The second question of the forum was about what technology you would like to see, either in your lifetime or in the far distant future. It was either Andy or another colleague, Bob Gann, who suggested it would be really handy to have a way of pulling CO2 out of the atmosphere.
I suggested organic agriculture since, at least under some climatic conditions, soils that are farmed organically have more carbon in them than do conventionally farmed soils. On a global scale, that would represent a potentially large amount of carbon pulled from the atmosphere by plants and locked up in the soil.
Andy countered that organic might be OK in the rich countries where we already have plenty of food, but in many parts of the world people need more food, not less, and so switching to organic would mean a reduction in diet and/or increased deforestation (which in turn would increase atmospheric carbon) to make up in farmed land what organic would cost you in yield per acre.
It's a common argument, and it may ultimately be right, but there three areas that I think warrant more attention. At a minimum, they mean that it's a weaker argument than it seems. And it may actually be no argument at all:
- What do we take as our starting point?
- Smil's calculations
The lasting piece has to do with crop rotations. One of the basic tools in organic agriculture for maintaining soil fertility and diminishing pest pressure is to rotate crops. Where a conventional farmer might alternate between corn and soy, an organic farmer might have a four- or five-year rotation, with a year of corn, a year of soy, a year of a low-value food crop like oats, and a year or two of a non-food crop like alfalfa. So even if your corn and soy per acre in a given year is as good as a conventional farmer's, you're only growing those crops on half your acres, so your all-farm yield has gone down. That's the rich countries which already produce very high yields per acre.
Many farmers in poor countries are in a different situation. Many of them are farming nearly organically by default, not having the money or the access for fertilizers and pesticides. And they have very low yields. They have two ways to increase their yields. If they can somehow get their hands on fertilizer, pesticides, and irrigation water, they can follow the high-yield path of the rich countries. On the other hand, if they learn to farm in ways that build up the organic matter of their soils, they can raise their yields from where they are now, without the cash outlay, and sequester carbon into the bargain. There's a potential win-win here.
2. Smil's calculations The Czech-Canadian geographer Vaclav Smil has done a ton of work on energy flows in various economic processes. He also makes a point about the Haber-Bosch process quite similar to Andy's. You look at the nitrogen fixation that was being accomplished by bacteria before the Haber-Bosch process came along; you figure out how much food that could produce; you can then run a hypothetical, "How much food could we produce today if we didn't have Haber-Bosch?" A reasonable approach, but it has two assumptions that are too limiting.
First, he assumes that the average rate of fixation around 1910 is a good estimate of the best that can be expected today. But I'm not at all convinced that that's true. On the one hand, there's no justification for taking the best rate of fixation anyone has ever achieved and saying that that's what we should expect to be able to replicate everywhere. On the other hand, in a healthy soil food web plants will be more productive, converting more solar energy into sugar, which they can feed to the symbiotic bacteria on their roots that do the work of nitrogen fixation, leading to an increased rate of fixation.
Second, he assumes a fixed rate of efficiency of plants converting nitrogen in the soil into plant growth, when there's a lot of evidence that significant parts of the nitrogen put on our fields today simply washes away.
A well-tuned organic system can both capture more nitrogen than a conventional estimate would suggest, and convert more of that captured nitrogen into plant growth. It doesn't necessarily follow that we can fully replace Haber-Bosch, but we should be using a more sophisticated calculation of possible alternatives--and maybe we actually can fully replace it.
3. Meat Globally, 18% of the calories that humans have available to them come from animals, as opposed to direct consumption of plants. And 34% of the world's grain supply is used to feed animals.
In the U.S., the comparable figures are 27.5% of our diet from animals, and 43% of our available grain fed to them. In Europe the diet is also 27.5% animal, and the portion of the continent's grain that goes to feed animals is 58%. (That's not because they grow less grain; the 58% is out of the continent's supply, which includes net imports.)
(The data are from the Food Balance Sheets prepared by the United Nations Food and Agriculture Organization and available here.)
I am not a vegetarian. I don't object to other people eating meat (that would be rather hypocritical, since I eat meat). I enjoy cheese, and milk, and ice cream, and omelets. I suspect that reducing our meat consumption will not, all on its own, allow us to feed the world on organic agriculture--but it would do a big piece of the job.
For me, reducing my intake of animal-derived foods would entail changes in eating habits that apparently I wouldn't like (because nothing's currently stopping me from eating that way and I'm not doing it now--that's the economist talking). But we can be healthy on a diet of only 10% animal foods. Doing it as an individual choice feels good but from the perspective of the problem as a whole is rather ineffective. We can do it as social policy if we tax the sale animal-based foods, and we'd actually accomplish something.
If we're not willing to consider that change, how serious are we about pulling carbon out of the atmosphere?