What is compressed natural gas ?

What is compressed natural gas ?What is compressed natural gas ?

Compressed Natural Gas (CNG) is a fuel that consists mainly of methane (CH4) compressed to less than 1% of its volume at standard atmospheric pressure. This compression makes CNG an efficient way to transport and use natural gas. CNG is used in place of gasoline, diesel fuel, and propane/LPG, offering several advantages including lower emissions of pollutants and greenhouse gases.


CNG is stored and transported in hard containers at a pressure of about 3,000 to 3,600 pounds per square inch (psi). It’s used in traditional gasoline internal combustion engine cars that have been modified or in vehicles specifically manufactured for CNG use, often in the form of buses, trucks, trains, and some small scale vehicles like forklifts.

The benefits of CNG include:

  1. Environmental Benefits: CNG burns cleaner than petroleum-based fuels. Vehicles running on natural gas typically emit fewer pollutants and greenhouse gases than those running on gasoline or diesel.
  2. Cost Benefits: Depending on local natural gas prices, CNG can be significantly cheaper than gasoline or diesel.
  3. Energy Security: Using CNG can reduce dependence on imported oil, as natural gas is abundantly available in many countries.
  4. High Octane Rating: CNG has a high octane rating, which can lead to increased efficiency in engine performance.

However, there are also challenges associated with CNG, such as the need for special refueling infrastructure, the reduced range of vehicles compared to gasoline (due to the lower energy density of CNG), and the initial cost of converting vehicles to CNG or purchasing CNG-specific vehicles.

How compressed natural gas is produced?

The production of Compressed Natural Gas (CNG) involves several key steps, starting from the extraction of natural gas from the ground to its compression into a state that makes it usable as a fuel for vehicles and other applications. Here’s an overview of the process:

  1. Extraction: Natural gas is extracted from deep underground reservoirs either onshore or offshore. This is typically done through drilling wells into natural gas-bearing formations. The extracted gas can be a mixture of various hydrocarbons, primarily methane, along with smaller amounts of ethane, propane, butane, and inert gases such as nitrogen and carbon dioxide.
  2. Processing: The raw natural gas extracted from the ground contains impurities and hydrocarbon liquids that need to be removed. The processing involves separating these components to produce pipeline-quality dry natural gas, which is almost pure methane. The separation process might include methods such as absorption, adsorption, and cryogenic expansion.
  3. Transportation to Compression Facility: Once processed, the dry natural gas is transported, often through pipelines, to a compression facility. This transportation can span from a few miles to hundreds of miles, depending on the location of the gas fields relative to the compression facility or end-use site.
  4. Compression: At the compression facility, the dry natural gas undergoes compression. This is a critical step in producing CNG. The gas is compressed to a pressure typically ranging from 3,000 to 3,600 pounds per square inch (psi) to reduce its volume and make it suitable for use in vehicles. High-pressure compressors are used for this purpose.
  5. Storage and Dispensing: After compression, CNG is stored in high-pressure containers at the compression facility. These containers are designed to hold the gas safely at the high pressures required. The CNG is then dispensed into vehicles or containers for transportation to the point of use through specially designed CNG dispensing stations, which are similar in operation to traditional gasoline stations but equipped to handle the high pressures of CNG.
  6. Vehicle Use: Vehicles that run on CNG are either specially manufactured for this purpose or are conventional vehicles that have been modified with a CNG conversion kit. These vehicles have high-pressure tanks designed to store CNG and a fuel system calibrated to use CNG as fuel.

The entire process of producing CNG is geared towards ensuring that the gas is delivered safely and efficiently to the end-user, with the compression stage being critical to condense the gas sufficiently for practical storage and use in vehicles.

