With more than 1,700 units identified at the end of 2022, methanization is constantly progressing in France. This method of energy production transforms biomass and organic waste to produce green gas, a real sustainable alternative to natural gas of fossil origin.

Produced from methanization, biogas and biomethane are often confused. Although they both belong to the green gas family, their properties and uses differ.

Here are the keys to differentiating these new renewable gases, at the heart of the future French energy mix, from the reduction of greenhouse gases and the decarbonization of uses.

Biogas, a product of methanization

The biogas and biomethane are both produced during methanization. Biogas is the raw gas generated during the first stage of this energy production process.

How is biogas produced?

Methanization produces energy Starting from the biomass and organic waste wet, liquid and dry. It uses a variety of inputs, including:

• Of agricultural residues : manures, cattle effluents, straw, intermediate crops for energy purposes (CIVE).
• Of food residues : collective catering waste, foods declassified by the food industry (edible oil, mustard, etc.)
• Of sludge from sewage treatment plants.

Methanization takes advantage of the natural biological process of anaerobic digestion to produce energy. Enclosed in a digester in the absence of oxygen, organic matter is broken down by microorganisms.

This fermentation process produces a gas, called biogas, and a co-product, digestate. A natural fertilizer, digestate is used by agriculture to nourish the soil.

What is the chemical composition of biogas?

The chemical composition of biogas varies according to the organic matter fermented during methanization. But he remains composed of more than 85% methane (CH₄) and carbon dioxide (CO₂), including 50 to 60% methane.

Biogas also contains dinitrogen (N₂), oxygen (O₂), ammonia (NH₃), hydrogen sulphide — or hydrogen sulphide (H₂S) — and water (H₂O).

What are the uses of biogas?

Biogas is unsuitable for the energy consumption of end customers. The presence of sulphurous hydroxides and water molecules makes it corrosive and prohibits its injection into the gas network. Its chemical composition also makes it a light gas, less concentrated in energy than natural gas.

On the other hand, biogas is used to produce electricity and heat, instead of fossil fuels.

Biogas can feeding a compatible gas boiler with green gas. Burned, it releases heat to heat a nearby source. Biogas is also valued in energy production systems by cogeneration, to simultaneously produce electricity and heat.

The combustion of biogas powers the engine to drive the alternator and generate electricity. The heat produced during combustion is recovered for heating and domestic hot water. According to the latest figures at the end of 2022, 1,191 installations in France produce electricity and/or heat by cogeneration from biogas.

Biogas is especially exploited by industry to decarbonize its uses. Companies that consume large amounts of energy, such as chemicals, refining or the food industry, use biogas to cover their heat and electricity needs and reduce their carbon footprint.

Finally, biogas can be valorized into... biomethane.

Biomethane, the purified form of biogas

If biogas is not used in its raw form, it is transformed into biomethane during the second stage of methanization.

How is biomethane produced?

Biomethane is a by-product of biogas, obtained after purification. Biogas purification consists in extracting CO₂, water, sulphur hydroxides and other chemical compounds, to keep only methane molecules.

With a high methane content, the gas obtained is called biomethane. Before being injected into the natural gas network, Biomethane is odorized to detect potential leaks of this colourless and undetectable gas.

What is the chemical composition of biomethane?

Once purified, biomethane is composed of 98% pure methane.

With a methane content and energy density equivalent to those of natural gas, biomethane stands out as its 100% renewable energy alter ego.

What are the uses of biomethane?

Because of its properties similar to natural gas, biomethane can be injected into gas transport and distribution networks. He feeds end consumers directly to cover all their consumption uses (heating, domestic hot water, cooking, industrial processes...). Some energy suppliers offer to subscribe to green gas offers.

At the end of 2022, 514 installations for injecting biomethane into the gas network were identified in France.

Reliable and competitive, CNG (Natural Gas for Vehicles) — and its renewable version bioNGV — offer power and autonomy capacities compatible with the majority of needs.

According to the latest figures at the end of 2022, this fuel is still confidential despite increasing growth. Nearly 12,500 light vehicles, 9,000 heavy vehicles, 7,500 buses and coaches, and 4,200 household garbage trucks run on CNG/BioNGV. But only 36% of CNG is of renewable origin and derived from biomethane.

What are the advantages of biogas and biomethane?

Although the uses of biogas and biomethane are different, these two green gases present, because of their similar production method, the same environmental, economic and social benefits.

Green gases, renewable energy that is predictable and storable

Biogas and biomethane are the first gases recognized as renewable and low-carbon. Derived from natural and organic resources, these green gases are part of solution to global warming and the energy transition. Biomethane is particularly easy to operate because of its properties similar to natural gas of fossil origin.

Biogas and biomethane offer two advantages over other renewable energies. Unlike wind power or photovoltaic, they are predictable energy sources, whose production varies according to the volumes of inputs known in advance. These gases are also easy to store to balance production peaks and consumption peaks.

Biogas and biomethane, carbon neutral gases?

There is no denying it: the production and combustion of biogas and biomethane emit greenhouse gases. But their carbon footprint is undeniably better than that of natural gas of fossil origin.

According to GRDF, the carbon balance of the injected biomethane is estimated at around 23.4 CO₂e/kWh, or one The balance is 10 times lower than that of natural gas. ADEME estimates that 1 kWh of biomethane injected into the gas network is equivalent to 200 g of CO emissions₂ avoided.

For some experts, the carbon footprint of biogas and biomethane would even be neutral. The quantity of CO₂ emitted into the atmosphere during the production and combustion of gases would be offset by the quantity of CO₂ captured by plants before decomposition. Before being waste, wood was in fact a tree that captured CO₂ in the air to live.

Methanization also prevents the decomposition of waste in the open air, source of greenhouse gas emissions. In particular, the fermentation process produces methane, a gas whose global warming power (GWP) is 25 times greater than that of CO₂ !

By decarbonizing industrial and domestic consumption, biogas and biomethane finally contribute to reduce the global carbon footprint of countries.

Methanization, a local energy production that cannot be relocated

The production of biogas and biomethane promotes development of a circular economy at the scale of a territory and participate in its energy sovereignty.

Upstream, methanization valorizes organic waste generated locally by farmers, communities, wastewater treatment plants and manufacturers. Downstream, renewable gas supplies power directly to nearby consumers. In addition, digestate fertilizes crops without chemical fertilizers.

The last advantage of this winning combination: the construction of methanization units supports the local economy, with creation of jobs that cannot be relocated.

An ecological solution for waste recovery

The production of biogas and biomethane transforms biomass, organic matter and residual household waste into a virtuous resource.

Methanization offers a ecological alternative to their transport, incineration and burial, whose impacts are harmful on the environment. Another advantage for communities: the price of waste recovery is twice cheaper with methanization.

Renewable, local and low-carbon energy, biogas and biomethane are asserting themselves as essential energy solutions for a more sustainable climate future.

But with 1.6% of gas consumption in France coming from biomethane in 2022, is the 10% objective set by the Energy Transition Law for Green Growth (LTECV) by 2030 achievable?

The rapid development of renewable gas production — up by 61% between 2021 and 2022 — and the acceleration of production and injection projects suggest that gas consumption will be increasingly carbon-free.