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From: J Thomas on 18 Jan 2010 16:15
Bill Miller wrote:
> "J Thomas" <jethomas5(a)gmail.com> wrote
>> Bill Miller wrote:

> Here is a better link to the experiment itself:
>
> http://www.gasresources.net/AlkaneGenesis.htm
>
>>> http://www.gasresources.net/

Your other link gave a link to that.

>> I'm not an expert in any of this. My own background leads me to think
>> in terms of biological transformations that are hard to study in the
>> lab.
>>
>> Any time there's an exothermic chemical reaction involving chemicals
>> that could adsorb to a bacterial cell, there's the possibility that
>> there are bacteria which use that reaction for their own energy. In
>> practice the bacteria that use the reactions that release the most
>> energy will tend to dominate, and if there are enough of them to
>> support something that eats bacteria, then the slow-growing bacteria
>> may get eaten faster than they can reproduce. So bacteria that slowly
>> convert carbohydrates to hydrocarbons and water might survive well in
>> lignite beds where they grow slowly but nothing else grows faster. And
>> bacteria that slowly convert linear hydrocarbons to polycyclic
>> hydrocarbons and methane might survive there. Etc. But it's hard to
>> study such things in the lab, because if you study bacteria that have a
>> doubling time of a few months then your grant is likely to run out
>> before you get results.
>
> Understood. *If* a biotic process exists and is s l o w enough, then not
> only might the grant run out, but also the sands in the researcher's
> great hourglass!
>
>> So if you have organics trapped underground at a depth where bacteria
>> can grow, it makes sense that they'd produce many of the things in
>> petroleum, and those things would head upward if they could, and some
>> of them would get trapped before they reached the surface. Methane that
>> came from lower levels and also methane produced near the
>> petroleum/water interface would tend to push petroleum out of the trap.
>> Methane would also leave the trap both at the bottom and through
>> whatever joints let it through.
>>
>> As a handwaving exercise it makes perfect sense that some of the oil
>> would have a biological origin -- if there are biological materials
>> that oil could be made from, oil will be made from them. Places that
>> get too hot for bacteria might possibly create oil inorganically.

Though the paper you linked to says that it won't happen without great
pressure and temperature, and maybe a sudden drop in temperature but not
pressure is also required.

>> Petrogeologists who find oil can usually point to a source strata that
>> they think supplied biological carbon. That isn't proof, of course.
>> Also they use that thinking when they look for oil so it's all biased
>> samples.
>
> Yeah. Kinda like the drunk that was looking for a dropped quarter under
> the street light rather than in the dark alley where he dropped it. If,
> by chance the quarter rolled out of the alley and under the light, then
> for the rest of his life he'd look for quarters where the light was
> better.

They have often found oil that way. They ought to do a statistical
analysis and notice how the times they have drilled with "better" sources
versus "worse" sources to get some idea how much difference that has made
to results. Of course, they can't be sure about how good the sources
actually are, so this will not say how much their sources really affect
the results, but if they find that the predictions of oil sources don't
have much effect on their results then they should give them lower weight
or maybe no weight when choosing where to drill next.

Unfortunately how they choose where to drill is mostly proprietary
information so we can't very well tell how they actually make those
decisions. Although perhaps if the information about where they actually
drilled and some estimate of their results is public we could try to
reverse-engineer it.

At any rate, starting from two entirely different theories about how the
oil got there, both approaches have found a lot of oil.

>> If you figure that the amount of methane etc that has been produced
>> must have been far more than the amount that gets trapped, it would
>> require a very different sort of seafloor in the old days. Much of the
>> seafloor must have been anaerobic, and there would be a thick rain of
>> dead stuff falling onto it. Modern oceans appear to produce less than a
>> millimeter of sediment per thousand years. If that was the original
>> source for the oil, we are no longer making very much of it.
> >Presumably for some reason
>> the oceans in those days were very productive while now they are
>> comparatively dead.
>
> I've seen some figures indicating that CO2 was at least 10X as plentiful
> during the Triassic (3000 ppm) than today. That alone would seem to
> account for a *much* more active accumulation of carbonate-bearing
> detritus than what we see today. (Although if atmospheric CO2 continues
> to increase, then we should expect to see an acceleration in aquatic
> detritus "fall" as more available Carbon is trapped in shells and bones.
> )

The more CO2 in the oceans, the less of the carbonate reaches the bottom
-- the small stuff gets dissolved as it sinks. A higher proportion of
silica exoskeletons would reach the bottom, along with lots of organics.
That might give us enough biological stuff to make oil from. Old oceans
would be very different from today's oceans. For that matter, 10X CO2 in
the air would not be very good for human beings. Let's hope that such
times don't return before we go extinct.

> BTW Saturn's moon, Titan seems to be "awash" with liquid hydrocarbons.
> It stretches credibilty that this petrochemical accumulation might also
> be biotic-caused.

The key fact there would be that Titan has so much of the stuff. If they
have lots of life then the life could rearrange things, in the same way
that it's claimed our high-oxygen atmosphere came from life. But Titan
would have to have the precursors regardless of the details of what
arranged them.

