Nitrous oxide, perhaps better known as laughing gas, is produced from agriculture, industry and coal plants. It has long been known as a powerful greenhouse gas. But it is largely forgotten in climate negotiations, the UN Environment Programme (UNEP) says.
Yet emissions urgently need to be reduced, UNEP argues, because nitrous oxide (N2O) has also become the main destroyer of the ozone layer and so is a danger to humanity on two fronts.
A UNEP report, Drawing Down N2O, written by scientists from 35 organisations, shows the damage currently done by the gas and suggests ways of reducing emissions that would improve agricultural yields and save $23 billion in fertilizer costs.
The report says N2O is the third most important greenhouse gas emitted to the atmosphere by human activities. One ton of N2O has an impact equal to 300 tons of carbon dioxide, CO2.
Since the industrial revolution manmade emissions have increased the level of N2O in the atmosphere by 20%, and unless action is taken, the report says, another 5.3 million tons will be released by 2050.
The gas lasts up to 120 years in the atmosphere, where it drifts upwards to damage the ozone layer. Now that chlorofluorocarbons (CFCs) and chlorine-based chemical emissions have been reduced, N2O is the largest single cause of ozone depletion. Unless emissions are curbed the gas could undo the work of the Montreal Protocol in reducing the size of the ozone “hole”.
No laughing matter
Achim Steiner, executive director of UNEP, said that from the viewpoint of the climate negotiations, tackling N2O emissions could be crucial in keeping the world temperature increase below the 2°C danger level agreed by governments.
“UNEP’s role is to draw the attention of this conference to the science so that politicians can act”, he said. “Although this is known as laughing gas, it is far from a laughing matter as far as its effect on the ozone layer and the climate is concerned. It has a disproportionate impact on global warming because of its warming properties and long lifetime in the atmosphere.”
The report says that emissions can be reduced by increasing the efficiency of farmers in using fertilizer and so minimizing the loss of nitrogen to the environment. Other options include reducing meat consumption, as producing meat protein causes more emissions than plant protein.
Controlling emissions from just two chemical processes that produce adipic acid and nitric acid would reduce global emissions by 5%, says the report.
Controlling forest fires and the burning of biomass and improving the combustion efficiency of stoves would also help significantly. Wastewater treatment that recycles nutrients as fertilizer would also ease the problem.
Prof Rabi Ravishankara, from the US National Oceanic and Atmospheric Administration, said: “This is the forgotten gas of both climate and ozone. It is a natural gas, but it stayed in a steady state in the atmosphere until human beings began to interfere with the natural balance of things.
“It is a problem because it is a very good greenhouse gas and it stays so long in the atmosphere. It is an unintended release from many of our activities, but we could do much to stop this happening. That is what this report is about.”
