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Home , Liquid fuel, Natural gas

Natural Basics

Natural gas powers about 150,000 vehicles in the United States and roughly 22 million vehicles worldwide.1 vehicles (NGVs) are a good choice for high-mileage fleets— such as buses, taxis, and refuse vehicles—that are centrally fueled or operate within a lim- ited area or along a route with natural gas fueling stations. The advantages of natural gas as an alternative include its domestic availability, estab- Heavy-duty natural gas vehicles are a good choice for long-haul fleets that operate along a lished distribution network, route with natural gas fueling stations. Photo by Saturn Lounge Photography, NREL 28496 relatively low cost, and emis- sions benefits. range. Natural gas is sold in units distribute natural gas to and from of - or diesel-gallon equiva- most locations in the lower 48 states. What is natural gas? lents, which is based on the Natural gas is an odorless, gaseous content of a gallon of gasoline or (RNG), or mixture of —pre- . biomethane, is produced from decay- dominantly (CH4 ). The ing organic materials like municipal fuel is widely used for heating and How and where is solid waste from , cooking, production, natural gas produced from wastewater treatment , and industrial use. Although it is and distributed? animal , or waste. After a proven, reliable impurities are removed, the gas pro- Most natural gas is drawn from wells that has long been used to power duced from these operations is ready or extracted in conjunction with vehicles, only about one-tenth for use in vehicles or for distribution crude oil production. The produc- of 1% of natural gas is currently through existing pipelines. Because tion of fossil natural gas in the used this way. Because it is a gas, it it is produced from non- United States has increased signifi- must be stored onboard a vehicle sources, RNG qualifies as a renew- cantly in recent years as advances in either a compressed gaseous or able fuel under the federal Renew- in technologies liquefied state. Compressed natural able Standard (RFS) and a have enabled access to . gas (CNG) is typically stored in a low fuel under California’s Most of the natural gas used in the tank at a pressure of 3,000 to 3,600 Low Carbon Fuel Standard. Thus, United States is produced in North pounds per square inch. RFS credits are available to offset America. The United States has a the higher cost of RNG as com- vast natural gas distribution system, (LNG) is pared to fossil natural gas. In 2014, which can quickly and economically super-cooled and stored in its roughly 20 million gasoline-gallon form at -260°F in insulated tanks. equivalents of RNG received credits Because liquid is more dense than gas, more energy can be stored by 1. “Worldwide NGV Statistics,” NGV Journal, volume. This makes LNG favor- accessed August 6, 2015. www.ngvjournal. able for trucks that need a longer com/worldwide-ngv-statistics/

VEHICLE TECHNOLOGIES OFFICE cleancities.energy.gov VEHICLE TECHNOLOGIES OFFICE • June 2016 • Page 2 under the RFS. This is less than one inspected and, if the vehicle has -duty vehicles are typically percent of estimated production ever been in an accident, whether configured as dedicated or bi-fuel potential. Learn more about RNG the tank was inspected afterwards. models, and heavy-duty vehicles are on the AFDC website (afdc.energy. CNG fuel tanks have a useful life configured as dedicated or dual- gov/fuels/natural_gas_renewable.html). of 15, 20, or 25 years, depending fuel models. Dual fuel engines are on how they were certified by the traditionally limited to heavy-duty Is natural gas safe for original manufacturer. All CNG applications and are slightly more use in vehicles? tanks carry a label that states the fuel-efficient than their spark- Just like conventional vehicles, expiration date. This date can also ignited, dedicated counterparts, but NGVs must comply with all appli- be found on a label near the fueling a dual-fuel system is more complex cable regulations, including Federal connector, and on the label under and requires onboard storage of Motor Vehicle Safety Standards the hood of the vehicle. both types of fuel. (FMVSS). Compared to gasoline and diesel fuel, natural gas has a How do NGVs ? How well do NGVs higher A CNG fuel system transfers high- perform? (the point at which a gas or vapor pressure natural gas from the tank NGVs are similar to gasoline or can ignite in air without a spark or to the engine while reducing the fuel diesel vehicles with regard to power, flame being present), making unin- pressure to meet the operating acceleration, and cruising speed. tentional autoignition less likely. In requirements of the engine’s fuel- Natural gas has a higher addition, because it is lighter than management system. Just as in a octane number than gasoline air, natural gas dissipates quickly. gasoline engine, the fuel-air mix- (120+ compared to 84-93 for Fuel tanks on natural gas vehicles ture is compressed and ignited by a gasoline), and some original equip- are strong and extremely puncture spark plug to produce power. LNG ment manufacturers (OEMs) offer resistant, and they undergo testing engines operate similarly; the LNG dedicated engines optimized to take according to stringent standards. is converted to a gas before it is advantage of this higher rating.4 Once in use, they must be inspected injected into the engine. This can result in improved per- in a qualified facility every formance and fuel economy over three years (36 months) or 36,000 There are three types of NGVs: non-optimized engines. The driving miles, whichever comes first.2 The range of NGVs is generally less National Protection Associa- • Dedicated vehicles are designed to than that of comparable gasoline tion, U.S. Department of Trans- run only on natural gas. and diesel vehicles. This is because portation, and other organizations • Bi-fuel vehicles have two separate natural gas has a lower energy con- provide these and other safety fueling systems that enable them tent and less overall energy can be guidelines for NGVs, as well as for to run on either natural gas or stored in the same size tank as the 3 natural gas fueling equipment. A gasoline. This provides the flex- more energy-dense gasoline or diesel list of applicable codes and stan- ibility of using either fuel or both, fuels. Extra storage tanks or the use dards is available on the AFDC effectively increasing overall of LNG can help increase range. (afdc.energy.gov/pdfs/48611.pdf). vehicle range. What NGVs are available? Considerations for CNG tanks • Dual-fuel vehicles use natural A wide variety of light-, medium-, When purchasing a CNG vehicle, gas with some diesel fuel for and heavy-duty NGVs are available customers should be mindful of the ignition assistance, allowing and suitable for various applica- FMVSS inspection requirements them to operate much like tions. Buyers can purchase vehicles and the useful life of the fuel tank. conventional compression- through OEM dealerships or have If the vehicle is used, it is important ignition (e.g., diesel) engines. existing vehicles converted to natu- to determine when the tank was last ral gas after they’ve already been in service.

