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Treacodactyl Downsizer Moderator
Joined: 28 Oct 2004 Posts: 25795 Location: Jumping on the bandwagon of opportunism
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dougal
Joined: 15 Jan 2005 Posts: 7184 Location: South Kent
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Posted: Mon Jul 04, 05 7:04 pm Post subject: |
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tahir wrote: |
it's more about how clean the combustion is from all theses new woodburning stoves and boliers and how it compares to a modern gas boiler. |
Modern boiler inovations are more about collecting more energy than further reducing pollutants. More energy efficiency of course means less CO2 for a given amount of heat. A gas boiler produces very little indeed apart from CO2 and water. There's very little NOx produced, the temperature being much lower than the combustion in a car engine. And the "Natural Gas" fuel is very (chemically) pure Methane, (which is a very simple compound, CH4). There's precious little sulphur - even the famous smell is a deliberate trace addition. There's practically no particulates. The purpose of annual "servicing" is largely to ensure that combustion is 'complete' and as little CO as possible is produced.
Its *very* clean-burning.
But mains gas supplies are fossil carbon.
However, it is perfectly possible (if not entirely practical for most folk) to bio-generate your own Methane, from renewable sources. Judyofthewoods has already provided pointers to the french guru Jean Pain.
In contrast, woodburners have a much more chemically complex fuel, with a variety of long-chain carbohydrates and some "aromatics" with ring-based structures. Consequently, combustion is much more difficult to complete.
When smoking food we are trying to use the active chemical products of very incomplete combustion. And those same chemical products of incomplete combustion are the "dangerous" pollutants!
Slightly more complete combustion gives sooty deposits. But, IIRC, wood gives larger (and so less harmful) sooty particles than coal.
Fossil fuels are essentially the remains of prehistoric vegetation. The sulphur in coal (and that extracted from liquid and gas petrochemicals) originated in the vegetation.
Modern wood is going to contain sulphur, but its not as concentrated as it becomes in coal.
We know that excessive use of raw coal produced fearsome pollution - the London "peasoupers" from Dickens to the 1950's. And ISTR that woodsmoke produces similar problems in some "third world" cities.
However, I would expect a modern, controlled domestic burner (especially those using chipped fuel) to be able to burn much more completely than those open fires, but never as cleanly as a gas boiler.
Apart from air pollution, the ash, in quantity would also be of concern.
The energy used in creating the stove wouldn't be massive, and the product lifetime should be very long.
One catch is "locally produced" fuel. The energy density is relatively low, so transport cost is relatively high...
So, while avoiding fossil carbon usage, with woodburning there is some price to pay in terms of pollution. I think the real question becomes whether that is a price worth paying.
So, not quite perfect, and not for everyone, but with local access to fuel, much better than most. |
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dougal
Joined: 15 Jan 2005 Posts: 7184 Location: South Kent
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Treacodactyl Downsizer Moderator
Joined: 28 Oct 2004 Posts: 25795 Location: Jumping on the bandwagon of opportunism
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Bugs
Joined: 28 Oct 2004 Posts: 10744
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dougal
Joined: 15 Jan 2005 Posts: 7184 Location: South Kent
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sean Downsizer Moderator
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Jonnyboy
Joined: 29 Oct 2004 Posts: 23956 Location: under some rain.
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dougal
Joined: 15 Jan 2005 Posts: 7184 Location: South Kent
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mochyn
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sean Downsizer Moderator
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oldhibberd
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farmwoody
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Bugs
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Nanny
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