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Hairyloon

I'd dismissed this one as a stupid idea...


http://www.motherjones.com/environment/2015/12/discovery-racing-extinction-methane-bags-timelapse
dpack

that might be a load of bullocks to fit with bags and what about static sparks? a herd doing a hindenberg impersonation would be horrible.

considering what i was just reading about tar sand oil extraction and super scale strip mining for coal i recon moo gas is a fairly minor issue.
Rob R

One issue for the free ranging cattle might be lack of production but it's always bugged me why, with so many animals kept indoors (allegedly) are we not collecting the gas as it leaves through the ventilation systems? Perhaps for exactly the same reason.
Ty Gwyn

Be interesting to hear from Slim on the thinking of his French counterpart on this subject.
Slim

Be interesting to hear from Slim on the thinking of his French counterpart on this subject.


The short answer is: It's complicated.

I don't know enough about the methane end of things to want to risk saying anything that could be off-base. (I know what I don't know in this case). I have seen folks link polyunsaturated fatty acid (PUFA) rich feeds with methane reduction, but haven't read into much yet. I think that a lot of conventional folks like to say that they generate less methane per amount of product produced with high corn diets, but I am guessing that is over-simplifying things as well (ignoring carbon budgeting of growing corn versus grazing and haying)

I will say that contrary to the article, it isn't as simple as "just adding some linseed" for those farmers that are using primarily corn silage. Firstly the linseed must be process for the PUFA to be available, and secondly they easily run the risk of milk fat depression because they probably have their herd on the verge of ruminal acidosis as it is, and a slug of PUFA might push them into milk fat depression, which can be enough of an income loss to warrant not caring about your methane.

More info: https://ecommons.cornell.edu/bitstream/handle/1813/39200/4Harvatine_manu.pdf?sequence=2

It's a different story with grass/alfalfa feeding, as that is a lot less likely to verge on acidotic rumen conditions anyway.
Ty Gwyn

Fully agree with you on the Acidosis angle,

It was the mention of an increase in grass diet to combat methane release i was interested in your point of view?
Hairyloon

it's always bugged me why, with so many animals kept indoors (allegedly) are we not collecting the gas as it leaves through the ventilation systems?

It will be very dilute by then and I think it is not easy to refine.
If somehow you ventilated less, so that gas built up to a level that would be useful, then there would be risk of explosion.
Mistress Rose

The same problem with decomposing rubbish. We have several of them round Portsmouth, often with ventilators attached. In fact the highest point of Portsmouth is a man made rubbish heap which has been nicely grassed and planted with trees, and must be sinking at an appreciable rate.

As we have discussed elsewhere, the amount of fossil fuel/greenhouse gas involved in producing grain or other arable crops on unsuitable land that is better grazed by cattle is probably worse than the amount that cows produce.
Rob R

it's always bugged me why, with so many animals kept indoors (allegedly) are we not collecting the gas as it leaves through the ventilation systems?
It will be very dilute by then and I think it is not easy to refine.
If somehow you ventilated less, so that gas built up to a level that would be useful, then there would be risk of explosion.

By my reckoning it'd be in the region of 0.036% when combined with the air exiting a cow, versus 0.00018% in the atmosphere. They're already looking at technology to capture methane from the atmosphere so I would have thought that starting with a concentration of 200 times that of air would be more logical. I'm not a chemist though, so perhaps it becomes more problematic to extract higher concentrations.

Stopping it coming out to increase the energy balance in cattle is likely to be the more beneficial route to take though, and I expect we'll see more of that in the coming years.
Behemoth

Assuming the could collect and contain it as HL says you're then in a world of moving pressurised explosive gases and a hatful of regs. Not impossible though. A more effective way to generate gas may be through digesting the slurry. dpack

from a dilute amount in air the major problem i can see would be the energy in/energy out equation.

getting the methane out could be fairly simple either chemically or using physical properties and fractionally distilling liquid air but both ways it would be an expense rather than a profit/energy supply.

re the minor amounts involved the effort might be better put to battery tech and renewable/low impact energy sources except perhaps in the case of landfill methane capture
Hairyloon

If you consider the thermodynamics of a distillation, the overall net energy transfer is zero.
It is almost certainly nigh on impossible to actually run one that way, but it may be possible to get relatively close...

