CO2e Meaning, Definition, Calculation, and Examples
The proliferation of greenhouse gases (GHGs) like carbon dioxide, methane, and nitrous oxide in the atmosphere as a result of human activities such as the burning of fossil fuels is one of the leading causes of climate change and global warming. To address this, 196 countries, including the UK, signed the Paris Agreement in 2015, which aims to limit temperature increase to 1.5 °C above pre-industrial levels.
Terrascope’s SaaS-based platform is designed to help enterprises in the UK measure their GHG emissions accurately and efficiently, which is a critical step towards setting realistic, science-backed emission reduction goals. The platform uses machine learning and AI to help a variety of UK-based companies create a roadmap towards their decarbonisation goals and focus on the highest impact reduction activities to achieve their sustainability targets.
What are greenhouse gases?
Greenhouse gases are a group of gases that are naturally present in the earth's atmosphere or released through human activities.
The Kyoto Protocol, signed by the UK in 1998, identified six GHGs as the main contributors to global warming. These gases include CO2, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride.
Carbon dioxide (CO2) is the most prevalent GHG, accounting for about 76% of global GHG emissions. CO2 is primarily produced by the burning of fossil fuels, such as coal, oil, and gas, which are used for transportation, industry, and homes. Methane, primarily from agriculture, contributes 16% of GHG emissions; and nitrous oxide, mostly from industry and agriculture, contributes 6%.
What is CO2e and how is it different from CO2?
CO2e, or Carbon Dioxide Equivalent, is a unit of measurement used to compare the impact of GHGs on the environment. CO2e provides a unified way to express the contribution of each GHG to climate change. It is based on a GHG’s global warming potential (GWP), which measures how much heat a GHG traps in the atmosphere compared to CO2 over a specific time period — typically 100 years. The GWP of CO2 is set to 1 and the GWPs of other GHGs are expressed relative to CO2.
In other words, CO2e helps enterprises compare the impact of different GHGs. It also allows for the creation of carbon offset programs, which can fund projects that reduce emissions.
For example, methane has a GWP of 28-36, which means that it traps 28-36 times more heat than CO2 over a 100-year period. Agricultural activities are the predominant source of methane emissions, be it livestock emissions like manure, gastroenteric releases or cultivating crops such as rice.
Curbing methane emissions is a crucial step for agricultural enterprises on the road to net zero. The US Environmental Protection Agency (EPA) found that methane concentrations in the atmosphere have doubled over the last two centuries, primarily due to human-related activities. In 2022, total UK territorial GHG emissions were 417.7 million tonnes CO2e (MtCO2e).
How to calculate CO2E?
The calculation of CO2e involves multiplying the amount of a GHG emitted by its GWP.
How is CO2e used?
CO2e is a widely used measure that has a direct impact on enterprises. In environmental management, companies use CO2e to track and reduce their GHG emissions and meet sustainability goals. In climate policy, governments use CO2e to establish regulations and policies that aim to reduce emissions and allocate carbon credits in cap-and-trade systems. Meanwhile, in carbon trading, CO2e is used as a currency for companies to buy and sell emissions allowances.
There are also many ways in which we use CO2e in daily life.
- Driving a car: The combustion of gasoline in a car engine emits carbon dioxide and other GHGs. The amount of CO2e emitted depends on the type of vehicle and how much it is driven. As a rough estimate, the average passenger car emits around 0.2 to 0.4 kilograms of CO2e per kilometre driven. Assuming an average driving speed of 60 kilometres per hour, driving your car for one hour would result in approximately 12 to 24 kilograms of CO2e emissions. In 2022, the transport sector in the UK was the largest emitting sector accounting for 34% of carbon dioxide emissions. However, it is worth noting that this is just an estimate and actual emissions may vary based on other factors such as driving conditions, vehicle age, and maintenance.
- Using electricity: Generating electricity often involves burning fossil fuels, which emits carbon dioxide and other GHGs. The amount of CO2e emitted per unit of electricity depends on the source of the electricity, such as coal, natural gas, or renewables.
- Travelling by airplane: Airplanes emit large amounts of carbon dioxide and other GHGs into the atmosphere. The amount of CO2e emitted depends on the distance travelled and the type of aircraft. In 2021, emissions from the international aviation fuel were estimated to be 13.3 million tonnes of CO2e in the UK. This figure nearly doubles in 2022, i.e., 26 MtCO2e.
- Heating or cooling a building:Heating or cooling a building often involves using energy from fossil fuels, which emit GHGs. The amount of CO2e emitted depends on the type of fuel used and the efficiency of the heating or cooling system.
- Recycling: Recycling materials instead of sending them to a landfill can reduce greenhouse gas emissions by reducing the need to produce new materials. The amount of CO2e saved depends on the type and amount of materials recycled and the energy required to recycle them.