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



Joined: 21 Jul 2011
Posts: 10818

PostPosted: Sun Dec 13, 15 8:56 am    Post subject:  Reply with quote    

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



Joined: 20 Nov 2008
Posts: 15237
Location: Today I are mostly being in Yorkshire.
PostPosted: Sun Dec 13, 15 10:33 am    Post subject: Reply with quote    

Mistress Rose wrote:
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



Joined: 28 Oct 2004
Posts: 31902
Location: York
PostPosted: Sun Dec 13, 15 10:58 am    Post subject: Reply with quote    

Hairyloon wrote:
Mistress Rose wrote:
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



Joined: 20 Nov 2008
Posts: 15237
Location: Today I are mostly being in Yorkshire.
PostPosted: Mon Dec 05, 16 5:14 pm    Post subject: Reply with quote    

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



Joined: 21 Jul 2011
Posts: 10818

PostPosted: Tue Dec 06, 16 8:50 am    Post subject: Reply with quote    

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

Hairyloon



Joined: 20 Nov 2008
Posts: 15237
Location: Today I are mostly being in Yorkshire.
PostPosted: Tue Dec 06, 16 8:53 am    Post subject: Reply with quote    

Mistress Rose wrote:
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



Joined: 02 Nov 2004
Posts: 34018
Location: Hereford
PostPosted: Tue Dec 06, 16 10:12 am    Post subject: Reply with quote    

Mistress Rose wrote:
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



Joined: 02 Jul 2005
Posts: 35408
Location: yes
PostPosted: Tue Dec 06, 16 2:01 pm    Post subject: Reply with quote    

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.

donít detonate your shed

Hairyloon



Joined: 20 Nov 2008
Posts: 15237
Location: Today I are mostly being in Yorkshire.
PostPosted: Tue Dec 06, 16 2:44 pm    Post subject: Reply with quote    

dpack wrote:
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



Joined: 02 Jul 2005
Posts: 35408
Location: yes
PostPosted: Tue Dec 06, 16 3:03 pm    Post subject: Reply with quote    

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



Joined: 21 Jul 2011
Posts: 10818

PostPosted: Wed Dec 07, 16 7:15 am    Post subject: Reply with quote    

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



Joined: 20 Nov 2008
Posts: 15237
Location: Today I are mostly being in Yorkshire.
PostPosted: Wed Dec 07, 16 9:33 am    Post subject: Reply with quote    

Mistress Rose wrote:
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



Joined: 02 Nov 2004
Posts: 34018
Location: Hereford
PostPosted: Wed Dec 07, 16 11:51 am    Post subject: Reply with quote    

It's bloody good ice cream.

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

Hairyloon



Joined: 20 Nov 2008
Posts: 15237
Location: Today I are mostly being in Yorkshire.
PostPosted: Wed Dec 07, 16 12:03 pm    Post subject: Reply with quote    

Nick wrote:
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



Joined: 02 Nov 2004
Posts: 34018
Location: Hereford
PostPosted: Wed Dec 07, 16 2:18 pm    Post subject: Reply with quote    

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.

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