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Hydrogen/Natural Gas (HCNG) Fuel Blends

Natural gas can be blended with hydrogen to make HCNG. Vehicles fueled with hydrogen/natural gas blends (HCNG) are an initial step toward the hydrogen-based transportation of the future. HCNG vehicles offer the potential for immediate emissions benefits, such as a reduction in nitrogen oxides (NOx) emissions. At the same time, they can pave the way for a transition to fuel cell vehicles by building early demand for hydrogen infrastructure.

The U.S. Department of Energy (DOE) supports light- and heavy-duty HCNG projects. DOE's Advanced Vehicle Testing Activity (AVTA) teamed with industry partners to construct and operate a hydrogen and compressed natural gas (CNG) generation and fueling facility in Phoenix, Arizona. The facility provides pure hydrogen, pure CNG, or HCNG blends to light-duty test vehicles that have been independently modified to operate on these fuels. For more information, visit AVTA's Hydrogen Blended Fuel Vehicles project.

DOE's Natural Gas Vehicle Technology Forum supported a project to develop heavy-duty HCNG engines and transit buses. The HCNG (20% hydrogen, 80% CNG) engines demonstrated lower emissions, including a 50% reduction in NOx, than similar engines fueled with CNG alone with no significant change in fuel efficiency. Chassis dynamometer emission testing confirmed the substantial NOx reduction due to HCNG when the engines were integrated into transit buses. For more information on the project, see the Westport Innovations Hydrogen Enriched Compressed Natural Gas Web site and the following documents:

Bar chart with emissions level (in grams per brake-horsepower-hour [g/bhp-hr]) on the y-axis and pollutant type on the x-axis showing a 50% reduction (1.0 g/bhp-hr vs. 2.0 g/bhp-hr) in nitrogen oxides (NOx) emissions from a heavy-duty engine fueled with a hydrogen-compressed natural gas blend (HCNG) compared with an engine fueled with compressed natural gas (CNG) over the AVL drive cycle. Also shown are reduced emissions of non-methane hydrocarbons (NMHC), NOx plus NMHC, methane (CH4), total hydrocarbons (THC), and carbon monoxide (CO) from the HCNG-fueled engine compared with the CNG-fueled engine.

Engine dynamometer emission results, showing 50% NOx reduction with HCNG vs. CNG.