China, Hong Kong's Sources of N2O Emissions
Key Insights
2024 N2O Emissions Profile
Hong Kong's anthropogenic N2O emissions totalled around 0.44 megatonnes CO2e in 2024. Waste was the largest source, at about 0.19 megatonnes CO2e and 43.5% of emissions, rising by roughly 0.004 megatonnes CO2e per year over the ten years to 2024. Energy contributed around 0.12 megatonnes CO2e (28.0%) and Other 0.10 megatonnes CO2e (22.7%), both declining by about 6% per year. Agriculture was smaller at roughly 0.03 megatonnes CO2e (5.7%) and broadly stable to falling.
Historic Agriculture Emissions
Agricultural emissions began at around 0.002 megatonnes CO2e in the early 1850s and rose gradually, then more substantially after the late 1930s. They peaked at roughly 0.06 megatonnes CO2e in 1972, before declining to around 0.03 megatonnes CO2e by the late 1990s. Emissions remained near that level thereafter, ending at about 0.03 megatonnes CO2e in 2024.
Historic Energy Emissions
Energy emissions were near zero in the nineteenth century and remained small until around 1970, when they reached roughly 0.03 megatonnes CO2e. They then rose rapidly through the 1970s and 1980s, peaking at about 0.49 megatonnes CO2e in 1999. Emissions declined after that high point, reaching around 0.12 megatonnes CO2e in 2024.
Historic Waste Emissions
Waste emissions began at about 0.008 megatonnes CO2e in the early 1850s and increased steadily through the following century, reaching around 0.11 megatonnes CO2e by 1971. They remained broadly stable until the end of the 1990s, then resumed rising. Waste emissions reached their highest level, about 0.19 megatonnes CO2e, in 2024.
Historic Other Emissions
Other emissions started at roughly 0.02 megatonnes CO2e in the early 1850s and rose gradually to about 0.07 megatonnes CO2e by 1970. Growth accelerated thereafter, reaching a peak of around 0.37 megatonnes CO2e in 1999. They then declined steadily, ending at approximately 0.10 megatonnes CO2e in 2024.
Background
The chart shows a national breakdown by source of the yearly nitrous oxide (N2O) emissions from human activities and processes, expressed as weight in megatonnes (Mt). Human-induced emissions are the main driver of the increasing atmospheric nitrous oxide that is warming our planet. The sources of human nitrous oxide emissions are
- Agriculture
- Energy
- Industry
- Waste
- Other
Agriculture
Emissions related to agriculture are mainly from the use of synthetic fertilizers and manure management.
Synthetic fertilizer, used for agricultural processes, contains a lot of nitrogen. That nitrogen in the soil reacts and causes considerable N2O emissions. The use of excess fertilizer, meaning more fertilizer than the plants can use to grow, causes even higher relative emissions. Applying the right amount of fertilizer at the right time can reduce N2O emissions. There are many technical solutions to reduce emissions while keeping, or even increasing, agricultural yields.
When manure is left on the field or otherwise managed in dry processes, it emits considerable amounts of nitrous oxide. Manure can be managed by wet processes, which reduces nitrous oxide emissions but increases methane emissions. Some technical solutions focus on modifying the animal feed to reduce the nitrogen in the manure, thereby reducing nitrous oxide emissions.
Energy, Industry, Waste, and Other
All non-agricultural categories together have much lower emissions than agricultural emissions alone.
N2O emissions related to energy are almost all from the combustion of fossil fuels. For example, the combustion of fossil fuels in power plants, cars, and airplanes not only causes CO2 emissions but also emits nitrous oxide (N2O). Any advances to reducing fossil fuel dependency will thus also reduce nitrous oxide emissions.
Most industry-related emissions are from the chemical industry for producing fertilizer, nylon, and similar products. Technologies are available to reduce emissions in these processes.
Nitrous oxide emissions from waste come from, for example, wastewater treatment and landfills.
Wikipedia: Nitrous oxideIPCC: AR6, 5.16 Anthropogenic nitrous oxide (N2O) emissions
Units and Measures
N2O emissions are expressed in the total weight in megatonnes per year. 1 Megatonne is equal to 1 million tonnes.
Wikipedia: MegatonneWikipedia: Global warming potential
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National N2O emissions data through 2024 is from the PRIMAP-hist dataset, which combines several published sources into a historical emissions time series.
The Key Insights paragraph was created using a large language model (LLM) in combination with our data, historic events, and a structured approach for best accuracy by separating the context generation from the interpretation and narrative.
Data Sources
PRIMAP-hist The PRIMAP-hist national historical emissions time series (1750-2024)
Update cycle: Every few monthsDelay: Less than 1 yearCredits: Gütschow, J.; Busch, D.; Pflüger, M. (2025): The PRIMAP-hist national historical emissions time series v2.7 (1750-2024). zenodo. doi:10.5281/zenodo.17090760