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The next round of emission regulations will bring signiÞ -cant impacts to the design, construction, and operation of U.S. commercial and government vessels starting in 2014. The impending EPA Tier 4 regulations directly apply to high and medium-speed diesel engines used in workboats, ferries, small cargo ships, and government vessels. These regulations represent the most signiÞ cant reduction of marine emission levels to date, speciÞ cally in the form of nitrogen oxides (NOx). Natural gas fueled engines present one path to com- pliance, but not the only path. For diesel engines, compliance can be achieved with specialized emission control technolo- gies in the form of after-treatment or on-engine measures. With limitations in availability of clean fuels, diesel engines are often the only feasible or cost effective solution. EMISSION POLLUTANTS The U.S. EPA and IMO regulate speciÞ c exhaust emis- sion components as prescribed in 40 CFR and MARPOL Annex VI, respectively. Table 1 is a summary of these com- ponents and respective reduction solutions. EPA R EGULATIONS Since 2008, the EPA has been phasing in increasingly stringent emissions requirements in steps, or ÔTiersÕ. Current U.S. marine diesels meet EPA Tier 2 or Tier 3 depending on their engine category. EPA Tier 4 is the latest step of regu- lations starting in 2014 and impacts all new marine diesel engines greater than 800 hp with per-cylinder displacements less than 30 liters. Tier 4 imposes major reductions in NOx, particulate matter (PM), and hydrocarbons (HC). The re- duction of NOx, about 70% from Tier 2 levels, imposes the greatest implications to the vessel designers, shipbuilders, and operators. Since NOx results directly from fuel com- bustion at high temperatures, reduction requires specialized on-engine (primary) and/or off-engine (secondary) technol- ogies, or the use of cleaner fuels like natural gas. EMISSIONS REGULATIONS EPA Tier 4 Emission Regulations EPA Tier 4 Emission Regulations Implications on U.S. Vessel Design, Construction, and Operations By Mark MasorTable 1 42 MNNovember 2013MN November2013 Layout 32-49.indd 42MN November2013 Layout 32-49.indd 4210/28/2013 3:20:31 PM10/28/2013 3:20:31 PM