Applications of compressed natural gas

Compressed Natural Gas (CNG) is a versatile fuel that has several applications across various sectors due to its environmental benefits, cost-effectiveness, and availability. Here are some of the primary applications of CNG:

1. Transportation

  • Vehicles: CNG is widely used as a fuel for vehicles, including cars, buses, and trucks. CNG vehicles produce fewer emissions compared to those running on gasoline or diesel, making them a more environmentally friendly option.
  • Fleets: Many government and private fleet operators use CNG vehicles due to their lower operating costs and reduced emissions. This includes buses, delivery trucks, and utility vehicles.
  • Public Transportation: CNG is commonly used in public transport systems, including city buses and taxis, to reduce air pollution in urban areas.

2. Industrial Applications

  • Power Generation: CNG can be used in power plants as a cleaner alternative to other fossil fuels for electricity generation.
  • Manufacturing: In industries, CNG can serve as a fuel for boilers, furnaces, and other heating applications, providing a cleaner alternative to coal or oil.

3. Residential and Commercial Use

  • Heating: CNG can be used for heating purposes in residential and commercial buildings, including space heating, water heating, and cooking.
  • Cogeneration: CNG can be used in cogeneration systems to produce both heat and power efficiently for buildings or industrial processes.

4. Agriculture

  • Farm Equipment: CNG is being used to power farm equipment, providing a cleaner and often more cost-effective fuel alternative to diesel.
  • Greenhouses: CNG can be used for heating greenhouses, supporting year-round plant growth with reduced environmental impact.

5. Refuse and Sewage Treatment

  • Waste Collection Vehicles: Garbage trucks and other waste collection vehicles are increasingly using CNG due to the lower emissions and potential for fuel cost savings.
  • Sewage Treatment Plants: CNG generated from the treatment of sewage can be used as a fuel for various applications, including running the facility’s equipment.

6. Marine Applications

  • Ships and Ferries: CNG is beginning to be used in the marine sector, powering ships and ferries with a cleaner fuel alternative, contributing to the reduction of marine pollution.

The adoption of CNG across these applications is often driven by the desire to reduce emissions, lower fuel costs, and increase energy security by relying on more widely available natural gas resources. As technologies for compressing, storing, and using CNG continue to improve, its applications are likely to expand further.

Distribution and Use of CNG

The distribution and use of Compressed Natural Gas (CNG) involve several steps and infrastructure components to ensure that it is safely and efficiently transported from production sites to end-users. Here’s an overview of how CNG is distributed and used:

Distribution Infrastructure

  1. Production Site: CNG production begins at natural gas processing plants where raw natural gas is cleaned and processed to remove impurities and extract valuable hydrocarbons.Distribution and Use of CNG
  2. Compression Stations: After processing, natural gas is compressed at compression stations to reduce its volume and make it suitable for transportation and storage. The gas is compressed to a high pressure, typically around 3,000 to 3,600 pounds per square inch (psi).
  3. Storage Facilities: Compressed natural gas is stored at the compression site or at a separate storage facility. It is stored in high-pressure containers that are designed to handle the specific pressure requirements of CNG.
  4. Transportation: CNG can be transported from the storage facilities to refueling stations or end-users using specially designed tube trailers (cylinders mounted on trailers) or by pipelines. Tube trailers are particularly useful for areas not served by pipelines.
  5. Refueling Stations: CNG is dispensed to vehicles at refueling stations equipped with special high-pressure pumps. These stations can be standalone or co-located with traditional gasoline or diesel fueling stations.

    Fuel pistols close up and tanker truck at the gas station
  6. Pipeline Distribution: In some cases, CNG can be distributed directly to consumers through pipelines, especially for industrial or residential use where natural gas pipelines exist.

Use in Various Sectors

  1. Transportation Sector: CNG is widely used as a fuel for vehicles. It powers cars, buses, trucks, and fleets of various types. CNG vehicles have specially designed high-pressure fuel tanks and modified engines to run on natural gas.
  2. Public Transportation: City buses, taxis, and other public transportation vehicles often use CNG due to its lower emissions, contributing to cleaner air in urban areas.
  3. Industrial Applications: Industries use CNG for power generation, heating, and as a fuel in manufacturing processes. It’s chosen for its efficiency and lower environmental impact compared to other fossil fuels.
  4. Residential and Commercial: In areas where natural gas pipelines are available, CNG can be used for heating, cooking, and water heating in homes and commercial buildings. It offers a cleaner and often more economical alternative to other fuels.
  5. Utility Services: Some utility companies operate vehicles and equipment on CNG, including service trucks and maintenance vehicles.

