OT: Chatham House study reveals biomass not as carbon neutral as thought

[Chris Hogg]

and

[Tim Streater]

Bit article about it in the Times today, too.

And a lament on BBCR4Today yesterday morning about how many studies in the biotech area are not reproducible - meaning that any results they purport to give are worthless.

The reasons range from peer pressure, pressure on journals to be at the cutting edge, "tidying up" of data, pressure on funding bodies to be seen to be getting results - all the usual rubbish which we have seen elsewhere (can't for the life of me think where though, at the minute).

[tim...]

but is the problem one that it doesn't work in principle

or merely because we are burning stuff that has come from too far away and has caused more pollution being transported than we are saving

but then we have to add in the "cost" of transportation for the alternative fuels that we would have used

tim

[Chris Hogg]

I've not read the papers line by line, but AIUI the argument is that felling and shredding actual trees for biomass fuel, as opposed to using just saw-mill waste and trimmings, increases the CO2 content of the atmosphere in the short term, while re-growth only reduces it in the long term. It takes only a few weeks/months to fell a tree, shred it and burn it, whereas it can take many decades, possibly centuries, to re-grow a tree of the same size.

Shreddings and saw-mill waste left to rot on the forest floor produce CO2 over a timescale comparable to that for combustion, so don't contribute to atmospheric CO2 over a different time-scale to burning.

Each of the two links I gave has in turn a link to a PDF of the actual papers, near the bottoms of the respective pages.

and

[dennis]

Its not exactly new. Anyone except harry can see that cutting down forests and burning them is not carbon neutral in any real meaning of the word.

[GB]

What if you take a patch of barren land and grow something that's fast growing - willow for example - that grows for say 3 years before you cut it down and burn it?

Is that reasonably carbon neutral?

[dennis]

That depends on how its planted and harvested.

[Tim Watts]

Don't they also produce methane which is far far worse as a greenhouse gas?

[Chris Hogg]

Possibly, but I associate methane production with anaerobic decomposition, for example inside peat bogs or in the bottom of stagnant ponds (see marsh gas

). Shreddings left to rot in the open air wouldn't produce much, I don't think, but I may be wrong.

[The Natural Philosopher]

No. What we have to do is simply use a free market. If wood costs more than coal, chances are there is more energy and labour involved ion producing it.

So burn coal instead.

[The Natural Philosopher]

Probably. But its rotten firewood.

[Bill Taylor]

Actually, if properly dried, it is perfectly good firewood. It's very low density, so you get less energy out of it per unit volume than something like oak, but it burns very well. I'm using a couple of cu.m. of our coppiced willow at the moment and it's heating the house nicely

Of course if you're foolish enough to try and burn it as soon as it's been cut, it's terrible firewood..

[Chris Hogg]

Yebbut...could you fuel a 1GW power station with it? What area of willow would you need to have planted to do that, and what drying/storage capacity would you need before it's burnt?

OOI is your couple of cu.m of dried coppiced willow chipped/shredded or just loose stacked as rods, and how long does it last in your situation - days/weeks/months?

[Martin Brown]

In the short term methane is a worse GHG but in an oxygen rich atmosphere it has a relatively short half life before it becomes CO2.

I agree that it makes sense to burn saw mill waste locally, but not to plant and chop down forests ship them half way round the world to meet some renewable target obsession. Wood is just not energy dense enough!

[GB]

Having read the newspaper article about this - my attention span is too limited for the CH study - it seems that US forests are chopped down, the wood is chipped, and then it's shipped across the Atlantic to be burned here. I don't think you have to do much of a study to realise that that is nowhere near carbon neutral. Why take perfectly good timber and burn it? All the waste bits, maybe, but that's not what's happening.

[Bill Taylor]

In theory. When they started using biomass there was a lot of interest in the agricultural industry about growing for biomass power stations. It was generally either miscanthus or short rotation willow coppice which would probably have been chipped. I don't know if anyone is still producing biomass for power stations in the UK. It wasn't cheap enough and they probably couldn't produce the quantities neede, so it's mainly imported now.

It's used in a log boiler, so they're cut to length (about 20") and stored stacked under cover for a year or two to dry. The lot I'm using at the moment looks as if 1.5 cu.m. is going to last about 10 days, but the weather's warm at the moment. Over all we'll burn 15-25 cu.m. a year depending on weather, how warm we keep the house and if the wood is dense or not. We burn any dry wood, not just willow.

[Tim Streater]

It's well known that a small country like the UK was never going to be able to grow enough to make biomass viable. And if you can't do that, why bother?

[The Natural Philosopher]

yes.

Willow averages at about 0.5W/sq. metre, so you would need around 2 billion square meters or around 2,000 square kilometres..

So 14 kilometres square give or take.

Dont ask :-]

a cubic meter a day is not unheard of to heat a large house in scandinavia.

[Huge]

Market distortions caused by Government diktat/subsidy.

[Tim Streater]

45 kilometres square, Shirley.

Where we gonna find a square of land 45km on a side in the UK that's just sitting there doing nothing?