Yesterday I printed off and read through the AECB 'report' by Nick Grant and Alan Clarke, twice. I then printed off and read through Sune Nightingale's 'short response' twice. This morning I read through them both again, twice.

I don't know where Sune is coming from on this, given that the central tenet of Grant and Clarke's article is about biomass not being the carbon-free alternative to fossil fuels that it's being made out to be by its advocates, that point clearly stated in the opening paragraph, which in essence is the executive summary of the report, everything thereafter giving background to the logic that brought them to this conclusion, which seems a pretty logical one to me.

I was irritated by Sune's insistence that Grant and Clarke advocate the use of fossil fuels over biomass. "The report effectively encourages the use of fossil fuels or nuclear...". No it doesn't.

All I got from the AECB report was an understanding that Grant and Clarke, after much research and consultation with others, are saying that, effectively, the use of biomass is (and this is the conclusion I reached after reading the actual words on the page rather than between the lines) at best no worse than fossil fuel and potentially worse than fossil fuel in terms of REDUCING CARBON EMISSIONS.

Now, anyone who has closely followed the debate between Renewablejohn and Brian Wilson, wouldn't have had a problem with the use of biomass per se, just with biomass used without due diligence in terms of designing plants to a high enough standard, such as the one advocated by John and lobbied for by Brian. Having had the chance to read the AECB report at leisure, I'm now wondering about another aspect of the argument for their widespread use and the potential for our growing dependence on them - their effectiveness in reducing CO2!

Posted By: suneHow am I increasing nett Co2 levels, how would they be lower if I installed a gas boiler?

It does take energy to cut, prune, process, what form is this energy in, electrical or chemical, not a 'cost free' option. It is the total emissions not just one portion of them that is important, this is the problem that needs better addressing.

Saying that 'if I did not do something' is a bit like saying 'if all my electricity was nuclear or renewable', it by definition puts constant or bounds on things.

I've been trying to stay out of this debate as I didn't have the energy to join a 500 post debate (and didn't think that it would achieve much even if I did).

However on reading sune's posts I really must second them.

In addition I know numerous people who burn an ocasional open coal fires for character and can't face blocking the chimney. After years of gentle suggestion that a wood burner might be a better idea they were starting to come round to the idea that a stove might be a good idea just when the 'wood burning is evil' type headlines start comming out. Some might say i exaggerate but I'd swear I heard Chris Evans on radio two quoting something along these lines yesterday!

Posted By: owlmanYer don't get "OWT FER NOWT"

Too true, horses for courses as they say, but not so how how 'green' they are these days. It is the 'sustainability' debate all over again, give to one by the very nature of it you have to take from the others

Posted By: SteamyTeagive to one by the very nature of it you have to take from the others

Not in all instances, that is part of the content of my response - a lot of wood that is burnt cannot and/or would not be used for anything else. Woodfuel also makes other forest products more viable so in fact in some cases it is give to one and give to another.

Hi SteamyTea - in the context of the biomass paper the answer to what you just said is a definite no.
The paper is about co2 emissions.


In a wider context - yes. And in fact I do leave piles of brash and branches in my hedges as deliberate habitat.

Hi SteamyTea - not sure about that, but I did train as a zoologist so I have got used to reading lots of scientific papers....

I would say that gas only wins if you only consider the point and time at which it is burnt.

But in my example of my heating system, if I installed a gas boiler the overall co2 emissions from the whole system would be a lot higher.
So how, in my example, can gas win?

<blockquote><cite>Posted By: sune</cite>Hi SteamyTea - in the context of the biomass paper the answer to what you just said is a definite no.
The paper is about co2 emissions.


