, it is the first page (only) of a paper on the subject, and I am rather reluctant to spend the $34 to access the entire thing. But, from what I know on the subject, the sort of catalyst used is a type of metal surface catalyst. After a while, the catalyst surface would be totally covered in the carbon and would stop working. The paper says as much. In later pages, they discuss a method they have devised involving 'partial gasification' to regenerate the catalyst. Sounds to me like it involves converting the deposited carbon to CO and/or CO2 gas, therefore right back where we started. Without reading the entire paper, I cannot know for sure, but similar methods are discussed in other papers on the subject, and they involve CO2 as the eventual form of the carbon when they are finished with it.

But, regardless of these issues, constructing the catalyst takes energy, as does the mining and processing of the raw materials to make it. And in the case of this particular catalyst, the Al present in it takes LOTS of energy to smelt out of the Al ore. Furthermore, this process takes place at an elevated temperature. 500C to 800C, per the paper. This takes energy. Also, the catalyst must be periodically regenerated. Again, this takes energy. Not to mention the likelyhood that the carbon will wind up as CO2. Also, the methane must be purified, at least somewhat, or the hydrogen output of this process won't be pure enough thus poisoning the catalyst in the hydrogen fuel cell. Again, energy. Also, the surface properties of the catalyst which enables it to 'crack' the methane will degrade over time. It won't last forever. Nothing does. Every period of time (of some or another length) you will need to totally replace the catalyst, further adding to the energy costs. And none of this includes any costs for construction and maintenance and infrastructure to support the site.

Adding up all this energy required to start and run the process, there is the very real possibility that it is a very sizable fraction of the possible energy yielded by the hydrogen. Why not just use the electricity (hopefully generated from non fossil-fuel sources) required to set-up and maintain this process directly, powering directly whatever it was you were going to use the hydrogen for?

About the only reason to 'crack' methane into hydrogen and carbon that makes any economic sense is if you need the hydrogen itself for some other industrial process as a raw material input... for instance, the production of ammonia?

... Furthermore, this process takes place at an elevated temperature. 500C to 800C, per the paper. This takes energy. ... Not to mention the likelyhood that the carbon will wind up as CO2. ... powering directly whatever it was you were going to use the hydrogen for? ...

The high process temperature is not too much of an issue. You can use heat exchangers to recover the exhaust heat to pre-heat the intake. Boost that with a heat pump and you lose very little energy despite the high process temperature.

The exhaust CO2 is advantageous in that the exhaust is in just one place. Ideal for sequestering away somewhere non-polluting.

Using the hydrogen to power whatever directly then only produces steam as the exhaust (no CO2 there).


The only problem with that scenario is in how to conveniently transport the hydrogen from the source plant to the multiple points of use... Hence the continuing development of hydrogen storage methods.

It's our only planet,
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

The fuel cells use what is called a Proton Exchange Membrane, Platinum based(PEM). When Hydrogen(or Methanol.. technology a bit different but same base principle) is placed on one side of the membrane, and oxygen(often just in the form of air, the other gases pass by fairly un-changed) on the other, the membrane allows the proton (naturally attracted to the oxygen) to pass through, but freeing up the electron to be passed to an electrical circuit, and doing some work before it re-unites with the proton. Once it does re-unite, it completes the water molecule, and the steam passes through.

Electrolizers simply (not through heat, although they can get warm) attrack the oxygen to one electrode, and hydrogen to the other. I have read of PEM's being used in this process as well, but I do not fully understand it. But this is a way to store energy. If it can be generated, and re-used onsite, there is no transport cost(other than perhaps some extra water, which contains a lot of storage capacity per gallon). Energy can be generated when available(wind/solar/tidal/etc) and re-used when needed.

in heat splitting(this can be dual purpose of cooling things, such as a nuclear reactor, although I am still not a fan) The hydrogen and oxygen are not naturally seperated, but since oxygen is heavier and hydrogen lighter, it can be jetted from the top and bottom of a chamber in fairly pure form. Of course once the heat is removed, any remaining is going to convert to water.

the "HHO" Gas( somewhat tongue in cheek reference to a conspiracy theory) can not be stored. Only the seperated gases will not re-combine. But the oxygen can be safely vented, And atmospheric air used as the oxygen source to re-combine.

