The EU and more than 110 countries have committed to becoming carbon neutral by 2050. One of the most critical steps to achieving that goal is finding sustainable alternatives to fossil fuels.
Biomethane, or renewable natural gas (RNG), is a carbon-neutral fuel that has a significant role in helping the world reduce carbon emissions and sustainably power the economy of the future.
Biomethane is produced using anaerobic digestion, which captures the methane emissions from fermenting organic material such as agricultural and food waste.
The product of this process is called biogas, which is then filtered using specialised upgrading equipment that removes contaminants to produce gas that has a methane content of greater than 95 percent.
Known as biomethane, renewable natural gas (RNG), or green gas, this fuel can be used interchangeably with fossil natural gas. It can be compressed or liquefied and used to power vehicles or injected directly into any existing gas grid to replace fossil natural gas.
Biomethane production reduces methane emissions—a greenhouse gas 80 times more potent than carbon dioxide CO2—burning this green gas still emits carbon into the atmosphere.
Because it still emits CO2, many people ask, “how is biomethane carbon neutral?”
Let’s explore this question to learn what makes this renewable fuel carbon-neutral or even carbon-negative.
The biogenic carbon cycle
Burning fossil fuels brings more greenhouse gases into the atmosphere
Burning fossil fuels releases carbon dioxide (CO2) that has been stored underground for millions of years as part of the long-term carbon cycle.
Fossil fuels come from carbon-rich organic matter like dead plants and marine organisms buried and preserved in rock layers during the Earth’s ancient history.
Using them as fuel results in a net increase in the total carbon dioxide in the atmosphere in the short term and represents the most significant cause of global warming.
Burning biomethane doesn’t increase the amount of carbon in the atmosphere
Using biomethane emits carbon that has been stored in organic waste as part of the biogenic or short-term carbon cycle.
The CO2 in the organic materials used to produce biomethane has recently been part of living organisms. This is CO2 that has been sequestered, or stored as part of the natural biogenic carbon cycle that offsets the carbon emissions that happen when organic material decays or is consumed by animals.
While the combustion of biomethane, which has almost the same composition as natural gas, emits carbon dioxide, the carbon in biomethane originates from recently fixed atmospheric CO2 by the organic matter during its growth phase.
In a nutshell, the carbon released from burning biomethane is part of a natural cycle that has occurred for millennia and does not add more carbon into the atmosphere.
Methane is a greenhouse gas 80 times more potent than CO2 during the first 20 years after it’s released into the atmosphere. It accounts for about half the net rise in global average temperature since the pre-industrial era.
In 2021, more than 100 countries worldwide signed the Global Methane Pledge to reduce methane emissions by at least 30 percent from 2020 levels by 2030.
Achieving this goal could eliminate a temperature rise of over 0.2 degrees Celcius by 2050 and reduce more than eight gigatons of CO2 equivalent (GtCO2e) emissions from entering the atmosphere by 2050.
By capturing methane from decaying organic waste, biomethane production is helping to achieve this goal by reducing the amount of methane that´s emitted into the atmosphere.
Conversely, burning fossil natural gas releases methane sequestered underground for millions of years. This causes more methane to accumulate in the atmosphere and exacerbates the problem of global warming.
Replacing fossil fuels
According to the European Biogas Association, the EU’s biomethane production could reach 151 BCM by 2050. This would replace up to 40 percent of Europe’s total fossil natural gas consumption.
Reducing fossil fuel consumption by that much would keep approximately 1 billion metric tonnes of carbon dioxide from entering the atmosphere. That’s the equivalent of stopping ~117 billion litres of gasoline consumption.
Biomethane’s potential for reducing fossil fuels is highest in the heavy-duty and marine transport industries.
As greenhouse gas emissions in the EU have decreased over the past ten years, CO2 emissions from fossil-fuel-powered heavy-duty vehicles have increased. This makes it a critical sector to decarbonise and one that’s difficult to electrify.
Projections by Natural Gas Vehicle Association EU (NGVA) show that LNG-fuelled heavy-duty transport is expected to increase ten times to 280,000 vehicles by 2030—or 25 percent of the EU market share for trucks.
Compared to powering these trucks with other fuel technologies, using a mix of LNG and Bio-LNG to fuel these trucks would produce 50 percent less carbon emissions.
If companies fuelled their trucks with 100 percent Bio-LNG produced from manure, their greenhousegas (GHG) emissions could even be carbon negative. (We’ll explore biomethane’s carbon-negative potential further below.)
Regarding shipping, the number of LNG-fuelled vessels is set to increase significantly. In 2021, more than 30 percent of new ship builds were LNG-fuelled.
A 20% blend of Bio-LNG can reduce GHG emissions by 18% on a tank-to-wake basis. When running on 100% Bio-LNG, GHG emissions can be reduced by 93%. And further reductions are possible depending on the origin of the Bio-LNG.
Biomethane can be carbon-negative
The term carbon negative refers to the practice of emitting less than zero carbon dioxide or equivalent greenhouse gasses. It involves offsetting more carbon through carbon capture, sequestration, or avoidance than you release into the atmosphere.
Biomethane’s ability to capture methane and reduce CO2 emissions by replacing fossil fuels helps make it carbon neutral. But when biomethane is produced from animal manure, it can even be carbon-negative.
Manure emits significant amounts of methane into the atmosphere. Using it to produce biomethane captures, optimises, and utilises this methane instead of allowing it to be released into the atmosphere through open storage.
Digestate, a byproduct of the biomethane production process, is also a rich natural fertiliser. Farmers can use it to reduce the number of synthetic mineral fertilisers they use.
The production chain for synthetic nitrogen fertilisers is responsible for a total of f 1.13 Gigatons CO2 equivalent (GtCO2e). That’s 10.6 percent of all global agricultural emissions and 2.1 percent of all global GHG emissions.
One scientific study concluded that the annual amount of digestate used to fertilise an area of one hectare could avoid 25.8 to 44.5 milligrams CO2 equivalent (MgCO2e). There are a total of 5 billion hectares of farmland worldwide. If farmers used only digestate to fertilise their soils, it would reduce the emission of 223 tonnes of CO2 equivalent each year.
Along with its benefits for agriculture, carbon capture, and utilization is another aspect of biomethane production that can contribute to its carbon neutrality.
Biomethane upgrading removes CO2 from raw biogas, which produces a highly concentrated CO2 stream. It can then be used as feedstock for the chemical industry or in industrial processes such as manufacturing new construction materials.
Building carbon-negative biomethane plants
The EU and many countries globally are working together to reach net-zero emissions by 2050 and slow the pace of global warming—today.
Because it’s a carbon neutral—and even carbon negative—fuel, biomethane has a significant role in helping achieve these goals.
We’re actively contributing to this mission as a developer, builder, owner, and operator of biomethane plants in the EU and beyond. Learn more about how we’re helping here.
Biomethane will play a key role in decreasing emissions from this sector by replacing fossil fuels in LNG-powered vehicles.