A Carbon Offset, also called a "carbon credit", is a financial asset that can be bought and sold freely. One carbon offset equals one metric ton ( approx 2.200 lbs) of carbon dioxide. In gas form, one ton of carbon dioxide would fill a balloon 30 feet in diameter. Burning 120 gallons of gasoline releases one metric ton of carbon dioxide into the atmosphere. A carbon offset is generated by reducing or displacing carbon dioxide or other greenhouse gas emissions. The reduction can come from either preventing the gases from being emitted in the first place - or from sustainable practices that promote the growth of plant life and root systems. Carbon sequestration is an ecosystem service that describes the process of removing carbon dioxide from the air naturally, where as "carbon capture "is the process of doing it artificially. Trees, plants and grass naturally absorb carbon dioxide through photosynthesis. Generally speaking, an acre of well-managed, non-grazed grassland can sequester about 1 metric ton of carbon
dioxide per year. By selling carbon offsets, a landowner is able to monetize one of the ecosystem services they are providing. Eligible carbon offest projects must follow California State project rulebooks ( called "protocols" ). Specifically, the California Air Resources Board ( "ARB" ), the agency that is administering the cap and trade program, has approved protocols for Avoided Forestry Conversion, Improved Forest Management, Afforestation, Agriculture Methane, Ozone Depleting Substances, and Urban Forestry projects. The California State Government is also in the process of reviewing protocols for Agricultural ( Rice ), and mine methane projects. Projects do not have to be located in California to be eligible to sell their offset into the California market.