Natural Gas

Natural gas is a domestically produced alternative fuel that is readily available to end-users through the utility infrastructure. It can produce significantly fewer harmful emissions than gasoline or diesel when used in natural gas vehicles.

Natural gas is a mixture of hydrocarbons, predominantly methane (CH4). As delivered through the pipeline system, it also contains hydrocarbons such as ethane, propane, and other gases such as nitrogen, helium, carbon dioxide, hydrogen sulfide, and water vapor.

Natural gas has a high octane rating and excellent properties for spark-ignited internal combustion engines. It is non-toxic, non-corrosive, and non-carcinogenic. It presents no threat to soil, surface water or groundwater.

Natural gas accounts for approximately one quarter of the energy used in the U.S. Of this, about one third goes to residential and commercial uses, one third to industrial uses, and one third to electric power production. Only about one-tenth of one percent is currently used for transportation fuel.

The vast majority of natural gas in the United States is considered a fossil fuel because it is made from sources formed over millions of years by the action of heat and pressure on organic materials. There are three types of Natural gas made into fuel:

1. Compressed Natural Gas (CNG)
2. Liquefied Natural Gas (LNG)
3. Renewable Natural Gas (RNG), also known as “biomethane”, is a pipeline-quality vehicle fuel. It is produced by purifying biogas, which is generated through anaerobic digestion of organic materials—such as waste from landfills and livestock—or through thermochemical processes, such as gasification. RNG qualifies as an advanced biofuel under the Renewable Fuel Standard. Because RNG is chemically identical to fossil-derived conventional natural gas, it can use the existing natural gas distribution system. 94% of all on-road fuel in natural gas vehicles in calendar year 2025 was RNG.

Compressed natural gas and liquefied natural gas are considered alternative fuels under the Energy Policy Act of 1992. The horsepower, acceleration, and cruise speed of natural gas vehicles are comparable to those of equivalent conventional vehicles. Compared to conventional diesel and gasoline vehicles, natural gas vehicles can produce some emissions benefits.

There are three types of natural gas vehicles:

1. Dedicated: Designed to run only on natural gas.
2. Bi-Fuel: Can run on either natural gas or gasoline.
3. Dual-Fuel: Diesel fuel ignition assistance to natural gas fuel usage (generally limited to heavy-duty vehicles)

Frequently Asked Questions: 

• What is the current status/state of natural gas fueling infrastructure?

As of 2026, there are 30 Compressed and Liquefied Natural Gas Fueling stations across Wisconsin. You may identify stations that sell RNG by selecting the “Include only stations that sell RNG” option under the Natural Gas fuel filters. This allows users to find CNG and LNG stations that offer RNG for transportation use:

• What are the latest Natural Gas Rates?

You can compare the latest Natural Gas rates here.

• How can fueling station operators address safety concerns for installing CNG stations near residential areas?

In general, when designed, permitted, and operated in compliance with national and local codes, CNG stations do not pose a significant risk to adjacent neighborhoods. Natural gas is lighter than air, dissipates rapidly, and is harder to ignite than conventional fuels. It is the same fuel used to heat your home, cook your meals, and dry your clothes. If accidentally released into the environment, natural gas is less hazardous than petroleum fuels. Storage and delivery systems for NGVs are governed by the National Fire Protection Association (NFPA). In particular, NFPA 52, the Vehicular Natural Gas Fuel Systems Code, defines specific safety requirements for NGVs and their fueling facilities. It is important to note that local fire marshals and permitting authorities do not approve stations that fail to meet these requirements. Routine safety evaluations are needed to be re-certified by a U.S. Department of Transportation recognized certification lab,

• What is the difference between a fast-fill and time-fill CNG fueling station?

CNG vehicles can be fueled using time‑fill, fast‑fill, or combination‑fill station configurations. These station types differ primarily in fueling speed and typical use cases.

Time‑fill stations fuel vehicles slowly over an extended period, typically several hours. Vehicles are connected directly to a compressor and are often filled overnight. Time‑fill stations are best suited for fleet operations where vehicles return to a central location and remain parked for long periods, such as transit buses, refuse trucks, or delivery fleets.

Fast‑fill stations provide fuel at a rate similar to conventional gasoline or diesel stations. Natural gas is compressed on site and stored in high‑pressure tanks, allowing vehicles to refuel quickly during the day. Fast‑fill stations are commonly used at public retail locations or fleet depots where quick turnaround is required. New, larger stations also have compressor systems that directly fill vehicles when storage systems become depleted, allowing continued filling at a quicker rate.

Combination‑fill stations incorporate both time‑fill and fast‑fill equipment. These stations allow fleets to time‑fill vehicles overnight while also providing fast‑fill dispensers for daytime use or public access.

• What are some ways to tell if a natural gas fueling station is dispensing RNG?

Unfortunately, fueling stations that dispense RNG often do not label the station or the pump with “RNG” even if it is being dispensed through the natural gas pumps, as it is not legally required. Per the Code of Federal Regulations Title 16 Part 309 – Labeling Requirements for Alternative Fuels, fueling stations are required to identify the fuel type (e.g., CNG), but are not required to disclose the fuel origin. We recommend confirming if a fueling station dispenses RNG by contacting station operators directly and asking if the stations are directly fueled by an RNG production source or connected to a local natural gas pipeline, which might have RNG in the mix.

More Information can be found at these sources

• Alternative Fuels Data Center
• America’s Natural Gas Alliance (ANGA) represents North America’s leading independent natural gas exploration and production companies. ANGA works with industry, government, and customer stakeholders to promote increased demand for and continued availability of our nation’s abundant natural gas resource for a cleaner and more secure energy future.
• American Gas Association (AGA) founded in 1918, AGA represents more than 200 local energy companies that deliver clean natural gas throughout the United States. Today, more than 68 million residential, commercial, and industrial customers across the nation receive their reliable, affordable supplies of natural gas from AGA members, and natural gas meets almost a quarter of America’s energy needs.