Sunny side up please

Amy Leech - 26 April 2012

SunThe first law of thermodynamics, and probably the only one I can ever remember, says that energy cannot be created or destroyed - it may be transformed or moved – but it definitely does not appear from thin air.

Plants use a lot of energy. Every day they busy themselves converting all sorts of energy, gases and matter into the elements and nutrients they need to grow. The energy they have converted is then passed on to us via these nutrients – they make up the food we eat.

So, when you eat eggs, toast, or perhaps last night’s curry for breakfast – the energy in your food is likely to have come from somewhere, and something, far removed from your plate.

I have to admit I’ve never really stopped to think this simple reality through before.

Nitrogen is the element that plants require in greatest amount, a lack of nitrogen will quickly hold back their growth; which is why Fritz Haber was handed the Nobel Prize for Chemistry when he mastered the process of manufacturing nitrogen artificially. Suddenly, a plant’s favourite food was cheap and cheerfully easy to make... the use of manufactured nitrogen on farms exploded, along with crop yields.

The trouble is, a fire only lasts as long as you can fuel it.

Spreading manufactured fertilisers on the ground is like throwing petrol on a fire and expecting it to burn through the night. It’s not a long-term sustainable solution. The energy input gives you a burst of warmth – increased yields – but these soon die down without another dousing. And so, the plants, the soil and the farmer become dependent on external inputs.

It turns out that manufactured fertilisers are not as cheap and cheerful as we first thought, in fact they are pretty costly, in more ways than one… as the Soil Association’s new report ‘Just Say N2O’ explains.

Manufacturing nitrogen is energy intensive, fuel is needed to power the process but also to create the nitrogen itself – manufactured fertilisers are estimated to account for between 40-68% of on- farm energy use. As the non-renewable energy we use to manufacture nitrogen become scarcer the fertiliser becomes more expensive too, and so the price of the end product – food – rises.

All this energy consumption is also having an impact on emissions from farming. The GHG emissions from the production of 1kg of manufactured nitrogen are estimated to be between 3.2-6.6kg of CO2 equivalent.

And, because we douse the land with nitrogen, too much, too often, or at the wrong time, it is estimated that 40-70% of fertiliser nitrogen applied to crops is lost – through run-off, leaching through the soil, or gaseous emissions. This wasted nitrogen has both environmental and economic consequences.

Thankfully there is, and always has been, an alternative. Manufactured nitrogen may sound unnatural, but there’s nothing artificial about making nitrogen – plants were doing it long before Fritz Haber was a twinkle in his mother’s eye.

Organic farmers up and down the country are seeing the numerous benefits of avoiding the use of manufactured fertilisers to power their plants. By using legumes, which 'fix' nitrogen in their roots as they grow instead, they turn energy from the sun straight into nitrogen to feed their crops, and to feed us.

While it can't be denied that manufactured fertilisers have boosted crop yields beyond what we thought was possible a century ago, it's time to seriously consider the consequences of this dependency. What other environmental limits are being broken by using nitrogen fertilisers? And what can we do to reverse the damage that has been done?

Just remember, the energy we use to power crop growth ends up in the food we eat. It is estimated that half of the protein consumed by humans is made from nitrogen that originated from manufactured fertilisers. I really don’t fancy fertilisers, and all the baggage that goes with them, for breakfast – next time I’ll ask for mine sunny side up!

Amy is Research Assistant at the Soil Association.

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