John Sherrell

I was asked on a post about the difference between biogenic and fossil methane and it's a question that deserves a post of it's own because we meet this question again and again. So, firstly, all biogenic methane (from cattle, rice paddies, compost heaps, wetlands etc) is part of the current carbon cycle. CO2 is photosynthesised from the atmosphere by plants and converted into carbon. When that carbon breaks down due to being digested (plant dies or is eaten), it breaks down into CO2 and is returned to the atmosphere. However, a small portion is sometimes converted to methane because it breaks down in an anaerobic environment. Fossil fuel methane was formed the same way but millions of years ago and so is not part of the current carbon cycle. During the process, it got locked away in permanent geological storage where it remained until we dug it up and released it. This leads to 3 key differences between biogenic methane and fossil methane being released into the atmosphere today. 1) When the CO2 is taken from the atmosphere today and some of it is converted to methane, it means that less CO2 is returned to the atmosphere than was taken out. The methane breaks down into CO2 again after about 12 years, completing the cycle. The current inventory states that all the CO2 removed is also all returned as CO2 as well as being returned as methane which is, of course, not possible. In the case of fossil methane, there is no removal to take into account. That took pace millions of years ago. 2) Biogenic methane operating in a cycle can have different impacts on the concentration of methane in the atmosphere: If it is coming from a constant, stable source then the same amount is broken down and 'removed' as is added every year so the concentration in the atmosphere stays the same. It's like putting €10 into your bank account and then taking €10 back out. The amount in your account stays the same. If the source is growing (like increasing the number of cows) then the amount of methane emitted this year is bigger than previous years so it will increase the concentration in the atmosphere. The majority of the emissions will be 'constant' and not increase the concentration but the volume that is 'new' will increase the concentration. If the source is decreasing, then less will be returned to the atmosphere this year than has broken down and will result in a lower concentration of methane in the atmosphere. Fossil methane only has 1 impact, all of it increases the concentration in the atmosphere because all of it is additional to the current cycle, not part of it. 3) When biogenic methane released to the atmosphere breaks down, it does not create an increase in CO2 in the atmosphere. It is merely completing the cycle. You aren't adding anything or removing anything, it is the same gas cycling round. When fossil methane breaks down, all of it adds CO2 to the atmosphere because it didn't remove anything from the current cycle in its creation. And what is really important to understand is that while science acknowledges all these differences and is working on ways to account for them better, the current GHG inventory system takes no account of these differences. It counts all biogenic methane and fossil methane as exactly the same - additional. If you want to understand more about how our figures are actually calculated, how farmers are impacted and why proposed carbon taxes on food production should not be allowed, you can get the book in kindle and paperback editions in all Amazon stores. For Irish readers, the UK Amazon store will not ship the paperback to Ireland but you can get it from the German Amazon store here: amazon.de/dp/B0CQDH5JRW

It's funny how much denial there is around the emissions figures from agriculture being wrong - which they are. This is just a fact and here are the ways in which they are wrong: 1) Overestimated - in Ireland, the volume of actual methane that comes from cows is overestimated by around 20%. 2) Over-multiplied - across the globe the volume of methane is multiplied to give a CO2 equivalent figure which the IPCC say overstates the warming by methane from cattle by 300 - 400%. 3) The CO2 that produces the methane is counted as being returned to the atmosphere as both CO2 and methane which is incorrect. But that's just the methane. We also have: 4) Emissions from non-agricultural activities is included in 'agriculture' - such as commercial use of fertilisers by forestry, sporting facilities (like golf courses), amenity facilities, County Councils etc. 5) Every farm creates both removals and emissions. Only emissions from livestock, fertiliser and agricultural transport are counted in 'agriculture'. All the removals are counted in LULUCF (Land Use, Land Use Change & Forestry). So as an example, grass growing in a field is in LULUCF. But the second a cow eats it, it moves into 'agriculture'. 6) The 'decarbonisation' exception in reporting guidelines means that farmers who provide fuels to other sectors (such as cattle carcasses being used for biofuels in transport) are not recognised for the contributions they make already in 'decarbonising' other sectors because they are 'invisible'. Try for a second to imagine how you would feel if you were treated this way by your government. All the good you do is either invisible or in another sector where it doesn't count. All the bad you do is over-estimated, over-multiplied and double-counted. Farmers have every right to be angry. And every right to seek to have it corrected. And every right not to be taxed, denied essential services or otherwise penalised on the basis of figures that we know are wrong. And yes, I do know what I'm talking about. I spent 18 months researching and writing a book about it. For those in Ireland who would like to order the paperback and can't get it on the UK Amazon store, you can get it here: amazon.de/dp/B0CQDH5JRW