2. Fuel Container Integrity, 49 C.F.R. 571.304 (Oct. 1, 2011). 3. “NFPA 52: Vehicular Gaseous Fuel Systems Code,” National Association, accessed August 6, 2015, nfpa.org/codes-and-standards/ document-information-pages?mode=code&code=52. 4. AFDC Fuel Properties Comparison (afdc.energy.gov/fuels/fuel_properties.php).

CLEAN CLEAN VEHICLE TECHNOLOGIES OFFICE • June 2016 • Page 3

important to understand these and ask to review documentation on emissions compliance as well as the conversion practices, procedures, and training. Consult the Conversions page on the AFDC website for additional details (afdc.energy.gov/vehicles/ natural_gas_conversions.html).

How much do NGVs cost? The of an NGV is higher than that of a comparable conventional fuel vehicle; however, NGVs can provide an acceptable return on investment (ROI) for many fleets because of the fuel’s relatively low price. New OEM light-duty NGVs cost approximately $6,500 to CNG vehicles are fueled with easy-to-use, pressure-sealed fueling connectors. Photo by Pat Corkery, NREL 18188 $10,000 more than comparable gaso- line vehicles, and heavy-duty NGVs cost $30,000 or more than their How can I find reliable and Natural Gas Vehicles for America counterparts. The price depends on EPA-compliant vehicles? (NGVAmerica) Vehicle Availability the fuel-tank capacity and whether page (ngvamerica.org/vehicles/vehicle- All natural gas fueling systems must the vehicle is purchased from a availability/). be certified to meet U.S. Environ- dealer or is an in-service vehicle that mental Protection Agency (EPA) has been converted. The mainte- In some cases, buyers can order or California Air Resources Board nance and operation costs of NGVs select OEM models with gaseous- (CARB) emissions standards. For are similar to those of their gasoline fuel “prep packages,” which allow a list of EPA-certified natural gas or diesel counterparts. Fleet manag- a qualified system retrofitter or conversion systems and engines, ers will also need to consider both vehicle modifier (QSR or QVM) to see the EPA website (epa.gov/otaq/ the cost of fueling infrastructure, install the EPA- or CARB-certified consumer/fuels/altfuels/altfuels.htm if they do not currently have access natural gas fuel delivery system and epa.gov/otaq/certdata.htm#lsi). to existing fueling sites (see page 4), before the vehicle is delivered to Note that, as EPA states, the list is as well as the potential cost of any the customer. not comprehensive and there may upgrades that may be required to their maintenance facilities. be certified conversions that do Converting in-service vehicles not appear on the list. EPA adds Owners should insist upon an Tax credits and other incentives conversion systems upon request of EPA- or CARB-certified system the conversion manufacturer and may also be available to help reduce when converting in-service vehicles. the cost of fuel, vehicles, and infra- advises checking the list periodically However, ensuring a high-quality for updates. Customers should ask structure. See “How do I calculate conversion requires attention to the ROI for NGVs?” on page 5. to see and verify a manufacturer’s numerous additional details. Sys- EPA or CARB certificate. tem manufacturers may perform Is it easy to fuel an NGV? the conversion themselves or work Purchasing new vehicles CNG vehicles are fueled with easy- closely with a QSR/QVM. A well- To find available OEM natural to-use, pressure-sealed dispensers. qualified QSR/QVM will have gas vehicles and engines, see the The amount of time it takes to fill established procedures and techni- AFDC Vehicle Search (afdc.energy. a tank depends on several factors, cal training for the installation pro- gov/afdc/vehicles/search) or the including how the fueling station is cess, as well as best practices. It is configured. Time-fill stations fuel