In a wider context - yes. And in fact I do leave piles of brash and branches in my hedges as deliberate habitat.</blockquote>

I agree the paper is about CO2 emissions

My problem with the authors seems to be there lack of understanding of how an efficient biomass energy CHP plant actually works. Because biomass produces such clean CO2 unlike coal it can be utilised to enhance the growing of food crops in greenhouses. At present we have the wasteful practice of burning gas to produce the CO2 and then because the gas is creating to much heat the vents have to be opened to cool the greenhouse down. How stupid is that.

http://homeharvest.com/carbondioxideenrichment.htm

You can even buy the kit from your local garden centre

Considering CO2 creation in biomass cycle planting a tree in certain soils requires 10 yrs of growth to sequestrate CO2 released by cultivation. CO2 created by transport can be significant due to low energy density . Reality in industrial use of biomass in UK i.e. powerplants details typical 2.57kg CO2/useful kWh for wood and 2.7kg/kWh for straw. I understand N.G. 385g/kWh . We should also note NOX creation/kWh is some 12 times higher than N.G. and we know NOX impact is some 296 times higher than CO2.
We can of course hope for possible ideal use utilising locally sourced feedstock and combustion in high efficiency CHP incorporating BAT to minimise hazardous emissions. The question is where are the projects in the UK , operating or planned . Burning biomass brings immediate large CO2 emissions, this can be delayed by utilising biomass in construction or superior alternatives.
I note report today that exposure to combustion emissions can stunt growth, interesting they detail coal and vehicles but not biomass although it also produces the hazardous ingredient.

Posted By: SteamyTeaWhat difference does it make to the CO2/kWh when the fuel was made?

A big difference. Sustainably managed forests are constantly uptaking co2 right now and it is partly this that makes sequestration of co2 in buildings by building with timber such a good idea. I agree that building with wood is a great idea, I just disagree when it comes to the blanket statements in the discussion paper as they do not always apply, in fact in many instances they do not.

The same reasoning is used by a chap called Calverd to 'show' that if we abolished livestock we could reduce CO2 emissions by around 21%. Simon Fairlie covers this in his clear, informative and very funny book 'Meat: A Benign Extravagance', page 158.

"The same idea is expressed in facile bumper stickers on the lines of 'if you think CO2 is a problem, hold your breath'. But most people discard the thought almost immediately because any carbon released into the atmosphere by a >living animal< is carbon that has previously and helpfully been withdrawn from the atmosphere by what is known as the short term carbon cycle.......>Vegetable matter obtains its< CO2 from the atmosphere through photosynthesis, >so when when animals breath out, they are< merely returning to the atmosphere carbon dioxide.......previously withdrawn from it.

Now the same applies to the wood fuel cycle. If you look at the paragraph above you will see that I have enclosed a couple of parts within symbols > like this <. All one needs to do is replace the first set of words with 'burning wood', the second with 'Trees obtain their', and the third with 'so when wood is burnt we are'.


The fossil fuel cycle cannot be viewed in the same way as the forest cycle because:
1 - the length of the cycle is very very very long,
2 - sequestration of fossil fuels is not occuring at anything like the rate that it used to - it is largely a cycle that occurred in the past.
3 - we are burning the fossil fuels at a faster rate than they are being made - the equivalent use of trees would be deforestation with no replanting.

Posted By: BrianwilsonBurning biomass brings immediate large CO2 emissions, this can be delayed by utilising biomass in construction or superior alternatives.

Brian - this argument relies on it being viable to build with the wood that is burnt. Not all wood that is burnt could or would be built with if it was not burnt, so it is only in some situations that you can apply this argument - as I went over in more detail in my response.
In my example of how I heat my house it is clear that the wood I use would not be built with if I did not burn it - so that makes it very clear that the argument is not universal, it needs qualification. You and indeed the authors suggest that you all have the same focus which is that the arguments in the discussion paper are really targeting large scale industrial use - if that is the case then this should be in included in the text because as it stands the blanket statement that 'wood is not a low co2 fuel' is false. Certainly is in my example - or do you differ with reference to my example?

And lastly:

Posted By: SteamyTeaNot really comparing like for like at all because what would happen if your hedge got some nasty bush disease, would you stop using your wood burner?

Well this is a good fossil fuel analogy. The nasty bush disease (which would presumably leave all my trees dead, yes?) has the same end result within the cycle as using fossil fuels at a much faster rate than they are made. As to what I would do - well I would keep as much of the wood from my hedge as I could to burn and I would replant with something resistant - luckily in the tree cycle I have the time and chance to do this.

?

