Monday, November 22, 2010

Monday Morning Mariner: Diesel Emissions Standards

If you own, operate, service or build marine diesel engines, you probably already know that emission standards for these engines started getting tighter in the the mid-90s, and the regulations, both national and international, are ratcheting up almost every year for the next several years.

In the US, the Environmental Protection Agency (EPA) regulates air pollution and sets standards for machinery that produces pollution. I once had an EPA lawyer as a passenger on several cruises who was surprised that the agency didn't inspect our vessels. I told her I had never in more than a decade seen an EPA inspector and had never heard of anyone who had. In the ever more restrictive regulatory environment, that may change, and soon.

The EPA divides marine diesel engines into two types, those with a cylinder displacement below 30 liters, and those with a cylinder displacement 30 liters and above. The first type includes everything from the smallest diesel engines up to the main propulsion on tugs, towboats, and small freighters and passenger vessels. These engines may even include the auxiliary engines on larger vessels. The second type -- so-called Category 3 diesel engines -- includes the main propulsion on most large ships. The stated goal of the new regulations is to reduce both the sulfur particulate emissions (PPM) and nitrogen oxide (NOx) content, both of which "contribute to public health problems."

Requirements for small diesel engines. The new regulations require that emissions of PPM be cut but 90 percent of current levels and that NOx emissions be cut by up to 80 percent by the time the rule is fully implemented. The rules also include:

  • the first-ever emissions standards for remanufactured engines with capacity more than 600kw
  • emission standards for newly-built engines, which began in 2009
  • emission standards for newly-built engines with "high-efficiency catalytic after-treatment technology" built beginning in 2014.

Requirements for Category 3 diesel engines. Larger engines built after April of 2010 will have to meet the same standards called for in Annex VI of the MARPOL treaty (International Convention for the Prevention of Pollution from Ships). Not only will newly-built engines have to conform to these standards, all large marine diesel engines will have to meet emission requirements reducing NOx by 80 percent beginning in 2016.

Compliance strategies. There are several ways operators and engine manufacturers are trying to comply with the regulations:

  • Use of biodiesel. Biodiesel produces much reduced PPM, NOx is another matter. Some laboratory studies show more NOx emissions in biodiesel than in standard diesel, while some "real world" studies show the opposite. Almost all the studies were conducted in a non-marine environment.
  • Electronic controls. Replacing mechanical valves, cylinders, and fuel injectors -- the latter often combined with high-pressure pumps -- with electronically-controlled ones can not only reduce emissions, but increase fuel efficiency.
  • Repowering. Several manufacturers such at MTU, Lugger, and John Deere are building diesel engines specifically geared to meet the new emission standards, but other companies are looking at alternative ways to meet the requirements. A recent trial by Foss Maritime found significantly reduced emissions, fuel costs, and engine hours by switching to the engine/battery hybrid technology similar to that used by automobiles like the Prius. Smaller vessels are finding microturbine gas engines efficient and needing less periodic maintenance.
  • Processing emissions. Generator exhaust in particular can be reduced by filtering it with water, or using catalytic or heating elements.

For a study on the health effects of diesel emissions from the The Annals of Occupational Hygiene, click here.

A comparison of the sulfur PPM from various types of diesel fuel can be found at DieselNet here.

For the EPA's information page on NOx, click here.

The text of the EPA rules regulating marine diesel engines can be found in several parts of the Code of Federal Regulations Title 40.
  • For marine engines under 37kw, check here and here.
  • For marine engines 37kw and above check here and here.
  • For marine engines more than 130kw check here.

For the text of Marpol Annex VI check here.

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