Firstly, what is nitrous oxide and why is it a problem?
Nitrous oxide (known as N2O) is a potent and long-lived greenhouse gas contributing to global warming. It traps around 273 times more heat than carbon dioxide and remains in the atmosphere for up to 110 years, and emissions are rising each year. N2O is one of the six greenhouse gases recognised by the United Nations Framework Convention on Climate Change (UNFCCC). After carbon dioxide and methane, nitrous oxide is the third most important greenhouse gas when it comes to warming potential, so its reduction is important to countries meeting their commitments to Paris Agreement goals to fight climate change.
In addition to being an important greenhouse gas, N2O also contributes to ozone depletion, posing a dual threat to environmental health. Ozone traps ultraviolet radiation from the sun, and protects all life on Earth from harmful levels of exposure to this type of radiation. Elevated levels of N2O can also detrimentally affect air quality and lead to respiratory problems among local populations.
So, where does nitrous oxide come from?
A majority of human-caused N2O emissions come from nitrogen-based fertilizers and manure used on farms, but these sources of N2O are the most challenging to reduce. Most of the remaining emissions come from industrial sources, with around 14% of all human-caused N2O emissions coming from the industry and energy sectors.
Industrial sources of N2O can be mitigated with abatement technologies existing today, which requires retrofitting industrial plants like has been done in case of industrial methane emissions. China and the US are the two largest emitters of nitrous oxide from industrial sources, accounting for around 80% of these sources of nitrous oxide. Both countries have committed to take action to tackle this, but more can still be done.
Ok, let’s look at some of the major industrial sources more closely.
Chemical manufacturing:
– The production of adipic acid, which is critical in nylon manufacturing, generates N2O as a byproduct. More recently, the processes involved in producing nylon have become increasingly scrutinized due to their particularly high N2O emissions. In 2021, 11 adipic acid plants in China and one in the US emitted around half a million metric tons of N2O, equivalent to the annual greenhouse gas emissions of 31 million automobiles. Adipic acid has wide uses including for other synthetic fibers like polyurethane and PVC, and in some medicines and food.
– Additionally, nitric acid production, a chemical essential for fertilizers and explosives, involves the oxidation of ammonia during which nitrous oxide is released. Nitric acid emissions link agricultural and industrial sources of N2O.
– There are also smaller amounts of emissions associated with the production of caprolactam, used mainly for making a type of nylon – nylon 6 – used in fibers and plastics.
Global energy production:
– While fossil fuel combustion – the process of burning coal, oil, natural gases or other fossil fuels to create energy – primarily releases carbon dioxide, it can also lead to nitrous oxide emissions. The nitrogen content in fossil fuels, along with specific combustion conditions, can facilitate the formation of N2O at high temperatures.
– Since 80% of the world’s energy still comes from fossil fuels, it is important to consider the contribution of N2O emissions as part of energy production.
There are additional sources of nitrogen oxide that extend beyond the farm and industrial sources, including in the treatment of wastewater and through biomass burning.
So, what are the solutions that can already address the industrial sources of N2O?
Implementing catalytic processes in industry:
– There are catalysts that exist for nitrous oxide decomposition which can convert N2O back into nitrogen and oxygen, preventing its release into the atmosphere. Industries involved in producing nitric acid and adipic acid can benefit from adopting these technologies to capture and utilize nitrous oxide emissions.
– Catalytic destruction of N2O in these ways has very high efficiency rates when abating emissions: 99% for adipic acid and 94% for nitric acid.
– This technology is a capital expenditure, but roughly 80% of the abatement potential is estimated to be achievable at break-even prices between $0 and $20 per tonne of carbon dioxide equivalent.
– There are also several selective catalytic processes which can remove up to 80% of N2O emissions from stationary fossil fuel combustion too, and even with 60% uptake, can cut these emissions by half by 2050.
Alternatives for industry:
– Promising alternatives are being investigated for adipic acid, though this is not likely to be possible for nitric acid.
– Shifting fuel from coal and oil to natural gas or renewables in transportation and stationary combustion sectors will serve to reduce both carbon and N2O emissions.
Government policy and regulation:
– Governments should establish regulations aimed at reporting N2O emissions and create an enabling environment to reduce N2O emissions from industrial sources, which could take the form of robust protocols to create a high integrity credit market or other policies as appropriate. A US nonprofit organization has taken steps toward establishing emissions reduction credits and this is an option that could be part of several solutions to address N2O emissions.
– There is significant potential for international cooperation, with US and China leading, on industrial N2O emissions mitigation, as was acknowledged in the Sunnylands Statement, to enhance bilateral cooperation on climate change.
– Multilateral or bilateral financing should assist with the cost-effective abatement of N2O emissions in lower-income countries.
So, what’s next then?
By implementing existing technologies, improving regulatory frameworks, and fostering industry cooperation, it is possible to reduce N2O emissions and work towards a more sustainable future. There is a huge opportunity, in particular, in China to implement technology across all its adipic acid producers. Understanding and tackling the industrial sources of N2O is a collective responsibility of industries and governments.
You can get involved.
Climate Advisers is co-hosting an in-person and virtual event with the Institute for Governance & Sustainable Development (IGSD) and the Asia Society Policy Institute, on Tuesday, July 23rd at 9am EST at the National Union Building – An Overlooked Climate Opportunity in the US and China. The event will focus on the reduction of industrial nitrous oxide (N2O) emissions in the US and China. Register for in-person attendance here and virtual attendance here.
Climate Advisers is also in the process of building a new initiative to increase global ambition to address N2O emissions. To stay informed, visit n2oaction.org and subscribe for updates. If you are interested in getting involved directly, please contact Mumukshu Patel, Senior Director of Food & Agriculture at Climate Advisers on patel@climateadvisers.org.
