Almost all the talk of climate change in the media focuses on CO2, as it is the most abundant greenhouse gas (GHG) on earth. It is not, however, the most potent. Not by a long shot. Over a 20-year period, methane is around 86 times more effective at trapping heat than CO2. This is worrying since humans have caused, in just 300 years, an increase in global methane from 715 parts per billion to 1774 parts per billion, the highest level in 650,000 years. That works out to about a fifth of all global warming, making methane the second most significant GHG on earth. Roughly 60% of all atmospheric methane is the result of human practices like large-scale animal agriculture and poorly-managed landfills.
Before I get going, I would like to acknowledge the paper “Biotechnological conversion of methane to methanol: evaluation of progress and potential” as it proved to be an extremely useful research source on this topic.
New research has shown that it may be possible for us to convert methane into fuel cheaply, quickly and on a large scale. The key to this energy revolution will be exploiting a type of bacteria known as methanotrophs. Methanotrophs are incredibly abundant in nature. They account for 8% of all heterotrophs on earth (organisms like us that have to ‘eat’ rather than photosynthesising their food). Methanotrophs were first identified way back in 1906 but in the 1970s, 100 types were isolated, characterised and compared in a landmark study. These incredible bacteria are capable of converting methane into methanol very easily, a process that has been referred to as the holy grail of modern chemistry. If we could perform this conversion as easily as methanotrophs, we could seriously cut down our GHG emissions.
In May of 2019, researchers at Northwestern University identified the cofactor involved in catalysing the conversion of methane to methanol, providing a huge step forward in our understanding of how methanotrophs carry out this incredible process. Methanotrophs are known to carry out the conversion using an enzyme called methane monooxygenase (MMO), but the researchers have now identified the copper ion which accelerates this process and the site at which that copper ion is bound.
Methanol is an energy-rich fuel that can be used for everything from automobiles to electricity generation. In fact, methanol can be put straight into a standard internal combustion engine, meaning that we would not need to design new types of engines in order to make the switch. Burning methanol in an engine produces 20-25% less GHGs than burning petrol, but even these emissions are cancelled out by the fact that methane is removed from the atmosphere to produce the fuel. In other words, it’s already better than burning petrol, and the fact that it removes methane makes it better still. Remember, methane is far more potent than CO2 as a GHG. By converting methane to methanol then using the methanol as fuel, you are essentially converting methane to CO2, which causes much less global warming. The conversion happens at a ratio of 1:1, meaning that simply converting methane to CO2 would result in a serious decline in GHGs in the short term. In addition, the energy you get from burning the methanol means that you don’t have to burn as many fossil fuels, further lowering the carbon footprint of the process.
Right now, we are able to convert methane to methanol. In fact, we have been doing this on a relatively large scale for quite some time now. In 2015, the global demand for methanol was 70 megatons. The difference between current methods of converting methane to methanol and using methanotrophs instead is the temperature and pressure under which the reaction can be carried out. Current methods require temperatures of 900 degrees Celsius and pressures of 3 megapascals. In other words, that is roughly the same temperature as lava and roughly the same pressure that is exerted on a submarine 1,000 feet below the sea. Methanotrophs can perform the same conversion at room temperature and atmospheric pressure (the normal pressure at sea-level). This is known as ‘ambient conditions’ and describes the temperature and pressure wherever you are reading this article (provided you are not reading this in a volcano or a submarine).
The problem with needing extremely high temperature and pressure to perform the reaction is that it requires a lot of energy, cancelling out many of the gains made with respect to GHG emissions. That energy needs to come from somewhere and 9 times out of 10 that somewhere is fossil fuels. In addition to this, the process is currently too expensive to be economically viable, a factor that hugely influences whether or not a technology enters the mainstream. If we can harness methanotrophs’ ability to convert methane to methanol at ambient temperature and pressure, the process will become far cheaper, far quicker and far more environmentally friendly.
There is an important distinction to be made between low affinity and high affinity methanotrophs. Low affinity methanotrophs are found only where there are high concentrations of methane (more than 40 parts per million). So far, every strain of methanotroph we have isolated has been low affinity. High affinity methanotrophs, on the other hand, can perform the conversion at ambient levels of methane (less than 2 parts per million). Isolating and exploiting high affinity methanotrophs is the real holy grail, since this would allow us to convert the methane in the air all around us into fuel rather than just being able to perform the conversion in places where concentrations of methane are high.
