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February 07, 2017   |   Diesel Technology Forum

Policy Insider

Getting Big Things Done, Like Generating 96,000 Pounds of Clean Air

Upgrading the oldest engines in very large applications to the latest clean diesel technology that meet “Tier 4 requirements” can generate enormous clean air benefits.

Diesel is known for getting big things done. Construction equipment and farm tractors build roads and help feed the world. Even bigger pieces of equipment – think of locomotives and tug boats – are capable of moving and pushing even bigger things. What’s more impressive... the tons of emissions reductions and clean air benefits from the newest generation of clean diesel technology.

Diesel engines are prided for their durability and longevity. The bigger the engine, the longer it will perform in the field. Introducing the latest clean diesel systems in the big applications becomes tricky. For example, a new clean diesel engine that powers a tug boat and meets the latest “Tier 4” emissions standard established by the U.S. EPA, is 94 percent cleaner than the oldest engines and there are quite a lot of the older generation engines in service. 

Upgrading the oldest engines in these very large applications to the latest clean diesel technology that meet the “Tier 4 requirements” can generate enormous clean air benefits. Upgrading a single tug boat engine can eliminate 96,000 lbs of oxides of nitrogen, a smog forming compound, each year. While this seems like a big number in the abstract, in practice, the air quality benefits of this single engine upgrade are enormous. 

One tug boat engine upgrade is equivalent to replacing 76 pre-1992 Class 8 trucks with a new diesel model or replacing 74,000 gasoline passenger cars with a plug-in electric model. That’s impressive. Still yet, when it comes to reducing NOx for a fixed investment, replacing the oldest and biggest engines may be the cheapest choice. Repowering 13 of the oldest tug boats engines with “Tier 4” models can reduce NOx by 600 tons at an estimated total cost of just $6.5 million, according to recent U.S. EPA estimates. While this may sound expensive, it is quite a bargain when considering the cost of switching passenger cars to EVs.

Options to reduce 600 tons of NOx 

PROJECT # of Projects to Generate 600 Tons of NOx Reduction Cost Per Project Total Cost
Tug Boat: Engine Upgrade 13 $500,000 $6,500,000
Heavy-Duty Truck: Replacement 936 $110,000 $102,960,000
Car Replacement with EV Technology 923,077 $35,000 $32,307,695,000


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Ezra Finkin
Director, Policy

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