12 July 2013

We all know that a high carbon footprint damages the environment, but so does your nitrogen footprint, through increasing pollution and reducing biodiversity.

Now Scientists at Lancaster, Virginia and Oxford universities have produced a web-based tool that allows anyone living in the UK to see their own ‘nitrogen footprint’ and take action to reduce it.

The tool is known as the N-Calculator. It asks users to put in information so the tool can calculate the likely effect that the food that they eat or the transport they take has on the environment through nitrogen pollution. It is hoped that the tool will lead to more people choosing sustainable ways of living.

Nitrogen pollution is already a major environmental problem that is causing significant damage to air and water quality across the UK and globally.

“It’s not like pollution that you can see,” said Dr Carly Stevens, of Lancaster Environment Centre. “You don’t see that a river is nitrogen rich, there isn’t a nitrogen smog, so this tool is important to make people aware about how much nitrogen they create and why too much nitrogen is bad.”

Nitrogen runoff from farms and man-made effluents are largely responsible for algal blooms that affect river systems, whilst atmospheric nitrogen pollution is leading to significant losses of biodiversity.

Most of the nitrogen pollution arises out of agricultural processes used in the growing of crops or grazing of animals, they warn. In addition, a significant proportion of the average UK nitrogen footprint comes from vehicle emissions, because burning fossil fuels produces nitrogen oxides.

‘Nitrogen is essential for growing crops for food or high quality grass for cattle, as any farmer knows,’ said Paul Whitehead, Director of the Natural Environment Research Council’s Macronutrient Cycles programme at the University of Oxford, which funded the development of the UK N-Calculator.

‘However, the widespread use of nitrogen fertilizer to boost crop production has resulted in a runoff of excess nitrogen from farms into our rivers, lakes and groundwaters.’

The researchers used publicly available data such as national atmospheric data, national land use and farm statistics, to make the calculations. The N-Calculator website also makes recommendations for how to lessen your ‘nitrogen footprint’ through changing your lifestyle.

Cutting back on road and air travel, choosing renewable energy and, most importantly, altering the balance of the foods contained in your diet will make a difference.

‘Unlike your carbon footprint, what you eat is the most important factor determining your nitrogen footprint,’ said Dr Stevens. “Small changes to your habits can make a big difference, in particular reducing the amount of meat you consume.”

While vegetables have a much smaller nitrogen footprint than meat, different types of meat also have a different impact. The researchers have calculated that beef generates twice as much nitrogen as pork, and almost three times as much as chicken or fish. The difference occurs because of the amount of nitrogen that is lost during the food processing cycles. Simply stated, the larger the animal, the larger its nitrogen footprint because it takes longer to get to ‘market weight’.

The amount of nitrogen pollution from crop production varies with the amount of fertilizer applied and the efficiency of the crop. Nitrogen losses can also occur during food processing and even through household-level food waste.

“Think of all the nitrogen that goes into producing the food that you throw away,” Dr Stevens said.

Universities are starting to use the tool to show students how one individual can alter and help restore a natural cycle like nitrogen. The researchers suggest that the tool could be used by the wider community, particularly schoolchildren, to explore more sustainable ways of living.

The UK tool has been developed from one originally created in the US by award-winning scientist James N Galloway and his research colleagues, Allison Leach, at the University of Virginia, Albert Bleeker of ECN and Jan Willem Erisman of the Louis Bolk Institute, both of The Netherlands.