Volvo Truck's plan to commercialize DME technology

Last week, Volvo Truck announced that it will be the first North American heavy-duty vehicle manufacturer to offer trucks fueled with dimethyl ether (DME). Volvo plans to commercialize the trucks in 2015, and is partnering with Oberon Fuels and Safeway Inc. now to evaluate the vehicles in fleet operations.

Volvo thinks that DME has a number of advantages over conventional diesel and other alternative fuels. The DME engine is based on the stock diesel engine with modifications to the fueling system and controls strategy. Because the DME engine is based on the conventional platform, the DME engine can match the diesel engine torque curves and provide comparable fuel efficiency. DME has no carbon-to-carbon bonds, so fuel combustion results in virtually no particulate emissions, eliminating the need for a particulate filter. One particular advantage of DME over natural gas vehicles is that there is no need for costly and heavy high-pressure or cryogenic storage tanks, since DME is stored as a low-pressure liquid. Another is that leakage is not as critical an issue in terms of climate impacts, since the global warming potential of DME gas is roughly comparable to carbon dioxide.

There are compensating disadvantages, of course. The volumetric energy density of DME is roughly half that of diesel, so to achieve range equivalent to a conventional vehicle about double the tank volume is needed. And DME trucks do require selective catalytic reduction (SCR) for control of nitrogen oxides (NOx) to meet the EPA’s NOx engine emission standards, which were fully implemented in model year 2010 (though in that regard they’re no different than conventional vehicles).

But what really excites its backers is that DME is a non-toxic, non-carcinogenic fuel that can be synthesized from any bio-based material or conventional natural gas. Oberon Fuels has developed a proprietary process for small-scale DME production, which aims to take advantage of the great range of feedstock options. The goal of the project team is to locate production facilities in areas with readily available waste biomass (e.g., cow manure, municipal solid waste, landfill gas, etc.) so that the lifecycle emissions are minimized, and the DME fuel can be sold at a price point competitive with diesel. The first plant will go online in the Imperial Valley in California in 2014 and produce enough DME to fuel 100–150 trucks per day.

Volvo’s DME technology will be available in its D13 engine platform, which is the top-selling heavy-duty vehicle engine worldwide. From a policy point of view this is a noteworthy development. Having another alternative fuel engine commercially available in the heavy-duty vehicle market motivates the question of how non-diesel fuel engines and vehicles will be treated in the EPA and NHTSA’s Phase 2 fuel efficiency and GHG regulation. In the Phase 1 regulation, there are separate standards for diesel and non-diesel engines (see the ICCT policy update for a comprehensive summary). In addition, the other countries and regions who are currently developing heavy-duty vehicles policy measures must grapple with how to integrate non-diesel engines into performance standards. Some of the issues that must be addressed include the choice of evaluation metric (i.e. should different fuel engines/vehicles be evaluated based on CO2 or energy content?) and whether or not there will be different standards for diesel and non-diesel (e.g. gasoline, natural gas, DME) engines/vehicles. As more non-diesel fuel options become commercially available in the heavy-duty vehicle sector, these issues of will be increasingly important in a number of venues worldwide.

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