several billion years ago, On a mass of rock floating around the Sun, small bundles of organic molecules somehow came together and came to life in a process that scientists still don’t fully understand.
When these first life forms were busy merging in the primordial soup, Earth’s atmosphere was a very different mix, a breathless mass of mostly nitrogen and carbon dioxide (CO2). Some of the earliest microbes to evolve on Earth, therefore, digested organic material in conditions of low or no oxygen. They produced exhaust gases, including methane and CO2.
Today, these critters known as methanogens are still with us, fermenting in heaps of garbage and manure, in sewage treatment plants and at the bottom of stagnant water, happily eating decaying matter and turning it into gases, including a boatload of methane.
That’s a problem because methane is a greenhouse gas and it’s about 27 times more capable of heating the planet than CO2. World leaders at COP26 last year agreed to cut methane emissions by 30% by 2030, though Australia notably refused to commit.
But methanogens can also be put to good use – this is where the up-and-coming biogas industry comes into play. Biogas is a mixed gas that mainly consists of methane, CO2 and hydrogen sulphide and can be used as a fuel. Biomethane is similar but consists mostly of methane. Biogas can be converted into biomethane by cleaning and processing.
Biogas plants, viewed as a potent part of a potential future green energy mix, feature specialized facilities where organic waste—animal feces, sewage, decaying plant matter—are digested by archaea and bacteria to produce these gases.
When burned, biogas and biomethane behave much like natural gas, releasing energy (which can be used for electricity), CO2 and water. Crucially, however, the CO2 released when biogas was burned was essentially the same CO2 that was recently consumed by the creature that produced the organic matter, so it’s already part of the biosphere — meaning the atmosphere has no CO2 is added.
“Biogas is considered a renewable resource because its cycle of production and use is continuous and it produces no net carbon dioxide,” explains Semra Bakkaloglu, researcher at the Sustainable Gas Institute (SGI) at Imperial College London, UK.
“As the organic material grows, it is transformed and used. It then grows back in a constantly repeating cycle,” says Bakkaloglu.
trouble in paradise?
So far so good, but this process has pitfalls. This week, Bakkaloglu and co-authors published the results of a new study in the journal one earth, Investigating methane leaks along the European biogas supply chain.
What they found was alarming. The total methane emissions along the European biogas supply chain can amount to 18.5 megatons of methane emissions per year. That’s double the estimate by the International Energy Agency (IEA), which reported just 9.1 megatons in 2021 out of an estimated 185 megatons of total methane emissions from the global energy sector in the same year.
That is, while total Methane emissions from the biogas supply chain are lower than emissions from oil and natural gas, the amount of methane released relative to total gas production is much higher.
It’s a blow to the burgeoning bioenergy sector. But what is the solution? And why do we need biogas at all?
Who produces biogas?
Around the world, biogas production has been adopted by facilities such as farms, landfills and sewage treatment plants. Farmers can, for example, set up on-site anaerobic digestion plants that they feed animal manure or food waste to produce biogas or biomethane that they can either use for their operations or feed back into the grid for a fee.
To get the right bacteria and archaea, producers can buy a culture from other companies that are already connected to the biogas supply chain.
“When we make yoghurt at home, we use the old yoghurt to make the new one,” says Richard Blanchard, bioenergy systems expert at the University of Loughborough, UK. “We have the bacterial culture, we put it in the milk and then make the new yogurt, leaving some to make the next batch.”
It is similar with the bacteria-archaea mixture required for anaerobic digesters.
You take your seed of your existing organic matter from a fermentor full of bacteria and then seed the next fermentor.
The world’s largest biogas producers include Germany, Italy, the Czech Republic and France. Australia, on the other hand, is a much smaller producer – in 2017 there were 272 biogas plants in this country, half of them in landfills.
But the Australian biogas industry is set to grow. In 2021, the first large-scale biogas plant to convert cow manure and other organic waste was announced for Nowra, NSW, and according to the Australian Renewable Energy Agency (ARENA), Australia’s total estimated biogas potential is 103 TWh (terawatt hours). would equate it with Germany.
What has biogas ever brought us?
According to Richard Blanchard, biogas and especially biomethane can be a very useful fuel.
“It’s a flexible fuel because we can use it whenever we want,” explains Blanchard.
“Methane can be stored in pressure bottles. It’s the same as natural gas in the sense that once you’ve cleaned it and cleaned it of impurities, you can feed it into the gas network and move it quite easily.
“We can use it to generate electricity, we can cook with it, we can heat with it. So it gives us the same benefits as natural gas.”
Another big advantage of biomethane in particular, Blanchard says, is that it has a higher energy density than mixed gas, so you need to use less of it to get the same amount of electricity.
Some estimates suggest biogas could produce 5% of UK electricity in the future.
“Five percent is nothing to sneeze at,” says Blanchard. “Nuclear power produces 10% of our (British) energy so it’s not a small amount.”
Eventually, provided that emissions are drastically reduced elsewhere, biogas could be one of the few sources of CO2 emissions in a future energy mix – to keep overall greenhouse gas emissions down.
And there is another incentive to streamline the biogas supply chain. Some industrial processes require extraordinarily high temperatures, which are most easily generated with gas. These include steel and cement manufacturing, two of the well-known problem children of the transition to net zero.
But Blanchard points out that researchers are studying how other energy sources, such as solar power, could generate the required heat.
“So whether it will matter depends on what the heat sources might be,” he says. “It will be very interesting to see how we can do these energy-intensive processes.”
Regardless, the biogas sector is gaining momentum, with a number of countries offering financial incentives to producers.
“With the growth of biomethane due to national decarbonization strategies, urgent efforts are needed for the biomethane supply chain to address not only methane emissions but also the sustainability of biomethane,” says Bakkaloglu.
In Australia, which is currently mired in an acute energy crisis, leading companies and industry leaders have called for a move away from natural gas on the grounds of energy security and climate commitments. In an open letter, organizations including the Australian Industry Group, National Farmers Federation, Property Council and Clean Energy Council recommended a faster transition to alternatives, including electrification and hydrogen and biogas.
So what’s the solution?
In their study, Imperial researchers identified a number of key faults behind the methane leaks, including intermittent emission patterns that make tracking them difficult, underutilization of processing equipment, and inadequate operation and maintenance.
The authors note that compared to the oil and gas industry, the biogas sector suffers from poorly designed and managed facilities and fewer resources for monitoring and maintenance.
The good news is that the researchers were able to identify the culprits: 62% of the leaks were concentrated in a small number of facilities and pieces of equipment within the chain, which they call “super emitters”. Knowing this will allow them to make the chain tighter.
“Preventing biogas methane emissions from negating the overall benefits of biogas use requires urgent attention, including continuous monitoring of biogas supply chains,” says Bakkaloglu.
“We believe that with the right detection, measurement and repair techniques, all emissions can be avoided,” she says. “We need better regulation, continuous emissions measurements and close collaboration with biogas plant operators to address methane emissions and meet the Paris Agreement targets.”