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?
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.