Safety and Regulations

The distribution and use of CNG are subject to stringent safety standards and regulations to prevent leaks and ensure the safe handling of high-pressure gas. These include standards for CNG containers, refueling infrastructure, and vehicle tanks, as well as training for personnel involved in the CNG industry.

The distribution and use system for CNG is complex, involving multiple steps and specialized equipment to ensure that CNG is delivered safely and efficiently to the end-users. As infrastructure continues to develop and technology advances, the use of CNG is expected to expand further into new markets and applications.

Organic Composition of Exhaust and Evaporative Emissions from Gasoline and Some Alternate Fuels

The organic composition of exhaust and evaporative emissions from vehicles varies significantly depending on the type of fuel used. Gasoline, as well as alternate fuels like ethanol blends (E85), biodiesel, compressed natural gas (CNG), and liquefied petroleum gas (LPG), all produce different profiles of pollutants. Here’s an overview of the key components and considerations for each:


  • Exhaust Emissions: Gasoline combustion typically generates carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), particulate matter (PM), and carbon dioxide (CO2). The hydrocarbons can include a wide range of volatile organic compounds (VOCs), including but not limited to, benzene, toluene, ethylbenzene, and xylenes (BTEX), which are of particular concern due to their toxicological properties.
  • Evaporative Emissions: These include the release of unburned gasoline vapors, which contribute to the formation of ground-level ozone and smog. The evaporative emissions consist mainly of a complex mixture of VOCs.

Ethanol Blends (e.g., E85)

  • Exhaust Emissions: Ethanol and ethanol-blended fuels typically result in lower CO, HC, and PM emissions but may increase acetaldehyde and formaldehyde emissions. NOx emissions may increase or decrease depending on the engine technology and operating conditions.
  • Evaporative Emissions: Ethanol blends can increase the volatility of fuel, potentially leading to higher evaporative losses. However, modern fuel systems are designed to minimize these emissions.


  • Exhaust Emissions: Biodiesel combustion generally leads to reduced CO, HC, and PM emissions compared to petroleum diesel. However, NOx emissions can increase with biodiesel. The specific composition of biodiesel, which can vary based on the feedstock (e.g., soybean oil, used cooking oil), also influences the emission profile.
  • Evaporative Emissions: Biodiesel has a lower volatility than petroleum diesel, which generally results in lower evaporative emissions.

Compressed Natural Gas (CNG)

  • Exhaust Emissions: CNG vehicles emit lower levels of CO, HC (including lower levels of toxic hydrocarbons), and PM compared to gasoline vehicles. NOx emissions can be lower or comparable. Methane, a potent greenhouse gas, is a significant component of CNG exhaust emissions.
  • Evaporative Emissions: CNG has minimal evaporative emissions due to its gaseous state and the closed fuel system design of CNG vehicles.

Liquefied Petroleum Gas (LPG)

  • Exhaust Emissions: LPG combustion typically results in lower CO, HC, NOx, and PM emissions compared to gasoline. The primary components of LPG (propane and butane) lead to a different VOC emission profile than gasoline.
  • Evaporative Emissions: Similar to CNG, LPG has very low evaporative emissions due to its storage under pressure as a liquid and the closed nature of the fuel system.

It’s important to note that the emission profiles can vary widely based on the vehicle type, engine condition, fuel formulation, and operating conditions. Advanced emission control technologies and fuel additives can further influence these emissions. Regulatory standards continue to evolve to address the environmental and health impacts of these emissions, pushing for cleaner combustion and fuel technologies.

