Carbon offset production flows to regions or industries that have a lower price of carbon—unless carbon can be purchased from that area, which offsets effectively permit, equalizing the price. Carbon offsets may represent six primary categories of greenhouse gases: carbon dioxide (), methane (CH), nitrous oxide (NO), perfluorocarbons (PFCs), hydrofluorocarbons (HFCs), and sulfur hexafluoride (SF). Carbon offsets have several common features: In 2009, 8.2 billion metric tons of carbon dioxide equivalent changed hands worldwide, up 68 per cent from 2008, according to the study by carbon-market research firm Point Carbon, of Washington and Oslo. But at EUR94 billion, or about $135 billion,
Carbon dioxide clathrate Type I clathrate for the first time by von Stackelberg & Muller (1954). On Earth, CO hydrate is mostly of academic interest. Tim Collett of the United States Geological Survey (USGS) proposed pumping carbon dioxide into subsurface methane clathrates, thereby releasing the methane and storing the carbon dioxide (Michael Marshall, 2009). As of 2009, ConocoPhillips is working on a trial on the Alaska North Slope with the US Department of Energy to release methane in this way, (ConocoPhilips, January 2010, New Scientist, no. 2714, p. 33). At first glance, it seems that the thermodynamic conditions there favor the existence of