Facebook LinkedIn

Wednesday August 2 2023

What is Biomethane?

Biomethane is seen as one of the most important renewable gases of the future and, for many, is seen as one of the key elements for providing energy security to nations while also playing a role in tackling the energy crisis.

While biomethane isn’t a new technology, it has seen a rapid rise in popularity in recent years around the world and its importance in the energy mix is growing.

It is seen as having an important role in the push to decarbonise our economies and offers an attractive solution to tackling waste as the global population continues to grow and consume more.

But, what is biomethane and what can biomethane be used for? Is biomethane environmentally friendly and can biomethane be classed as a green gas? In this blog we answer these questions and look at how biomethane is produced, how it differs from natural gas and the future of biomethane.

How is biomethane made?

Biomethane is made from biogas generated in anaerobic digesters which break down organic matter in an oxygen-free environment. In this process, typically waste organic material is allowed to decompose in an airtight system and the breakdown of this matter produces a range of gases including methane, CO2 and a small range of other gases.

The biogas is generated from three main technologies – biodigesters, landfill gas recovery systems and wastewater treatment plants.

Biodigesters are airtight containers or tanks and the organic material is diluted in water and added to the system so it can then be broken down by microorganisms in a carefully controlled manner. Feedstocks in biodigesters are carefully monitored to maximise the potential of gas production and optimise the environment for the microorganisms.

In landfill gas recovery systems, the municipal solid waste decomposes naturally under anaerobic conditions and this produces biogas that can then be captured using pipes and extraction wells. In many instances compressors are also used to drive the flow of gas to a central collection point.

At wastewater treatment plants, systems are included to recover organic matter, solids and some key nutrients, such as nitrogen and phosphorous, from the sewage sludge. This sludge can then be treated and fed into anaerobic digesters to produce biogas.

What is biomethane made from?

Biomethane can be made from a variety of organic matter and this is known as feedstock for the anaerobic digestion process. These feedstocks typically come from crop residues, animal manure, food and green waste, industrial waste and wastewater sludge.

With crops, the remains from the harvest of grains, sugar beet, beans and oilseeds are used and provide a rich source of feed for the microorganisms. Critically, this single feedstock approach can make it much more predictable to know the value of it to the microorganisms (or the calorific value) and easier to control the critical reactions in the digester.

Animal manure is another key feedstock and has great value in helping to manage waste produced by livestock. This as a feedstock is not as predictable or consistent in terms of calorific value as crop residues but is still a valuable source for the microorganism reactions. The digestate produced from the process can also be a valuable fertiliser for adding to fields.

Food, green and industrial waste is also a valuable source and is being pushed as a priority for anaerobic digester operators as councils seek to divert refuse from landfill. The challenge with this waste is that it can vary dramatically in quality and can feature a range of contaminants that the digester won’t be able to break down.

The last feedstock is wastewater sludge, which is processed solid organic matter recovered from sewage treatment plants.

Many anaerobic digestion operators also use energy crops for feedstock. These are crops specifically grown to provide feed for the digestion process.  While this brings advantages to the process by creating a predictable, single-source, calorie-rich feedstock for digesters, it is a controversial option because it takes up land that could be used to grow food for consumption and neglects to tackle the waste issue.

Energy crops also require inputs such as fertiliser, which are often produced from fossil fuels, and this negatively impacts the green credentials of biomethane.

Many Governments, including the UK Government, are now putting strict limits on the use of energy crops in anaerobic digesters and are setting targets for the amount of waste used to qualify for the financial incentives associated with this form of energy production.

What is the difference between biogas and biomethane?

Biogas is the mixture of gases produced during the anaerobic digestion process and the quantities of each can vary depending on the feedstock. It is primarily made of methane with CO2 and a small amount of other gases included in the mix.

The methane content of biogas typically ranges from 45% to 75% with CO2 making up the majority of what’s left. Carefully managed anaerobic digesters can deliver substantial quantities of methane and it’s important to monitor the internal reactions to maximise the potential of the digester.

Biogas can itself be used to generate electricity and heat or as an energy source for cooking but biomethane is different as it is a near pure source of methane and can be used as a substitute for natural gas.

To produce biomethane, biogas is upgraded  to remove the CO2 and any other contaminants through a dedicated system that scrubs the other gases out and leaves a clean, reliable source of energy. Biomethane is similar in properties to natural gas that it is also known as the renewable natural gas and can be used in all applications from heating homes to fuelling cars.

Is biomethane environmentally friendly?

As we’ve said, biomethane is identical to the fossil fuel natural gas and this often causes some confusion around the green credentials of biogas.

Both natural gas and biomethane are produced from the breakdown of organic materials and methane is a more potent greenhouse gas than carbon dioxide when released into the atmosphere.

On the face of it, both appear to be as equally damaging to our environment but there are some fundamental differences.

Natural gas is classed as a fossil fuel as it methane derived from fossilised organic remains over millions of years, deep underground. This process also means it is only available in limited amounts and in limited locations, meaning some countries are vulnerable to energy security issues.

Biomethane, however, is produced from ‘fresh’ organic matter which makes it a renewable source of energy that is available worldwide.

The process of producing biomethane also ensures harmful methane emissions from decomposing waste are captured and prevented from escaping into the atmosphere and further contributing to climate change. This controlled waste disposal also prevents pollution and leaching from landfill which can contaminate waterways and impact wildlife.

As an added bonus, the use of biomethane also means we are using less fossil fuels and this helps to cut the emissions of greenhouse gases.

What can biomethane be used for?

We’ve already spoken about how biomethane is almost identical to natural gas and this means it has a wealth of uses and can be used in all of the applications where you’d see natural gas.

This includes electricity generation, water heating, space heating, cooking and manufacturing. But perhaps one of the most exciting new uses for biomethane is it’s potential for powering vehicles.

Many manufacturers are providing vehicles that can be powered by biomethane as it is en efficient and eco-friendly alternative to conventional fossil fuels. Tractor manufacturer New Holland has already produced the first methane-powered tractor so farmers can use the biogas being generated on their farms to power their key farm operations.

Elsewhere, we are also starting to see fleets of heavy goods vehicles switching to methane power. Many manufacturers have invested in anaerobic digestion plants to manage waste and provide heat and power but are also now using that gas to fuel their logistics too.

Put simply, biomethane is a versatile and valuable renewable source of energy that offers a great alternative to fossil fuels. It’s potential for helping to balance energy security while also tackling key issues around waste is seeing a huge surge in the number of anaerobic digesters around the world.

If you have any questions about the production of biomethane or want to know more about anaerobic digestion, speak to one of the Birch Solutions team at enquiries@birchsolutions.co.uk