A COUPLE of weeks ago we looked at the different strengths or global warming potential (GWP) of various greenhouse gases, those gases that are contributing to global temperature rises and climate change.
One of the stronger greenhouse gases is nitrous oxide (N2O), which is known as laughing gas and was once commonly used as an anaesthetic.
It has a GWP about 300 times higher than carbon dioxide and takes quite a long time, over 100 years, to break down in our atmosphere.
This strength and long life make N2O the third most important greenhouse gas we need to control – it means that even though the weight of N2O produced in 2009 was only 0.02 per cent of the total weight of greenhouse gases, it accounted for six per cent of the GWP.
So where does N2O come from? Well we make some when we produce energy, some comes from business and industry, some comes from the fuels we use for transport and some from waste treatment.
But most, about 80 per cent, comes from farming and over 90 per cent of this comes from soils. In fact, N2O from soil accounts for over half of the greenhouse gases produced by farming in the UK and nearly all the GWP.
However, farming wasn’t always responsible for such a high proportion of the UK’s N2O production.
If we go back to 1990, when figures were first produced, we find that industry produced almost as much N2O as farming, and almost all of that by making adipic acid, a chemical that may not be familiar to many but one that is a stepping stone to a very familiar product, nylon.
Since 1990, N2O production by industry has fallen by 95 per cent, mainly through improving processes so that any N2O involved is captured before it reaches the outside world.
Unfortunately, controlling N2O in farming isn’t so straightforward. For example, N2O is produced by natural soil processes involving bacteria known as nitrification and denitrification, as well as being produced when we grow nitrogen-fixing crops like peas and beans.
This means that soils will always be making some N2O.
Nevertheless, the way we farm can significantly increase the amount of N2O being produced by these natural processes.
Any farming operation that increases the amount of nitrogen that is in the soil will give N2O production a boost. These operations include the obvious, such as applying nitrogen-containing fertilisers and manures, to the less obvious, such as ploughing and draining.
Clearly, it isn’t sensible to try and stop N2O from farming as this would mean we would have to stop growing food.
But we can make best use of new or possibly old techniques to farm in ways that make less N2O – since 1990 we’ve cut N2O production from soils by 20 per cent by taking more and more care over soil management and fertiliser use – hopefully further cuts will follow in the coming years.
You can find details of UK greenhouse gas emissions on the Department for Energy and Climate Change web site at http://bit.ly/hyZjW2.
There is an explanation of the soil nitrogen cycle on Wikipedia at http://bit.ly/K24Rn.
And, as always, we’ll be happy to help with information on all aspects of local sustainability in Berwick. Contact Sustaining Berwick at www.sustainingberwick.org.uk, call Berwick Community Trust on 01289 330955 or contact Robert Leetham on 01289 306790 or firstname.lastname@example.org with any comments or suggestions.