Using Grasslands for Carbon Sequestration: a Viable Weapon against Global Warming?

grasslands in marin county california

If we want to slow climate change, we have to reduce our carbon emissions, right? Yes… but that’s not the whole story. We’ve still got carbon dioxide in the atmosphere at dangerous levels (391.57 parts per million average for 2011, up fromΒ 389.78 ppm). Sure, that will eventually work its way back into the soil, but probably not in our lifetimes, or those of the next several generations. In fact, we’ll probably just have to suffer the consequences of that concentration of CO2… right?

Maybe. A project in West Marin, California (where else, right?) is studying the possibility of speeding up carbon sequestration in rangelands, grasslands, and other available spaces (and increasing the amount of topsoil to boot). Dubbed the Marin Carbon Project, this joint effort amongΒ the UC Cooperative Extension, Marin Organic, the Marin Agricultural Land Trust, the Marin Resource Conservation District, the USDA Natural Resources Conservation Service and Nicasio Native Grass Ranch is working with a pretty basic hypothesis: adding judicious amounts of compost to soil will increase carbon sequestration by increasing photosynthesis in plants (which, of course, takes carbon out of the air).

A peer reviewed study of the Project’s work will come out later this Summer; an article at Bohemian.com provides a glimpse of what came from the Project’s experiments. According to writer Stett Holbrook, “…researchers spread a half-inch layer of compost onto John Wick and Peggy Rathmann’s Nicasio ranch to see what impact it might have on banking soil carbon.” The results were well beyond what anyone expected:

After one year, the test plots showed a sequestering of at least one ton of carbon per hectare. A year later, without adding any additional compost, they found another ton of carbon in the soil. A year later, the same thing. And the next year, too.

Pretty exciting, huh? Definitely. I’d have to wonder about the climate impact of the compost itself, though: as Steve Savage pointed out Β three years ago, the release of methane from industrial-scale composting is worrisome, and could offset other gains. The scientists in this project do plan to look at the whole lifecycle of the management approaches they’re studying, and determine the full greenhouse gas costs of them.

No doubt there are many among you with more scientific background than me, so fire away: what do you think of this approach to sequestering atmospheric carbon?

Thanks to longtime friend @alimoves for the heads up on this one…

Image credit: cwohlers via photo pin cc

  1. Steve Savage

    When they do their entire life cycle analysis they may get some less encouraging results. They will need to count all the fuel from collecting stuff, hauling it to a composting facility, turning it, reloading it, hauling it many miles to Marin, and then spreading it. We are talking huge quantities here – tons/acre. There is the methane generated during composting – lots. Then you have to remember that these areas are sloped so when it rains the compost or nutrients in it can be washed into streams. Composts are also rarely balanced in terms of N and P with Phosphorus usually being in excess. That isn’t a good thing to throw around.

    If this is coming from the food waste program in SF, one could take credit for emissions that don’t happen from the land fill, But actually the good citizens of SF should be sending food waste down the disposal as much as possible. Their water treatment facility (if it is at all modern) has a way to intentionally turn biosolids into methane and use that to generate electricity. What is left after that process would possibly be a better thing to spread on the hillsides.

Leave a Reply

Your email address will not be published. Required fields are marked *