Just in case anyone here wants to start thinking about it any, the boiling point of methane is -161°C at 1.013 bar and, Critical temperature is -82.59 °C...
Slim

Assuming the could collect and contain it as HL says you're then in a world of moving pressurised explosive gases and a hatful of regs. Not impossible though. A more effective way to generate gas may be through digesting the slurry.

Methane digesters are very common around here:
http://www.greenmountainpower.com/innovative/cow/
Mistress Rose

I think the only sensible way of extracting methane is by digesters. I have been thinking for years that they were the way to go for organic rubbish, and they are now reasonably common on farms.

Hairyloon, you have to put a lot of energy into compressing/cooling the gas before you can distil out all the different gases.
Hairyloon

Hairyloon, you have to put a lot of energy into compressing/cooling the gas before you can distil out all the different gases.
You do, but you can use some of that energy to compress/cool the next lot of gas.
Mistress Rose

But for the small amount of methane you would extract, is it worth while. If you are taking out a number of different gases and using all of them, particularly the 'easy' ones like carbon dioxide it might be worth while, but the cost in terms of energy and money would have to be looked at very carefully. Hairyloon

But for the small amount of methane you would extract, is it worth while.
My instinctive answer was not. But the man with the cows put forward a persuasive argument that it might be worth thinking about a little.
Rob R

But for the small amount of methane you would extract, is it worth while.
My instinctive answer was not. But the man with the cows put forward a persuasive argument that it might be worth thinking about a little.

I did say (allegedly) - I don't actually think it's significant enough, but people with other agendas claim otherwise.
Hairyloon

I was looking for something else when I happened upon this thread again and coincidentally was recently looking at a DIY liquid nitrogengenerator, so perhaps the cowshed methane extraction is not beyond the backyard engineer after all.

And if we really wanted, we could put the cattle in a turnstile thingy and have them drive the compressor...
Mistress Rose

Certainly liquefying it would be a lot easier than liquefying nitrogen. Why on earth would anyone want to make liquid nitrogen at home? Hairyloon

Certainly liquefying it would be a lot easier than liquefying nitrogen. Why on earth would anyone want to make liquid nitrogen at home?
Because they can?
Nick

Certainly liquefying it would be a lot easier than liquefying nitrogen. Why on earth would anyone want to make liquid nitrogen at home?

It's quite hard to buy and it's a requirement to make the best ice cream?
dpack

reality check

any attempts at compressing flammable gasses are fraught with danger

the obvious issues are :

flammable

gas to liquid gives pressure vessel/pipe failure risks (shrap and fire issues)

admixture with air is explosive as gas (,electrical sparks etc) or when being compressed via pressure/heat of compression (see gas/air diesel type engines)

barge pole is my first thought. as i have worked with 2000psi hydrogen and gas axe bottles even methane makes me a little nervous.

it could be done but there are technical safety issues that need addressing at an early stage in any plans so as to have a low risk of a very nasty surprise.

don’t detonate your shed Wink Rolling Eyes
Hairyloon

reality check

any attempts at compressing flammable gasses are fraught with danger...

My thinking was to produce liquid air and use that to chill the methane rich atmosphere to condense the methane: practically no compression involved.

Though not thinking seriously about it as I don't have a cowshed...
dpack

liquid air has multiple issues as well. even compression can cause a variety of problems .

i recon even if this stuff can be done in a backyard (which seems possible as most things can be done in a scrapheap challenge, rough chemistry ,nuclear reactor in a dustbin sort of way ) there could be a long list of nasty surprises before the kit and process is perfected.
Mistress Rose

I think making the liquid nitrogen first would be more difficult than just making the liquid methane. I suppose if you could chill the exhaust air from the cow shed to the right temperature using a similar apparatus, you should be able to extract the methane, but not sure it is worth it. Hairyloon

I think making the liquid nitrogen first would be more difficult than just making the liquid methane.

More work certainly, but probably not any more difficult.

Quote:
I suppose if you could chill the exhaust air from the cow shed to the right temperature using a similar apparatus, you should be able to extract the methane, but not sure it is worth it.


