Emission Reduction Unit
Encyclopedia
The Emission reduction unit (ERU) is a trading unit under the Kyoto Protocol representing a reduction of greenhouse gas
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...

es under the Joint Implementation
Joint Implementation
Joint implementation is one of three flexibility mechanisms set forth in the Kyoto Protocol to help countries with binding greenhouse gas emissions targets meet their obligations. JI is set forth in Article 6 of the Kyoto Protocol...

 mechanism, where it represents one tonne of equivalent reduced.

To allow comparison between the different effects of gases on the environment, scientists have defined multipliers for gases that compare their greenhouse potency (global warming potential
Global warming potential
Global-warming potential is a relative measure of how much heat a greenhouse gas traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide. A GWP is calculated over a specific time...

) relative to that of carbon dioxide.

One example of a Joint Implementation
Joint Implementation
Joint implementation is one of three flexibility mechanisms set forth in the Kyoto Protocol to help countries with binding greenhouse gas emissions targets meet their obligations. JI is set forth in Article 6 of the Kyoto Protocol...

 project resulting in an emission reduction unit, is the production of biogas
Biogas
Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. Organic waste such as dead plant and animal material, animal dung, and kitchen waste can be converted into a gaseous fuel called biogas...

es by landfill
Landfill
A landfill site , is a site for the disposal of waste materials by burial and is the oldest form of waste treatment...

 sites. These gases consist of mainly methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

 which escapes to the atmosphere if it is not collected. The main reason for dealing with methane is that it has a 100-year global warming potential multiplier of 25 compared to carbon dioxide (i.e. has 25 times the greenhouse potency). Collection of methane is usually accompanied by its combustion. Burning one tonne of methane produces nearly 3 tonnes of , thus reducing its greenhouse effect
Greenhouse effect
The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere...

by (25-3=22) ERU.
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