Natural Gas Vehicle Basics Heavy-duty NGVs for long-haul fleets that operate along a route with natural gas Natural gas powers about 175,000 fueling stations. Photo from Saturn Lounge Photography, NREL 28496 U.S. vehicles and more than 23 million vehicles worldwide.1 Natural gallons of LNG contains the energy regulations, including Federal Motor gas vehicles (NGVs) are a good equivalent of a gallon of gasoline. Vehicle Safety Standards (FMVSS). choice for high-mileage (high fuel-use) Compared to gasoline and diesel fuel, fleets—such as buses, medium- How and where is natural gas natural gas has a higher autoignition and heavy-duty trucks, and refuse produced and distributed? temperature, so it takes significantly vehicles—that are centrally fueled Most natural gas is drawn from wells more heat for the fuel to ignite without or operate within a limited area or or extracted in conjunction with crude oil a flame or spark. This makes uninten- along a route with natural gas fueling production. U.S. production of natural tional ignition less likely. In addition, because it is lighter than air, natural stations. The advantages of natural gas has increased significantly in recent gas dissipates quickly. gas as an alternative fuel include years. Most U.S. natural gas is produced in North America. The United States its domestic production, established NGV fuel tanks are strong and extremely has a vast distribution system, which distribution network, relatively low puncture resistant, and they undergo can quickly and economically distribute testing according to stringent standards. cost, and emissions benefits. natural gas to and from most locations in Once in use, they must be inspected in the lower 48 states. What is natural gas? a qualified service facility every three Renewable natural gas (RNG), or years (36 months) or 36,000 miles, Natural gas is an odorless, gaseous 4 biomethane, is produced from decaying whichever comes first. The National Fire mixture of hydrocarbons—predominantly organic materials like municipal solid Protection Association, U.S. Department methane (CH ). The fuel is widely used 4 waste from landfills, sewage from waste- of Transportation, and other organizations for heating and cooking, electric power water treatment plants, animal manure, or provide these and other safety guidelines production, and industrial use. Although food waste. After impurities are removed, for NGVs, as well as for fueling equip- it is a proven, reliable alternative fuel that 5 the gas is ready for use in vehicles or for ment. A list of applicable codes and has long been used to power vehicles, distribution through existing pipelines. standards is available on the AFDC less than 1% of natural gas is currently RNG qualifies as a renewable fuel under (afdc.energy.gov/pdfs/48611.pdf). used this way.2 Because it is a gas, it the federal Renewable Fuel Standard must be stored on board a vehicle in (RFS) and a low-carbon fuel under 1 either a compressed or liquefied state. In “NGVAmerica – Vehicles.” Accessed January 2020. California’s Low Carbon Fuel Standard. www.ngvamerica.org/vehicles. the United States, compressed natural gas (CNG) is typically stored in a tank at a In 2018, more than 305 million gasoline- 2 “Natural Gas Consumption by End Use,” U.S. Energy Information Administration. Accessed January 2020. pressure of 3,600 pounds per square inch. gallon equivalents of RNG received www.eia.gov/dnav/ng/ng_cons_sum_dcu_nus_a.htm. credits under the RFS.3 This constitutes Liquefied natural gas (LNG) is super- 3 “Spreadsheet of RIN Generation and Renewable Fuel significant progress toward renewable Volume Production by Fuel Type for the Renewable cooled and stored in its liquid form at goals, despite the fact that RNG produc- Fuel Standard,” U.S. Environmental Protection −260°F in insulated tanks. Because liquid tion is still a small fraction of estimated Agency. Accessed January 2020. www.epa.gov/ is denser than gas, more energy can be fuels-registration-reporting-and-compliance-help/ potential. Learn more about RNG on the spreadsheet-rin-generation-and-renewable-fuel-0. stored by volume. This makes LNG Alternative Fuels Data Center (AFDC) favorable for trucks that need a longer 4 U.S. Department of Transportation, National Highway (afdc.energy.gov/rng). Traffic Safety Administration, Compressed Natural Gas driving range. CNG is sold in units of Fuel Container Integrity, 49 C.F.R. 571.304 (Oct. 1, 2011). gasoline- or diesel-gallon equivalents, Are NGVs safe? 5 “NFPA 52: Vehicular Natural Gas Fuel Systems which is based on the energy content of Just like conventional vehicles, NGVs Code,” National Fire Protection Association. Accessed a gallon of gasoline or diesel fuel. LNG January 2020. nfpa.org/codes-and-standards/all- must comply with all applicable codes-and-standards/list-of-codes-and-standards/ is sold as a liquid gallon, where 1.5 detail?code=52. engines are traditionally limited to Purchasing new vehicles heavy-duty applications and can be more To find available OEM NGVs and