Working Paper

Feasibility of IMO Annex VI Tier III implementation using selective catalytic reduction

In 2008 the Marine Environmental Protection Committee (MEPC) of the International Maritime Organization (IMO) agreed upon progressively stricter limitations for nitrogen oxide (NOx) emissions from vessels based on their date of engine installation, with the strictest Tier III requirements to take effect in designated Emission Control Areas (ECA) beginning in 2016. At MEPC-66 in April 2014, an amendment that would delay the introduction of the Tier III standards to 2021 will be considered based on concerns arising from perceived equipment, supply chain, and cost barriers raised at MEPC-65.

This paper investigates the current status of selective catalytic reduction (SCR), a technology that is key to meeting Tier III requirements. Challenges and costs of the technology, including applicability to various engine and vessel types, potential environmental side effects, urea and catalyst availability and disposal, and anticipated system costs, are discussed. Based on this evaluation of technological capabilities and history of successful application of SCR technology to maritime vessels, no substantial equipment, supply chain, or cost barriers exist that would necessitate the delay of IMO’s Tier III requirements.