Posted By: SteamyTeaPlease don't think that I am a 'business as usual' Luddite

Not at all - I think I know you better than that by now!

Not all wood can be built with. It makes sense to burn the rest for heat whilst also doing lots of other sensible stuff as much as possible like insulating.
The wood that can be built with acts as a short term store of co2. All for the good. So pushing wood as a building material is a good idea.
Depends on the situation.
We are not using wood in the same way in which we are using fossil fuels - we are not deforesting and not replanting, quite the reverse forest cover is on the up. Plus the woodfuel can make the timber building product production more economically viable.


A years worth of timber emissions are captured in a year, if that were not the case then forest cover would be decreasing.

Thinking of my example - the lowest overall co2 emissions result when I burn the wood and do not install an oil or gas boiler, do you agree? If not please tell me where I am going wrong.

Posted By: suneThinking of my example - the lowest overall co2 emissions result when I burn the wood and do not install an oil or gas boiler, do you agree? If not please tell me where I am going wrong.

Your CO2 emissions are linked to your fuel type and the amount of energy used, CO2/kWh, do you agree with that? You keep coupling your ability to absorb CO2 emissions. Let us de-couple them and see if the logic stacks up.

Table of CO2/kWh (www.resurgence.org)

Gas (Piped) 0.206
Electric (Grid) 0.43
Gas (bottled) 1.5
Wood 1.779
Oil 2.518
Coal 2.523

So for any given energy demand mains gas will be the lowest and coal will be the highest. Wood is in the top half, a bit worse that bottled gas, your most likely choice.
So how is wood burning producing less when it does not?

Now let us couple them to land area (have to use a closed system here because that is what you are doing).
Every square metre of land, on average, in the UK receives 950kWh of solar energy. Plants have a energy conversion rate of around 3%. So a square metre of land can produce about 28.5 kWh of stored energy.
Therefore of every kWh you use you need 0.04 m^2
Multiply 0.04 by your demand (in kWh) and if your hedge has a greater area than this then you personally are absorbing CO2 and if it is less then you are benefiting from others CO2 emissions

My total domestic energy demands is currently 11,000 kWh/y
So I would need 438 m^2 of bio-energy crop to substitute this (not taking processing into account).


If I was to use nothing but mains gas (none here so I don't) I would need factor of 8.4 less (about what I have, 50 m^2)
Electric would come out 4.2 less (twice what I have 104 m^2).

Now I have no idea what area your hedge is or your domestic energy demand is, but you can work that out.

What I am saying is that the assumption and calculations that you have made are wrong. It is unfair to allow absorption of biomass but not fossil fuels (some may argue that this is the reason forest cover is increasing, I think it is increased use of fossil fuel allowing less use of biomass as a fuel).

Edit 14:02 (Archers Time)
So my conclusion is that unless you can show that every molecule of CO2 from your wood burning is, at the very least, matched by your plant growth CO2 uptake you cannot claim that your wood burning is CO2 neutral.

Posted By: suneBut what that misses out is that if I do not burn it then it rots releasing the same co2 into the atmosphere plus some methane

Yes but not all of it, some is sequestered into the land and could eventually become a fossil fuel. Seems to be some confusion here about rates and reserves.

Nice picture....

Yep some would probably be sequestered. Not as much as used to be sequestered but some will be (a clue there from the anaerobic production of methane).
We need to refer back to that paper you posted a link to ages ago which, amongst other things, showed forest sequestration rates if we want to try to get to a figure.
But do remember also that in the same paper it shows that the co2 uptake rate for unharvested forest is lower than that for harvested forest. Doesn't really apply to my hedge - as I take out more or less mature trees but it does to forest.

I still say that my example, where I burn the wood, is the lowest co2 option when compared to an oil or gas boiler.

Posted By: SteamyTeaMy point is, does your hedge exactly absorb as much CO2 as burning your hedge produces? If it does not then it is getting the CO2 (for growth) from somewhere else

Where would my hedge be getting its carbon from if not the atmosphere?

If I used gas and did not burn the tree then it would rot releasing nearly the same CO2 as it absorbed and some methane.
Same goes for a PV panel - the trees would still rot.....