Mitigation of industrial N2O – Low-hanging fruit in industrialised countries

In a recent study on behalf of the Nitric Acid Climate Action Group (NACAG) we found significant ‘low-hanging fruit’ mitigation potential for emissions of nitrous oxide (N2O) from chemical industry and a lack of dedicated climate policies. Wolfram Jörß summarises the results.

Nitrous oxide accounted for some 6% of total greenhouse gas emissions in 2020, as reported to the United Nations by UNFCCC Annex I industrialised countries. While the bulk of these emissions comes from agricultural soils and is relatively hard to mitigate, some industrial processes give rise to significant N2O emissions which are easy to abate, in particular by using high-efficiency catalysts: Three notorious production processes are for nitric acid, adipic acid and caprolactam. In all cases, N2O is generated through the oxidation of nitrogen compounds during the production process. Nitric acid is needed for the production of fertilisers and explosives, while adipic acid and caprolactam are important plastic precursors.

2020 process emissions of N2O from chemical industry in industrialised countries worldwide are estimated at 47 Mt CO2e in total. Of that sum, 76% came from nitric acid production, 17% from adipic acid production and 7% from caprolactam production (Figure 1). Among the countries and regions studied, the ones contributing most to N2O emissions are Russia, the USA, the EU, Australia and Trinidad and Tobago for nitric acid production, the USA for adipic acid production, and the EU, the USA and Russia for caprolactam production. For the purposes of the study, ‘industrialised countries’ were defined as countries not identified by the OECD as eligible for official development assistance (ODA); ‘emerging economies’ like China or India are thus not included.

Climate policies affecting N2O emissions from chemical industry are absent in particular in Russia, the USA and Trinidad and Tobago. The European Union, while covering N2O from nitric and adipic acid production under the EU-ETS, employs no policies effectively addressing N2O emissions from caprolactam production.

For production of nitric acid (HNO3), average emission intensities per country range from very high levels of 8‑9 kg N2O/t HNO3 (Trinidad and Tobago, Russia) to relatively low levels of 0.5 kg/t and less for Western European countries and Korea. While a comparison of national average emission intensities (Figure 2) provides a first top-down indication of N2O mitigation potential for ambitious climate policies, ‘low-hanging fruit’ mitigation potentials in presently unabated nitric acid plants were estimated additionally: These add up to 63% of total N2O emissions from nitric acid production estimated for 2020 (23 Mt CO2e mitigation potential out of 36 Mt CO2e 2020 emissions). Such mitigation potentials are mainly found in Russia, the USA and Trinidad & Tobago. Single further nitric acid plants without abatement were identified in Australia and Japan. In Australia, however, a retrofit is reported to be underway.

Adipic acid production is carried out in only six of the industrialised countries studied, i.e. the USA, Japan, Korea and EU Member States France, Germany and Italy. Emission intensities range from very high 40 kg N2O/t adipic acid (USA) to as low as 2-4 kg/t and below for the EU and Korea (Figure 3). While ambitious mitigation is taking place in Japan, Korea and the EU, mitigation efforts in the USA are insufficient, as available mitigation equipment appears to be operated poorly.

Caprolactam production is carried out in 10 of the industrialised countries studied, i.e. the USA, Russia, Japan, Korea and the six EU Member States Belgium, Czech Republic, Germany, Netherlands, Poland and Spain. Emission intensities range from very high 9 kg N2O/ t caprolactam (USA and Russia) to as low as 2 kg/t for Japan and Korea (Figure 4). Even lower emission rates were reported for EU Member States Poland (0.6 kg N2O/t) and Germany (nearly complete elimination). While ambitious mitigation is taking place in Japan, Korea and some EU Member States, mitigation efforts are insufficient in the USA, Russia and other EU countries. Unlike nitric acid and adipic acid production, N2O emissions from caprolactam production are not covered by the EU-ETS.

The study report presents 15 country briefs (Table 1) which set out the scale of the respective industries, current regulatory framework conditions affecting N2O emissions, N2O abatement efforts in place, and estimates of current N2O emissions, emission intensities and mitigation potentials. The countries and regions covered are Australia, Canada, Chile, the European Union, Israel, Japan, the Republic of Korea, Norway, Russia, Saudi Arabia, Singapore, Trinidad and Tobago, United Arab Emirates, United Kingdom, United States of America.

Wolfram Jörß works as a Senior Researcher at the Energy & Climate Division at the Oeko-Institut in Berlin.

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