Greenhouse Gas
NF3 is a greenhouse gas, with a global warming potential (GWP) 17,200 times greater than that of CO2 when compared over a 100 year period. Its GWP would place it second only to SF6 in the group of Kyoto-recognised greenhouse gases, although NF3 is not currently included in that grouping. It has an estimated atmospheric lifetime of 740 years, although other work suggests a slightly shorter lifetime of 550 years (and a corresponding GWP of 16,800).
Although NF3 has a high GWP, for a long time its radiative forcing in the Earth's atmosphere has been assumed to be small, spuriously presuming that only small quantities are released into the atmosphere. Industrial applications of NF3 routinely break it down, while in the past previously used regulated compounds such as SF6 and PFCs were often released. Research has questioned the previous assumptions. High-volume applications such as DRAM computer memory production, the manufacturing of flat panel displays and the large-scale production of thin-film solar cells in regions with insufficient ecological awareness continues to increase the emissions of NF3.
Since 1992, when less than 100 tons were produced, production has grown to an estimated 4000 tons in 2007 and is projected to increase significantly. World production of NF3 is expected to reach 8000 tons a year by 2010. By far the world's largest producer of NF3 is the US chemical company Air Products & Chemicals. An estimated 2% of produced NF3 is released into the atmosphere. Robson projected that the maximum atmospheric concentration is less than 0.16 parts per trillion (ppt) by volume, which will provide less than 0.001 Wm−2 of IR forcing. The mean global tropospheric concentration of NF3 has risen quasi-exponentially from about 0.02 ppt (parts per trillion, dry air mole fraction) at the beginning of the measured record in 1978, to a July 1, 2008 value of 0.454 ppt, with a rate of increase of 0.053 ppt yr−1, or about 11% per year, and an interhemispheric gradient that is consistent with these emissions occurring overwhelmingly in the Northern Hemisphere, as expected. This rise rate corresponds to about 620 metric tons/y of 2009 NF3 emissions globally, or about 16% of the NF3 production estimate of 4000 metric tons yr−1. This is a significantly higher percentage than has been estimated by industry, and thus strengthens the case for inventorying NF3 production and for regulating its emissions. One study suggests that the contribution of the NF3 emissions to the overall greenhouse gas budget of thin-film Si-solar cell manufacturing is overestimated. Instead, the contribution of the nitrogen trifluoride to the CO2-budget of thin film solar cell production is compensated already within a few months by the CO2 saving potential of the PV technology.
The UNFCCC, within the context of the Kyoto Protocol, decided to include nitrogen trifluoride in the second Kyoto Protocol compliance period, which begins in 2012 and ends in either 2017 or 2020. Following suit, the WBCSD/WRI GHG Protocol is amending all of its standards (corporate, product and Scope 3) to also cover NF3.
Read more about this topic: Nitrogen Trifluoride
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