Biomethane: What is the so-called green gas and what is it for?

Biomethane is a renewable gas that is obtained from the treatment of organic waste. Its composition is very similar to that of fossil natural gas, since it is mainly made up of methane (CH₄), which allows it to be used in the same applications (heating, cooking, electricity generation or as fuel for vehicles).

How is biomethane or green gas produced?

Biomethane production begins with anaerobic digestion, a biological process in which microorganisms decompose organic matter in the absence of oxygen. This process takes place in facilities called digesters and results in a gas known as “biogas,” composed primarily of methane and carbon dioxide, plus small amounts of other gases.

Once the biogas is obtained, it undergoes a purification process. In this phase, carbon dioxide, water vapor and other impurities are eliminated, increasing the concentration of methane to levels similar to those of natural gas. The resulting gas is biomethane, which can be injected directly into the gas network, compressed for use as fuel, or stored for later consumption.

Now that we know what green gas or biomethane is, let’s see what the main differences are between biomethane and natural gas:

• Origin and renewability: natural gas is a fossil fuel that is extracted from underground deposits formed over millions of years. Its availability is limited and its use contributes to the depletion of non-renewable resources. Biomethane, on the other hand, is produced from recent organic waste, such as agricultural, livestock or urban waste. This makes it a renewable energy source.
• Environmental impact and emissions: in terms of emissions, natural gas releases carbon dioxide when burned, contributing to the increase in greenhouse gases. Biomethane also emits CO₂ during combustion, but is considered virtually carbon neutral. This is because the carbon released is part of the natural cycle of organic matter, since it was previously absorbed by plants and crops.
• Security and supply: Natural gas is often dependent on imports and geopolitical factors, which can affect its price and availability. Biomethane, when produced locally from waste, promotes energy autonomy, reduces external dependence and provides greater stability to the supply.

For more information about natural gas, don’t miss this article: “What is natural gas and what is it for?”

Biomethane stands out for its versatility, since it can be used in practically the same areas as natural gas. Let’s see what its most relevant uses and applications are:

• Domestic and residential use: biomethane can be used for heating, hot water and cooking.
• Industrial applications: biomethane can be used in sectors such as food, chemicals, ceramics or paper, among others, totally or partially replacing fossil gas.
• Generation of electricity and heat: this gas is used to generate electricity and heat in cogeneration facilities. This type of system jointly takes advantage of electrical and thermal energy, increasing overall performance and reducing energy losses.
• Transportation fuel: one of the applications with the greatest potential is its use as fuel for vehicles. Biomethane can be compressed (bioCNG) or liquefied (bioLNG) and used in passenger cars, buses, trucks or heavy transport fleets.
• Injection into the gas network: once purified, the biomethane can be injected directly into the existing gas network. This allows renewable energy to be distributed on a large scale, stored in current infrastructure and used when necessary, something that is not always possible with other renewable sources.

Biomethane is presented as one of the renewable alternatives with the greatest potential to reduce the environmental impact of the current energy system. Let’s analyze what its most important environmental benefits are:

1. Reduction of greenhouse gas emissions: as it is produced from organic waste, the direct release of methane into the atmosphere is avoided, a gas with a warming power much greater than that of carbon dioxide.
2. Sustainable use of waste: the production of biomethane makes it possible to recover waste that would otherwise end up in landfills or be managed less efficiently.
3. Improvement of soil and water quality: the production process generates a by-product called “digestate”, rich in nutrients such as nitrogen, phosphorus and potassium. Used correctly, it can replace chemical fertilizers, improving soil quality and reducing groundwater pollution caused by excessive use of synthetic fertilizers.
4. Less impact on ecosystems: unlike the extraction of fossil fuels, biomethane production does not require drilling, fracking or large extractive infrastructure that alters the natural environment. Here we explain “How fracking works”.

The capacity of this gas to take advantage of waste, reduce emissions and use existing infrastructure places it in a strategic position for the coming years. Its use is especially relevant in sectors that are difficult to electrify, such as certain industries, heavy transport or heating in buildings already connected to the gas network.

Technological advances are making it possible to optimize both the production and purification of biogas. New anaerobic digestion techniques and more efficient upgrading systems are reducing costs and increasing energy performance.

Expansion and development

In the coming years, a significant increase in the number of biomethane plants is expected, especially in rural areas with high availability of agricultural and livestock waste. This development favors local energy production, generates employment and contributes to the revitalization of rural economies.

The future of biomethane also depends largely on energy and environmental policies. Favorable regulations, economic incentives and clear production objectives can accelerate its implementation and attract investment.

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