14 Sep 2010

More on the biomass debate

My last post resulted in the following email:


I came across your blog this morning. I’ve seen a few discussions lately about the “greenness” of wood burning and I have a question of sorts you might be able to shed a little light on.

If I developed a mechanical widget that pulled CO2 out of the atmosphere and reacted it with some black magic producing useable energy and returning the CO2 a brief instant later to the atmosphere at the same rate it was removed a brief instant earlier, no doubt I’d qualify for all sorts of subsidies, praises and accolades.

So why is it, when I do the same thing over a slightly longer period of time, it’s suddenly as bad or worse than sending equivalent tonnages of carbon that’s been sequestered for a few tens or hundreds of million years into the atmosphere? On that time scale, burning even 100 year old wood is a very short carbon cycle.

Burning a 100 year old chunk of wood is simply putting back the carbon that was in the atmosphere 100 years ago, not increasing the total on a geological time scale and doing so prevents adding some amount of fossil carbon to the total in circulation.

We can’t, but if we could live entirely off burning wood, growing new wood at the same rate we consumed old wood and not release another atom of fossil carbon into the atmosphere, the natural sequestration of carbon would ensure that atmospheric carbon levels would decline very quickly, wouldn’t it?

So why all the fuss over burning wood?

Just curious.


Rick Gresham
Portland, OR

The nice thing about this letter is that you can immediately see the good points of the pro-biomass burning argument. Burning biomass is just fine because it doesn't add a whit to atmospheric CO2. Surely it can be at least part of the solution? You might just as well draw energy from the destruction of wood as let it rot naturally? All good points.

But the counter points are just a little stronger.

• The finite globe. There isn't and never will be anything like enough biomass available to burn to keep 6-10 billion people warm and happy. It will be a struggle to keep everyone fed. So why encourage burning it? It's not the solution.

• OK, you can't eat trees. But it's a two stage process. The first bit - the growing of it - is good news for atmospheric CO2; the second bit - the burning - is bad news. On balance they cancel each other out, but how much better it would be if we could encourage the first bit and delay the second bit. If the gap between growing and burning could be extended from 100 years to 200 years, then we are giving the atmosphere an extra 100 year breathing space at a time it could surely do with it. Therefore, it follows that if we should subsidise anything, it should be the use of biomass as a building material, thus extending the capacity of biomass to lock up carbon for longer than would happen naturally.

• There is a British-centric argument going on here which may not translate in woody Oregon. We have a proposal on the table to introduce a subsidy for burning biomass, the first of its kind in the world, to be known as the Renewable Heat Incentive. It's controversial, as you can imagine. So the argument here isn't just whether it's good or bad to burn biomass, but whether it's a good idea to give money to people to get them burning it.

• Rick's widget would be something new. It would be a miracle. It would change everything. In contrast, timber and biomass resources are things we are already blessed with. They do act like this miraculous widget, but only if everything that is burned is subsequently replaced. In other words, only if the resource is sustainably managed. That bit is critical. In fact, it's key. If we subsidise the burning of biomass, we risk upsetting this balance. People will hunt out biomass to burn without any guarantee that what they harvest will be replaced. And the more the craze for biomass grows, the bigger this pressure will become.

• We are not talking about a few wood burning stoves here. They are not the problem. It's the industrialisation of the process which threatens everything. If you start switching coal-burning power plants over to biomass (and it's already happening), then this supposedly huge untapped resource is very rapidly going to be coming under pressure. The more pressure on the resource, the less likelihood it will be managed sustainably. Just ask the fishermen.


  1. Anyway, burning biomass isn't even theoretically CO2 neutral over whatever timescale, once the CO2 costs of extracting, processing and distributing said biofuel is taken into the calc, let alone the embodied/lifetime resource calc on the equipment needed to burn it and heat things with it. In a basic peasant society, at most horse- (or slave-)powered, harvesting and burning biomass in basic appliances, then yes, truly or very nearly CO2-neutral, as release of stored CO2 from chawed-up forest floor is minimal, and the horse/man workforce's fuel is itself entirely part of the CO2 cycle. I'm not all advocating a return to that - everything we do (and eat) nowadays is CO2/resource-positive, as unavoidably as the un-natural electromagnetic soup that we all bathe in. We can burn CO2-positive biomass maybe but that and everything else has to be well overbalanced by CO2/resource-negative things (like carbon sequestration, for a start) yet to be invented, or even seriously thought about as the only possible way out of the present mess.

