HFC-23 (CHF3) emission trend response to HCFC-22 (CHClF2) production and recent HFC-23 emission abatement measures 1Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA
2Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA
3Center for Global Change Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
4Eindhoven Centre for Sustainability, Technical University Eindhoven, Eindhoven, The Netherlands
5Centre for Australian Weather and Climate Research, CSIRO Marine and Atmospheric Research, Aspendale, Victoria, Australia
6School of Chemistry, University of Bristol, Bristol, UK
7School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
Received: 13 Apr 2010 – Published in Atmos. Chem. Phys. Discuss.: 25 May 2010Abstract. 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.
Revised: 23 Jul 2010 – Accepted: 13 Aug 2010 – Published: 25 Aug 2010
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 mol−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.
Citation: Miller, B. R., Rigby, M., Kuijpers, L. J. M., Krummel, P. B., Steele, L. P., Leist, M., Fraser, P. J., McCulloch, A., Harth, C., Salameh, P., Mühle, J., Weiss, R. F., Prinn, R. G., Wang, R. H. J., O'Doherty, S., Greally, B. R., and Simmonds, P. G.: HFC-23 (CHF3) emission trend response to HCFC-22 (CHClF2) production and recent HFC-23 emission abatement measures, Atmos. Chem. Phys., 10, 7875-7890, doi:10.5194/acp-10-7875-2010, 2010.