7.4.3.3 Chlorine manufacture

The TAR (IPCC, 2001a) reported on the growing use of more energy-efficient membrane electrolysis cells for chlorine production. There have been no significant developments affecting GHG emissions from chlorine production since the TAR.

7.4.3.4 N₂O emissions from adipic acid, nitric acid and caprolactam manufacture

N₂O emissions from nitric and adipic acid plants account for about 5% of anthropogenic N₂O emissions. Due to significant investment in control technologies by industry in North America, Japan and the EU, worldwide emissions of N₂O (GWP = 310 (IPCC,1995)) from adipic and nitric acid production decreased by 30%, from 223 MtCO₂-eq (61 MtC-eq) in 1990 to 154 MtCO₂-eq (42 MtC-eq) in 2000 (US EPA 2006b). Some of the reduction was due to the installation of NO control technology to meet regulatory requirements. By 2020, global emission from the manufacture of adipic acid and from the manufacture of nitric acid are projected to grow to 177 MtCO₂-eq (48 MtC-eq). Developed nations account for approximately 55% of emissions in both 2000 and 2020 (US EPA, 2006b). Experience in the USA, Japan and the EU shows that thermal destruction can eliminate 96% of the N₂O emitted from an adipic acid plant. Catalytic reduction can eliminate 89% of the N₂O emitted from a typical nitric plant in a developed country (US EPA, 2006a). Mitigation potential at nitric acid plants can range from 70% to almost 100% depending on the catalyst and plant operating conditions (US EPA, 2001, Continental Engineering BV, 2001). Costs range from 2.0 to 5.8 US$/tCO₂-eq (7.3 to 21.2 US$/tC-eq) (2000 US$) using a 20% discount rate and a 40% corporate tax rate, and a maximum mitigation potential of 174 MtCO₂-eq (44 MtC-eq) is projected in 2030.

Global N₂O emissions from caprolactam production in 2000 were estimated at 10 to 15 MtCO₂-eq (2.7 to 4.1 MtC) (EDGAR, 2005). IPCC (2006) indicates that these emissions can be controlled to a high degree by non-specific catalytic reduction.