From SCDigest's On-Target E-Magazine

- June 12, 2013 -

Logistics News: A New Alternative Truck Fuel Enters the Playing Field

DME is Little Known, but Volvo Trucks Announces Aggressive Plans, Pilot with Safeway

SCDigest Editorial Staff

There has been a flurry of activity and investment around natural gas powered trucks in the US, with the promise of reducing operating costs, carbon emissions, and dependence on foreign oil, as the US rapidly builds out its natural gas producing capacity using new fracking techniques. (See T. Boone Pickens
on the Present and Future of Natural Gas Freight Trucks.)

But is there a new kid on the energy block that may give compressed or liquid natural gas a run for its money?

SCDigest Says: If Volvo's claims stand up, DME may have upped the "game-changing" ante considerably. What Do You Say? Click Here to Send Us Your Comments Click Here to See Reader Feedback

Maybe so, as Volvo Trucks announced a partnership in California last week to test trucks that run on a fuel called dimethyl ether (DME).

What is DME? It is a type of gas in widespread use in some parts of the world as a cooking fuel similar to propane, and nearly everywhere as propellant in aerosol sprays.

It can be produced from methane, which is found in many forms, such as cow and chicken manure to rotting grass clippings, landfill gas, and natural gas itself.

The ability to create DME out of many sources is just one attribute that could give it an advantage over natural gas. Others include the fact that DME burns so cleanly that it leaves no soot and emits just a fraction of other pollutants. DME produces 95% fewer carbon emissions than does diesel, and some 70% fewer than natural gas.

In fact, DME burns so cleanly that Volvo says a truck engine using DME does not require an exhaust gas recirculation, diesel particulate filter, or variable geometry turbocharger.

But almost no one uses DME as a transportation fuel. At a press conference announcing the upcoming pilot with Safeway, Volvo did say one small firm with just 10 trucks is using DME successfully right now in Sweden.

Another DME advantage over natural gas is that the modifications to make existing diesel trucks work with the fuel are relatively modest. A special injection system must be added as well as different cylinder heads to handle high fuel flow. Additionally, simple steel fuel tanks must be added to store the DME on the truck, the same type of tank used for propane, rather than the more expensive tanks required for compressed and liquefied natural gas now appearing on commercial trucks.

DME stores at about 75 pounds per square inch and at ambient temperature, versus 3,600 psi for CNG and minus 260 degrees for LNG.

Volvo says there are similar storage efficiencies for local filling stations, versus the cost to build a natural gas filling facility.

What's more, Volvo says its engineers have developed a way to efficiently produce DME in small quantities, so that production can be developed locally and regionally, using skid-mounted, small-scale production units that cost-effectively convert biogas and natural gas to DME.

Volvo says there are some downsides. DME might require the use of selective catalytic reduction, which the company says will not be known until a couple of years. DME will likely have to be treated with a lubricant to protect valves. And DME only packs about 50% of the energy content of diesel fuel, meaning a truck will have to carry about twice the amount of DME over diesel to go the same distance. (Despite all its negatives, traditional oil remains a very energy-efficient fuel.)

(Transportation Management Article Continued Below)