Compressed natural gas price per gallon

The price of Compressed Natural Gas (CNG) can vary depending on the location and market conditions. As of early 2024, the national average price for CNG was about $2.95 per Gasoline Gallon Equivalent (GGE). In Southern California, for example, CNG prices at public access stations were listed in the range of $2.28 to $2.50 per gallon. These prices include all applicable utility tariffs, surcharges, and local, state, and federal taxes​ (Alternative Fuels Data Center)​​ (Socalgas)​.

For the most current and specific pricing in your area, it’s a good idea to check local CNG stations or utility providers. Prices can fluctuate based on factors like crude oil prices, supply and demand dynamics, and regional taxation differences.

Compressed natural gas codes and standards

The codes and standards for Compressed Natural Gas (CNG) are crucial for ensuring safety, compatibility, and efficiency in its use, especially for fueling vehicles and operating fueling facilities. Despite the lack of harmonized international codes and standards, which poses a barrier to the global adoption of Natural Gas Vehicles (NGVs), there are significant standards in place that guide the industry.

Key standards include ISO 14469-2:2007, which relates to CNG vehicle nozzles and receptacles, ensuring a secure and safe connection between the fuel dispenser and the vehicle’s fuel tank. ISO 15500-9:2012 specifies tests and requirements for the pressure regulator, a critical component for managing the high pressures under which CNG is stored and dispensed. The International Organization for Standardization (ISO) has an active technical committee working on standards for natural gas fuelling stations for vehicles, aiming to address the current lack of international harmonization​ (Wikipedia)​.

In the United States, the National Fire Protection Association’s NFPA 52 Vehicular Natural Gas Fuel Systems Code is a comprehensive standard that covers the safety aspects of CNG fuel systems in vehicles and fueling facilities. It includes requirements that mitigate fire and explosion hazards associated with CNG and LNG (Liquefied Natural Gas) engine fuel systems​ (NFPA)​.

Furthermore, the Fiedler Group highlights the importance of various codes and standards in the design, installation, operation, and maintenance of CNG fuel dispensing facilities. Notably, the 2012 International Fire Code (IFC) Chapters 23 and 53, along with NFPA 30A and NFPA 52, provide detailed guidelines for building construction, electrical installations, operational requirements, and general fueling station requirements for CNG, among other alternative fuels​ (Fiedler Group)​.

These standards play a crucial role in promoting safety and efficiency in the use of CNG, guiding the industry towards sustainable practices and ensuring the reliability of CNG as an alternative fuel. For more detailed information on these codes and standards, you can refer directly to the ISO, NFPA, and Fiedler Group websites.


Compressed Natural Gas (CNG) represents a cleaner, more cost-effective alternative to traditional petroleum-based fuels for various applications, particularly in the transportation sector. Its production involves extracting natural gas, processing it to remove impurities, compressing it to high pressures for storage and transportation, and ultimately dispensing it to end-users through specialized infrastructure. CNG offers significant environmental benefits, including reduced emissions of harmful pollutants and greenhouse gases, compared to gasoline and diesel.

In terms of pricing, CNG can offer economic advantages, with prices often lower than those of gasoline and diesel, although they can vary by region due to factors such as supply, demand, and local taxation. As of early 2024, the national average price for CNG in the United States was approximately $2.95 per Gasoline Gallon Equivalent (GGE), with specific prices in regions like Southern California ranging from $2.28 to $2.50 per gallon.

The broader adoption of CNG is supported by the development of infrastructure such as compression stations, storage facilities, and refueling stations, along with advancements in vehicle technology that allow for efficient use of CNG in cars, buses, trucks, and fleet vehicles. Despite these advantages, the growth of CNG as a mainstream fuel source is influenced by factors including the availability of refueling infrastructure, the initial costs associated with converting vehicles to CNG, and the energy density of CNG compared to liquid fuels.

Overall, CNG presents a viable alternative to traditional fuels, with benefits that can contribute to energy security, economic savings, and environmental sustainability. As technology and infrastructure continue to evolve, CNG may play an increasingly significant role in the global energy mix​ (Alternative Fuels Data Center)​​ (Socalgas)​.

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