Another way this process might reduce GHGs is by creating an incentive for oil companies to stop ‘flaring’ natural gas when exploring for oil. As you bring the oil to the surface, natural gas comes with it. To prevent pressure building up in the pipes, the gas is burned (which is why you sometimes see oil wells with flames shooting out the top). 4% of all natural gas which is extracted worldwide is flared. Using 2017 figures, that works out to 139 billion cubic meters of gas wasted every year (nearly 1 and a half trillion Kwh). That is slightly more energy than is used each year in India, a country with nearly one and a half billion people. Since natural gas is around 85% methane, development of cheap methane-methanol conversion techniques would provide an incentive to capture and store the gas rather than burning it unnecessarily and releasing huge amounts of GHGs into the atmosphere in the process. This is an example of how we can use our current knowledge of low-affinity methanotrophs to begin cutting down on emissions.
Transporting methane is currently very difficult, since it is a gas under ambient conditions. Liquids take up far less space than gases and are also far more energy-dense. By converting methane to methanol, we seriously boost how much potential energy can be carried by a single truck. By cutting down on how many trips are required to transport the same amount of energy, we also cut down on the fuel required for transportation. Efficiency gains such as this will be vital in our transition to a sustainable society if we wish to retain our current levels of comfort.
Burning methanol is also far cleaner than burning petrol, releasing half the carbon monoxide and just 1 eighth of the nitrous oxide. Over a 100-year period, nitrous oxide has a global warming potential 265-298 times greater than CO2. The reason you don’t hear as much about it in the media is that we release far less nitrous oxide into the atmosphere than we do CO2 or methane. The problem of climate change is so huge and so urgent, however, that we need to look at ways to reduce every GHG all at once by whatever means possible. An eightfold reduction in nitrous oxide from transport would go a long way.
One possible issue with this technology is that methane is only more potent than CO2 in the short term (a century or two). It could be argued that since CO2 stays in the atmosphere for thousands of years, we are simply pushing the problem back without solving it. To this I would reply that we are dangerously close right now to setting off feedback loops which would take climate change out of our hands and make the problem unsolvable. By procrastinating on this massive issue, we give ourselves time to develop technologies that can capture CO2 on a large scale as well as technologies that can provide us with clean energy. In other words, we are in desperate need of a band-aid.
Another objection might be that the process provides a financial incentive to keep fracking for natural gas when really we need to be leaving it in the ground. This objection, I think, holds more water. While burning methanol is more environmentally friendly than simply burning the natural gas, it is less environmentally friendly than not burning it at all. One way to respond to this is by arguing that it is naïve to think that we will stop extracting natural gas and oil any time soon. Global energy demand is huge and rising and these needs must be met somehow. It is better to meet them using efficient new technologies than to continue the practices that got us into this mess in the first place. In addition, if we can develop this technology to the point where we can remove atmospheric methane rather than just converting natural gas to liquid, it could actually result in negative emissions, meaning that we would be simultaneously meeting our energy needs and reducing our impact on the environment. The potential for this technology is massive.
Conversion of methane to methanol under ambient conditions and on a large scale would be a huge step forward in developing the green energy infrastructure that is required if we are to transition to a low-carbon world. I’ve said it so many times before, but it bears repeating that if we don’t make this transition very soon, the consequences will be extremely severe for humans and other animals around the globe. We are talking about a worldwide shortage of food and water, an increase in the frequency and severity of natural disasters, rising sea-levels and much more.
Climate change is happening right now all around us, from the wildfires of California to the hurricanes of Puerto Rico. How we respond in the coming years determines whether this will be a difficult century on one hand, or a complete transformation of the Earth that could last for hundreds of thousands of years on the other. So long as we can limit warming to below the levels required to trigger feedback loops, I have faith that humans can ride out the storm relatively unscathed. It is worth remembering, however, that this is the greatest challenge our species has ever undertaken. This is why the development of technologies like methane to methanol conversion is so critical and so time-sensitive. This tech will not solve the problem all by itself, but it will give us some time and breathing room to overcome the larger issue.