California Air Resources Board

California Dimethyl Ether Multimedia Evaluation Final Tier I Report 

Prepared by the University of California, Davis and the University of California, Berkeley (February 2015)

Dimethyl ether (DME) is a new fuel that could help address environmental and fuel security issues. DME can be produced from a variety of feedstocks, including natural gas or bio-methane. Current production is focusing on methane-containing feedstocks, but gasification of any suitable organic source can lead to the syngas chemistry products with DME as one of the more energy efficient options. DME is a gas under ambient conditions with properties similar to those of LPG and can thus be stored as a liquid under moderate pressure, therefore not requiring the high pressure containers used for CNG or consideration of the cryogenic conditions of LNG. DME produced from bio-methane (from landfill gas or the decomposition of manure, for example) would be a non-fossil, renewable fuel.

Since DME is a new fuel, the California Air Resources Board (CARB) must provide a “multimedia risk assessment” before adopting new fuel specifications (as required by California Health and Safety Code, Section 43830.8). Further, existing law states that the “California Air Resources Board cannot adopt any regulation establishing a motor vehicle fuel specification unless a multimedia evaluation is conducted to determine whether the regulation will cause a significant adverse impact on the public health or environment” (California Senate Bill 140, 2007). The purpose of this multimedia risk assessment is to provide the State of California information that will allow an informed decision as to the relative health and environmental impacts to the State’s resources, human health and environment posed by the use DME as a transportation fuel.

As a result, the California Environmental Protection Agency (Cal-EPA) has initiated a program to assess the multimedia life-cycle impacts of DME use in California. This Tier I report is the first step in a three-tier process evaluating the cumulative health and ecological impacts from releases to air, surface water, groundwater and soil at all stages of the DME life-cycle: production, storage and distribution, and use. The risk posed by DME as a diesel alternative is assessed as a relative risk compared to ultra low California sulfur diesel currently in use.