Material Insights · Understanding the Material World

CNG, LPG and biogas distribution: How it works

Why methane must be squeezed while propane only needs pressure

What this tab covers How the energy actually moves, step by step: the science that makes it work and the engineering that makes it practical.

Where there are no pipes, gas travels in pressure vessels: methane squeezed to about 250 bar (CNG), propane and butane kept liquid under modest pressure (LPG), and upgraded biogas injected into the grid or bottled.

Step by step

  1. Compress or liquefy at the sourceCNG compressors raise pipeline gas to about 250 bar. LPG, separated from natural gas or refinery streams, stays liquid simply by being held under pressure.
  2. Move in bulkCNG fills banks of composite cylinders on trailers or containers. LPG moves in very large gas carriers (VLGCs) at sea, rail cars, road tankers and some pipelines.
  3. Stock and fillCNG stations keep a cascade of high, medium and low pressure cylinders for fast filling; LPG is stored in spheres or bullet tanks and bottled into cylinders.
  4. Deliver the last mileTrucks, vans and handcarts take cylinders to homes, shops and farms; empties come back for refilling.
  5. Biogas routeBiogas from digesters is stripped of carbon dioxide and impurities to near-pure methane (biomethane), then injected into gas networks or compressed into cylinders.

The science

Methane cannot be liquefied by pressure alone at room temperature, so CNG relies on squeezing: at 250 bar it is roughly 250 times denser than at atmospheric pressure (ideal-gas estimate, calculated; real methane deviates somewhat). Propane and butane have larger molecules that attract each other more, so a few bar turns them liquid at ordinary temperatures, making LPG far easier to store and carry. Biogas is roughly half methane, half carbon dioxide; removing the carbon dioxide gives biomethane.

The engineering

CNG cylinders range from all-steel (Type 1) to carbon-fibre wrapped plastic liners (Type 4), about 75% lighter than steel. LPG cylinders are welded steel or composite with a valve and pressure relief device; terminals use spheres, and ships use refrigerated or pressurised tanks. Biomethane upgrading uses water scrubbing, membranes, amines or pressure-swing adsorption, then a grid entry unit checks quality and odorises the gas.

Key numbers

CNG module working pressure 250 bar at 15 C, emptied down to 10 bar7 Gas carried by a 40-foot Type 4 CNG module 8,720 kg (11,970 cubic metres) in 114 cylinders7 World LPG supply, 2024 more than 370 million tonnes1 VLGC fleet, end 2025 421 ships, 105 on order2 Biomethane injected into European gas grids, gas year to September 2025 43.2 TWh (about 4.3 bcm, calculated)8

Sources

  1. Q&A: Global LPG growth defies 2024 headwinds (on the WLGA and Argus Statistical Review of Global LPG 2025) Argus Media, 2025
  2. Q4 2025 Earnings Presentation BW LPG, 2026
  3. Mobile Pipeline X-STORE ADR gas modules datasheet Hexagon Agility, 2025
  4. ENTSOG Report on Annual Renewable Gas Injections into Gas Networks 2026 ENTSOG, 2026