CLEAN CITIES CLEAN VEHICLE TECHNOLOGIES OFFICE • June 2016 • Page 4 vehicles overnight, taking advantage Average Fuel in the U.S. of off-peak rates and 5 smaller (and less expensive) compres- Gasoline sion equipment. Fast-fill stations fill 4 Diesel vehicles rapidly using larger compres- CNG sion equipment and high-pressure 3 gas-storage systems. Ambient air 2 temperature and fill speed also affect the final fill volume in CNG vehicle Dollars per GGE 1 tanks. See an illustrated interactive animation of these effects on the 0 Apr. 2000 Jul. 2002 Nov. 2004 Feb. 2007 Oct. 2008 Apr. 2010 Mar. 2013 Oct. 2014 Sep. 2011 AFDC website (afdc.energy.gov/vehicles/ cng_tank_animation.html).

LNG stations are structurally simi- Date of Report lar to gasoline and diesel stations Figure 1. Average retail fuel prices in the United States for gasoline, CNG, and diesel in because they deliver a . dollars per gasoline gallon equivalent (GGE). Source: AFDC Average Retail Fuel Prices in the U.S., There are three options for LNG afdc.energy.gov/data/10326. fueling: mobile, containerized, and customized large stations. In Public fueling stations Locator mobile app from the AFDC mobile fueling, LNG is delivered There are nearly 1,000 public natural website (afdc.energy.gov/stations). by a tanker truck that has on-board gas stations across the United States, To obtain the best fuel price at metering and dispensing equipment. including more than 900 offering public fueling stations, fleet manag- A containerized station, or starter CNG and almost 100 offering LNG. ers should negotiate competitive station, includes a , To find stations in your area, visit pricing. Using stations without such dispensing equipment, metering, and the Alternative Fueling Station an agreement may result in paying required containment (for spills or Locator or download the Station higher prices. ). A custom station has greater storage capacity and is tailored to meet fleets’ needs. Fueling LNG vehicles requires special procedures, training, and protective equipment, but the process is not difficult.

As with all vehicles, proper safety precautions must be taken when fueling NGVs.

How much does natural gas cost and where is it available? Historically, the average retail price of natural gas has been lower and more stable than that of gasoline and diesel (see Figure 1). This makes nat- ural gas a good option for fleets that use large amounts of fuel. However, The of Sacramento deployed more than 100 LNG refuse trucks, as well as the fleet managers should carefully con- fueling stations and maintenance facilities to support them. The project resulted in sider their options when establishing millions of dollars saved and more than 1,900 tons of annual emissions private fueling or using public sites. averted. Learn more at afdc.energy.gov/case/1424. Photo by Randall Benton, courtesy of Zonar Systems

