Engineers at Volvo Trucks are exploring the possibility of using dimethyl ether, or DME, as an alternative fuel in North America, following successful field tests in Europe.

DME is produced from natural gas or biomass such as wood byproducts and can be burned in diesels with few changes. In the field trials in Sweden, the DME is produced from "black liquor," a waste byproduct of paper and pulp production. Energy efficiency is high, and carbon dioxide emissions are as much as 95% lower than diesel exhaust.

Volvo Group is overseeing hundreds of thousands of miles of customer field-testing of DME-powered trucks in Europe, says Ron Huibers, sales and marketing president for Volvo Trucks North America.

Strong results from 10 vehicles operating in a variety of applications indicate DME holds much promise as a heavytruck fuel, Volvo says. The company believes DME could become a viable alternative to natural gas based on performance, environmental impact, safety and distribution.

DME mirrors the performance qualities and high energy content of diesel while significantly reducing greenhouse gas emissions, Huibers says. It is an excellent compression ignition fuel - like diesel, it uses a commonrail fuel system and requires no spark ignition mechanism.

It does not require cryogenic temperatures, like liquefied natural gas, or high storage pressures, like compressed natural gas's 3,600 psi. DME is handled like propane, with tank pressures of 75 psi, and it is nontoxic. DME burns with a blue flame and does not produce the soot that diesel does. Thus, it requires no diesel particulate filter and might not need diesel exhaust fluid.

The fuel packages densely enough to allow long-range operations or to allow room for vocational truck equipment on the frame, Huibers says. The infrastructure to supply DME to trucks will develop with the market.

Little DME is now being made in the U.S., but Volvo is aware of a new DME plant under construction in Imperial County, Calif., and believes more will follow.

DME working in Sweden

In Volvo's home country of Sweden, J-Transportation in Gothenburg is running with DME in the tanks, as well as DHL and the Swedish Mail in Jonkoping. In the north, trials are being conducted with a regional logging truck and a regional transporter that runs paper rolls from a mill to a nearby port for shipping.

It takes 1.8 times as much DME to run a truck compared to ordinary diesel.
A 40-ton-GCWvehicle that normally uses 4.2 liters (1.1 gallons) of diesel per 10 km (6.2 miles), instead consumes some 7.6 liters (about 2 gallons) when operating on DME, says
Per Salomonsson, project manager for the DME trials. Or, in more familiar terms in the U.S., a vehicle that gets around 6 mpg on diesel would get a little better than 3 mpg on DME.

Driving impressions

A drive of one of Volvo FH models in field tests with DHL in Sweden shows the DME-fueled truck behaves like any diesel truck, with some small exceptions.

The DME engine is a bit more difficult to start and cranks a few extra seconds on the starter. After it starts, the 13-liter engine with 440 horsepower fires up and forcefully pulls away. It also runs much quieter than the diesel variant.

The DME engine is a diesel engine with another fuel system and a modified engine control. The common rail system has low injection pressure. Fuel system seals are DME-resistant.

In its daily work, this truck runs two shifts, running 270 km (about 170 miles) in the daytime and 350 km (about 215 miles) at night.

These trucks are not yet commercially available, mainly because there is no fuel distribution network organized. There are currently only four filling locations in Sweden: Stockholm, Jonkoping, Gothenburg and northern Pitea. The bio-DME is produced and distributed by Preem Fuel Company. The working distance of the trucks has been extended from 500 (about 310 miles) to 800 kilometers (nearly 500 miles).

Volvo is currently the only OEM to provide a DME engine. Policymakers, politicians and market forces must work together to establish the necessary distribution network to make DME fuel available in a larger scale. Only then will it be commercially viable for DME to become an alternative to diesel.