The energy sector produces the most greenhouse gases of any industry, responsible for roughly 75% of all human-caused emissions worldwide. Within that broad category, electricity and heat production alone accounts for about 34% of global emissions, making it the single largest source. These figures come from 2019 data compiled by the Intergovernmental Panel on Climate Change, the most comprehensive global accounting available.
But “industry” can be sliced many ways. The answer shifts depending on whether you count the electricity a factory uses under “energy” or “manufacturing,” and whether you group all fossil fuel activity together or break it into power plants, cars, and furnaces. Here’s how the major sectors compare and where the biggest opportunities for reduction exist.
Global Emissions by Sector
The IPCC breaks global greenhouse gas emissions into five main sectors. In order of their share:
- Electricity and heat production: 34%
- Industry (manufacturing, construction, mining): 24%
- Agriculture, forestry, and land use: 22%
- Transportation: 15%
- Buildings: 6%
These categories can be misleading on their own. The “buildings” figure only counts fuel burned directly inside buildings for heating and cooking. If you include the electricity those buildings consume, the share jumps to 16%. Similarly, the “industry” figure covers on-site fuel burning and chemical processes at factories but routes their electricity use back to the power sector. The World Resources Institute offers an alternative breakdown that groups all energy-related activities together, including electricity, transportation, manufacturing, and building energy use, and finds the energy sector accounts for 75.7% of global emissions.
Why Electricity and Heat Top the List
Power generation dominates because the world still relies heavily on coal, natural gas, and oil to produce electricity. Coal-fired power plants are the worst offenders, releasing roughly twice the carbon dioxide per unit of energy as natural gas plants. Heating systems in colder climates add to the total, particularly in regions that burn coal or oil for district heating.
The electricity sector also acts as a multiplier for other industries. When a steel mill or data center runs on coal-generated power, those emissions show up under “electricity and heat production” rather than under the industry that consumed the power. This accounting choice is why the energy sector’s share looks so dominant, and why electrifying industries only reduces total emissions if the grid itself gets cleaner.
Heavy Industry: Steel, Cement, and Chemicals
Manufacturing and construction account for about 12.7% of global emissions when you include their energy use, plus another 6.5% from industrial processes like chemical reactions in cement kilns and blast furnaces. Among heavy industries, iron and steel production stands out. The sector emits roughly 2.6 billion tonnes of CO2 equivalent each year, consuming about 7% of global energy supply and producing 7 to 9% of all human-caused carbon dioxide. That makes steel the single highest-emitting heavy industry.
Cement production is the next largest industrial source, followed by the chemicals sector. These industries are particularly difficult to decarbonize because their emissions don’t just come from burning fuel. The chemical reactions involved in turning limestone into cement clinite, or reducing iron ore into metal, release CO2 as a byproduct of the process itself. You can’t eliminate those emissions simply by switching to renewable electricity.
Agriculture and Land Use
At 22% of global emissions, agriculture and land use represent the third-largest sector. Unlike energy and industry, which primarily release carbon dioxide, agriculture is the dominant source of two other potent greenhouse gases: methane and nitrous oxide.
Livestock are a major contributor. Cattle and other ruminants produce methane during digestion through a process called enteric fermentation. Manure management adds both methane and nitrous oxide. Rice paddies, which keep fields flooded for much of the growing season, create the oxygen-free conditions where methane-producing microbes thrive. Synthetic nitrogen fertilizers, widely used to boost crop yields, release nitrous oxide as soil bacteria break them down. Deforestation rounds out the sector’s impact, releasing stored carbon when forests are cleared for cropland or grazing.
Transportation: Roads Dominate
Transportation accounts for about 15% of global emissions, and the breakdown within the sector is lopsided. Road vehicles are responsible for the vast majority. In the United States, where transportation data is especially detailed, light-duty trucks (SUVs, pickups, minivans) account for 37% of transportation emissions, medium and heavy-duty trucks for 23%, and passenger cars for 20%. Commercial aviation contributes about 7%, ships and boats 3%, and rail just 2%.
The global picture follows a similar pattern. Personal and freight vehicles burning gasoline and diesel produce far more emissions than planes or ships, simply because there are so many more of them operating so many more hours per day.
Fossil Fuel Extraction and Methane Leaks
Beyond the emissions from burning fossil fuels, the process of extracting and transporting them releases enormous quantities of methane. The International Energy Agency estimates that the energy sector was responsible for around 145 million tonnes of methane in 2024, more than 35% of all human-caused methane emissions. Oil operations contributed about 45 million tonnes, coal mining over 40 million tonnes, and natural gas operations nearly 35 million tonnes.
These “fugitive emissions” occur at every stage. Drilling sites vent or flare gas. Pipelines leak at joints and compressor stations. Abandoned wells and closed mines continue releasing methane for decades. The IEA estimates that abandoned facilities alone emitted about 8 million tonnes of methane in 2024, with nearly 5 million tonnes coming from old coal mines (mostly in China) and about 3 million tonnes from abandoned oil and gas wells (nearly 40% in the United States). In the oil and gas industry specifically, upstream operations like drilling and processing account for about 85% of methane leaks.
Methane is roughly 80 times more potent than carbon dioxide over a 20-year period, so even relatively small volumes have an outsized warming effect.
Waste and Landfills
Waste management is a smaller but significant source. It ranks as the world’s third-largest source of human-caused methane, accounting for about 20% of the global methane total. Most of that comes from organic material decomposing in landfills and open dumps, where the absence of oxygen drives bacteria to produce methane instead of carbon dioxide. Wastewater treatment contributes as well, though solid waste is the larger share.
Fashion and Consumer Goods
Some industries don’t fit neatly into one sector because their emissions are spread across energy, manufacturing, and transportation. The fashion industry is a prominent example, responsible for up to 10% of global carbon emissions when you account for textile production, dyeing, shipping, and disposal. Emissions from clothing and footwear consumption rose from 1.0 to 1.3 billion tonnes of greenhouse gases over the 15 years leading up to 2015, driven largely by the rise of fast fashion and shorter product lifecycles.
How the U.S. Compares to the Global Picture
The United States emitted 6,343 million metric tons of CO2 equivalent in 2022. The sector breakdown differs from the global average in one notable way: transportation rivals the power sector as the top emitter. That’s because the U.S. has a car-dependent culture with high per-capita driving, and its electricity grid has shifted more toward natural gas and renewables than many other countries. Globally, coal-heavy grids in China, India, and Southeast Asia keep electricity and heat production firmly in first place.