A Practical, Low-Temperature Abatement Opportunity
Nitrous oxide (N₂O) is now seen as a major greenhouse gas that has not received enough attention, even though it plays a big role in climate change and ozone layer damage. Most discussions focus on carbon dioxide (CO₂) and methane (CH₄), so N₂O is often called the “forgotten greenhouse gas,” even though it has a much larger environmental impact.
How N₂O and NOx emissions affect climate change.
This article looks at how N₂O and NOx emissions affect climate change, the limits of current control methods, and why ozone-based oxidation systems are a practical and cost-effective option for reducing industrial emissions.
Why Nitrous Oxide Matters
N₂O has a much higher global warming potential than CO₂
Nitrous oxide stays in the atmosphere for about 120 years, making it a long-lasting greenhouse gas. Since before the industrial era, its levels have risen from about 270 ppb to over 336 ppb in 2024, mostly because of human activities.
Each molecule of N₂O has a much higher global warming potential than CO₂. According to the United Nations Environment Programme (UNEP) and the Food and Agriculture Organisation (FAO), N₂O is now the main cause of ozone layer depletion.
Because N₂O is both a greenhouse gas and damages the ozone layer, it is a major climate concern and should not be overlooked.
Distinguishing N₂O from NOx
N₂O VS NOx
It is important to tell the difference between nitrous oxide (N₂O) and nitrogen oxides (NOx) because they behave differently in the environment and need different treatment methods.
- NOx (NO and NO₂) are short-lived pollutants that cause smog, acid rain, and can harm people’s health.
- N₂O, by contrast, is a well-mixed, long-lived greenhouse gas with severe climate and ozone-layer impacts.
N₂O reacts in the upper atmosphere to form nitrogen oxides, which speed up the breakdown of ozone. This reduces the atmosphere’s natural shield against harmful ultraviolet rays.
Sources of Nitrous Oxide Emissions
Sources of Nitrous Oxide Emissions
Agriculture
About 75% of human-caused N₂O emissions come from agriculture. Using synthetic nitrogen fertilizers and managing livestock manure upsets the natural nitrogen cycle. This allows soil microbes to convert excess nitrogen into N₂O through nitrification and denitrification.
Managing manure adds about 10% more to agricultural N₂O emissions, especially when it is stored or spread on fields.
Industrial and Urban Sources
Industrial activities make up about 5% of global human-caused N₂O emissions, mainly from:
- Nitric acid production (fertilisers, explosives)
- Adipic acid production (nylon, foams)
Wastewater treatment is a fast-growing source of N₂O. If the biological nitrogen removal process is not well managed, it can release N₂O. In the United States, N₂O emissions from wastewater went up by 42% from 1990 to 2019.
Pathways to Emission Reduction
The Global Nitrous Oxide Assessment says that up to 40% of human-caused N₂O emissions could be cut by 2050 with current technology.
Key pathways include:
- Precision fertiliser application
- Nitrification inhibitors and green ammonia
- Industrial emission abatement
- Optimised wastewater treatment processes
Among these, reducing industrial emissions is considered the quickest and most cost-effective step in NOx Abatement Technologies
Selective Catalytic Reduction (SCR) and Selective Non-Catalytic Reduction (SNCR) are common ways to control NOx, but they have some built-in drawbacks:
- Require operating temperatures of 300–400 °C
- High energy consumption and CO₂ generation
- Risk of ammonia slip
- Reduced efficiency under variable load conditions
- Limited performance in high-sulphur or high-particulate gas streams
As emission rules become stricter, these problems make it harder for SCR systems to reach near-zero emissions goals.
Where Ozone Oxidation Can Help
Diagram showing ozone injection into flue gas to oxidise NO and NO₂ into water-soluble nitrogen oxides, followed by removal in a wet scrubbing system.
NOx control methods that use oxidation have improved a lot in recent years and are now a practical alternative to systems that use ammonia.
Ozone oxidation converts relatively iOzone oxidation changes NO and NO₂, which do not dissolve well in water, into forms like N₂O₃ and N₂O₅ that dissolve easily. Wet scrubbers can then remove these as acids or turn them into nitrate salts. NOx removal efficiencies exceeding 90%, even under challenging conditions involving high sulphur content, acid gases, and fluctuating process loads.
Biozone’s Low-Temperature Oxidation (LTO) Process
Biozone’s NOx control system makes ozone on site from oxygen. This process copies natural reactions that happen in the atmosphere, but does so in a controlled industrial setting:
- Ozone is generated on demand in precise quantities.
- Oxidation of NO and NO₂ to water-soluble compounds
- Efficient removal via wet scrubbing
- No hazardous chemical storage
- The oxygen produced as a by-product does not create any environmental or workplace risks.Nature process meets stringent BACT and LAER performance guidelines established by authorities such as the South Coast Air Quality Management District (California).
Cost and Energy Comparison: SCR vs Ozone
Capital Cost
- SCR system: ~R4.0 million
- Biozone ozone system: ~R1.5 million
- SCR costs approximately 263% more than equivalent ozone-based systems.
- Ozone: 52 kJ per gram of NO removed
- SCR requires approximately 269% more energy than ozone-based oSCR uses about 269% more energy than ozone-based oxidation. Systems can also be deployed as polishing stages to enhance the performance of existing abatement systems, including SCR units, thereby enabling compliance with future near-zero-emission standards.
As global emission rules become stricter, ozone-based oxidation provides a way to achieve:
- Retrofitting existing plants
- Designing new low-emission facilities
- Integrating NOx and SOx abatement
- Supporting acid recovery processes
The Way Forward
Southern Africa has many chances to test and use these systems. Past tests by Anglo Platinum showed that ozone-based systems could cut NOx to 6 mg/m³, but larger pilot projects were not finished.
Looking ahead, working with industrial gas suppliers like BOC, Air Liquide, or Air Products could speed up commercial use. Projects in South Africa could help support expansion to other countries.
A Dual Climate Opportunity
Nitrous oxide is both a major climate risk and a clear chance for action. Ozone-based oxidation offers a practical, low-temperature, and cost-effective way to control industrial NOx and N₂O emissions.
When engineered correctly, ozone systems deliver:
- High removal efficiency
- Lower capital and operating costs
- Reduced secondary emissions
- Alignment with future regulatory framework
This makes ozone oxidation an important tool for cutting emissions in a meaningful way while helping industries stay competitive.
Biozone’s ozone-based oxidation systems are built to turn atmospheric chemistry into dependable, large-scale emission control for industry.
