HFC-23 (also known as CHF3, fluoroform or trifluoromethane) is a potent greenhouse gas (GHG), with a global warming potential (GWP) of 14 800 for a 100-year time horizon. It is an unavoidable by-product of HCFC-22 (CHClF2, chlorodifluoromethane) production. HCFC-22, an ozone depleting substance (ODS), is used extensively in commercial refrigeration and air conditioning, in the extruded polystyrene (XPS) foam industries (dispersive applications) and also as a feedstock in fluoropolymer manufacture (a non-dispersive use). Aside from small markets in specialty uses, HFC-23 has historically been considered a waste gas that was, and often still is, simply vented to the atmosphere. Efforts have been made in the past two decades to reduce HFC-23 emissions, including destruction (incineration) in facilities in developing countries under the United Nations Framework Convention on Climate Change's (UNFCCC) Clean Development Mechanism (CDM), and by process optimization and/or voluntary incineration by most producers in developed countries. We present observations of lower-tropospheric mole fractions of HFC-23 measured by "Medusa" GC/MSD instruments from ambient air sampled in situ at the Advanced Global Atmospheric Gases Experiment (AGAGE) network of five remote sites (2007-2009) and in Cape Grim air archive (CGAA) samples (1978-2009) from Tasmania, Australia. These observations are used with the AGAGE 2-D atmospheric 12-box model and an inverse method to produce model mole fractions and a "top-down" HFC-23 emission history. The model 2009 annual mean global lower-tropospheric background abundance is 22.6 (±0.2) pmol molg -1. The derived HFC-23 emissions show a "plateau" during 1997-2003, followed by a rapid ∼50% increase to a peak of 15.0 (+1.3-1.2) Gg/yr in 2006. Following this peak, emissions of HFC-23 declined rapidly to 8.6 (+0.9-1.0) Gg/yr in 2009, the lowest annual emission of the past 15 years. We derive a 1990-2008 "bottom-up" HFC-23 emission history using data from the United Nations Environment Programme and the UNFCCC. Comparison with the top-down HFC-23 emission history shows agreement within the stated uncertainties. In the 1990s, HFC-23 emissions from developed countries dominated all other sources, then began to decline and eventually became fairly constant during 2003-2008. By this point, with developed countries' emissions essentially at a plateau, the major factor controlling the annual dynamics of global HFC-23 emissions became the historical rise of developing countries' HCFC-22 dispersive use production, which peaked in 2007. Thereafter in 2007-2009, incineration through CDM projects became a larger factor, reducing global HFC-23 emissions despite rapidly rising HCFC-22 feedstock production in developing countries. © Author(s) 2010.
CITATION STYLE
Miller, B. R., Rigby, M., Kuijpers, L. J. M., Krummel, P. B., Steele, L. P., Leist, M., … Simmonds, P. G. (2010). HFC-23 (CHF3) emission trend response to HCFC-22 (CHClF 2) production and recent HFC-23 emission abatement measures. Atmospheric Chemistry and Physics, 10(16), 7875–7890. https://doi.org/10.5194/acp-10-7875-2010
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