Carbon Sequestration Introduction

CO₂ Is a Greenhouse Gas
Carbon dioxide, or CO₂, is a natural component of air that helps reflect the Earth's infrared radiation back to the surface, causing heat to be retained, as in a greenhouse. Without CO₂, the planet would be inhospitable, with daily surface temperatures varying by hundreds of degrees. The amount of CO₂ in the air had been relatively constant for ten thousand years until the Industrial Revolution in the 1800s. Since then, the world’s population has grown tremendously, as has the use of coal, oil, and natural gas. Because CO₂ is a primary product of combustion, the atmospheric concentration of CO₂ has been on the rise. At the same time, average temperatures throughout much of the world have inched up and other climatic changes have been documented, indicating a connection between our use of fossil fuels and climatic effects.

There’s No “Silver Bullet” for Curbing Global CO₂ Build-Up
Because CO₂ accumulates in the atmosphere before being removed by natural processes, slowing and ultimately reducing atmospheric CO₂ concentrations will require deep cuts in man-made CO₂ emissions. Emissions reductions of that magnitude are a complex challenge that will require multiple solutions, including more efficient energy use, alternative fuels, electric-drive transportation, electricity from non-CO₂-emitting energy sources, and carbon sequestration.

Carbon sequestration refers to the “capture” of CO₂ and its long-term storage away from the atmosphere. Indeed, it is sometimes called "carbon capture and storage" (CCS). CO₂ can be captured in two basic ways—by enhancing natural processes that remove it from the air and by modifying industrial plants to remove CO₂ from process or exhaust gases before their release.

CO₂ Capture, Transportation, and Geologic Storage
CO₂ captured at industrial facilities needs to be stored in a location where it won’t escape to the atmosphere or interfere with human activities and the environment. Typically this means injecting it deep underground into secure geologic formations, such as depleted oil and gas reservoirs, unmineable coal beds, or saline formations (porous sandstone filled with saltwater), where the CO₂ will remain for centuries or millennia. In some cases, CO₂ can be used to enhance oil and natural gas production. Pipelines are often used to transport CO₂ from the point of capture to the point of injection for storage.

Terrestrial Sequestration
Plants absorb CO₂ from the air during photosynthesis and ultimately metabolize and store carbon as tissue (biomass) or transfer it to the soil. Changing the way that forests, rangelands, agricultural lands, and wetlands are managed can increase the amount of carbon stored by plants and soil. Known as terrestrial sequestration, this approach can hold carbon intact for decades or centuries.

Technology Validation Projects Are Urgently Needed
Neither terrestrial nor geologic carbon sequestration is currently a commercial technology; hence the need for the WESTCARB research partnership (and work by others). Terrestrial sequestration appears to be simpler and less expensive than industrial CO₂ capture and geologic storage, but it has a lower ultimate storage capacity and may require more management to prevent inadvertent CO₂ releases (through fires, for example). The economics of geologic storage improve when the captured CO₂ can be sold for enhanced oil and natural gas recovery.

While helping stem increases in global CO₂ concentrations, terrestrial and geologic sequestration can also affect local and regional economies. Accordingly, WESTCARB is exploring ways to maximize the co-benefits of sequestration projects. WESTCARB is also working to engage the public in discussions of health and safety, socio-economic, and environmental issues as it conducts regional carbon sequestration studies and field tests.