fuel-efficient than their spark-ignited, engines, see the AFDC Vehicle Search dedicated counterparts. A dual-fuel (afdc.energy.gov/afdc/vehicles/search) system is more complex, requiring or the Natural Gas Vehicles for America diesel exhaust aftertreatment and onboard (NGVAmerica) Vehicle Availability page storage of both types of fuel at all times (ngvamerica.org/vehicles/availability). (whereas bi-fuel vehicles can operate on either fuel exclusively). A variety of In some cases, buyers can order OEM light-, medium-, and heavy-duty NGVs models with gaseous-fuel “prep pack- CNG vehicles are fueled with easy- are available and suitable for various ages,” which allow a qualified system to-use, pressure-sealed fueling applications. Buyers can purchase retrofitter or vehicle modifier (QSR or dispensers. Photo by Dennis Schroeder, vehicles through OEM dealerships or QVM) to install the EPA- or CARB- NREL 48723 have in-service vehicles converted. certified fuel delivery system before the vehicle is delivered to the customer. Considerations for CNG tanks How well do NGVs perform? Converting in-service vehicles When purchasing a CNG vehicle, NGVs are similar to gasoline or diesel customers should be mindful of the vehicles with regard to power, accel- Owners should insist upon an EPA- or FMVSS inspection requirements and eration, and cruising speed. Natural CARB-certified system when converting the useful life of the fuel tanks. For used gas has a higher pump octane number vehicles. System manufacturers may vehicles, it is important to know when than gasoline (120+ compared to 84–93 perform the conversion themselves the fuel tanks were last inspected, the for gasoline), and some OEMs offer or work closely with a QSR/QVM. A expiration date, if the vehicle has been in dedicated engines optimized to take well-qualified QSR/QVM will have an accident, and whether the tanks were advantage of this higher rating.6 This can established procedures and technical inspected after. CNG tanks have a useful result in improved performance and fuel training for the installation process, as life of 15, 20, or 25 years, depending on economy over nonoptimized engines. well as best practices. It is important how they were certified by the original The driving range of NGVs is generally to understand these and ask to review equipment manufacturer (OEM). All less than that of comparable gasoline and documentation on emissions compli- CNG tanks carry a label with the expira- diesel vehicles because with natural gas, ance as well as the conversion practices, tion date. This date may also be found on less overall energy content can be stored procedures, warranty, and training. a label near the fueling connector and on in the same size tank. Extra natural gas the label under the hood of the vehicle. storage tanks or the use of LNG can help How much do NGVs cost? increase range for larger vehicles. The price of an NGV is higher than Types of NGVs available that of a comparable conventional fuel There are three types of NGVs: How can I find reliable and vehicle; however, NGVs can provide EPA-compliant vehicles? an acceptable return on investment • Dedicated vehicles are designed to run (ROI) for many fleets because of fuel All NGVs must be certified to meet only on natural gas. cost savings. NGVs can cost thousands U.S. Environmental Protection Agency of dollars more than comparable gaso- • Bi-fuel vehicles have two separate (EPA) or California Air Resources Board line- or diesel-powered vehicles. The fueling systems that enable them to run (CARB) emissions standards. For a list price depends on the fuel tank capacity, on either natural gas or gasoline. This of EPA-certified conversion systems number of tanks required, and whether extends overall vehicle range by adding and engines, see the EPA website (epa. the vehicle is purchased new from an the distance that can be driven on each gov/vehicle-and-engine-certification/ OEM or is an in-service vehicle that has fuel separately. lists-epa-compliant-alternative-fuel- been converted. The maintenance and conversion-systems). Consult the • Dual-fuel vehicles use natural gas operation costs are similar to those of Natural Gas Vehicle Conversions page blended with some diesel fuel for their gasoline or diesel counterparts.7 and the publication What Fleets Need ignition assistance, allowing them For dedicated NGVs, maintenance costs to operate much like conventional to Know About Alternative Fuel Vehicle compression-ignition (e.g., diesel) Conversions, Retrofits, and Repowers on the AFDC for additional information on engines. 6 “AFDC Fuel Properties Comparison,” Alternative Fuels conversions (afdc.energy.gov/vehicles/ Data Center. Accessed January 2020. afdc.energy.gov/ Light-duty vehicles are typically config- natural_gas_conversions.html). fuels/fuel_properties.php. ured as dedicated or bi-fuel models, and 7 “Alternative Fuel Life-Cycle Environmental and heavy-duty vehicles are configured as Economic Transportation (AFLEET) Tool 2018,” dedicated or dual-fuel models.