As the world’s toughest emission standard, EU Stage V places the most stringent limits on the emission of particulate matter, nitrogen oxides, carbon monoxide and hydrocarbons from non-road mobile machinery.

The implementation of EU Stage V replaced the various and multi-layered standards across multiple countries with one regulation. EU Stage V also covers previously unregulated engines, along with marine engines above 19 bkW and previously unregulated marine engines above 560 bkW.

The increased restrictions have encouraged manufacturers to implement various exhaust gas aftertreatment technologies to control and manage engine emissions—such as diesel oxidation catalysts, diesel particulate filters, selective catalytic reduction and exhaust gas recirculation.

The United States’ Environmental Protection Agency’s Tier 4 tightens emission standards for new nonroad compression ignition (diesel) engines used in heavy equipment and off-road machinery across different industries. The standard significantly reduces allowable levels of nitrogen oxides (NOx) and particulate matter found in diesel engine exhaust.

Like EU Stage V, U.S. Tier 4 requires manufacturers to implement different strategies for treating diesel exhaust. In the case of reducing NOx, a selective catalytic reduction (SCR) system passes exhaust through a diesel particulate filter to remove different compounds. Exhaust is further treated with diesel exhaust fluid (DEF)—a mixture of urea and distilled water—to reduce NOx into water and nitrogen.

This standard has encouraged innovation in engine design and exhaust treatment, leading to new levels of fuel efficiency and reduction in emissions (e.g., NOx and PM emissions).

The International Maritime Organization (IMO) is a United Nations agency that sets standards and regulations for safety, security and environmental protection as it pertains to international shipping. IMO Tier III regulates NOx emissions in Emission Control Areas (ECAs) as designated by MARPOL Annex VI. The standard is applied to marine diesel engines installed in ships constructed on or after the following dates and operating in the following ECAs:

1. January 1, 2016, and operating in the North American ECA and the United States Caribbean Sea ECA; or
2. January 1, 2021, and operating in the Baltic Sea ECA or the North Sea ECA.

While the IMO does not have legislative powers, its regulations are regarded as the international standard and have been adopted throughout the world to help mitigate maritime pollution.