Storing Carbon

Jim Lovelock, of the Gaia hypothesis (the idea of earthly life as a self-regulating organism, maintaining conditions, especially climate conditions, favorable to itself) thinks our civilization has had it. By 2100 perhaps 1 billion people will be left. I tend to agree with him but would put things a little later—200 million people by 2200. This is not necessarily a bad thing, except for those poor souls who must live through the demographic catastrophe. (We could of course engineer our own demographic collapse by limiting woman to one child. Population would fall to 1.6 billion by 2100 and the carbon problem would solve itself. How to do such a thing is a puzzler.)

Lovelock thinks we must start pulling carbon out of the atmosphere immediately to keep climate from flipping into a new, unfriendly regime. He may be right: for the last 650,000 years, the carbon dioxide content of the atmosphere has fluctuated between 180 and 300 parts per million. For the last 8000 years of most favorable climate that has seen the flowering of human agricultural civilizations, the carbon dioxide content of the atmosphere has fluctuated between 250 and 290 parts per million. It is now over 380 parts per million and growing by 1-2 parts per million every year.

Lovelock thinks the only reasonable way to sequester sufficient carbon from the atmosphere to stabilize the climate is to bury it. He thinks schemes like burying the carbon dioxide from burning coal are too expensive, too dangerous, too late and too little (and perhaps too nuts). Burying organic carbon has been proposed before: to cut forests and bury the trees in long ditches below the depth of decomposition, thus locking up their carbon. The forest regrows, storing more carbon in its trees, which are cut and buried again. The idea is also somewhat nuts but a variation on it is less nuts. Most of the carbon plants fix through photosynthesis is returned to the atmosphere, from where plants recycle it once again, every year. This amount of carbon dwarfs what we emit and a considerable amount of it is fixed by crop plants. We could take such carbon—corn stalks; grain straw; food waste; waste wood, such as old pallets, or demolition waste—and turn it, through a low oxygen combustion, into charcoal, and then, instead of burying the charcoal, spread it on the fields that grew it. Charcoal was used 1000 years ago by native farmers in the Amazon Basin to improve their soils, which otherwise would grow crops for only a year or two after being cleared. Most of the nutrients in tropical forest soils are stored in the vegetation: when that is removed and the ash from burning the trees leached away, few nutrients are left. When charcoal is added with ash (producing charcoal makes some ash and puts some carbon dioxide into the atmosphere), the charcoal provides a place for nutrients to attach, prevents leaching and encourages the growth of bacteria that increase the soil’s biomass. So-called Amazonian “black earths” contain charcoal, plant wastes, human urine and manure, fish guts and bones, broken pots. The fields were huge compost heaps. Present day peasant farmers in the Amazon seek out old black earths to farm, since their soils are much more fertile than the surrounding ones. Charcoal remains stable for 50,000 years. So the carbon remains locked up from the atmosphere for that time.

This method gives farmers a way of fertilizing their fields and storing a measured amount of carbon, for which they could be compensated. Natural grasslands store carbon more or less permanently in their soils (as long as the sod isn’t broken, perhaps half a ton to a ton an acre a year) but this gives grain farmers a way to do it too. How long one could keep adding carbon is unclear but black earths in the Amazon range from a foot to eight feet deep. Will we do it? I doubt it. It’s too sensible, too easy and too nuts.


Well I’m off for two weeks. No more posts for a while. Gotta keep up my carbon footprint, lower my winter heating bills. Suppose airline passengers paid $50 a ton for farmers to store carbon as charcoal, then they could fly guilt free.