China, Hong Kong's Sources of CH4 Emissions
Key Insights
2024 CH4 Emissions Profile
In 2024, Hong Kong's anthropogenic methane emissions totalled around 4.8 megatonnes CO2e. Waste dominated, at roughly 4.7 megatonnes CO2e or 97.1% of emissions, rising by about 0.05 megatonnes CO2e per year over the ten years to 2024. Fugitive emissions were 0.07 megatonnes CO2e (1.4%) and rising, while fuel combustion was 0.05 megatonnes CO2e (1.0%) and declining. Livestock contributed 0.03 megatonnes CO2e (0.5%) and increased slightly; crop emissions were negligible and falling.
Historic Livestock Emissions
Livestock methane emissions began at around 0.001 megatonnes CO2e in 1851 and rose gradually through the early twentieth century. They increased more substantially after the 1920s, peaking at roughly 0.1 megatonnes CO2e in 1972. Emissions then fell sharply into the early 1990s and fluctuated at low levels thereafter, ending at around 0.03 megatonnes CO2e in 2024.
Historic Fugitive Emissions
Fugitive methane emissions were negligible until the late 1960s. They then rose gradually, reaching around 0.04 megatonnes CO2e by the mid-1990s, before continuing upward at a slower pace. Emissions reached their historical peak of roughly 0.07 megatonnes CO2e in 2024, the same level recorded at the end of the period.
Historic Waste Emissions
Waste methane emissions started at around 0.005 megatonnes CO2e in 1851 and rose steadily through the first half of the twentieth century. Growth accelerated after the early 1950s, climbing from roughly 0.5 to 3.4 megatonnes CO2e by 1995. They continued increasing thereafter, reaching a peak of around 4.7 megatonnes CO2e in 2024.
Historic Crop Emissions
Crop methane emissions were near zero in the nineteenth century, becoming more material from the 1930s and rising to a peak of roughly 0.08 megatonnes CO2e in 1961. They then declined rapidly through the 1960s and 1970s. Crop emissions remained negligible after that, ending near zero in 2024.
Historic Fuel Emissions
Fuel-combustion methane emissions remained low through the nineteenth and early twentieth centuries, then increased after 1945. Growth accelerated from the mid-1980s, reaching a peak of roughly 0.1 megatonnes CO2e in 1999. Emissions subsequently declined overall, although they varied at low levels, ending at around 0.05 megatonnes CO2e in 2024.
Background
The chart shows a national breakdown by source of the yearly methane (CH4) emissions from human activities expressed as weight in megatonnes (Mt). In the scientific literature, these are referred to as anthropogenic emissions. Human-induced methane emissions increase atmospheric methane, which is warming the Earth. The sources of human methane emissions are
- Livestock
- Fugitive emissions from the fossil fuel industry
- Crop production
- Fossil fuel combustion
- Waste management
- Other processes
Methane's Global Warming Potential
Methane has a much higher Global Warming Potential (GWP) than CO2. However, Methane emissions in the atmosphere decay with an average lifetime of about 12 years so its long term warming-effect is much less compared to CO2 which stays on average for hundreds of years in the atmosphere. Meaning: Methane's short term warming effect is much higher, but long term warming effect is much lower. A reduction in emissions can cause a rapid decline in its atmospheric levels.
Livestock
Livestock emits methane that is produced in the animals' digestive system. Most methane is emitted from the mouth during rumination. A much smaller amount of methane is emitted from the manure. Depending on how the manure is managed, i.e., wet or dry, more methane is emitted. Wet management leads to higher methane emissions than dry management. However, dry management also emits nitrous oxide (N2O), which is another potent greenhouse gas.
Fugitive emissions from fossil fuel industry
Fugitive methane emissions are from the intentional and accidental release of methane, which happens during the extraction, storage, and transportation processes in the fossil fuel industry. Examples are methane leaks during oil and gas handling, storage, transport, incomplete combustion, and many more. Also, methane is deliberately ventilated from mines during the extraction of coal.
Methane is a primary part of “gas”, also called “natural gas” or “fossil gas”. Natural gas is used, for example, for heating and electricity generation, whereby it emits CO2 during the combustion process. However, when natural gas leaks (unburned) it contains a lot of fugitive methane emissions.
Waste
Waste from landfills and wastewater produces a lot of methane when biodegradable material breaks down without oxygen.
Crop production
Crop production emissions are largely from rice cultivation, which generates large amounts of methane during plant growth. These emissions are from flooded paddies, which create the swamp-like environment of rice fields. There are agricultural techniques to reduce emissions significantly, like periodic drainage and aeration. Rice is the main staple for about half the world's population, and its emissions are a significant part of total human methane emissions.
Fuel combustion
Fuel combustion emissions are mostly from the incomplete combustion of fossil fuels. As mentioned before, natural gas consists largely of methane, and when the combustion does not happen completely, methane enters the atmosphere.
Other
Other human-induced methane emissions include industrial processes and product uses.
Wikipedia: Anthropogenic Sources of Atmospheric MethaneIPCC: AR6, 5.2.2.2 Anthropogenic CH4 emissions
Units and Measures
CH4 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 methane 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