The Greenhouse Gas Protocol (GHG Protocol) is a joint initiative of the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD). This protocol provides the most widely used standards worldwide for accounting for greenhouse gas emissions1.
Origins and Objectives
The GHG Protocol was established in 1997 to address the growing need to standardize the quantity and type of greenhouse gas emissions. Both organizations, WRI and WBCSD, recognized the need to create standards to be followed for accounting for greenhouse gases, in order to more efficiently monitor their spread.
Functioning
The GHG protocol involves voluntary participation and provides the tools and methodologies for calculating greenhouse gas emissions. Although CO2 is often the only gas talked about, there are a total of six greenhouse gases, namely: carbon dioxide (CO2), sulfur hexafluoride (SF6), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and nitrogen trifluoride (NF3).
Scope 1, 2, 3
Emissions of these gases can be of two different types: direct (scope one) or indirect (scope two and three).
- Scope 1: Includes all emissions from sources owned or controlled by the companies in question, such as fossil fuels used to heat buildings.
- Scope 2: Concerns purchased electricity and steam. These energy sources produce indirect emissions, as their production physically occurs outside the company, not under its control.
- Scope 3: Involves other indirect emissions along the entire supply chain, including those resulting from the use of energy for the production of products and materials purchased externally.
Dissemination
The GHG Protocol is widely spread today: according to its website, in 2016, 92% of the companies listed in the Fortune 500 used this method to track their carbon footprint.
What does CO2eq (equivalent) mean?
The term “CO2eq” or “CO2 equivalent” is a measure used to compare emissions of various greenhouse gases based on their global warming potential (GWP). This measure converts the quantities of other gases into the equivalent quantity of carbon dioxide with the same global warming potential12.
For example, the GWP of methane over 100 years is 27, while that of nitrous oxide is 298. This means that an emission of 1 ton of methane and nitrous oxide are equivalent in terms of global warming effect to emissions of 27 and 298 tons of carbon dioxide, respectively. In other words, emitting a gram of CO2eq is equivalent to emitting a gram of CO2, in terms of the resulting warming effect. This unit is used to compare and sum together the contributions of different greenhouse gases, especially to estimate the carbon footprint associated with human activities.
What does GWP mean?
The term “GWP” stands for “Global Warming Potential”. This measure indicates how much a greenhouse gas is able to absorb infrared thermal radiation in the atmosphere over a certain period of time, relative to the same mass of carbon dioxide (CO2). The GWP is calculated in relation to the GWP of 1 kg of CO2 over 100 years.
For example, if it is said that the gas R404A has a GWP of 3922, this means that it is 3922 times more potent than CO2 in warming the climate. In other words, the GWP provides a common scale for measuring the climatic effects of different greenhouse gases. The GWP takes into account how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame considered. GWP values are periodically compiled and reviewed in reports by Working Group I of the Intergovernmental Panel on Climate Change (IPCC).
What are the main greenhouse gases?
The most dangerous greenhouse gases are:
Water Vapor (H2O): Water vapor is the most abundant greenhouse gas in Earth's atmosphere12. An increase in Earth's surface temperature increases the amount of water vapor the air can hold, leading to enhanced warming.
Carbon Dioxide (CO2): Carbon dioxide is the second most important greenhouse gas12. Human activities, particularly the combustion of fossil fuels, contribute to its concentration in the atmosphere.
Methane (CH4): Methane comes from both natural and artificial sources. Methane contributes to ozone depletion, as well as acting as a greenhouse gas. Methane's global warming potential is rated at 72 over a 20-year timeframe.
Nitrous Oxide (N2O): Nitrous oxide is used as a propellant for aerosol sprays, an anesthetic and recreational drug, an oxidizer for rocket fuel, and to enhance engine power in motor vehicles. It is 298 times more effective in trapping heat compared to carbon dioxide (over a 100-year period).
Chlorofluorocarbons (CFCs): CFCs are synthetic gases that have been widely used in the past, for example in air conditioners, refrigerators, and some plastic foams. They are very stable in the atmosphere and can remain there for a long time, contributing to the greenhouse effect.
Sulfur Hexafluoride (SF6) and Perfluoromethane (PFC-14): These gases are much more potent than carbon dioxide in causing global warming. Compared to carbon dioxide, sulfur hexafluoride causes 23,500 times more warming and perfluoromethane causes 6,630 times more warming.
It is important to note that, although some greenhouse gases are more "potent" than others in terms of global warming potential, the total amount of each gas present in the atmosphere is also a determining factor.
