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Greenhouse Gas Inventory Reference Cheat Sheet
A printable reference covering Kyoto greenhouse gases, CO2e, GWP, activity data, emission factors, and inventory scopes for grades 9-12.
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A greenhouse gas inventory estimates how much climate-warming gas is released by a school, city, company, or country. This cheat sheet helps students organize the main gases, units, and calculation steps used in environmental science. It is useful because inventories turn real-world activities, such as driving, heating, and electricity use, into comparable emissions data. Students can use it to check formulas, understand reports, and avoid common unit errors. The core idea is that emissions are calculated from activity data and an emission factor. Different gases are compared using global warming potential, or GWP, which converts each gas into carbon dioxide equivalent. Inventories often separate emissions into Scope 1, Scope 2, and Scope 3 categories to show where emissions come from. Good inventories clearly state boundaries, data sources, assumptions, units, and uncertainty.
Key Facts
- Total emissions are commonly estimated with the formula emissions = activity data x emission factor.
- Carbon dioxide equivalent is calculated with the formula CO2e = mass of gas x GWP.
- GWP compares how much heat a greenhouse gas traps relative to CO2 over a chosen time period, often 100 years.
- The main Kyoto greenhouse gases are CO2, CH4, N2O, HFCs, PFCs, SF6, and NF3.
- Scope 1 emissions come directly from sources an organization owns or controls, such as fuel burned in its boilers or vehicles.
- Scope 2 emissions come from purchased energy, such as electricity, steam, heating, or cooling used by an organization.
- Scope 3 emissions are other indirect emissions in the value chain, such as commuting, waste disposal, purchased goods, or product use.
- An inventory boundary defines which locations, activities, gases, and time period are included in the emissions total.
Vocabulary
- Greenhouse gas inventory
- A greenhouse gas inventory is a measured or estimated list of emissions from defined sources over a specific time period.
- Activity data
- Activity data is the measurable amount of an activity that causes emissions, such as liters of fuel used or kilowatt-hours of electricity consumed.
- Emission factor
- An emission factor is the amount of greenhouse gas released per unit of activity, such as kg CO2 per gallon of gasoline.
- Carbon dioxide equivalent
- Carbon dioxide equivalent, or CO2e, is a common unit that expresses different greenhouse gases as the amount of CO2 with the same warming effect.
- Global warming potential
- Global warming potential, or GWP, is a number that compares a gas's heat-trapping effect to carbon dioxide over a set time period.
- Inventory boundary
- An inventory boundary states what sources, places, gases, operations, and dates are included in the greenhouse gas inventory.
Common Mistakes to Avoid
- Mixing mass units, such as kg and metric tons, gives totals that are off by factors of 1,000. Convert all emissions to the same unit before adding them.
- Adding different gases without converting to CO2e is wrong because CH4, N2O, and fluorinated gases do not have the same warming effect as CO2. Use CO2e = mass of gas x GWP before combining gases.
- Using the wrong emission factor for a fuel or region can make the inventory inaccurate. Match the factor to the activity, fuel type, location, and year whenever possible.
- Counting the same emissions twice can inflate the total. Check whether a source belongs in Scope 1, Scope 2, or Scope 3 and keep categories clearly labeled.
- Leaving out the inventory boundary makes the result hard to interpret. Always state the time period, included sites, activities, gases, and major exclusions.
Practice Questions
- 1 A school burns 2,000 therms of natural gas in a year. If the emission factor is 5.3 kg CO2 per therm, what are the annual CO2 emissions in kg?
- 2 A lab releases 4 kg of CH4. If the 100-year GWP of CH4 is 28, what is the release in kg CO2e?
- 3 A building uses 150,000 kWh of electricity. If the electricity emission factor is 0.38 kg CO2 per kWh, what are the Scope 2 emissions in metric tons CO2?
- 4 Why is CO2e needed when comparing emissions from carbon dioxide, methane, and nitrous oxide in one inventory?