The fossil fuel industry has been trying hard to promote gas in many forms as “sustainable” or “green”. There are different ways of producing gas that the industry calls renewable, but this term is misleading. Is it sustainable or green to create dependence on waste, cut trees for biomass, and produce methane with the same chemical structure and characteristics as fossil gas?
Why does the fossil fuel industry want to promote the idea of non-fossil gas? As big infrastructure operators generally push for gas use in Europe, using the magic idea of renewable gas is very handy for them to justify decades of infrastructure buildout that serves both fossil and non-fossil gas. The question is: Does it add up? Will these gases significantly reduce CO2 emissions? Where does the feedstock for these gases come from? Does all this make economic sense?
Here are a few of the issues that need to be taken into account when we’re talking about non-fossil “renewable” gas.
Biogas: The Biofuels Deja-vu
Since their introduction, biofuels have earned a lot of criticism for their role in land grabs, displacing food crops for energy, loss of biodiversity, climate change and pollution. While biofuels – liquid fuels based on biomass – turned out to be a very bad idea, something similar seems to have been re-introduced through the back door: biogas. Biogas is a mix of gases generated through the breakdown of organic matter through anaerobic digestion (digestion in the absence of oxygen).
Feedstock for biogas, for example, can be waste, sewage sludge, energy crops, manure or biomass. Using waste to generate energy can make sense in a few limited cases but we should not lock ourselves into a society dependent on producing enough waste that we can heat our homes or cook. Also, using manure will turn into an issue sooner rather than later, quite apart from the fact that manure does not automatically create methane and to a big extent it can be avoided. Biogas production is no justification for big agribusiness. But in Europe, big factory farms may only get built because they commit to produce biogas.
Biomethane: The Little Brother of Fossil Gas?
Biogas can be cleaned of impurities and upgraded until its methane content is high enough to be injected into the grid. The gas is then called biomethane. Unlike biogas, which can only be consumed locally, biomethane can be transported using the same infrastructure used to transport fossil gas. Its name already reveals a big part of the problem biomethane entails: Just like natural gas, it mainly consists of methane, which can leak during transport, upgrade, distribution and use. It also and emits significant amounts of CO2 during combustion, just like natural gas. Considering the small carbon budget Europe has left, biogas should have no role in our energy future.
Power-to-Gas – Losing The Efficiency
So-called “renewable hydrogen” is produced by using surplus electricity from wind and solar installations to split water molecules into oxygen and hydrogen in a process called power-to-gas (P2G). One issue with this process is that a lot of energy is lost: The overall efficiency of a fuel cell heating system with “renewable hydrogen” is estimated at 45%; less than half of the energy put into this process can be used for heating.
Another problem with P2G is that it cannot be injected into the existing gas grid: it is only feasible to add around 10% hydrogen to the current natural gas system. There is a pilot project in Leeds (the Leeds City Gate project) to adjust the local grid so it can transport hydrogen. Still, this option is not only very costly, but also far from being applicable at a larger scale.
Power-to-Gas to Produce Synthetic Methane/Synthetic Natural Gas
Another way of producing methane is using renewable power and the power-to-gas technology to generate synthetic methane, or synthetic natural gas (SNG).
Adding one step on top of the process of generating hydrogen, it results from making hydrogen react with CO2 and turning it into methane. Compared to the direct use of renewable energy, this process is highly inefficient and only a small part of the original energy added to the process is finally available in form of SNG. This also implies that huge amounts of renewable energy (and surface area) would be needed to generate all the required energy that is then converted into methane.
The other question is where the CO2 will come from. While using CO2 from industrial processes decreases efficiency even further and is only possible close to industrial sites, capturing the needed CO2 directly from the air would be the only way to get at least somewhere near carbon neutrality. Nevertheless, the surface area of direct air capture facilities with a capacity of one gigawatt needed to produce SNG is around 27-180 soccer fields. SNG would thus not only need vast amounts of surface area for CO2 capture, but also for creating the needed renewable energy used in this process.
SNG has the exact same composition and thus (similarly to biomethane) the same negative impact on the climate as methane from natural gas, even though methane emissions that are released during extraction of natural “fossil” gas do not apply to SNG.
Non-Fossil Gases Avoid Real Green Solutions
Apart from the issues with low efficiency, creating climate-harming methane with clean renewable energy is more than ironic. Not only is the outcome costlier, land-consuming and similarly bad for our climate as burning fossil gas, but it also blocks real solutions that deal with excess renewable energy, such as batteries, needed interconnections to bring the generated electricity to consumers, and clever storage systems on different scales.
Furthermore, fossil gas will always stay cheaper than the so-called renewable gases. So what would be the incentive for the gas industry to switch to them, particularly since they already sell fossil gas claiming that it is an asset for our climate? Only stringent laws could force a real switch to non-fossil gases and stop the industry from carrying on with business as usual. But do we want these gases in the first place? With a serious look at our climate, at the potential of renewable energy and storage solutions, and taking into account that biogas might suffer the same fate as biofuels, the answer should be: No. Energy efficiency and real renewables are the right way, not a gas wolf in green clothing.