Biomethane: what it is, how it is produced and its role in the circular economy

Biomethane is a renewable gas almost identical to natural gas, made up mostly of methane, obtained by upgrading the biogas generated from organic waste. Once it reaches a quality equivalent to natural gas, it can be injected into the gas grid, used as a transport fuel or feed industrial processes, directly replacing a fossil fuel.

Its appeal is twofold: on one hand it makes use of waste that would otherwise release methane in an uncontrolled way and, on the other, it produces dispatchable renewable energy. That is why biomethane has become a prominent piece of the circular economy and of decarbonisation strategies.

What biomethane is

Biomethane is the result of purifying biogas until its methane content rises above 95%, removing CO2, water vapour and other impurities. That purification process is known as upgrading. While raw biogas has a limited calorific value because of its high CO2 content, biomethane is interchangeable with fossil natural gas.

Three concepts should not be confused, summarised in the following table:

How biomethane is produced

Biomethane production follows two main stages.

Anaerobic digestion

The first is anaerobic digestion: microorganisms break down organic matter in the absence of oxygen, inside a digester, releasing biogas. The feedstock includes livestock waste (slurry, manure), sewage sludge, the organic fraction of municipal waste or agri-food by-products. A particular case is landfill gas, captured from the decomposition of waste already deposited.

Besides biogas, anaerobic digestion produces a digestate that can be used as an organic fertiliser, closing the nutrient cycle.

Upgrading to biomethane

The second stage is upgrading, which separates methane from CO2 and impurities using technologies such as water or amine scrubbing, pressure swing adsorption (PSA) or membranes. The result is a gas ready to be injected into the grid or compressed and liquefied for transport use.

Uses of biomethane

Because it is equivalent to natural gas, biomethane has very versatile applications:

• Grid injection, to decarbonise existing domestic and industrial consumption without changing infrastructure.
• Transport, especially heavy-duty and maritime transport, where electrification is harder, as compressed (bio-CNG) or liquefied (bio-LNG) gas.
• Thermal and industrial uses, replacing natural gas in processes that require process heat.

Role in the circular economy and decarbonisation

Biomethane fits squarely into circular logic because it turns waste into an energy resource and returns nutrients to the soil through the digestate. At the same time, it prevents the methane from that waste, a greenhouse gas far more potent than CO2 in the short term, from escaping into the atmosphere. This dual function aligns it with corporate zero waste strategies.

Framework in Spain and the European Union

In the European Union, the REPowerEU plan set the target of producing 35 billion cubic metres (bcm) of biomethane per year by 2030, as part of the strategy to reduce dependence on imported gas.

In Spain, the Biogas Roadmap, approved in March 2022, sets the national course: it aims to multiply biogas production by 3.8 to exceed 10.4 TWh per year in 2030. Around 55% of that production would be turned into biomethane for heavy mobility or grid injection, and its development would avoid on the order of 2.1 million tonnes of CO2 equivalent per year. Deployment is progressing: by the end of 2025 Spain had more than twenty biomethane plants in operation, still far from the country's estimated potential.

Advantages and challenges of biomethane for companies

For a company, biomethane offers several advantages over other renewable options. Because it is compatible with the existing gas infrastructure, it allows thermal and industrial consumption to be decarbonised without replacing equipment, which is especially valuable in high-temperature processes that are hard to electrify. It also contributes to security of supply as a local resource and to the recovery of a company's own waste, generating income or savings from by-products that were previously a cost.

It also raises challenges worth keeping in mind:

• Feedstock availability: production depends on a steady supply of nearby organic waste, since transporting it long distances reduces the environmental benefit.
• Production cost: today it is usually higher than that of fossil natural gas, so its competitiveness depends on the support framework and the gas price.
• Certification of origin: for a company to count biomethane as renewable in its carbon footprint, it needs guarantees of origin proving its source.

Well designed, biomethane fits into a circular economy strategy that reduces waste, emissions and fossil fuel dependence at the same time.

Frequently asked questions

Is biomethane the same as biogas?

No. Biogas is the mixture of methane and CO2 that comes directly from anaerobic digestion. Biomethane is that biogas upgraded to a quality equivalent to natural gas, which lets it be injected into the grid and used in transport.

What waste is it produced from?

From livestock waste, sewage sludge, the organic fraction of municipal waste and agri-food by-products, plus biogas captured at landfills. These are wastes that, without recovery, would release methane in an uncontrolled way.

Why is it considered renewable if it emits CO2 when burned?

Because the CO2 released is part of a recent biological cycle: it comes from organic matter that absorbed carbon shortly before, unlike fossil natural gas, which introduces into the atmosphere carbon stored for millions of years.

Turn your waste into data that supports your strategy

Using organic waste to produce energy is a circularity lever, but to prove it you need to measure and trace those flows well. Manglai helps companies manage their waste, track its traceability and quantify the environmental impact of recovering it versus disposing of it.