LNG (liquefied natural gas): what it is and how it transforms transport

Liquefied Natural Gas (LNG) is natural gas that has been refrigerated to -162°C, the temperature at which it becomes liquid. When liquefied, its volume is reduced by up to 600 times, which greatly facilitates its storage and transport over long distances, especially to areas that do not have access to gas pipelines.

LNG is composed mainly of methane (over 95%), although its composition may vary slightly depending on the source of the natural gas. Once at its destination, it is regasified at regasification facilities to be injected into the grid or used as fuel. Spain is the European country with the largest number of regasification plants, giving it a unique strategic position in gas supply in Europe.

The transformation of natural gas into LNG follows these steps:

1. Extraction and pre-treatment: Natural gas is extracted from the reservoir and purified to remove impurities (water, CO₂, H₂S).
2. Liquefaction: the gas is progressively cooled to -162 °C in liquefaction plants located in producing countries.
3. Storage and Loading: LNG is stored in double-walled cryogenic tanks and loaded onto specialized LNG tankers.
4. Maritime transport: LNG tankers transport the LNG to destination countries. Spain imports LNG from the US, Qatar, Nigeria, Algeria, and Peru, among others.
5. Regasification or use as fuel: in the destination country, LNG can be regasified for injection into the gas grid or maintained in a liquid state for use as fuel in equipped ships and heavy-duty vehicles.

Although Liquefied Natural Gas (LNG) and Compressed Natural Gas (CNG) come from the same source, their main difference lies in the storage state and specific applications for each. Both are energy-efficient alternatives, but they are designed to meet different needs depending on the type of transport and distance.

• LNG liquefies at extremely low temperatures, which reduces its volume by up to 600 times.
• Facilitates storage and transportation over long distances, both by land and by sea.
• Used as fuel in a wide variety of applications: fuel for ships, heavy trucks, and as a source of energy in remote areas.
• Promotes low-carbon solutions in long-distance transportation.

• It is compressed at high pressures, without changing its gaseous state.
• Simplifies storage and transportation over shorter distances.
• Mainly used in lightweight vehicles, buses, and some service trucks.
• It is perfect for urban and regional transport, with an ever-expanding refueling infrastructure.

In short, while LNG is the preferred solution for long-distance and industrial applications, CNG is better suited to local and urban needs. Both represent significant advances toward a more sustainable energy future.

In the maritime transport sector, LNG represents a significant environmental improvement over traditional heavy fuel oil (HFO), especially in local emissions:

• CO₂ reduction: 20% and 30% lower life cycle emissions compared to fuel oil.
• Removal of sulfur oxides (SOx): 100% reduction of SO₂ emissions.
• NOx reduction: up to 80-90% lower nitrogen oxide emissions.
• Particulate matter removal: virtually zero fine particulate emissions.
• Compatible with existing infrastructure: LNG engines are a mature technology and Spanish ports already have established bunkering infrastructure.

The use of LNG as a marine fuel in Spanish ports has experienced significant growth in recent yearsy.

• LNG supplied to ships in Spanish ports exceeded 8.1 TWh in 2025, representing significant growth compared to previous years.
• Renewable bioLNG operations are now underway, which can help reduce maritime transport’s carbon footprint when meeting applicable sustainability criteria and drive progress toward the sector’s decarbonization goals.
• Spain boasts well-established infrastructure for supplying LNG to vessels, supported by bunkering activity across its ports.
  
• The Port of Barcelona leads LNG bunkering in Spain, with 231,787 m³ supplied in 2025 and 545 operations. Nearly 30% of cruise calls in Barcelona in 2025 were made by LNG-powered ships.

In addition to the maritime sector, LNG has a growing presence in heavy-duty road transport. LNG trucks offer a viable alternative to diesel for long distances.

The advantages of LNG in road transport include reduced engine noise, lower particulate emissions, and compatibility with Low Emission Zones (LEZ) regulations. The network of LNG supply points for road transport is expanding across Spain and Europe, especially along major logistics routes such as the Mediterranean and the Atlantic Corridors.

BioLNG is the renewable alternative to conventional LNG. It is produced by liquefying biomethane derived from organic feedstocks, such as agri-food, agricultural or livestock by-products, provided they meet the applicable sustainability and certification criteria. Its main advantage is that it can be used in LNG-compatible infrastructure, engines, vessels, and trucks without major modifications, helping reduce life-cycle carbon emissions compared to fossil LNG.

Under the Renewable Energy Directive, bioLNG qualifies as a renewable fuel when meeting the sustainability, traceability and emissions reduction criteria set out in the applicable regulations. In maritime transport, its use is emerging through specific bunkering operations in European ports.

European regulations are accelerating the transition of maritime transport by driving the use of renewable and low-emission fuels:

• FuelEU Maritime Regulation (EU 2023/1805): establishes a progressive reduction in the greenhouse gas intensity of the energy used on board ships calling at European ports: 2% in 2025, 6% in 2030 and up to 80% in 2050.
• IMO Strategy 2050: The International Maritime Organization sets a target of achieving net-zero emissions from global shipping by 2050.
• EU ETS Regulation: since 2024, large ships operating in European ports must include their emissions in the European carbon market.

Repsol promotes various energy solutions to support the decarbonization of maritime and heavy-duty transport, combining LNG supply, bioLNG development, and other renewable fuels as complementary alternatives for carbon-neutral mobility:

• Collaboration with key sector players: we hold a strategic agreement with Brittany Ferries to supply this fuel to its vessels in Spain since 2022, with part of its LNG-powered fleet operating between the United Kingdom and northern Spain.
• Innovation and infrastructure development:  in 2023, we launched an LNG bunkering terminal in the port of Santander in 2023, designed for LNG-powered vessels and expected to deliver an estimated reduction of more than 12,000 tonnes of CO2 /year in the planned operations.
• We completed the first LNG bunkering operation in Spanish ports with total CO2 emissions offsetting in Cartagena, supplying 420 m³ of Liquefied Natural Gas to the vessel Fure Vinga. Through Repsol Trading’s Bunker Desk, a specialized marine fuel supply unit, we have completed over 150 LNG bunkering operations across 32 vessels in 8 Spanish ports in recent years.
• Agreement with Norwegian Cruise Line Holdings: an eight-year contract at the Port of Barcelona covering the supply of renewable marine fuels, including biofuels and the future incorporation of renewable methanol.
• Royal Caribbean: Repsol has agreements for the supply of renewable fuels across certain maritime operations.
• Renewable fuels for maritime transport: the Cartagena plant produces HVO and SAF from organic feedstocks, while the Tarragona Ecoplanta will produce renewable methanol starting in 2028.