Monday, February 16, 2015

Carbon Sequestration

The snow day is nearly over, but I learned something today I'd like to pass along. The term "carbon sequestration" can have at least two different meanings.

Soil Carbon Sequestration

Soil carbon sequestration is a process in which CO2 is removed from the atmosphere and stored in the soil carbon pool by plants through photosynthesis, with carbon stored in the form of soil organic carbon (SOC).

Since the industrial revolution, the conversion of natural ecosystems to agricultural use has resulted in the depletion of SOC levels. This is the combined result of reductions in the amount of plant roots and residues returned to the soil, increased decomposition from soil tillage, and increased soil erosion. Depletion of SOC stocks has created a soil carbon deficit that represents an opportunity to store carbon in soil through a variety of land management approaches. However, various factors impact potential soil carbon change in the future, including climatic controls, historic land use patterns, current land management strategies, and topographic heterogeneity. (Todd A. Ontl & Lisa A. Schulte, 2012)

Carbon Capture and Sequestration Technology

Carbon capture and sequestration (CCS) technology is the process of capturing waste CO2 from large point sources, such as fossil fuel power plants, transporting it to a storage site, and depositing it where it will not enter the atmosphere, normally an underground geological formation. (See EPA on CSS.) The energy requirements of sequestration processes may be significant (up to 25% of the energy output or more). By the industry's own admission, on a practical scale the hurdles are still enormous. Moreover, it would only work on point sources.

What I learned today, then, is that neither form of carbon sequestration is currently feasible on a large scale. But soil carbon sequestration is not only a potential means of reclaiming atmospheric CO2, but more importantly it is a way to reclaim our rapidly depleted soil. Carbon capture and sequestration technology, on the other hand, is merely an attempt to mitigate the continued use of fossil fuels using technology that is still prohibitively expense and of unproven safety.