I need to update a publication and would be grateful for any sources of information regarding this. Part L [2006] gives a figure of 0.194Kg/kWh. Is this accurate or is there an updated value out there somewhere?

I'll email you through some data when the server's up Mike

Agreed, but what is the current conversion factor? I wondered [being cynical] how accurate the Part L value was/is

http://www.nottenergy.com/energy-costs-comparison2

Mains Gas 0.194
LPG 0.234
Butane 0.210
Propane 0.190

and to compare

GSHP 0.121
Seasoned wood 0.025
Electricity 0.422

"Seasoned wood 0.025"

There appears to be no reference to where this "data" came from on the Notts website:

Edit add:

1 tonne fuelwood: Approx toe = 0.3125 Thus one fuelwood: 3750 kWh using UN data (UNECE). Others estimate much lower figures in the region of 2800 to 3500. Coal is 7000 or so.

Basic transport costs (before burning: Typical UK equivalents: 476 kg / tonne or less using Bath CE data
Thus, before burning CO2 costs are = 0.125 unless you burn the wood next to where it fell

The carbon in - out ratios cannot be significantly different for coal as they are essentially the same thing (though the calorific product may be slightly better for coal given the higher carbon densities). The carbon content of dried timber is about 40-50%: Thus the post burning costs of timber are about unity kg fuel in for kg CO2 out

Total outputs for timber are likely to be similar to, or worse than, any other combustion fuel: In the range of 0.25 to 0.4 Kg [CO2) /kWh.

IMO, It is a great shame that a public body would publish such misleading and unqualified data.

Do you mean 'in any fuel' or 'for any fuel' Tom?

There will be a difference between fuels depending on the molecular bonding

jon, isn't energy released directly proportional to the amount of carbon oxidised? Simple carbon to CO2 is exothermic. Or do we have to subtract from that the various energies endothermicaly (?) required to first break the carbon free from a variety of different-chain CH bonds? And add hydrogen to H2O - also exothermic?

I'm not sure endothermic is the right word but that's the idea Tom. Hydrogen content affects heat given out without producing Carbon. Nitrogen can be in some types of fuel together with all sorts of other elements.

jon

Right, and as coal is almost pure carbon, not hydrocarbon, so containing no hydrogen, every bit of coal energy must result in CO2 production, whereas all other fossil and bio fuels create part of their energy output out of CO2-free oxidation of hydrogen to water. That must be why coal is so 'dirty''. Do the various hydrocarbon fuels also differ significantly in their hydrogen to carbon ratio? Are we saying that oxidation of nitrogen (where present) is also part of the energy output?

Another emissions table here:

http://www.smfrancis.demon.co.uk/airwolvs/22emit.html

You could use it with the calorific values I gave earlier via a link to calculate CO2 / KWh

Posted By: jon'm not sure endothermic is the right word

Why /why not? AFAIK oxidising carbon to CO2 is very exothermic; hydrogen to H20 'fairly' exothermic; presumably before either of the above can happen, the CH hydrocarbon has to be split into C and H - is that endothermic or exothermic? Or is that a wrong way of looking at it. I'd like to understand - sounds important. I so regret throwing away my A level chemistry and physics text books and exercise books - those I could understand!

Hi Tom

Have to admit not to knowing the exact sequence of combustion for fuels or a particular fuel. This would need a chemist familiar with the combustion cycle of the fuel. I'm not sure it's important though other then as a note that fuels are not all carbon equal

jon

As far as i rember from my chemistry dgree your absolutely right fostertom. the brreaking of bonds (C-H,C-C,C-N) requires energy, forming new bond (C-O,H-O etc.) releases energy it is the diference between the energy needed to break the the bond and given out forming bonds , that determines whether a reaction is endothermic (uses energy) or exothermic gives out energy. This is why alot of reactions neen energy to start them (ignition) to break the bonds intialy.
Entropy change also comes into it (solid turning to gas results in an increase in entropy) but i shant go into that unless anyones really interested. I'm not sure i am.

Thanks all, I need to sift through all of this.

At the moment I'm facing a similar, related task:

What is the latest and most accurate figure for kg CO2 per m3 of natural gas when the boiler burn is quoted as being 90% efficient?

All suggestions welcome.