Natural Gas Technologies

Any type of vehicle can use natural gas as a fuel. Vehicles can be either "dedicated" or "bi-fuel", depending on whether they operate solely on natural gas or have gasoline as the backup fuel. Some heavy-duty applications operate on both diesel and natural gas simultaneously (dual-fuel).

Natural gas can be stored onboard a vehicle as compressed natural gas (CNG) at 3,000 or 3,600 psi or as a cryogenic liquid natural gas (LNG) at 20-150 psi.


Manufacturers have sought to optimize their engines in dedicated vehicles to take advantage of the unique properties of natural gas such as high octane. These vehicles have surpassed all others in delivering superior emissions performance. Moreover, NGVs have been certified to the most stringent emission standards.


Honda's Civic GX, with emissions at just one-tenth the stringent ultra low emission vehicle (ULEV) standard-can actually emit air cleaner than the ambient air in some cities, the "near-zero" emissions becomes "nearly unmeasurable".


It should be noted that Honda was able to achieve all this without sacrificing horsepower or performance. Today, the Civic GX remains the only vehicle certified in California as an "AT-PZEV" receiving Zero Emission Vehicle credits toward California's ZEV Mandate. It's also the first and only vehicle certified to the all-new Environmental Protection Agency (EPA) Tier II, "Bin-2" standard. Due to the benefits of natural gas, Honda gets to call it "Cleanest on Earth".

On the heavy-duty side, natural gas engines are now certified to the EPA's or California's emission standards. These engines are available from companies such as Cummins Westport, Deere Power Systems, and Westport Fuel Systems.


Even tighter emission controls on heavy-duty engines and trucks are scheduled for 2007 and 2010. NGVs, are already demonstrating that they can meet and exceed these standards and provide even greater emission reductions.

See PG&E's Natural Gas Fleet Program fact sheet (PDF, 208 KB) for more details.

The Hydrogen-Natural Gas Connection

Since natural gas (CH4), is primarily made up of hydrogen molecules, it is a logical transition fuel to get to future hydrogen technologies. See Natural Gas as the Bridge to Hydrogen fact sheet (PDF, 68 KB) for more details.

Vehicles fueled with hydrogen/natural gas blends (HCNG) are an option for fleets desiring to gain experience with hydrogen-based transportation fuels of the future. HCNG vehicles offer the potential for immediate emissions benefits, such as a reduction in nitrogen oxides (NOx) emissions, particulate matter (PM) and carbon dioxide (CO2). At the same time, they can pave the way for a transition to fuel cell vehicles by building early demand for hydrogen infrastructure.