After waiting nearly six months now for my wood pellet stove, I've had time to reflect on the coal burning stove we have now. From first impressions it's terribly environmentally unfriendly - the smoke, the visible dirt - but I have noticed that we use our heating much more efficiently now.

Unlike gas, oil and electricity, Coal is a physical thing - you have to put it on the fire and you quickly become aware of how much you are consuming. You also get an idea of how much you have to clean up in the morning. Our heating/hot water bill's are running at about 20 quid a month (and this is over the winter).

The distribution system for coal is quite efficient. The coal we use comes from Wales and we as a country have loads of coal left remaining (reducing the risk of 'international' energy supply).

So is coal really so bad?

Posted By: biffvernonelectrickery

I like that

[Highwayman as guest]

...and the best coal appliances are perhaps 60% efficient, and the fuel is higher carbon than oil. If you do the sums, you'll find that per kWh of useful heat, mains electricity is greener:

Gas condensing boiler, say 90% efficient: 0.19/0.9 = 0.21kg CO2/kWh
Oil condensing boiler, say 90% efficient: 0.27/0.9 = 0.30kg CO2/kWh
Coal at 60% efficient: 0.30/0.6 = 0.5kg CO2/kWh
UK average generating mix (2004 figures) 0.43kg CO2/kWh

Gravity hot water eliminates the electricity used by the pump - but so what? It is more carbon efficient to use an immersion heater!

Don't burn coal!!!!!

I am surprised that coal is being advocated on a green builing forum for anything other than leaving it in the ground.

There are a couple of key points here:

-The most important point about the use of coal though is that you physically have to put it in the burner. Unlike electricity, gas or oil, you can see how much you are using. You become aware of the consumption and minimise it. I wouldn't mind betting that the inefficiency during burning is off-set by reduction in consumption due to the visible and physical nature of the feeding of the fire.

-The coal comes from Wales to me via an efficient distribution network. I don't use a car or van collecting it myself as it's distributed to our community. Gas or oil could have come from anywhere, piped half way across Europe for all I know; and in the case of oil, is delivered by a series of tankers to your door.

-For those of us with no mains gas we have three key options: solid fuel, oil/bottled gas, electricity. Storage heaters are just nasty; GSHP requires infrastructure changes in your house; oil and gas may burner cleaner, but isn't that offset when the fuel travels half way round the world in pipe lines, storage and tankers to get to you; wood requires a good constant source; wood pellet just doesn't seem ready in the uk yet; and then there are coal boilers.

Have I missed something?

Biff - of course it does. The usual approach without details of a particular situation is to take the average UK generating mix, which gives you the (a bit out of date) figure of 0.43kg Co2 / kWh.

If you have your own renewable electricity the figures are of course different.


Nigel - "Coal does actually produce less co2 than electric heating" - at typical coal appliance combustion efficiencies no it does not! Figures above in previous post.


Coal in general - it is not all from Wales. We import from South Africa amongst other places. I don't know the proportions of imports vs 'homegrown'.

Isn't the figure [0.29kg/kWh] accurate regardless of efficiency? All of the coal is still burned.

So it all depends how the figure of 0.29kg/kWh is derived.

However, I do not understand how efficiency makes any difference to the actual amout of CO2 emitted from burning x amount of coal. The efficiency relates to how much of the heat is "used" and how much is wasted.

If the figure has come from DCLG documentation such as Part L then it will probably have been derived from first principles. I have attached a document which shows this for gas. [Courtesy of a colleague as I am no chemist]

Perhaps it is different for coal depending upon impurities?

UK average generating mix (2004 figures) 0.43kg CO2/kWh........? Someone has been reading the Building Regs and believes that these figures are based upon MEASURED data. Sadly, and unbelievably, this not the case. The B.Regs figures are based upon the PREDICTED fuel mix between 2005-2010 see http://www.bre.co.uk/filelibrary/CO2EmissionFigures2001.pdf for details.

The figure of 0.48 kg/kWh can be taken from the 2003-05 by the House of Lords Science and Technology Committee and was calculated totally independently by Dr Bob Everett at the Open Univ Energy and Environment Research Unit.
And more recent report to DEFRA (see this quarters BFF...the article by David Olivier) notes that emissions from electricity is closer to 0.55 kg/kWh.
The PDF also notes a figure of 0.568kg/kWh, though this relates to actual electricity generation data for 1998/1999 for England and Wales and may be a little out of date.

Coal is a fossil fuel. Burning wood, using solar, using a ground source heat pump powered by sustainably produced electricity are all C02 neutral once up and running.
Coal is useless if you are trying to eliminate your C02 emmissions (which is after all the plan) unless you plan to capture and store the C02 from your flue gases which I find unlikely.
Yes you see how much you use which is a good thing, but you do with wood as well.
You can also see how many pellets you use if you have a pellet stove with an integral pellet store.
Even if you transport the wood (for example in the form of pellets which are often delivered nationwide by pallet) it is still producing FAR less C02 per kW than coal.
There are now several nationwide suppliers of pellets in the UK: http://www.stovesonline.co.uk/services/wood-suppliers-full.asp" >http://www.stovesonline.co.uk/services/wood-suppliers-full.asp

The http://www.lowimpact.org/" >low impact living initiative offer some courses in things like making your own solar panels that you might find useful.