The concern there is the compression of flammable gas, though I am minded to think the concentration is low enough to be of little concern.

As to being worth it, almost certainly not (unless there is a good market for Nick's ice cream), but it is interesting as an intellectual exercise.
Nick

It's bloody good ice cream.

But, I no longer make it, as my source of free cold N2 has vanished.
Hairyloon

It's bloody good ice cream.

How good?
The cryo project looks like fun, but not so much fun as to make it worth the effort just for fun...

Quote:
But, I no longer make it, as my source of free cold N2 has vanished.


How cold do you need it for the ice cream?
Have you tried the dry ice & alcohol trick?
Nick

It's not just about freezing, it's about boiling. You can use dry ice, and this freezes it quickly which reduces crystal size, and makes it smooth. But the nitrogen method means you pour the liquid N2 straight into your mixture and it boils. So it freezes and creates millions of tiny bubbles which are trapped in the mix. No big crystals and a super smooth mouth feel. I hate that term, but it's appropriate here.

Last time I made it we'd used the dewar for storing mouse mammary glands in. Them vegetarians moaning about fivers with cows in? Bah, they know nothing.
Hairyloon

How much Nitrogen do you need for how much ice cream?

{Why am I trying to talk myself into this?}
Nick

It's not precise. A quick pour to make enough for the lab. Smile

I'd guess 300ml to make a litre.
Hairyloon

It's not precise. A quick pour to make enough for the lab. Smile

I'd guess 300ml to make a litre.
Does it scale up well enough?
If I build this thing I'll be wanting to make it by the gallon... Wink
dpack

on a commercial dairy scale (loseley) they put about 30 gallons of mix in a big pot and pull a handle to add l n down a pipe from a storage tank which iirc is topped up from a road tanker rather than made on site. they were making a few thousand gallons a week so perhaps to justify making your own l n you would be looking at quite a large scale operation.

the handle thing does make the process safer than free pouring (humans at minus 200 crack as well as rubber gloves and flowers Wink )
Mistress Rose

We had a delivery of liquid nitrogen from a tanker for our clean room too. We used the boil off as an inert atmosphere for various jobs in a glove box. Shane

reality check

any attempts at compressing flammable gasses are fraught with danger...

My thinking was to produce liquid air and use that to chill the methane rich atmosphere to condense the methane: practically no compression involved.

Though not thinking seriously about it as I don't have a cowshed...
Sorry - bit late to this one. It's a lot harder to have a browse since the work net nanny decided that Downsizer was an inappropriate website Rolling Eyes

Suggest that your plans to liquefy methane at atmospheric pressure may be slightly challenged by the -161 degrees that you'd have to get down to in order condense it. You'd have rather a lot of other liquids drop out on the way that you'd have to deal with before you started dropping out methane - my recommendation would be to use what you can to top up the mixed-refrigerant system that you'd need to supply your cryogenic heat exchanger (do let me know how you get on with designing one, by the way - there's only two companies in the world that make them and they keep their respective designs a closely-guarded secret. Try as I might, I can't replicate them). Oh - and although you only need minimal compression for the methane (downstream of purification, at least), you'll need significant compression power to drive your refrigerant circuit.

And as for storage - good luck, is all I can say.

Do let me know how you get on Wink
Mistress Rose

We might hear the bang to tell us Shane. Wink Not really a goer I wouldn't think, but the output of methane from cowhouses and landfill sites is probably sufficient to be useful if only it could be harnessed. Digesters are now being used for slurry and some rubbish, which was an idea I had a long time ago, but didn't have the expertise to do anything about. Hairyloon

Digesters are now being used for slurry and some rubbish, which was an idea I had a long time ago, but didn't have the expertise to do anything about.
Digesters are easy enough: shove enough crap in a bucket and off it goes...
There is a lot more to it if you want to optimise the process, but my initial test with a couple of buckets worked fine.
Hairyloon

Shane, did you look at the design on Instructables?
It's a few posts back...
Shane

Oh yeah - just found it. Looks like a fun rig.

There's a big, big difference between nitrogen and methane. One disperses almost immediately (and I would recommend that you never put a liquid nitrogen generator in a shed), one is very, very flammable indeed and will ignite in a catastrophic manner if it leaks.
Hairyloon

Oh yeah - just found it. Looks like a fun rig.

