I am sure those of you who studied Chaucer's Canterbury Tales
at school will forgive my use of the Old English word, but the story of methane begins with Benjamin Franklin investigating whether he could remove the unpleasant smell of farts by changing diet. His work on 'Flammable air' caught the attention of the Italian scientist, Alessandro Volta, who in 1756 described a flammable gas that he found bubbling out of marshland near Lake Maggiore. This gas was odourless, the smell of farts coming from other gases, but he had discovered the gas that is responsible for their flammability.
In the early 19th century, this gas was named methane and its molecule was shown to comprise one carbon and four hydrogen atoms (CH4). In this simple fact lie the clues to both its importance as a greenhouse gas and its possible role in ameliorating climate change.
John Tyndall in the mid-19th century showed that coal gas (which contains methane) was a powerful greenhouse gas but at that time, and indeed until the 1940s, methane was not known to be present in the atmosphere. Of course, it is now recognised as one of the two main gases responsible for the heating we are suffering from, much more potent than carbon dioxide (CO2) but fortunately present in a much lower concentration. Nevertheless, it is also rising rapidly and today, at over 1,800 parts per billion, it is 50% higher than it was 50 years ago.
Methane's effect on warming
The atmospheric warming attributable to methane is a bit complex as, while CO2 remains unchanged almost permanently, methane is broken down naturally by reaction with ozone to form CO2 and water, so its warming effect lasts a few decades after emission. This means that climate scientists note the short-term effect of a given mass over 20 years to be about 85 times greater than that of CO2, while over a century it is about 30 times more potent. In making estimates of likely warming, they often combine the two gases and speak about global warming potential (GWP) of emissions. Thus, the probable consequences of emissions, say from agriculture, can be estimated as total greenhouse gases equivalent to an amount of CO2, as CO2-eq. The important consequence of all this is that if we are to control the rise in temperature as rapidly as is necessary to avoid irreversibility, we must also reduce methane emissions drastically. Reducing CO2 emissions alone will take too long to achieve the effect we require over the next two decades.
Where does it come from?
Estimates of global methane emissions must be approximate and subject to correction as the science advances, but about 550-594 million tonnes annually were estimated in the decade up to 2017. About 40% of these are derived from natural release from wetlands and inland water (like the bubbles you may see in ponds and marshes) and 60% from man's activities. Our contribution is mainly from agriculture (animal husbandry, soil turning etc), rice growing, waste disposal, fossil fuel production, and biomass burning. The methane is largely produced by bacterial action on organic matter in conditions of low oxygen, which accounts for its association with deposits of other fossil fuels. The familiar flaring from oil rigs and chemical works represents burning of waste methane and the fires and explosions in coal mines were usually caused by ignition of methane escaping from the seam; the miners called it fire damp, from Dampf
, Early German for gas or vapour.
How can we control methane emissions?
Methane emissions must be dealt with separately by the different industries responsible for its production, notably fossil fuel production, agriculture, and waste disposal. Methane does have uses, notably as a fuel itself (some mines captured the gas and used it to power machines) but also in production of other chemicals. However, its burning produces CO2 which then must be dealt with by capture and burial to avoid contributing to climate change. It can be used to produce hydrogen and thus may have some potential as a source of a clean fuel. This is being promoted by industry sources as a step towards a carbon-free economy, so-called 'brown hydrogen', but as the process produces CO2 this must be captured and disposed of for the hydrogen to be used as a green fuel.
As individuals, our contribution in the mining/oil/gas sector is to reduce our need for fossil fuel and to encourage the industries concerned to divert to green energy. This has been successfully accomplished by the Danish Oil and Natural Gas company, now called Ørsted, which saw the opportunity that the UK and Scotland missed in the 1990s and from 2008 became the world's leading developer of offshore wind farms.
Capture and re-use/disposal of emitted methane is urgently necessary, especially in the poorly-regulated sector which is often found to be in poorer countries with little pollution control – for example, consider the way in which rich countries divert their mining activities to Africa. International agreements are necessary to reduce this exploitation and ensure control of emissions. Whenever you see flaring, you are watching CO2 being produced and climate change being enhanced.
We are now seeing agriculture making important strides in reducing methane release from ploughing, and by making changes to crop sowing that also improve efficiency. Release from both ends of ruminants, mostly the mouth, is a major source and Benjamin Franklin's thoughts about diet are now being investigated by scientists, even the old Hebridean practice of feeding cows on seaweed. Changes in foodstuffs that reduce methane production in the stomachs of ruminants are a likely consequence. Scientific studies of land and fertiliser use, and disposal of waste may also be expected to lead to beneficial changes in this sector, as may studies of genetic factors controlling digestion.
Rice feeds almost half the world's population and produces about 15% of our emissions of methane. It is usually grown in flooded paddies which exclude oxygen and promote the growth of methane-producing microbes. The problem can be reduced substantially by careful water management, with sequenced flooding and drying but this is initially costly, and incentives for the millions of small farmers involved are necessary. Since China is a major producer of rice and is also suffering seriously from climate change, I would expect big advances in this area and hope these might spread round other less wealthy nations. This is a priority for climate-related finance.
What can an individual do about methane?
As with CO2, we can all do our little but important bit. I'm sure most of us have wondered what happens to our household waste and even many of you who do not remember the 1940s will have felt some twinges of conscience about how much waste we now dispose of. Much of this goes to landfill where it gets buried in anaerobic conditions and leads to methane production.
We can minimise what we throw out by carefully balancing what we buy against what we need and consume. Please note the difference between necessity and desire. In terms of food and garden waste, this organic material should be composted, and local authorities now usually provide this service. Compost makes a good fertiliser and if you have a garden or allotment, you will be familiar with the process. Composting does produce CO2 and some methane but, if it is well aerated, much less than landfill, so its global warming potential is lower. Advice is easily obtained online.
Aside from waste disposal, we can also adjust our diet as outlined in my previous article. Buying local produce is good not only for saving transport costs but is also encouraging for those local producers who run greener operations. Reduction of meat intake is a step towards encouraging diversion of farming from livestock towards more crops.
Some of you will have enjoyed the television programme, The Good Life
. Others, rather older, will still regret the loss of the radio series, Dick Barton
, to be replaced by a programme intended to give advice to farmers in the austere post-war years. The Archers
continues and still occasionally slips in hints on sustainable agriculture, but there is now a strong scientific base in agriculture, arboriculture and farming, and the UK is well-placed in this sector to respond to climate change.
Whether we as a population are equally ready to join Richard Briers and Felicity Kendal in playing our parts is perhaps doubtful, but I hope many of us will try to do our bit. A healthy lifestyle will aid us and our successors to adapt better to the inevitable climate-related problems ahead but, more importantly, the more of us who change to a greener lifestyle, the more likely are recalcitrant politicians and their advisors to take note and adjust national and international policy.
Anthony Seaton is Emeritus Professor of Environmental and Occupational Medicine at Aberdeen University and Senior Consultant to the Edinburgh Institute of Occupational Medicine. The views expressed are his own