And.. I am rambling.. probably enough for tonight.

---

Janice

Hydrogen will take a gigantic amount of power to produce. Only done through nuclear.

Suggest you talk to the tree-huggers at the EPA and the Sierra Club and start looking at reality.

when they "crack" natural gas(fossilized to remain on topic) to make hydrogen,
the given is there. They are releasing H2.

All other components are either impurities or polutants. Unless you have specific information that leads you to believe the carbon is released in solid form, and which form, the assumption is that it would be released to the atmosphere as either CO or CO2, or other greenhouse gas.

Again, a BAD idea.

Why it is a bad idea is more than covered in other threads.

Natural gas, as you've noted is predominantly methane, and it's the methane in natural gas that is cracked. I think the article I linked (here the link again) on catalytic cracking describes the process of cracking reasonably well. If there were free oxygen in the cracking chamber, it would react with the CH4 and form CO2 + H2O. If there were any atmospheric venting from the chamber H2 would have to be released. So I think we can safely assume that little to no venting takes place. Thus C must precipitate, most likely at a sot like substance.

According to that article, the first paragraph describes commercial hydrogen extraction. As is. It mentions the carbon being released to CO or CO2.

Again, regardless of what the natural gas, coal, and petroleum people would like to tell us, fossil fuels are what we are trying to move away from.

Commercial production of hydrogen remains a dirty business, with the exception
of extracting hydrogen from water. Unfortunately the dirtiest methods are the most commercially favored. As long as they do not have to clean up their own mess.

Do keep in mind, the hydrogen in tanks, or any other form is merely a way to store and transport potential energy. It takes net energy to produce, and that is where clean and green alternatives become vital. generating hydrogen is one of many ways to store energy until it is needed.

The article says:

Conventional processes for hydrogen production yield relatively pure hydrogen streams, upon conversion of CO to CO2 by the water gas shift reaction.

and:

For PEM fuel cells, traces of CO must be reduced to low ppm levels (typically below 5-10 ppm). The conventional process (namely steam methane reforming) cannot achieve such low concentrations of CO without the use of an expensive purification process

and:

The general equation describing methane cracking is:

CH4 -> C + 2 H2

There are two reactions in "conventional" steam methane reforming:

CH4 + H2O + heat -> CO + 3 H2
and
CO + H2O + heat -> CO2 + H2

Energy is also required in this process (nothing is free). There is a catalysis for these reactions, though it's platinum based and thus expensive. MajorKong, there's an older paper here that provides details of earlier experiments using direct catalytic conversion of CH4 into C and 2 H2, note that the catalyst can be reused ("regenerated samples show no significant decrease in methane conversion after up to 10 cycles of cracking and regeneration").

While direct conversion may not be the predominant commercial process, due to the additional heat requirements, there are places (e.g. nuclear energy plants) where such heat may be relatively cheap. I imagine that further research is underway to improve the efficiencies of the direct conversion path as it does not result in the production of CO2.

FWIW, I did start out by saying "If I understand the cracking process correctly (and I could well be wrong) ...". Seems there's at least three different cracking processes, (steam methane, "direct methane", and "direct steam") with varying heat requirements and catalysts. Of these three only steam methane results in the output of CO2, and "direct steam" does not explicitly require any fossil fuels (though the heat has to come from somewhere).

Adding up all this energy required to start and run the process, there is the very real possibility that it is a very sizable fraction of the possible energy yielded by the hydrogen. Why not just use the electricity (hopefully generated from non fossil-fuel sources) required to set-up and maintain this process directly, powering directly whatever it was you were going to use the hydrogen for?

Seems to me this is a critique of almost any form of energy production; in and of itself it does not strike me as a reason to abandon investigation of H2 fuel cells as a technology.

It is fine that you wish to keep methane (CH4) out of the atmosphere. In keeping with that desire, I hope that you refrain from eating meat or dairy from certain animals -- specifically from cows.

I am lactose intolerant, which pretty much rules out dairy products for me.

---

I think you'll find it's a bit more complicated than that ...