There's a big, big difference between nitrogen and methane. One disperses almost immediately (and I would recommend that you never put a liquid nitrogen generator in a shed)...
Where else should I keep it when it's not in use? Is too big to go in the basement. Confused

I'm not clear why you are pointing that out either: they are obviously very different...
But thinking on, if you're gradually chilling air 'till it liquefies, then isn't the methane going to drop out first, followed by the oxygen...
I imagine a bucket with a mix of liquid methane and oxygen is not a good thing to have...
dpack

"I imagine a bucket with a mix of liquid methane and oxygen is not a good thing to have..."

ummmm, set up the camera at a respectful distance before you try.

i'm not sure it is even possible to get to the bucket stage in your shed.

this crew dont mention buckets Laughing

it lives in a slightly bigger incarnation , still no buckets Laughing
Hairyloon

this crew dont mention buckets Laughing
But they do mention a spark plug: it seems they don't expect it to go off spontaneously... Wink
Nick

No one who blows themselves up expects it to combust spontaneously, I guess. Hairyloon

Well, there is a 20 degree difference in boiling points and I can't believe the chiller works that fast, so it should be easy enough to run them off into separate buckets... dpack

fingers in ears

ctrl methane will pull up 5 rather relevant bits. as a mixture it needs a little bit of a poke to set it off but not much of a poke even at cryogenic temps and the mix range for a surprise is fairly broad.

JUST DON'T . if you do let us know so i can sandbag the windows Laughing Laughing Laughing
Hairyloon

JUST DON'T . if you do let us know so i can sandbag the windows Laughing Laughing Laughing
I've already told you that I don't have a cowshed...
dpack

true but you do have a bucket of fermenting stuff and could probably find a lot of fermenting stuff. Laughing

like shane said compression and cryogenics have some complex issues,many of which can surprise the neighbours.

i wonder if there are chemical means to concentrate low levels of methane into a convenient space for later use ? .
adsorbsion or compounding might be a way to go, a bit like dissolving acetylene in acetone on pugging for gas axe bottles or using carbide for caving lamps.

maybe not for direct use but as a means of separation from a low concentration in air.
Hairyloon

true but you do have a bucket of fermenting stuff and could probably find a lot of fermenting stuff. Laughing

Actually I've upgrade the bucket to a barrel, but it leaks so I've not had any successful gas production from that. Sad
But, while it may want refining, I don't think it wants doing by fractional distillation: more likely a bucket of lime to take out the CO2, but it did burn well enough straight out of the bucket so I think that is unnecessary.
How to store and regulate the gas flow are the only real questions I have on that count.
dpack

the old " tin can floating over water " gasometers seemed to work pretty well.

low tech and reasonably safe they also provide a positive pressure for the feed to use pipe.
Hairyloon

the old " tin can floating over water " gasometers seemed to work pretty well...
Yes, but I'm not convinced that they scale down that well.
dpack

how many litres of lp methane do you get from a barrel of ferment?

i recon scrapheap challenge ( and some bath sealant ) should give the materials to test the principle on a backyard scale

iirc methane isnt very soluble in water and unless there is a big surface area of water exposed re gassification to atmostphere should be minimal but any leaks from any cause would be a hazard as well as a loss of product

a simple bubble trap in an inverted bottle on a small batch of ferment should give some idea of the size of gasometer required and solubility issues.

a gasometer is just two vessels that fit one inside the other with the lower one full of water, the top one rises ( between some guide poles is optional ) as it fills . seems pretty easy to make.

super simple picture

a lot safer than compression and cryogenics but still rather iffy unless you can gnt there is not enough air to give an explosive mixture.

numbers indicate methane isnt as bad as some things but anything with a 10% window of surprise needs reasonable caution.
Hairyloon

a gasometer is just two vessels that fit one inside the other with the lower one full of water, the top one rises ( between some guide poles is optional ) as it fills . seems pretty easy to make...
Yes, that is basically what I had as the first test, but the top barrel would need enough weight to provide proper pressure for the gas appliances. I only did it to check the principles: I didn't do any measuring. Embarassed

