First, carbon footprints… now you can calculate your ‘nitrogen footprint’

Researchers have calculated that beef generates about twice as much nitrogen as pork, and almost three times as much as chicken or fish. 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'.

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 in terms of nitrogen pollution. It is hoped that the tool will lead to more people choosing sustainable ways of living.

Scientists have warned that reactive nitrogen pollution is already a major environmental problem that is causing significant damage to air and water quality across the UK. 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.

''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. ''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'. Lifestyle choices affect your nitrogen footprint: reducing your nitrogen footprint means cutting back on road and air travel, choosing renewable energy and, most importantly, altering the balance of the foods contained in your diet.

''Unlike your carbon footprint, what you eat is the most important factor determining your nitrogen footprint,'' said Dr Carly Stevens of Lancaster University. ''By altering the amount and type of food that you eat, you can make a big difference to your impact on the environment.''

The difference in nitrogen levels occurs because of the amount of nitrogen that is lost during the food processing cycles. Simply stated, if you eat meat 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 fertiliser applied and the efficiency of the crop. Nitrogen losses can also occur during food processing and even through household-level food waste.

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 tool, first developed in the US, has been updated and adapted for UK users by researchers from Lancaster University under a project funded by the NERC Macronutrient Cycles programme at Oxford. The device was originally created 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.

''Solving the nitrogen dilemma is a major challenge of our time,'' said lead researcher Allison Leach of the University of Virginia. ''By calculating our individual impact, and taking small steps to reduce it, we can all play a part – and send a strong message to our national leaders that we want this issue taken seriously.''