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.
See Also Atmospheric Chemistry; Atmospheric Circulation; Atmospheric Pollution; Atmospheric Structure;Biogeo-chemical Cycle;Biosphere; Carbon Credits; Carbon Cycle;Carbon Dioxide (CO2); Carbon Dioxide Concentrations; Carbon Sequestration Issues;Carbon Sinks; Climate Change;Coal; Forests and Deforestation; Global Warming;Industry (Private Action and Initiatives);Natural Gas; Petroleum; Petroleum: Economic Uses and Dependency; Sink; Social Cost of Carbon (SCC).
“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).
In the context of trials, the isolation of a jury from the public, or the separation of witnesses to ensure the integrity of testimony. In other legal contexts the seizure of property or the freezing of assets by court order.
In jury trials, judges sometimes choose to sequester the jurors, or place them beyond public reach. Usually the jurors are moved into a hotel, kept under close supervision twenty-four hours a day, denied access to outside media such as television and newspapers, and allowed only limited contact with their families.
Although unpopular with jurors, sequestration has two broad purposes. The first is to avoid the accidental tainting of the jury, and the second is to prevent others from intentionally tampering with the jurors by bribe or threat. Trial publicity, public sentiment, interested parties, and the maneuverings and machinations of lawyers outside the courtroom can all taint the jurors' objectivity and deny the defendant a fair trial. Judges are free to sequester the jury whenever they believe any of these factors may affect the trial's outcome.
Jury sequestration is rare. Typically ordered in sensational, high-profile criminal cases, sequestration begins immediately after the jury is seated and lasts until the jury has delivered its verdict. It is unusual for juries to be sequestered longer than a few days or a week. Occasionally, however, jurors are sequestered for weeks. The 1995 trial of former football star O. J. (Orenthal James) Simpson for murder was highly unusual: the Simpson jury was sequestered for eight and a half months—half as long as the period Simpson was imprisoned while under arrest and on trial. The experience provoked protest from the jurors and calls for legal reform.
The sequestration of witnesses differs from that of jurors. Whereas jurors are kept away from the public, witnesses typically are ordered not to attend the trial—or follow accounts of it—until they are to testify. This judicial order is intended to assure that the witnesses will testify concerning their own knowledge of the case without being influenced by testimony of prior witnesses. Witness sequestration also seeks to strengthen the role of cross-examination in developing facts.
Other definitions of sequestration relate to property. In civil law, sequester has three distinct meanings. First, it means to renounce or disclaim, as when a widow appears in court and disclaims any interest in the estate of her deceased husband; the widow is said to sequester. Second, it means to take something that is the subject of a controversy out of the possession of the contending parties and deposit it in the hands of a third person; this neutral party is called a sequestor. Third and most commonly, sequestration in civil law denotes the act of seizing property by court order.
In litigation and equity practice, sequestration also refers to court-ordered confiscation of property. When one party sues another over an unpaid debt, the plaintiff may secure a writ of attachment. As another form of sequestration, this legal order temporarily seizes the alleged debtor's property in order to secure the debt or claim in the event that the plaintiff is successful. In equity practice—an antiquated system of justice that is now incorporated into civil justice—courts seize a defendant's property until the defendant purges herself of a charge of contempt.
In international law, the term sequestration signifies confiscation. Typically, it means the appropriation of private property to public use. Following a war, sequestration means the seizure of the property of the private citizens of a hostile power, as when a belligerent nation sequesters debts due from its own subjects to the enemy.