But I suspect that an increase in pressure is likely to repress the fermentation reactions, so I'm thinking the store wants to be separated from the reactor...
dpack

if the top vessel is only heavy enough to give say 1.5 atm i cant imagine it would retard the ferment much (i have opened bottles with far higher pressures from fermentations) but it would make for a non mechanical rig that works with no pumps etc .

a mix of floats and weights could be the way to go re getting a working pressure for ferment and use .

what point of use pressure is the feed to a standard gas ring ? that might be a number to work towards .
dpack

getting an anerobic system seems important for the ferment and to avoid any surprises so that needs designing in. Hairyloon

getting an anerobic system seems important for the ferment and to avoid any surprises so that needs designing in.
Well that is easy enough: a bucket full of water upside down in a bucket full of water·..
You do need the right bacteria though. I had assumed there would be some naturally in some of the anaerobic sludge I had accumulated about the place, but I had no sign of any production until I seeded it from another source...
Shane

I would recommend that you never put a liquid nitrogen generator in a shed
Where else should I keep it when it's not in use? Is too big to go in the basement. Confused
Okay, smarty pants - let me rephrase it to say "don't operate it in a confined space". The reasons why should be obvious, I would hope.

But thinking on, if you're gradually chilling air 'till it liquefies, then isn't the methane going to drop out first, followed by the oxygen...

From Wikipedia, typical biogas concentrations are:

Methane 50–75%
Carbon dioxide 25–50%
Nitrogen 0–10%
Hydrogen 0–1%
Hydrogen sulphide 0–3%
Oxygen 0%

I'd be surprised if that was all that was in it, and any impurities can become problematic for cryogenics. Oh - and 3% H2S will kill you, instantly, so you'll need to find a way to remove and dispose of that, as it will condense before the methane (which means you'll have a very strong concentration of H2S in your initial condensate).

The liquid nitrogen generator looks like a bit of fun, but I'd seriously stay away from liquefying flammable gases at home.

As for methane storage - here's one I made earlier Very Happy :

Mistress Rose

Well I hope Hairyloon isn't going for one that size Shane. We would blow up the whole of Yorkshire and a bit more with one of them. Very Happy

Hairyloon, if you take this project very far, do remember that air and methane can make an explosive mixture. A friends house was damaged rather badly from a natural gas leak in the early days. Her mother got some burns, but luckily wasn't too badly hurt, and the rest of the family got away with it because the lounge to kitchen door blew off its hinges so the main blast hit the wall.
dpack

h2s is about as toxic as hcn but has the added advantage of a very wide concentration of surprise range, more explosive than methane is a good way to think of it.

a sniff of 3% would be a very bad idea and iirc 4% is the lower limit of concentration of surprise in air.

if you wanted to remove it at lp running the gas stream via a chemical collector system ( trapping as fes using wire wool or filings is a possible answer) might work for small scale (cost is an issue) but in bulk flare it off is the option but that has a big environmental downside as you will mostly make so2 (and water so sulphurous acid is the main pollutant). ether way there are some rather trick pollution issues.

looking at the digester product gas if you run it strait to a burner same chemistry for the h2s applies ( ie so2[ aq ] as vapour ) which might not be wise to breathe but a gas leak in the kitchen would be seriously toxic from the h2s and smothering from the co2.
"natural" ie fossil gas is usually a lot cleaner from the ground than that biogas recipe and gets some hard core purification if it isnt.

my overall opinion is biogas might be green on the surface but there is some rather nasty chemistry to overcome if you look a bit more closely before domestic use is sensible.
Nick

Keeping the right bugs happy is the challenge in digesters. With a fixed food source hats not too hard but with mixed feed it's a nightmare. But the Product isn't purified before being pushed into the grid. dpack

good point, i spose much like brewing or cheese making the right bugs give the right product and avoid stinky batches. Hairyloon

With a fixed food source hats not too hard but with mixed feed it's a nightmare...

What kind of hats have you found best?
dpack

Hairyloon

Pushing the definition of hat there I think... Shane

trapping as fes using wire wool or filings is a possible answer
Hmmm - look up the word "pyrophoric" sometime
dpack

ahhh Embarassed
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