CLEAN CITIES CLEAN VEHICLE TECHNOLOGIES OFFICE • June 2016 • Page 5

Private fueling stations may cost anywhere from $5,500 for fleets with higher annual vehicle mile- Fleet managers planning to use a a residential unit to $850,000 for a age will experience shorter payback high volume of fuel may consider station to fuel fleet vehicles. A fast- periods. Payback is therefore linked building a new fueling station. CNG fill station may cost anywhere from to fleet size and type. Tax credits stations are typically located near $45,000 to $1.8 million. The wide and other incentives may also be existing natural gas pipeline infra- ranges result from the many vari- available to help reduce the cost of structure, whereas LNG is trans- ables, such as the number and type natural gas fuel, vehicles, and ported and delivered to stations of vehicles being fueled, required infrastructure, thereby shortening much like gasoline and diesel fuel. storage capacity, sizes, the payback . For more infor- Stations may be private access, open gas pressure, equipment used, mation, contact your local Clean to fleet customers, or available to number of posts and hoses, and Cities coordinator and see the AFDC the general public. installation costs. For more infor- Federal and State Laws and Incen- mation, refer to Costs Associated tives section (afdc.energy.gov/laws). For current information on on retail with Natural Gas Vehicle Fueling fuel prices, refer to the Clean Cities Infrastructure.5 According to the Two helpful tools include the Fuel Alternative Fuel Price Report (afdc. Energy Information Administration, Life-Cycle Environmental and Eco- energy.gov/fuels/prices.html). This an LNG fueling site can range from nomic Transportation (AFLEET) tool (greet.es.anl.gov/afleet), which estimates use, emissions, and cost of ownership of light- duty and heavy-duty vehicles for a variety of fuels; and the Vehicle and Infrastructure Cash-Flow Evalua- tion (VICE) model (afdc.energy.gov/ vice_model), which can be used to evaluate ROI and payback period for both natural gas vehicles and infrastructure.

How do NGV emissions compare with gasoline and diesel vehicle emissions? All new vehicles are equipped with effective emission control systems and must meet the same emissions standards, regardless of fuel type. Vehicles use the time-fill connection at the Oyster Bay, New York CNG refueling station. Consequently, tailpipe emissions Photo from Greater Long Island Clean Cities, NREL 23853 from NGVs (or any alternative fuel vehicles) are comparable to those report provides regional average $1 to $4 million.6 All infrastructure of gasoline and diesel vehicles retail prices for fueling stations and must comply with local codes and it can serve as a barometer on retail standards, and it’s important to fuel pricing in your area. 5. Smith, Margaret and John Gonzales, Costs involve the local authority having Associated with Compressed Natural jurisdiction early in the process. Gas Vehicle Fueling Infrastructure DOE/ How much does it cost GO-102014-4471, U.S. Department of Energy to install a natural gas How do I calculate the ROI Office of Energy Efficiency and Renewable fueling station? for NGVs? Energy, 2014, afdc.energy.gov/uploads/ publication/cng_infrastructure_costs.pdf. The cost of installing natural gas The ROI associated with natural infrastructure varies based on size, gas depends on a variety of factors. 6. “Annual Energy Outlook 2010 DOE/EIA- 0383(2010),” U.S. Energy Information Adminis- Because natural gas fuel is often less capacity, and the type of natural gas tration, ntl.bts.gov/lib/34000/34000/34012/ it dispenses. A time-fill CNG station expensive than gasoline and diesel, 0383_2010_.pdf.

CLEAN CITIES CLEAN VEHICLE TECHNOLOGIES OFFICE • June 2016 • Page 6

Fuel Tank (compressed natural gas)

Electronic Control Module (ECM)

Internal Engine (spark ignited) Pressure Relief Valve

Fuel Injection System Pressure Gauge Fuel Filler

Fuel Filters Fuel Line

This illustration shows a typical heavy-duty, Class 8 CNG truck. The various components of the CNG fuel system are highlighted. Illustration by Josh Bauer, NREL equipped with modern emissions Where can I learn more controls. According to ANL’s Green- about natural gas? house , Regulated Emissions, To learn more about natural gas as and Energy Use in Transportation a transportation fuel, visit the AFDC (GREET) model, light-duty vehicles Natural Gas Fuels and Vehicles running on conventional and shale pages (afdc.energy.gov/fuels/natural_gas. natural gas can reduce life cycle html). You can also contact your local by 11% Clean Cities coordinator (cleancities. (83% if running on RNG). In addi- energy.gov/coalitions.html) or visit the tion, because CNG fuel systems are NGVAmerica website (ngvamerica.org) completely sealed, the vehicles pro- for more information. For case stud- duce no evaporative emissions. For ies on natural gas vehicles, see the There are more than 800 public natural details, see the AFDC Natural Gas gas stations in the United States. Photo AFDC Case Studies page (afdc.energy. Vehicle Emissions page (afdc.energy. from iStock, 87365495 gov/case). gov/vehicles/natural_gas_emissions.html).

Clean Cities Technical Response Service 800-254-6735 • [email protected]

To view this and other Clean Cities publications online, visit cleancities.energy.gov/publications.

DOE/GO-102016-4853 • June 2016

Prepared by the National Laboratory (NREL), a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy; NREL is operated by the Alliance for , LLC.