Green gas: key for the energy transition

Catherine MacGregor often emphasizes that, "To achieve net-zero carbon while ensuring cost control for citizens and businesses, (…) we need to leverage all decarbonization levers." Renewable gases are one such essential lever, with the added benefit of enhancing regional energy independence.

The latest step towards these objectives was taken on April 16^th, 2024, when ENGIE announced the acquisition of two biomethane production units in the Netherlands. This acquisition strengthens ENGIE’s project portfolio in a key market.

What is green gas or renewable gas?

Biomethane, synthetic methane, renewable hydrogen, and e-fuels. These gases are produced from various types of waste or renewable electricity.

There are several types of renewable gas:

Biomethane

• Derived from the methanization of biodegradable waste, biomethane comes from purifying this biogas which is then reinjected into the network.

Syngas

• Syngas makes it possible to use inputs that complement those of biomethane. It is obtained through the pyrogasification of solid waste or the hydrogenation of liquid waste.

Hydrogen

• Mainly used to decarbonize industry and heavy mobility, hydrogen makes it possible to fully exploit the capacities of variable renewable energies by converting them into a storable form.

What are the advantages of renewable gas?

Environmental advantages

• They emit eight times less CO₂ than natural gas, making them an ideal transition energy.
• They facilitate decarbonization for households and industry
• They contribute to a circular economy by recycling waste.
   

Economic advantages

• Most of them are compatible with existing gas infrastructures.

Societal benefits

• They contribute to regional energy independence and energy security 
• They stimulate the local economy by creating jobs that cannot be relocated.

How to produce low-carbon gas?

There are several ways of producing green gas.

Methanization

Organic waste is sorted, mixed, and placed into a methanizer, where it is heated and stirred. As it ferments, bacteria transform it into biogas. 
To make the biogas compatible with natural gas, it must be purified (i.e., components other than CH4 must be removed). 
Several techniques can be used to separate carbon dioxide (CO₂) from methane to obtain pure biomethane, such as acid compound absorption, membranes, or cryogenics. Once purified, it will then be odorized for injection into gas networks.

Discover how biogas is produced through methanization:

Hydrothermal gasification

This emerging technology makes it possible to produce renewable gas from liquid wet waste and biomass, such as sewage sludge or digestate from methanization plants that cannot be spread on land. Once the mineral component of the waste has been extracted, the remaining water and organic matter are converted into a synthetic gas.

Pyrogasification

Pyrogasification enables the use of solid waste that is not currently recycled, such as wood residues, Waste Furnishing Components (WFC), plastics or Solid Recovered Fuels (SRF), to produce renewable or low-carbon gas that can be fed into the grid. This process, still under development, complements methanization by the production of renewable gas from non-fermentable dry biomass.

Discover how synthetic gas is produced with hydrothermal gasification and pyrogasification: 

Electrolysis

This is a process in which electrical energy is converted into chemical energy. Electrolysis is used to transform electricity produced from renewable sources into, in our case, renewable hydrogen.

Discover how electrolysis produces hydrogen:

How are green gases used?

Renewable gases, such as biomethane, hydrogen, and their derivatives, will play a crucial role in decarbonizing the economy. They can be stored, enhance the flexibility of the energy system, and be integrated into existing gas infrastructure, helping to keep transition costs low.

However, each has its own unique characteristics:

Read Our Special Report on Renewable Gases