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EPA Proposes Rule to Cut Diesel Locomotive and Marine Pollution

Proposed standards for switch locomotives. Line-haul engines have different standards, as do the multiple classes of marine engines. Click to enlarge.

EPA is proposing a new rule to significantly reduce air pollution from locomotive and marine diesel engines below 30 liters per cylinder displacement. The Clean Air Locomotive and Marine Diesel Rule would set stringent emission standards and require the use of advanced technology to reduce emissions.

When fully implemented, the Clean Air Locomotive and Marine Diesel Rule would cut particulate matter emissions from these engines by 90% percent and nitrogen oxides emissions by 80% compared to the current Tier 2 standards.

This would result in annual health benefits of $12 billion in 2030 and reduce premature deaths, hospitalizations and respiratory illnesses across the United States. These benefits would continue to grow as older locomotive and marine engines are replaced. Overall benefits are estimated to outweigh costs by more than 20 to 1.

By tackling the greatest remaining source of diesel emissions, we’re keeping our nation’s clean air progress moving full steam ahead. Over the last century, diesels have been America’s economic workhorse, and through this rule, an economic workhorse is also becoming an environmental workhorse.

—EPA Administrator Stephen L. Johnson

The proposal would significantly reduce harmful emissions from these engines through a three-part program:

  1. Tightening emission standards for existing locomotives when they are remanufactured.

  2. Setting near-term engine-out emission standards, referred to as Tier 3 standards, for newly-built locomotives and marine diesel engines; and

  3. Setting longer-term standards, referred to as Tier 4 standards, for newly-built locomotives and marine diesel engines that reflect the application of high-efficiency aftertreatment technology.

EPA is also proposing provisions to eliminate emissions from unnecessary locomotive idling and is asking for comment on a concept to reduce emissions from existing marine diesel engines when they are remanufactured. This proposal is part of EPA’s ongoing National Clean Diesel Campaign (NCDC) to reduce harmful emissions from diesel engines of all types.

The proposal cuts emissions from all types of diesel locomotives, including line-haul, switch, and passenger rail, as well as from a wide range of marine sources, including ferries, tugboats, yachts and marine auxiliary engines. This includes small generator sets to large generators on ocean-going ships.

The locomotive remanufacturing proposal would take effect as soon as certified systems are available, as early as 2008, but no later than 2010. Tier 3 standards for new locomotive and marine diesel engines would phase-in starting in 2009. Tier 4 long-term standards would phase-in beginning in 2014 for marine diesel engines and 2015 for locomotives. The rule also explores a remanufacturing program for existing large marine diesel engines similar to the existing program for locomotives. Other provisions seek to reduce unnecessary locomotive idling.



Clint LeRoy

This will catapult RailPower Technologies Corporation up in its ratings, as they currently produce Hybrid Locomotives and this is what the EPA certified their Locomotives as of back in Late December 2006. Hybrid Locomotives that don't need to sit and idle in the yards across North America. Currently meets Tier 4 Emission Standards.


Elimination of idling seems to be a sort of low-hanging fruit. It can be applied in the marine, railroad and even trucking contexts. Not only does it have atmospheric benefits, it also saves fuel, which is money. Admittedly, you have to install electric hookups and related equipment at layover facilities, but you start earning back some of that investment on the actual fuel savings, before you get into air quality and health benefits. On the other hand, cleaner-burning engines cost money to build and may come with mileage penalties -- so the only benefits there are the air quality and health benefits.

Those environmental and health benefits are almost certainly worth the investment many times over, but there is a distributional problem. Those savings are spread over a large number of people living in areas where diesel exhaust spreads, while fuel savings accrue directly to the company that owns the engines and facilities. It probably requires less government spending or coercion to implement the latter than the former. But then, getting even the former projects done is what government is for -- and I mean that remark in a serious way.

tom deplume

Locomotives seem an ideal use for anhydrous ammonia. I read somewhere that NH3 has about half the energy density of diesel fuel. Since there is no carbon then PM and CO, CO2 won't be a problem. Squirt a little ammonia into the exhaust with a SCR and NOx is removed. Almost all the NH3 produced already travels by train so hooking a hose between a tank car and an engine is no big deal. The solution is so obvious only presbyopia keeps TBTP from seeing it.


Isn't the already common urea injection systems basically "squirting a little ammonia into the exhaust"?


Yup.  On the other hand, ammonia production is a rather lossy process, so it makes little sense to use it for the primary fuel supply.


Any of these aforementioned tecks will require ULS bunker fuel and at present Im not sure if that exists.



These regulations are aimed at locomotives and "marine diesel engines below 30 liters per cylinder displacement." Such engines can be found on tugboats, fishing vessels, auxilliary power units, and possibly very small frieghters. Large ships, however, if they are modern enough not to use boilers, use very large bore marine diesel engines, which fall beyond the scope of these regulations -- i.e. each cylinder has a displacement larger than 30 liters. Those engines can continue to burn dirty bunker fuel.

This is not entirely bad, because if strict anti-idling regulations are implemented in port areas, they will release most of their garbage far from populated areas, minimizing the health impacts.

For a sense of the size of large modern marine diesels, see:


So what exactly would be the down-side to LS bunker fuel? Other than a small? hit to refiners bottom lines and lower bulk sulpher prices and higher hydrogen prices?

Stan Peterson

Tier three an Tier four regulations for locomotives can piggyback on the on road truck diesel cleanup technology.

Clean road diesels using ULS fuel and particle traps and SCR are committed for on road diesel for 2007 in the T2B5 standards. Locomotives can meet these standards too, an should do so at the the shortest possible lag time.

The re manufacturing rules are unique to the off road diesel movers, and a great idea. Locomotive diesels are really dirty now, even if all are hybrids. A mere five locomotives produce as much pollution as a power plant producing 250 MW, enough to power a town of 100,000 people.

California has arranged for locomotives to use ULS fuel. Somebody has to burn the dregs of the oil barrel. Right now its both the locomotives and the big ships. Eventually it will only the big ships, and only many miles from shorelines.

Thomas Pedersen

Quite often, the manufacturers of truck- and locomotive-size diesels are not the same, resulting in relatively poor technology transfer.

However that should not serve as an excuse to not implement the measures that have proven to work. Besides, it should be easier to fit new components to a larger, less industrialized engine, no?

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