Which Fossil Fuel Emits The Most CO2 & Greenhouse Gases?

We’ve already put together a guide on the carbon footprint of different energy sources for electricity production 

But, below is information on the carbon footprint specifically of the different fossil fuel energy sources

We look at measurables such as total global CO2 emissions, emission rates, and also with what fossil fuels are responsible for the most emissions in what are currently the two highest emitting countries – China, and the United States.

 

Summary – Fossil Fuel That Emits The Most CO2 & Greenhouse Gases

Which Fossil Fuel Emits The Most

It depends on the metric being measured, however, coal may be a top emitter across several metrics

Natural gas might emit the least of the fossil fuels, but this can change somewhat when taking into account total lifecycle emissions, and not just emissions at the combustion stage

For transport in particular, petroleum based products may be a top total emitter (because of how much of it is used), but other factors like emission rates and also fuel efficiency need to be considered for nuance 

It’s worth mentioning that several variables can impact emissions from the different fossil fuels – we list some of them in the guide below

 

Total Global CO2 Emissions, In Tonnes Per Year

In terms of total tonnes of annual CO2 emissions, coal appears to be the biggest emitter, followed by liquid oil

 

Total CO2 Emissions In China

Coal led China’s total CO2 emissions in 2016 in terms of gigatonnes of CO2 by a significantly large margin.

 

Total CO2 Emissions In The US

Oil led the United States’ total CO2 emissions in 2016 in terms of gigatonnes of CO2.

Gas and coal were relatively even in second and third

 

% Share Of CO2 Emissions In Japan

Coal and oil have an even split amongst fossil fuels for the highest % share of CO2 emissions in Japan

 

Emissions From Different Energy Sources In Different Countries May Vary Over Time

It’s worth mentioning that emissions totals can vary country by country, and year to year, as countries change the quantities of the energy sources they use in their energy mix

So, this is something to monitor over time as countries change their energy sources

 

CO2 Emissions Per Kilowatt Hour Of Electricity Produced

According to several sets of data, coal may emit the most CO2 per kilowatt hour of electricity produced, and natural gas may emit the least

 

Emissions During Combustion vs For The Whole Lifecycle Of An Energy Sources

Emissions can be measured during just the combustion stage

But, they can also be measured for the entire lifecycle of an energy source – including mining/extraction, transport, combustion and more

Breaking emissions down at just combustion vs for the entire lifecycle of an energy source may change it’s emissions footprint

 

CO2 Emissions At The Combustion Stage

Natural gas may have up to 50 to 60% less CO2 emissions than coal at the combustion stage,

Although, one report indicates that the type of power plant can impact this (i.e. whether it’s a new efficient power plant or a typical/traditional one)

Natural gas may also emit less during combustion than oil

 

Lifecycle Emissions Of Different Fossil Fuels

When taking into consideration lifecycle emissions at stages other than just combustion, one report indicates that up to 9% of natural gas’ emissions might happen during extraction and also transportation of natural gas

When considering total lifecycle emissions of natural gas and not just combustion emissions, one report indicates that natural gas might have a similar global warming effect as coal fired electricity

Another report that measured the total lifecycle CO2e per kilowatt hour of electricity produced from different fossil fuels indicated that coal was the top emitter, followed by oil, and then natural gas

It’s worth checking what the inclusions and exclusions in individual lifecycle emissions footprint studies were.

 

Emissions For Fossil Fuels Used In Transport

Fossil fuels used in transport may require a slightly different analysis than fossil fuels used for electricity generation.

Petroleum based fuel products like gasoline emit the most total emissions.

Natural gas appears to emit less tailpipe emissions than gasoline (a petroleum based fuel product)

Diesel emits more per gallon than gasoline, but has better fuel efficiency/mileage

There may be variables such as the type of vehicle that can impact emission rates for different fuels.

 

Fossil Fuel Emissions vs Other Energy Sources

This guide outlines the carbon footprints of other energy sources other than just fossil fuels.