  2. Hi Mark,

    'People will hunt out biomass to burn without any guarantee that what they harvest will be replaced. And the more the craze for biomass grows, the bigger this pressure will become.'

    But, the bigger will be the economic pressure to replace the burnt wood by growing more. You are ignoring basic supply and demand?

    We have to have a huge demand and supply of something to create usable energy. It is VERY much better if that something can be renewed infinitely, why not make wood a significant part of it?


  3. Thanks Mark

    Really appreciate your clarity, but only when i agree with you!

    I did think for a moment that someone had found a flaw in the argument. As I said on the AECB forum, I am hoping there is a flaw and that biomass really is low carbon as it would make my job easier when faced with a hard to insulate property such as a church that is to be converted to an office but apparentl 'can't' be insulated.


    Did you read the paper that Mark is referring to?


    I know you have read it but we think the problem is far greater than the transport and processing which is quite small really. The value in SAP accounts for this.


  4. Hi Nick,

    have you read what Mark wrote and what I wrote?

    In which case, why do we not discuss that instead of whether we read it or not?


  5. Hi Nick,

    'Did you read the paper that Mark is referring to?'

    Gosh effortlessly denigrating, i am impressed.
    Did you read Mark's post and mine?
    In which case why do we not discuss what he said and i said, rather than whether we read it or not?


  6. Peter I am sorry but I really didn't mean to be patronising it's just a several people have admitted to only reading about the paper but have not read the actual paper.

    The reason I wondered is that we do discuss the potential resource. Supply and demand may work for the imaginary widget as we could just make more and supply matches demand but biomass needs land, water and nutrients and time to grow.

    Also our main point is that if we can grow so much biomass that it would be significant as an energy source then lets do that and bury it to sort climate change.

    I think Mark explained this clearer than I am.

  7. I'm not expert on wood farming, but it seems to me that this argument against burning biomass leans heavily on the assumption that there is a free choice between growing biomass to burn and growing building lumber in excess of that which is currently grown.

    Is that actually true ? I suspect that (a) biomass for burning is a rather different kind of farming, on different land and (b) the market for building lumber is already well-supplied, so there is no great opportunity to grow lots of new wood to put into it. There would need to be a mechanism to increase the size of the lumber market to make that point work.

  8. Hi Mark,

    I wonder if you'd be interested to talking to me briefly about self-builds? I am a freelance journalist writing a piece for a website about building your own house and I need a case study. Can you help?!
    If so, could you please email me at sarahwarwick(at)gmail(dot)com

    Many thanks


  9. http://www.greenwisebusiness.co.uk/news/biomass-plants-threaten-uk-wood-panel-industry-campaign-says-1578.aspx

    it'c causing market distortions.

  10. Really enjoyed reading that letter. I'm going to tell you about a thing I have had a big issue with for a long time. All these governments have been harping on about emissions targets and I think these are a load of nonsense and very misleading. The most important thing is the net amount of emissions i.e. the amount produced against the amount consumed. Somewhere like Brazil obviously consumes more CO2 with the rainforests than say Hong Kong. I think the government should be using it's environmental taxes or subsidising farmers to grow the biggest CO2 consuming plants they can, and balance this with reducing carbon emissions.

  11. "Somewhere like Brazil obviously consumes more CO2 with the rainforests than say Hong Kong."

    Forest are carbon neutral, they only act as sinks if the amount of forest is growing, or the timber being taken from them is used permanently, something that does not apply to Brazil.

  12. I appreciate what you are saying, that the CO2 goes into the trees but it doesn't disappear. I guess what should have said was if you want less carbon in the atmosphere we need to encourage tree growing combined with either less trees cut down or alternatively all trees that are cut down being replaced. In the rainforest afaik great swathes of forest have been cut down but not replaced, surely this will have a negative impact on the CO2 level in the atmosphere.