sequestration?

To continue our brief overview of what carbon offsetting and carbon sequestration are, let's focus on the latter. New technology and ideas focused on carbon sequestration are aimed, in a general sense, at pulling CO2 out of our atmosphere. Whether by enhancing natural sinks, or by creating new sinks, the idea is to draw down this greenhouse gas or trap it at its source, and then sequester it, or isolate it from the atmosphere.

The website of the Department of Defense's Office of Science provides an overview of the technologies that currently exist or are being developed to sequester carbon. One idea, already being tried at one coal-fired power plant in West Virginia, is to trap carbon before it is emitted into the atmosphere and to store it underground, typically in empty oil reservoirs. A New York Times article about this plant describes the process: as CO2 passes through the flue, chilled ammonia traps it and compresses it into liquid form so that it can be injected some 9,000 feet below the surface of the earth.

The second major realm of sequestration technologies is enhancement of natural sinks on land. The projects focus mainly (as I understand them) on enhancing photosynthesis and carbon fixation, conversion of carbon into organic matter, reducing re-emission of CO2 through respiration, and increasing primary productivity in degraded lands and deserts. Examples include forest harvesting and pasture management (storage of CO2 in the soils of pasture lands).

A third focus area is on carbon sequestration in the ocean, as earth's oceans naturally represent about half of the world's atmospheric CO2 sink. Current proposed projects include fertilizing the ocean with limiting nutrients to enhance primary productivity and direct injection of CO2 into the deep ocean (1000m+). Great uncertainty surrounds both of these methods both in terms of effectiveness and environmental implications.

A final idea proposed on the DOE website is that of sequencing the genomes of microbes that generate or ingest carbon compounds. The DOE suggests that with greater understanding of the genetic pathways which allow organisms to manipulate carbon, we may some day be able to develop a microbial carbon sink, possibly one that converts methane to hydrogen.