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Summer 2007               Fueling Our Future

Ultra-Low-Sulfur Diesel
Ranking: Red

Verdict:
There are better fuels out there for cleaning the air and cooling the planet.

What is it?:
Conventional diesel is a component of petroleum that is separated out by heating crude oil to high temperatures. It is sometimes called “petrodiesel” to distinguish it from biodiesel.  Ultra-low Sulfur Diesel (ULSD), which contains less than one-tenth of the sulfur than conventional diesel once did, became nationally required by law for on-road diesel vehicles in 2006.

Historically, the sulfur in conventional diesel not only contributed to diesel’s bad reputation as “dirty and smelly” but also corroded and clogged pollution-reducing traps, which therefore weren’t used in most diesel vehicles. The resulting tailpipe pollution has been implicated in major public health problems, including asthma attacks, respiratory disease and heart attacks, according to the Clean Air Task Force.

Pros:
  • Per mile driven, diesel engines emit fewer greenhouse gases than gasoline engines. The lower greenhouse gas emissions of a diesel car—13 less tons less over the average car’s lifetime, according to the Union of Concerned Scientists—reflect the fact that although diesel causes higher emissions per gallon, that gallon can take a diesel car much farther.
  • In addition to drastically lowering sulfur emissions, ULSD will allow diesel engines to be equipped with more effective controls for reducing particulates and smog-forming nitrogen oxide emissions.
Cons:
  • Like gasoline, diesel is derived from petroleum, a non-renewable resource for which the US is dependent on overseas imports. And because it takes more petroleum to produce a gallon of diesel than a gallon of gasoline, diesel engines use up more life-cycle oil than their high fuel economy might lead you to believe.
  • The Union of Concerned Scientists concludes that the pollution reductions achieved by diesel engines could be more cheaply achieved by increasing the fuel efficiency of gasoline vehicles.
Current status:

Once diesel engines were more common in US buses and trucks than in passenger cars, but that’s changing—diesel passenger car sales have increased more than 80 percent since the year 2000 and are expected to double again by 2012. There are more than 13 million diesel vehicles on the road today.

Many conventional gas stations already offer ultra-low sulfur diesel (look for the mandatory-by-law ULSD sticker on the pump to be sure—it should indicate 15 ppm sulfur rather than the old concentration of 500 ppm), and diesel engine mechanics can be found in every city.

If you already drive a diesel vehicle, contact the manufacturer to find out if it offers or will offer a particulate filter retro-fit to further reduce pollution.

Should You Make the Switch?:

No. It might make sense as a short-term emissions-reduction strategy for a large fleet of trucks or buses, but if you’re looking to reduce the global warming emissions from your passenger transportation, there are better fuels out there than ULSD. If you already own a diesel vehicle, consider running it on biodiesel, instead, to really cut down your emissions.

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plug-in electric hybridbiodieselgas-electric hybridcellulosic ethanolnatural gasultra-low-sulfur dieselhydrogen fuel cellsE85 corn ethanol

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