several billion years ago, In a mass of rock floating around the Sun, tiny bundles of organic molecules somehow came together and, in a process scientists don’t yet fully understand, came to life.
When these early life forms were busy coalescing into the primordial soup, Earth’s atmosphere was mixed very differently, a breathless mass composed mostly of nitrogen and carbon dioxide (CO2). Therefore, some of the earliest microbes to evolve on Earth digested organic matter in low-oxygen or no-oxygen conditions. They produced residual gases, including methane and CO2.
These critters, known as methanogens, are still with us today, rotting in waste heaps and manure heaps, in sewage treatment plants and at the bottom of bodies of stagnant water, happily chewing up decaying matter and processing it. into gases, including a canister filled with methane.
That’s a problem, because methane is a greenhouse gas and is about 27 times more potent at warming the planet than CO2. World leaders agreed to cut methane emissions by 30% by 2030 at COP26 last year, though Australia notably refused to commit.
But methanogens can also be harnessed for good, which is where the burgeoning biogas industry comes into play. Biogas is a mixed gas composed mainly of methane, CO2 and hydrogen sulfide that can be used as fuel. Biomethane is similar, but is made up largely of methane. Biogas can be converted into biomethane through a clean-up process.
Biogas plants, seen as a potent part of a potential future green energy mix, have specialized facilities, where waste organic matter (animal feces, sewage, decaying plant matter) is digested by archaea and bacteria. to produce these gases.
When burned, biogas and biomethane act in much the same way as natural gas, releasing energy (which can be used to generate electricity), CO2 and water. But crucially, the CO2 released when the biogas is burned was essentially the same CO2 that had recently been consumed by the creature that produced the organic matter, so it’s already part of the biosphere, meaning there isn’t a net addition of CO2 to the atmosphere.
“Biogas is considered a renewable resource because its production and use cycle is continuous and does not generate net carbon dioxide,” explains Semra Bakkaloglu, a researcher at the Sustainable Gas Institute (SGI) at Imperial College London, UK.
“As organic material grows, it is converted and used. It then grows back in a continuously repeating cycle,” says Bakkaloglu.
Trouble in paradise?
So far, so good, but there are pitfalls in this process. This week, Bakkaloglu and his co-authors published the results of a new study in the journal a land, investigating methane leaks along the biogas supply chain in Europe.
What they found was alarming. Total methane emissions along the European biogas supply chain may represent 18.5 megatonnes of methane emissions per year. That is double the estimate by the International Energy Agency (IEA), which reported just 9.1 megatonnes in 2021, out of an estimated 185 megatonnes of total methane emissions from the global power sector in the same year.
That means that 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 is a blow to the burgeoning bioenergy sector. But what is the solution? And why do we need biogas anyway?
Who produces biogas?
Globally, biogas production has been absorbed by facilities such as farms, landfills, and sewage treatment plants. Farmers, for example, can build anaerobic digestion units on site, into which they feed animal manure or food scraps, generating biogas or biomethane that they can use to power their business or feed it back into the grid, for compensation.
To get the right bacteria and archaea, growers 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, an expert in bioenergy systems at Loughborough University, UK. “We have the bacteria culture, we put it in the milk, and then we make the new yogurt, leaving some for us to make the next batch.”
With the mix of bacteria and archaea needed for anaerobic digesters, it’s about the same.
It takes its seed from your existing organic matter from a bacteria-filled digester, and then seeds the next digester.
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 which were landfills.
But the Australian biogas industry is set to grow. In 2021, the first large-scale biogas plant, which converts cow manure and other organic waste, was announced in Nowra, New South Wales, and according to the Australian Renewable Energy Agency (ARENA), the estimated total biogas potential of Australia is 103 TWh (terawatt hours), which would put it on par with Germany.
What did biogas do for us?
According to Richard Blanchard, biogas and biomethane in particular can be a very useful fuel.
“It’s a flexible fuel because we can use it whenever we want,” explains Blanchard.
“With methane, you can store it in pressurized bottles. It’s the same as natural gas in that once you clean it and remove impurities, you can inject it into the gas grid and you can move it around pretty easily.
“We can use it to generate electricity, we can cook with it, we can use it for heating. Therefore, it gives us the same benefits that we get with natural gas.”
Another important advantage of biomethane in particular, Blanchard says, is that it has a higher energy density than mixed gas, so you need to use less to get the same amount of energy.
Some estimates suggest that biogas could produce 5% of the UK’s electricity in the future.
“Five percent you can’t sniff,” says Blanchard. “Nuclear power produces 10% of our (UK) power, so it’s not a small amount.”
Ultimately, he says that as long as emissions elsewhere are drastically reduced, biogas could be one of the few sources of CO2 emissions in a future energy mix, keeping total greenhouse gas emissions low.
And there is another incentive to strengthen the biogas supply chain. Some industrial processes require extraordinarily high heats, which are more easily produced using gas. These include steelmaking and cement, two of the known problem children in the transition to net zero.
But Blanchard points out that the researchers are exploring how other energy sources, such as solar electricity, could produce the necessary heat.
“So whether it will have a role depends on what the heat sources might be,” he says. “It’s going to be quite interesting to see how we can do these energy-intensive processes.”
Regardless, the biogas sector is picking up pace, with a number of countries offering financial incentives to producers.
“Given 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 biomethane sustainability,” says Bakkaloglu.
In Australia, currently in the midst of an acute energy crisis, business and industry leaders have called for natural gas to be abandoned for reasons of both energy security and climate commitments. In an open letter, organizations including the Australian Industry Group, the National Farmers Federation, the Property Council and the Clean Energy Council recommended a faster transition to alternatives, including electrification, hydrogen Y biogas
So what is the solution?
In their study, Imperial researchers identified a number of key flaws behind methane leaks, including intermittent emission patterns that make tracking difficult, insufficient use of processing equipment, and inadequate operations 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 managed to identify the culprits: 62% of the leaks were concentrated in a small number of installations and equipment within the chain, which they call “super emitters”. That knowledge will allow them to tighten the chain.
“To prevent methane emissions from biogas from negating the overall benefits of biogas use, urgent attention is needed, including continued monitoring of biogas supply chains,” says Bakkaloglu.
“We believe that with proper detection, measurement and repair techniques, all emissions can be avoided,” he says. “We need better regulations, continuous emissions measurements and close collaboration with biogas plant operators to address methane emissions and meet the goals of the Paris Agreement.”