The California Department of Food and Agriculture has approved specifications for dimethyl ether (DME) used as fuel in compression ignition engines. (The Department of Food and Agriculture Division of Measurement Standards has the responsibility for establishing and enforcing the quality standards for spark- and compression-ignition engine fuels sold in California. These include gasoline, diesel fuel, and other fuels such as biodiesel and hydrogen.)
This latest approval builds on earlier approvals and ongoing work by other regulatory bodies, including the US Environmental Protection Agency, the California Air Resources Board, and ASTM International, and will help accelerate commercial adoption of this low carbon fuel, commented Oberon Fuels, a California-based company that is the first to produce fuel-grade DME in North America. (Earlier post.)
The approval of the quality specifications opens the way for public sale of the fuel. The regulation was proposed on 25 July 2014; it was approved and filed with the Secretary of State, with an effective date of 1 January 2015. (Oberon had requested that the Department move forward with the adoption of the proposed regulations, even though widespread production and use of DME does not currently exist, the Department noted.)
This certification is a major step forward in developing the market for DME, especially for California-based heavy-duty fleets. Volvo Trucks is continuing to invest in DME because it delivers diesel-like performance with propane-like handling and will provide a faster ROI for truck customers than other alternative fuels. Each certification increases their confidence that the fuel is good for trucks and the environment.—Susan Alt, Volvo Group North America’s senior vice president of public affairs
Volvo Group has been collaborating with Oberon on commercial vehicle demonstrations of DME. (Earlier post.) Volvo originally had been targeting 2015 to begin limited production of DME trucks in North America, but subsequently decided not to set a commercialization date.
DME can replace petroleum diesel in modified compression-ignition vehicles if it meets established fuel quality specifications. ASTM has published a quality specification for DME as a compression-ignition fuel, D7901-14; the Department adopted this standard.
The combustion of DME does not produce particulate emissions because its chemical structure does not have the carbon-carbon bonds that can condense to form black carbon, or soot. The DME molecule also has a high ratio of oxygen to carbon atoms, which promotes cleaner burning. In contrast, the major components of diesel fuel do not contain oxygen. They consist of chains of carbon-carbon bonds that lead to the formation of soot particles during combustion.
By displacing petroleum diesel, the Department noted, DME can mitigate these negative health impacts, resulting in improvements in both environmental and public health throughout California.
Although the California Air Resources Board (ARB) has not yet certified a carbon intensity for DME, DME is a low carbon fuel that meets the requirements of the LCFS, the Department said in its statement of reasons. DME can thus make a significant contribution towards California’s LCFS and AB 32 goals and so can mitigate the contribution of the transportation sector to global warming. Last August, the EPA approved biogas-based DME for inclusion under the Renewable Fuel Standard and made it eligible for Renewable Identification Numbers (RINs) credits based on EPA findings that the fuel achieves a 68% reduction in greenhouse gases.
DME can be manufactured from a wide range of feedstock, including natural gas, dairy digester biogas, and other biomass sources. The production of DME is scalable and small production units can be located near dairies or other feedstock sources. The use of agricultural waste for DME production could also reduce agriculture’s 6% contribution to the state’s GHG emissions. In addition, biomass-based DME may even have net negative carbon content.
DME’s physical and combustion properties are very similar to those of propane. Therefore, DME may be handled using the same equipment, distribution, infrastructure, and dispensers used for liquefied propane gas (LPG). The safety procedures used with LPG can be used for handling DME.