 

Total Global CO2 Emissions

Total Global CO2 Emissions, In Tonnes Per Year

In terms of total tonnes of annual CO2 emissions, coal appears to be the biggest emitter, followed by liquid oil

 

From ourworldindata.org:

[Globally, annual per year CO2 emissions by fuel source, measured in billions of tonnes per year, in 2013, were:]

[Solid Fuel (Coal) was in first at 15.15 (Bt)]

[Liquid (Oil) was second at 11.79 Bt]

[Gas (Natural Gas) was third at 6.62, followed by Cement Production at 2.03, and Gas Flaring at 249.36 (Millions of tonnes)]

 

Summary Of Global Greenhouse Gas Emissions By Energy Source

See the full breakdown of global greenhouse emissions by energy source in this guide.

 

Total CO2 Emissions In China

Coal led China’s total CO2 emissions in 2016 in terms of gigatonnes of CO2 by a significant margin.

 

In 2016, Coal was at 7.17Gt of CO2, oil 1.38 and gas at 0.395.

 

Summary Of Greenhouse Gas Emissions By Energy Source In China

See the full breakdown of greenhouse emissions by energy source in China in this guide.

 

Total CO2 Emissions In The United States

Oil led the United States’ total CO2 emissions in 2016 in terms of gigatonnes of CO2.

Gas and coal were relatively even in second and third

 

In 2016, Oil was at 2.31Gt CO2, gas at 1.53Gt CO2, and coal at 1.38Gt CO2.

 

Summary Of Greenhouse Gas Emissions By Energy Source In The US

See the full breakdown of greenhouse emissions by energy source in the US in this guide.

 

% Share Of CO2 Emissions In Japan

Coal and oil have close to an even split amongst fossil fuels for the highest % share of CO2 emissions in Japan

 

[In Japan, coal] constitutes 38.2 percent of Japan’s CO2 emissions – an almost even split with oil, which accounts for 37.3 percent (chinapower.csis.org)

 

CO2 Emissions Per Kilowatt Hour Of Electricity Produced

According to several sets of data, coal may emit the most CO2 per kilowatt hour of electricity produced, and natural gas may emit the least

 

One set of data indicate that per kilowatt hour of electricity produced, CO2 emissions from the different fossil fuels are:

Coal releases 2.2 pounds, petroleum releases 2.0 pounds, and natural gas releases 0.9 pounds.

 

Another set of data indicate that per kilowatt hour of electricity produced, CO2 emissions from the different fossil fuels are:

Coal emits about 2.15 lbs of CO2 per kWh electricity [and natural gas is at] 1.22 lb of CO2

 

Emissions For Other Energy Sources Per Unit Of Electricity Produced

Read more about emissions per unit of electricity produced of other energy sources, other than fossil fuels, in this guide.

Renewables and nuclear essentially may have almost no emissions during electricity generation.

 

CO2 Emissions At The Combustion Stage

Natural gas may have up to 50 to 60% less CO2 emissions than coal at the combustion stage,

Although, one report indicates that the type of power plant can impact this (i.e. whether it’s a new efficient power plant or a typical/traditional one)

Natural gas may also emit less during combustion than oil

 

Natural gas emits 50 to 60 percent less carbon during the combustion process [than coal] (chinapower.csis.org)

 

From ucsusa.org:

Natural gas [has much lower] global warming emissions from its combustion … than those from coal or oil

Natural gas emits 50 to 60 percent less carbon dioxide (CO2) when combusted in a new, efficient natural gas power plant compared with emissions from a typical new coal plant

 

Lifecycle Emissions Of Different Fossil Fuels

Emissions from fossil fuels can occur at other lifecycle stages other than just combustion 

 

Lifecycle Stages Other Than Combustion Where Emissions From Natural Gas May Occur

Other than combustion, natural gas may be responsible for emissions at the following lifecycle stages:

– During drilling/extraction

Methane may leak when drilling for natural gas takes places

 

– During transport of natural gas in pipelines

Transporting natural gas as LNG may also add to it’s emissions footprint

Methane leaks may occur in pipelines during transport

 

From ucsusa.org:

… with natural gas, the drilling and extraction of natural gas from wells and its transportation in pipelines results in the leakage of methane

 

What Different Reports Indicate About The Lifecycle Emissions Footprint Of Natural Gas

Emissions from stages other than combustion may make up between 1% to 9% of natural gas’ total emissions according to several reports.

Another report indicates that the transport of natural gas may make up to a third of it’s total energy use.

When taking into account additional emissions, one report indicates that natural gas may be on par with coal fired electricity in terms of their emissions footprints

There may be different variables that impact the final emissions footprint of natural gas too

 

From ucsusa.org:

… Preliminary studies and field measurements show that these so-called “fugitive” methane emissions [from drilling and extraction of natural gas, and also leaks of methane rom transportation in pipelines] range from 1 to 9 percent of total life cycle emissions

Whether natural gas has lower life cycle greenhouse gas emissions than coal and oil depends on the assumed leakage rate, the global warming potential of methane over different time frames, the energy conversion efficiency, and other factors

 

From world-nuclear.org:

There are many advocates for the use of natural gas as an alternative to coal for electricity generation, on the grounds that it emits much less CO2 per kWh generated.

This is true on almost any basis of comparison, but it ignores the global warming potential of leaked natural gas, and the CO2 emissions in transporting it as LNG (up to one third of the energy is consumed in transport).

Leakage of 3% of the natural gas will bring it into approximate parity with coal-fired electricity in terms of global warming effect.

 

Lifecycle Emissions Of Different Fossil Fuels For Electricity Production

When measuring total lifecycle emissions by CO2e per kilowatt hour of electricity produced, coal was the top emitter, followed by oil, and then natural gas

 

One set of data lists the lifecycle emissions of the different energy sources when measuring carbon equivalent per kilowatt hour of electricity produced:

… conventional coal combustion [was] the highest emitter (at 1000g of CO2e/kWh), followed by newer coal gasification plants (800), oil fired electricity generation plants (650), and then current gas powered electricity generation (500)

 

Another set of data also had coal PC (pulversized coal) as higher emitting than combined cycle gas

 

Other Variables That Can Impact The Lifecycle Emissions Of Different Fossil Fuels

Other miscellaneous factors can impact the lifecycle emissions of different fossil fuels too, such as:

– The type of power plant being used

e.g. an older less efficient power plant vs a newer more efficient power plant 

 

– The type of technology used at the power plant

Such as whether carbon capture technology or devices are being used

 

Fossil Fuel Emissions In Transport

Total Emissions

Petroleum based fuel products like gasoline emit the most total emissions.

 

Tailpipe Emissions

Natural gas appears to emit less tailpipe emissions than gasoline (a petroleum based fuel product)

 

Considering only tailpipe emissions, natural gas … emits 15 to 20 percent less heat-trapping gases than gasoline when burned in today’s typical vehicle (ucsusa.org)

 

Emissions vs Fuel Efficiency

Diesel emits more per gallon than gasoline, but has better fuel efficiency/mileage

 

Variables In Transport Emissions

The type of vehicle is an example of a variable that can play a role in emissions from different fuels.

 

 

Sources

1. https://chinapower.csis.org/china-greenhouse-gas-emissions/

2. https://www.ucsusa.org/clean-energy/coal-and-other-fossil-fuels/environmental-impacts-of-natural-gas#.W9AW9BMzbR1

3. https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions

4. https://www.bettermeetsreality.com/carbon-footprint-of-common-everyday-things-products-foods/

5. http://www.world-nuclear.org/information-library/energy-and-the-environment/clean-coal-technologies.aspx

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