During the past century, the global consumption of nitrogen has seen a steady increase. In 1980, developed countries accounted for 70% of the world’s total nitrogen consumption. By 2010, it was the developing countries which accounted for 70% of the global nitrogen consumption. India is no exception to this. India is the second-highest consumer of nitrogen in the world after China. According to the Food and Agriculture Organization, China’s annual consumption of nitrogen is 44.97 million tonnes, while India consumes 16.48 million tonnes—four times more than Brazil’s annual consumption of 4.25 million tonnes.
Indian Fertiliser Scenario 2014, an annual publication of the department of fertilisers under the Ministry of Chemicals and Fertilisers, states that the use of urea in the country has increased by more than 50% since 2000—the per hectare consumption of nitrogen is at least 100 kg in eight Indian states, including Bihar, Punjab, Haryana, Uttarakhand, Uttar Pradesh, undivided Andhra Pradesh, Tamil Nadu and Puducherry.
What’s the concern?
The threats posed by nitrogen pollution are individually and collectively a huge problem for the global society today. The increasing rate of nitrogen use by humans has led to an imbalance in the nitrogen content in the environment.
- According to “Our Nutrient World”, a 2013 report of the United Nations Environment Programme (UNEP), human-induced nitrogen inputs or fertilisers and associated emissions from agriculture, fossil fuel burning, sewage and industrial waste have directly or indirectly far surpassed natural emissions, causing nitrogen pollution that has reached alarming levels.
- Another study shows that the annual economic loss in the US due to energy wastage and damages to the environment and human health from nitrogen pollution is $210 billion. “Our Nutrient World” estimated that the global cost of damage from nitrogen could go up to US $2,000 billion.
Nitrogen as an essential nutrient:
Nitrogen, which is a vital macronutrient for most plants, is the most abundant element in the atmosphere. A little over 78% of dry air on Earth is nitrogen. But atmospheric nitrogen, or dinitrogen, is unreactive and cannot be utilised by plants directly. Until the beginning of the 20th century, farmers depended on a natural process called nitrogen fixation for the conversion of atmospheric nitrogen into reactive nitrogen in the soil: nitrogen-fixing bacteria like rhizobia live symbiotically with leguminous plants, providing nitrogen to the plant and soil in the form of reactive compounds like ammonia and nitrate.
But the natural nitrogen cycle was inadequate to feed the growing population. Scientists Fritz Haber and Carl Bosch solved this problem by producing ammonia by combining atmospheric nitrogen with hydrogen gas at high temperature and pressure—known as the Haber-Bosch process. The Green Revolution, which was instrumental in establishing food security in the developing countries in the 1960s, was driven by artificial nitrogen-fixation. Today, about half of the world’s population depends on this process for its nutrition.
How Nitrogen turned into pollutant from nutrient?
Nitrogen is an inert gas that’s necessary for life. But we’re changing it into forms that are harmful, overloading the environment with it, and throwing the natural nitrogen cycle out of whack. Nitrogen compounds running off farmland have led to water pollution problems around the world, while nitrogen emissions from industry, agriculture and vehicles make a big contribution to air pollution.
- Over 80% of the nitrogen in soil is not utilised by humans. While over four-fifths of the nitrogen is used to feed livestock, only about six per cent reaches humans in case of non-vegetarian diet, as compared to the 20% that reaches the plate of a vegetarian.
- Nitrogen becomes a pollutant when it escapes into the environment and reacts with other organic compounds. It is either released into the atmosphere, gets dissolved in water sources such as rivers, lakes or groundwater, or remains in the soil. While it might lead to favourable growth of species that can utilise this nutrient, nitrogen as a pollutant is often detrimental to the environment and health.
- According to the World Health Organization, nitrate-contaminated drinking water can cause reduced blood function, cancer and endemic goiters. Surplus inputs of nitrogen compounds have been found to cause soil acidification. The lowering pH, as a result of the acidification, can lead to nutrient disorders and increased toxicity in plants. It may also affect natural soil decomposition.
Nitrogen pollution has a significant impact on the environment:
- It creates of harmful algal blooms and dead zones in our waterways and oceans; the algae produce toxins which are harmful to human and aquatic organisms (and indirectly affects fisheries and biodiversity in coastal areas).
- Contamination of drinking water. 10 million people in Europe are potentially exposed to drinking water with nitrate concentrations above recommended levels. This can have an adverse effect on human health.
- Food Security: Excessive nitrogen fertiliser application contributes to soil nutrient depletion. As the world needs to feed an ever growing population loss of arable land is major global problem.
- The release of Nitrous Oxide is essentially a greenhouse gas which is harmful to the environment.
What needs to be done now?
A simpler method of reducing nitrogen application is precision farming where small quantities of nitrogen are administered routinely instead of large doses applied uniformly over the field. Similarly, tablets and coated forms of nitrogen, when applied at the root level, release nutrients slowly. Supplemented with organic fertilisers and combined with optimal timing of application, sowing and watering, these methods have shown marked improvement over traditional efficiencies of nitrogen.
Nitrogen is central to India’s food production, but its use in our agriculture system has put us in a Catch-22 situation. We cannot produce enough food to feed the nation without nitrogen, but at the same time we cannot keep introducing higher quantities of nitrogen because of its polluting effects. The challenge for the current century is to optimise the uses of nutrition while minimising the negative impacts. Nitrogen pollution is an issue of improper management rather than inability. The costs of abating nitrogen pollution would be much less than the benefits to health and environment. A 20% increase in the rate of efficiency would save an estimated 20 million tonnes of reactive nitrogen by 2020, which equates to an improvement in human health, biodiversity and climate worth US $170 billion.