Is fertiliser more damaging than buring fossil fuels?

21 March 2010

Part of the show The Science of Farming

Question

Dear Chris
Also on a recent farming programme they explained that satelite pictures of farmland combined with computer programming of the distribition of fertilsers from a tractor could optimise yields using no more than the necessary amount of fertiliser. Suprisingly they stated that the fertiliser, I think made from petrochemicals, was about six hundred times more damaging than, I think the burning of fossil fuels.
Is this true and why is this so please?

Answer

We posed this question to Brian Thomas from the University of Warwick and Claire Domoney form the John Innes Centre...

Brian - Well I think it's not really a question of one or the other because I think as we've heard earlier, the manufacture of fertilisers involves a major amount of energy and contributes significantly to greenhouse gases, and therefore, you have to burn fossil fuels to obtain the fertiliser in the first place. I think in terms of fertiliser, it is possible to mitigate some of these problems. For example, as we've heard with plants that fix nitrogen, if we could extend that capability to others, that would help if we had a more efficient process for fixing nitrogen, more efficient than the Haber process, or we can get plants that use nitrogen more efficiently and there's a lot of work going on at the moment looking at the genetics of that particular aspect of crop production.

Claire - Yes and I think there is some debate as to how much of applied nitrogen fertiliser ends up as nitrous oxide. The IPCC estimates at about 1% ends up as nitrous oxide, but there are some papers in the literature which suggests that that's a three or four-fold underestimate, and it could in fact be much higher than that. So, I think there's a lot of discussion as to how much, but nitrous oxide is a greenhouse gas, much more potent than carbon dioxide by several hundred times.