A Norcal Waste Systems truck is refueled with liquid natural gas. LNG also can be used in medium-duty trucks, though less exotic spark ignition technology is normally used in place of high-pressure gas injection.
You’re used to filling up with good old diesel No. 2 derived from mineral crude oil, but some surprising new fuels could end up being available to you, especially if your truck comes home to roost every night near a big city.
Fuels that are in gaseous form pose challenges for use in a diesel engine, but many of those challenges have been dealt with. New technology such as high-pressure gas injection with a pilot shot of diesel fuel is an effective approach in heavy-duty engines. In medium-duty engines, necessary changes may include such departures from diesel design as putting spark plugs in the engine and lowering the compression ratio.
A common theme – and what might prove to be the Achilles’ heel for the emergence of some promising new fuels – is the need for centralized fueling. This may be necessary to tap city gas mains or equipment that liquefies natural gas, or to allow bulk purchase of a liquid fuel custom-blended by a local distributor.
Biofuels such as biodiesel and diesel-ethanol blends are compatible with present engines, though the latter need careful handling for safety reasons.
The National Biodiesel Board estimates that biodiesel consumption rose from 250 million gallons in 2006 to 450 million gallons in 2007. That’s well under 1 percent of the 170 billion gallons of gasoline and diesel fuel that Americans use annually.
Minnesota has required nearly all diesel fuel sold in that state had to be a 2 percent biodiesel blend since Sept. 29, 2005, though the requirement has been suspended for brief periods due to jelling problems during cold weather. The state of Washington will require sale of a 2 percent blend as of Dec. 1, 2008, or earlier if certain local availability
triggers are met. Iowa requires that 25 percent of sales at larger retailers be ethanol or biodiesel by 2010. Other mandates for use in state vehicles, tax incentives, or other goals have been legislated.
However, with demand for gasoline and diesel projected to double by 2025, pressure will continue to rise for use of any suitable alternative fuels.
Biodiesel reduces the carbon footprint of a diesel engine, which means that the CO2 it emits will be turned back into oxygen and sugars during later growing seasons. It also emits significantly less particulate. Its use has become politically and economically desirable because of its ability to reduce the consumption of foreign petroleum and stimulate agriculture and new refining activity in the United States.
Engine makers have been testing biodiesel in their products for years and have taken steps toward accommodating its use, most obviously via their biodiesel specifications. With consultation and a reliable supplier, you should be able to operate on blends ranging from 5 percent to 20 percent, depending on the engine manufacturer. Both Caterpillar and Cummins allow quality B20 that meets the American Society for Testing Materials standard, though Caterpillar recommends using oil analysis, as change intervals may need to be slightly tightened.
The decision to use a biodiesel blend will not automatically void your warranty, says Mike Powers, Caterpillar’s product development manager. On the other hand, realize that no problem caused by any fuel, including regular diesel, is covered by any engine maker’s warranty. The best policy is to understand the engine maker’s specifications and discuss all the facts with your dealer and service people before running it. Some experts believe that simply installing fuel heating equipment for winter, desirable even with regular diesel fuel, will greatly reduce cold weather trouble.
Caterpillar believes that clean diesel fuel, not biodiesel, “will be the preferred fuel for the future,” says Charissa Ebbert, the company’s product information manager. One reason is the complexity of the 2007 emissions system.