New tool to calculate 'nitrogen footprint' offers guide to pollution reduction

The tool will provide a guide to sustainability and pollution reduction for daily activities such as food consumption, travel and energy use.

Researchers at the University of Melbourne, Zhejiang University, University of New Hampshire and University of Virginia used the University of Melbourne as an example to put together Australia's first estimate of nitrogen footprint.

Their study, published in the Journal of Cleaner Production, shows institutions can have a large contribution to nitrogen pollution but also that they have significant potential and capacity to reduce this contribution.

The tool for establishing a nitrogen footprint calculates reactive nitrogen, which is the forms of nitrogen released to the environment from our daily activities such as food consumption, travel and energy. Like the better known 'carbon footprint', it is a sum of individual activities that add to the total nitrogen output.

Nitrogen has human and environmental health costs in the hundreds of billions of dollars and is a significant challenge to the sustainability of our society. One of the most well-known is the nitrogen run-off from agriculture in Queensland, resulting in damage to the Great Barrier Reef.

Faculty of Veterinary and Agricultural Sciences Professor and study co-author Deli Chen said: "Our earlier research showed that Australia has a large nitrogen footprint. At 47kg of nitrogen per person each year, Australia is far ahead of the US (28 kg of nitrogen per person per year), the second on the leader board of per capita reactive nitrogen emissions driven largely by a diet rich in animal protein and high level of coal use for energy.

"To understand more about Australia's footprint, we delved into the figures to measure institutional nitrogen footprint, using the University of Melbourne as our guinea pig."

The authors note that nitrogen pollution is often disguised as other global change issues, such as climate change, which nitrous oxides and nitrogen oxides contribute to, or harmful particulate matter 2.5, which ammonia gas contributes to.

They found that the University of Melbourne has a nitrogen footprint of 139 tonnes of nitrogen, with three factors playing dominant roles: food (37 per cent), energy use (32 per cent) and transport (28 per cent).

Faculty of Veterinary and Agricultural Sciences PhD candidate and study co-author Xia Liang said the institutional nitrogen footprint is a sum of individual activities at the workplace and the institutional activities, such as powering laboratories and lecture theatres in the case of a university.

"At the University of Melbourne, food plays a dominant role through the meat and dairy consumed," Xia Liang said.

"Nitrogen emissions from food occurs mainly during the production of food, whereas emissions from energy use is mainly from coal-powered electricity use and emissions from fuel used during business flights.

"We also modelled the steps that the University could take to reduce its nitrogen footprint. We found that it could be reduced by 60 per cent by taking action to cut emissions from the three main contributing factors: food, energy use and travel."

The study found 96 per cent of the nitrogen emissions occurred outside the University's boundaries. It also found that the detrimental effects are invisible to the person on the ground, with the burden of the pollution often borne far away.

"The good news is that if the University implements all the changes detailed in its Sustainability Plan -- which includes strategies for reducing carbon emissions, such as transition to clean energy (solar and wind), optimising energy use and buying carbon credits -- this would also reduce nitrogen pollution by as much as 29 per cent," Professor Chen said.