>> I looked over the link you provided. It sounds like the alternative
>> idea is to create hydrocarbons using the earth's heat as an energy
>> source.
>
> Correct.
>
>>The
>> carbon would come from, say, CaCO3 while the hydrogen would come from
>> H2O. I can imagine that this could happen, but to get one CH4 this way
>> you would have 1 Ca and 7 O left over.
>
> Please take a look at the link above. It shows what happens to the
> "extra" Calcium and Oxygen that you have postulated.

I don't see that it does. They said they used marble instead of graphite
because it's more oxidised and of lower chemical potential, to make the
experiment more "conservative". I don't see anything there about what
happened to the Ca or O. Maybe make highly alkaline calcium hydroxide, to
use the Ca and 2O and maybe one H? Make 5 or so hydrogen peroxides?
Oxidise the iron further? I was thinking in terms of carbonates from the
sea bottom getting subducted to a depth they could turn to hydrocarbons,
but maybe before that point the oxygen would already get separated out.

Anyway, they aren't obliged to have every detail worked out. It's
plausible something like this could happen, even though I don't see
exactly how it would go.

>> The oxygen would need to be
>> sequestered somehow because if it left the mantle with the CH4 then the
>> CH4 would be oxidised as soon as it reached bacteria that were ready
>> for it -- which typically happens at the surface, where there is
>> oxygen.
>
> That's only correct if the process is as you suggest -- with extra bits
> left over.

They calculated energy levels for various hydrocarbons assuming there was
sufficient hydrogen to turn it all into methane and no oxygen. Would the
energy levels of oxygen-containing compounds matter? It looks to me like
their analysis is incomplete to describe the experiment they did.

>> Their argument is that oil must have been produced at high temperature
>> and pressure, higher than the supposed biological sources could have,
>> because that's the only way to create molecules bigger than ethane.
>
> No. The arguent is that there is s dirth of eveidence that significant
> amounts of big molecules *are* sourced biotically. And there is
> laboratory evidence supporting the idea that abiotic petroleum *can* be
> made.

They argue that these molecules could not be produced at low temperatures
or pressures.

> It also raises a question that is more philosophical than
> physical/chemical. *If* big "organic-like" molecules *can* be made using
> an abiotic process, then we would seem to have a ready source of
> life-precursor materials.

That's already done. There are multiple ways to get organic molecules.

> Significant amounts of hand waving are allowed and expected in any reply
> to this!
>
> .>But
>> they are clearly wrong because bacteria easily produce molecules bigger
>> than ethane at temperatures not much above the boiling point of water,
>> and others consume them at room temperature when they have oxygen.

They say that nothing but methane and some ethane can be produced at less
than, say, 30 atmospheres and 1000 K. However, all living things produce
linear alkanes with up to 28 or so carbons, that each have a carboxyl
group on one end. The carboxyl group makes them easy to add to (and
subtract from), and it has some other useful properties. These fatty
acids are necessary for cell membranes, which each cell has pretty much
of.

When cells burn stuff for energy using oxygen, the final products tend to
be CO2 and H2O because they can get a lot of energy that way, enough to
work at getting rid of the CO2. When they operate anaerobically, they get
far less energy and they have to excrete their waste products against a
gradient of those waste products. So when the external concentration of
one waste product gets too high, then it makes sense to make a different
waste product even if they don't get as much energy from that reaction.
So for example, bacteria etc that grow on glucose without extra oxygen
tend to make a variety of products. Lactic acid, ethanol, butyric acid,
etc. They tend to make all the profitable waste products they can, in the
ratio that gives them the maximum energy after accounting for the cost of
excretion. Making petroleum would be similar. They'd juggle the oxygen
atoms to the places they could do the most good, and juggle the hydrogens
likewise. Also any excess sulfur. I'd hypothesise (without any real
evidence, the evidence might be there but I haven't looked) that such
bacteria would clip off the oxygen-carrying carboxyl groups to use them,
leaving the less-useful aliphatic chains "for later". (The assumption is
that they're using biological debris, which would include lots of fatty
acids.) The bacteria would be mostly living in the brine, perhaps
adsorbed to rocks, and the oil would rise into its own layer and so
reduce the gradient problem.

So, you have a fatty acid with a CO2H on one end. If you somehow stripped
the O2 off you could put 3H on the bare C and 3H on the O2H. You can get
6H by taking 3 methane molecules and adding them to the fatty acid first.
Do you get more energy by making two H2O than you lose by combining 3
CH4? I think so, provided there's plenty of methane available. But of
course the devil is in the details. This isn't the usual way to add to a
fatty acid. The usual way is to add an acetyl group in 4 steps, and the
acetyl group can come from anywhere -- for example, from glucose.

You could have lots of biological products that don't wind up in the oil,
if they precipitate out easily or are heavy. Have such things been found
at the bottom of the brine below an oilfield? Of course there doesn't
have to be any bottom....

I find either approach sort of plausible. Or a combination. If you get
abiogenic methane (with less pressure and heat than they propose) then
you could get bacteria producing oil from it provided they find a way to
make a profit doing that. And whether they can do that depends on what
other compounds are present. There's some methane in the water that comes
out of hydrothermal vents and some animals metabolise it, though a quick
look gives me the impression that sulfides and ammonia might be more
important. This methane probably isn't biogenic, unless we count
organisms in the seawater that get sucked in and heated etc to maybe
abiogenicly get turned into methane etc.

Again, sorry for all the handwaving but it's all I've got.
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