Sequestration

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Sequestration

Introduction

Sequestration refers to the active addition of carbon and other greenhouse gases to long-term reservoirs in their biogeochemical cycle. Industrialization has resulted in an increase in greenhouse gases in the atmosphere as a result of burning fossil fuels and removing forests. The goal of sequestration is to remove greenhouse gases from the atmosphere in order to slow the deleterious effects of climate change.

Historical Background and Scientific Foundations

Because industrialized processes depend heavily on fossil fuels, carbon dioxides and other greenhouse gases such as nitrous oxides and methane are removed from the fossil fuel reservoir and input into the atmosphere at an unprecedented rate. This results in global warming and climate change. In order to reduce emission into the atmosphere, some effort is being focused on developing technologies to capture carbon from the atmosphere and then store it in other biogeochemical reservoirs or reuse it. These processes are known as sequestration.

Current sequestration efforts are primarily focused on removing carbon dioxide from the atmosphere and adding it to four major reservoirs. The most promising technology for carbon dioxide sequestration is aimed at injecting carbon dioxide into geological formations. These include oil and gas reservoirs, coal seams that are unable to be mined, and deep saline reservoirs. Other efforts are focused on sequestering carbon dioxide in biological reservoirs including forests and oceanic phytoplankton by stimulating

growth of photosynthetic organisms. Methods of removing carbon dioxide from emissions using chemical and biological decarbonization concepts are also being studied.

Direct sequestration refers to immediate capture of carbon dioxide from power plants and using the carbon dioxide with enhanced oil recovery efforts. Indirect sequestration involves capture of carbon dioxide from the atmosphere and then using it to stimulate the growth of photosynthetic organisms, either in forests or in the ocean.

Whereas most sequestration efforts are aimed at carbon dioxide, there is some research into sequestration of nitrous oxides and methane, which are also released in the burning of fossil fuels. Nitrous oxides are a significant contributor to the formation of smog.

Impacts and Issues

In 1997, the President's Committee of Advisors on Science and Technology (PCAST) submitted a report titled, “Federal Energy Research and Development for the Challenges of the Twenty First Century,” which recommended that the U.S. Department of Energy (DOE) receive an increased budget for research and development for carbon sequestration technologies. Following that report in 1999, the joint Office of Fossil Energy and the Office of Science released a draft report “Carbon Sequestration: State of the Science,” which identified important areas of research that could develop methods for managing carbon emissions using sequestration. The DOE recognizes that the development of sequestration technology would provide additional time for technologies to develop low emission systems because it could offset emissions by power plants and other fossil fuel-burning systems.

WORDS TO KNOW

CARBON: Chemical element with atomic number 6. The nucleus of a carbon atom contains 6 protons and from 6 to 8 neutrons. Carbon is present, by definition, in all organic substances; it is essential to life and, in the form of the gaseous compounds CO₂ (carbon dioxide) and CH₄ (methane), the major driver of climate change.

FOSSIL FUELS: Fuels formed by biological processes and transformed into solid or fluid minerals over geological time. Fossil fuels include coal, petroleum, and natural gas. Fossil fuels are non-renewable on the timescale of human civilization, because their natural replenishment would take many millions of years.

GREENHOUSE GASES: Gases that cause Earth to retain more thermal energy by absorbing infrared light emitted by Earth's surface. The most important greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and various artificial chemicals such as chlorofluorocarbons. All but the latter are naturally occurring, but human activity over the last several centuries has significantly increased the amounts of carbon dioxide, methane, and nitrous oxide in Earth's atmosphere, causing global warming and global climate change.

PHYTOPLANKTON: Microscopic marine organisms (mostly algae and diatoms) that are responsible for most of the photosynthetic activity in the oceans.

PHOTOSYNTHETIC ORGANISMS: Plants and bacteria (cyano-bacteria) that practice photosynthesis, that is, the storage of energy from light in chemical bonds. All animals depend on this energy, either directly (plant-eaters) or indirectly (predators). The only exceptions are certain deep-sea organisms that derive their energy from hot springs ultimately powered by Earth's internal radioactivity.

RESERVOIR: A natural or artificial receptacle that stores a particular substance for a period of time

As of 2007, the DOE estimates that the cost of sequestering a ton of carbon that would have otherwise entered the atmosphere is in the range of $100 to $300. The DOE has set a goal to reduce these costs to $10 or less by 2015. In 2007 the DOE awarded its first large grants, totaling $318 million, to fund research into sequestration technologies and into the storage of carbon dioxide in deep saline reservoirs.

BIBLIOGRAPHY

Web Sites

“Carbon Capture and Sequestration Technologies.” Massachusetts Institute of Technology, 2007. <http://sequestration.mit.edu/index.html> (accessed October 22, 2007).

“Carbon Sequestration Research Program.” Department of Energy, September 19, 2007. <http://fossil.energy.gov/sequestration/> (accessed October 22, 2007).

“Report to the President on Federal Energy Research and Development for the Challenges of the Twenty-First Century.” President's Committee of Advisors on Science and Technology Panel on Energy Research and Development, November 1997. <http://www.ostp.gov/Energy/index.html> (accessed October 24, 2007).

Juli Berwald

Climate Change: In Context