Revisiting chloroform emissions from the pulp and paper sector: a brief communication

Abstract Halogenated very short-lived substances (VSLS) represent a growing source of chlorine to the stratosphere where they may contribute to ozone layer depletion. Chloroform (CHCl 3 ) is a prominent VSLS with poorly constrained anthropogenic sources that include its unintentional production when wood pulp is bleached for paper production. Recent assessments of the global CHCl 3 budget have relied on emission factors (EFs) for the pulp/paper (PP) sector derived some 35 years ago when industrial practices were markedly different. Here, we analysed data from the Pollutant Release and Transfer Registers of the USA, Canada and Japan. Combined with data on the national number of pulp mills and bleached wood pulp production volume, we derive plausible lower and upper limit EFs. These factors show a downward trend since the early 2000s, which we attribute to a continued phase-down in the use of ‘elemental chlorine’ bleaching in favour of ‘elemental chlorine free’ bleaching. The derived mean EFs for the period 2000–2020, expressed as the mass of CHCl 3 per air–dried tons (adt) of bleached pulp, are in close agreement for the regions considered: USA (39.8 ± 32 g/adt), Canada (38.6 ± 29.8 g/adt) and Japan (30.1 ± 8.6 g/adt). Assuming these factors are broadly representative of other world regions, a mean annual global CHCl 3 source of 3 (1–6) Gg yr −1 from the PP sector is estimated for the approximate 2000–2020 period. We conclude that the sector’s contribution to the global CHCl 3 budget has likely decreased considerably since the 1990s and that the use of older EFs to calculate present-day emissions should be avoided.