Reforestation & Biochar: Two Geoengineering Methods That Won't Cause More Harm ... - Treehugger: "
photo: US Forest Service via flickr
Geoengineering has been a slow burning controversy for some time now, with some truly wacky ideas proposed, as well as some which take a more sober look at the prospect of intentionally tinkering with the climate to stop the effects of human activity disturbing it in the first place. Let's look at a couple of those geoengineering methods which won't cause more harm than good: Biochar and Reforestation/Afforestation.
But Wait! What is Geoengineering?
Geoengineering when it comes to climate change refers to technological methods to reduce the amount of warming that occurs. These can be divided into two broad categories: Those which try to manage solar radiation (
injecting aerosols into the atmosphere, mirrors in space, etc) and those which attempt to suck carbon dioxide out of the atmosphere (
ocean iron fertilization,
artificial CO2 scrubbing trees, etc).
In the eighteen months or so there have been a couple of studies done which attempt to weigh the effectiveness, the speed, and the risks of different geoengineering methods. The Royal Society did one and scientists from the University of East Anglia did another, to name two.
They have slightly different findings than each other, when assessing specific methods' effectiveness and the amount of further research needed to before they are deployed, but in general techniques which remove CO2 from the atmosphere are less risky than those which attempt to manage solar radiation. As for effectiveness, there are ways in either category which could work more quickly and ones which work more slowly.
Often times the quick ways are the ones which carry the greatest risk of creating problems if things don't work as simulations predict. For example, injecting aerosols into the atmosphere to block the sun could work very quickly, but also trigger unintended weather consequences leading to geopolitical problems.
All of which makes slower-working methods like biochar and reforestation/afforestation more attractive.
Pine trees ready to plant. Photo: Trees For the Future via flickr.
Reforestation & Afforestation: More Trees = More CO2 Sucked From The Sky
If you follow TreeHugger regularly you probably know that the amount of CO2 that a given area of land can absorb changes depending on what a piece of land is used for, how much and what type of vegetation covers it. Higher biomass both above and below ground (think tropical rainforest for the former and boreal forest or forest on peaty soil for the latter) means greater potential for sequestering carbon.
Chop down all the trees in a forest and you've radically lowered the the forest's ability to suck carbon out of the atmosphere. When you replant the land with crops (whether for food or timber) you gain some carbon storage potential back, but it's at best no better than what you had and generally much lower. All of this is why deforestation is such a large component in global warming--nearly as many greenhouse gases are released from chopping down trees as the entire transportation sector.
Which is all a big lead-in to a pretty simple definition: If deforestation is the removal of forest cover, then reforestation is simply planting trees in areas that have been cleared to help regrow the forest; afforestation is planting trees in areas which either have never been forest or haven't been forest in many years.
There's no doubt that reforestation and afforestation could be serious help in reducing the effects of global warming--both the Royal Society and University of East Anglia studies agree on this regard--but if you think about how long it takes for trees to regrow, and all that biomass on the forest floor to rebuild, you can easily grasp that the benefits of planting more trees won't be seen overnight. It's not a switch you can turn on and start sucking CO2 from the atmosphere.
Biochar test plot after two passes of biochar spreading. Photo: Dynamotive Energy Systems.
Biochar: Enriching the Soil, Storing Away CO2
The effects of starting reforestation and afforestation programs are easily visible; the effects of biochar not so much, unless you dig up the soil.
Biochar is essential using charcoal made through pyrolysis of biomass and then burying it mixed in with the soil. It has a long history of use in Amazonia, where it's known as terra preta, for its benefits in making soil more fertile. In regards to long-term carbon storage potential, biochar can work on a millennial scale with, in most cases, no negative soil side effects. Some estimates show biochar having the potential to sequester one billion tons of CO2 each year.
Which, despite being no miracle cure for climate change, sounds really pretty great. The problems with biochar aren't with the technique itself, but with scaling it to a large enough level that it has a global impact. The Royal Society survey says that "substantial research" is needed to prove biochar's effectiveness when deployed widely. Some critics suggest that we'd need to chop down 4% of our forests to deal with half of our carbon emissions.
Clearly chopping down forest to produce biochar is a bad idea, and this really isn't the way to go about it. A more reasonable way is proposed by big biochar backer James Lovelock:
What we have to do is turn a portion of all the waste of agriculture into charcoal and bury it. Consider grain like wheat or rice; most of the plant mass is in the stems, stalks and roots and we only eat the seeds. So instead of just ploughing in the stalks or turning them into cardboard, make it into charcoal and bury it or sink it in the ocean. We don't need plantations or crops planted for biochar, what we need is a charcoal maker on every farm so the farmer can turn his waste into carbon.
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