IN MARCH, three farm machinery manufacturers announced how they will meet EPA's Interim Tier 4 (IT4) emission regulations for 174+ hp, off-road diesel engines. The regulations go into effect next year.

Case IH and New Holland plan to use Selective Catalytic Reduction (SCR). With this method, engine exhaust passes through the catalytic chamber, where it is sprayed with a nontoxic mixture of chemical urea and purified water. When the mixture combines with hot exhaust in the catalytic chamber, it is broken down into water vapor and nitrogen. The companies say advantages to this system include longer service intervals, lower fuel consumption, and wider fuel compatibility. AGCO is also using this approach for IT4.

John Deere plans to use cooled Exhaust Gas Recirculation (EGR) to meet IT4 regulations. This system cools and mixes measured amounts of exhaust gas with incoming fresh air to lower the engine's peak combustion temperature, thereby reducing oxides of nitrogen. To reduce particulate matter, exhaust gases are routed through an exhaust filter containing a diesel oxidation catalyst and a diesel particulate filter. Particulate matter is trapped in the filter and oxidized into nitrogen gas and carbon dioxide, then expelled through the exhaust pipe. John Deere says this technology is more operator friendly and less complex to maintain than an SCR system.