Hi Adrian

I do agree with what you are saying

Yes C02 is not the only thing to have in mind. But even if you transport the wood by truck from Poland, coal would still be a lot worse in terms of C02. Also in terms of other emissions eg sulphur. I do not think that the benefits of local production outweigh the extra emissions of coal - but I guess those are personal judgments.

Yes you are right pellet stoves are hard to source and have installed. But you are wrong in another respect - I have in fact tried to source lots of pellet stoves - I run a stove company so have come across the same problems but on a bigger scale. Yes it can be difficult to get installers, spares, and technical support that is nationwide. This lack of nationwide support is which is why we have steered clear of them until now. Not very cool if a client has a pellet stove and needs a part for it butthen has to wait 3 months for the bit to come from Canada! We have just sourced some pellet stoves that can be installed by a hetas registered installer (fairly easy to find) with nationwide technical support. The website is www.industrieolivieri.it but is in Italian. The backboiler models are factory set at a percentage of the output from 95 to 20 percent - your choice. An integral pellet hopper supplies the stove. You fill the hopper up. This means that they are not as complex to install as the stoves that have a separate pellet store. We will be supplying them shortly - and obvs will have info in English! I can let you know as and when we do if you are interested but did not post in this forum to try and sell you something, I was just being geeky!
There may be other pellet stoves with integral hoppers where there is parts and technical support local to yourself. They should be an easier option than the ones that have the separate pellet store, but the obvs you do have to fill them up yourself so they are not as easy in that respect.

If pellet is not the way to go and you are up for burning wood then why not just burn local wood? That is what I do - I burn locally sourced logs in two wood burners to heat my house. If you happen to run out of logs then you could always revert back to coal. Or if you want something more automated perhaps look at a wood gassification boiler like the range of ViGas boilers that can take logs. They are a bit more like a gas boiler in that they sort of manage themselves.

Yes you are right - it is difficult and expensive for the 'normal' person trying to integrate new technologies into existing heating systems in older houses (ie without multiple coil tanks etc). Plus the technologies are still fairly young in the UK and so have perhaps not quite settled down yet. Plus the heat store / heat combination tanks available that can let you combine all these heat sources are pretty expensive - thats what I found anyway!
Plus some plumbers do not seem to be able to get their heads around combining an open and closed system by using a heat tank / multi coil tank, whatever you want to call it. It is a bit of a minefield out there.

Maybe we should all just start wearing hats instead like people used to do in England presumably to keep themselves warm (and stylish).

: )

Sune

Wow, that's a serious amount of CO2. I've already moved to 50/50 coal wood as I've found a nice local supply, but I just still can't get away from the coal. No matter what the output of CO2, it's keeping a local industry going, I use it much less frequently than I would if I had oil/gas/electrical heating (i.e. I would use at least 3 times as much oil/gas/elec for heating) and per kg it burns for longer giving heat over a long period of time.

There must be someone out there that can do the math, but I recon I'm burning 5kg of coal and perhaps 5kg of wood max per day for a burn time of about 8 hours. Not sure how much CO2 gas/oil/elec would produce over those 8 hours.. is it that different?

Interesting - do the figures for gas and coal also include the process and transport energy too? Do they all also include the end-use burning/conversion efficiency typical for each fuel?
What's the figures for central heating oil and electricity? Wood chip/pellet? Transport petrol and diesel? Bio diesel, ethanol? Hydrogen?
Obviously, for all these fuels, these figures make 'typical' assumptions about how much process and transport and what burning/conversion efficiency, which could vary substantially depending on circumstances - e.g. Welsh coal versus Romanian or wherever it comes from; local logging by horse and axe with minimum forest-floor disturbance, versus chainsaws and forwarders; old iron boiler versus condensing; simple box-woodstove versus hi-tech.
Finally, what's the CO2 kg per GJ for the end-use burning alone? That should be a standard figure for all fuels, before figuring in different burning/conversion efficiencies.
Official car kg/mile figures are directly related to mpg. I wonder what assumptions are built in there.

Posted By: sune1 - the carbon content of each fuel type
2 - the energy per kg

I frequently suspect there's a source of confusion here. These 2 parameters as stated are possibly irrelevant, except for the purpose of sizing a bulk hopper or storage tank. All that really matters is that you burn an unspecified no. of kgs x, sufficient to produce y GJ and the result is z kg of CO2 - and the ratio between y and z should be identical for all fuels.

Often people talk as if releasing y GJ results in different values for z kg of CO2, depending on the fuel type. It's true that you get different values for z kg of CO2 when process and transport energy and the burning/conversion efficiency of the boiler etc are figured in, but as far as the pure burning of carbon is concerned, y and z are locked together regardless of fuel type.

Plus of course if it's a bio-fuel z kg of CO2 released doesn't matter because precisely z kg of CO2 have recently been absorbed in growing the biofuel - there's no nett atmospheric increase or decrease of CO2. Whereas if it's a fossil fuel z becomes entirely a nett atmospheric increase of CO2.

Posted By: sune5kg of wood makes 0.075GJ and produces about 0.525kg C02
5kg of coal makes 0.15GJ and produces 12.15kg C02

That's a total of 0.225 GJ

Using just gas to make 0.225GJ that would produce 12.15 kg C02
Using just coal to make 0.225GJ that would produce 18.23 kg C02
Using just wood to make 0.225GJ that would produce 1.58 kg C02

So, in summary, it looks like, if I burn 50/50 wood coal mix, I'll be producing just about as much CO2 as Gas doing the same job; but I won't have the risk in fuel supply and I will be buying a local product?