Info on our calculator

What’s Your Impact’s Greenhouse Gas Emissions Calculator concentrates on 4 main areas that make up the majority of most individuals' greenhouse gas emissions. The GGEC uses information from the EPA, Eurostat, US Department of Energy’s Energy Information Agency and other sources to produce an accurate assessment of the greenhouse gas emissions you create through your everyday actions.

Our calculator takes into account direct emissions that come directly from individual behaviors (such as those caused by traveling by car) as well as indirect emissions (such as emissions caused during the transportation of a t-shirt from the factory to the store). We do not use any fixed ratios to determine greenhouse gas emissions at any level and so the end result is a measurement that is done solely based on your personal choices which in the end is much more accurate and a lot more enlightening.

The following information explains how the emissions are calculated.

Basic Information

Location

To know the distance that your produce and products traveled to get to your house we need to know what city you live in (or live closest to). Your location is also used to determine which countries would be the usual trading partner for various goods and produce. For now the calculator has 4 regions: Canada, the USA, Europe/UK and Australia.

Size of household

Many households have more then one person, and things like your electricity/heating bill or grocery purchases are usually for everyone in the household, so our calculator allows the user to enter the number of people you live with. Since our calculator is designed to make calculations for individuals, emissions are divided, when necessary, by the number of people you live with to get per capita emissions. You can still use this tool to make calculations for your entire household by multiplying your per capita emissions by your household size.

What did you buy recently? (Indirect emissions)

The largest source of indirect CO2 emissions is created by the transportation of goods and produce. That also makes it an important source of personal emissions that are almost always omitted from other CO2 emission calculators. We at What’s Your Impact wanted to create a calculator that would take into account these indirect emissions by:

1. not using any national or global averages, and
2. by using a methodology that would try to mirror how things are transported in real life as closely as possible.

Now let’s take a look at how the calculations are made.

There are 3 types of items that you can add to your shopping cart: produce, clothing/footwear and electronics. Each of these items has a corresponding fixed weight assigned to them (except for produce). The main trading partners for each item in each region were determined using statistical data collected from the United Nations’ Commodity Trade Statistics Database.

At its base the calculator will figure out the distance that your item has traveled and then multiply it by an emission factor depending on which modes of transportation were used. When an item is shipped from one country to another it is assumed that it was first sent by ship unless the 2 countries are reasonably close by land. This is because marine freight is significantly cheaper than any other type of transportation and so we assume that cost will be the driving factor when selecting a shipping method.

Major ports used for route making purposes were selected mainly based on statistics from the IAPH and the AAPA World Port Rankings. Exporting countries have sometimes more than one major port while importing countries have 2 or 3 major ports to reduce overall shipping distances. Route selections and distance calculations have been verified using Netpas Distance.

After the item has reached the closest major port to your selected location, domestic shipping has to be calculated. The Bureau of Transportation Statistics’ National Transportation Statistics publication is used to determine what the share of total domestic freight tonnage was for each of the transportation modes (air freight accounts for 0.1% of total and was therefore omitted). Using these percentages we can distribute the domestic route across the different freight modes.

Now we need emission factors for each of the modes of freight shipping to determine how much CO2 was emitted. Using the Greenhouse Gas Emissions from the U.S. Transportation Sector report from the EPA we can determine the amount of emissions caused by heavy-duty freight trucks which we can then divide by total vehicle miles traveled by this type of vehicle to get a unit that would be kg of CO2 per mile.

The most common container size is the twenty-foot variety so we use this type of container for our calculations. Using average payloads for each of our three commodity types, taken from the FHWA’s Analysis of the Vehicle Inventory and Use Survey for Trucks with Five or More Axles, we then divide our previous result to produce a value of CO2 emissions per kg-mile transported.

Finally using energy intensity as a basis of comparison we can then determine emission factors for marine and rail freight as well. The energy intensities used in the calculations come from the Oak Ridge National Laboratory’s Transportation Energy Data Book. Multiplying these emission factors with our previous modal distance calculations we can calculate the total amount of indirect emissions produced for each item that was purchased.

Energy

Electricity

Electricity based emissions are calculated based on an emission factor that increases with the amount of fossil fuels that are used to generate your power. The emission factors are based either on national energy mix averages or fossil fuel percentage based energy mixes. The base for all emission factors is the American national average emissions factor for electricity from the Energy Information Administration’s Electric Power Annual. From this value all other emission factors were calculated.

We then multiply the emission factor by kWh used to get the total of CO2 emissions. For users who enter the cost of their monthly electricity bill, we divide the bill by the average retail price of electricity per kWh in their region to come up with the electricity used and then multiply by the emission factor for total CO2 emissions. The average retail price of residential electricity for: the US comes from the Energy Information Administration's Electric Power Monthly, the EU from Eurostat, Canada from Hydro Quebec’s Comparison of Electricity Prices in Major North American Cities and Australia from the IEA's Key World Energy Statistics.

Natural Gas

Natural gas emissions are calculated based on an emission factor in kilograms of CO2 per thousand cubic foot of gas found in the EPA’s Inventory of U.S. Greenhouse Gas Emissions and Sinks. We then multiply the emission factor by the amount of natural gas used to get total CO2 emissions.

For users who enter the cost of their monthly natural gas bill, we divide the bill by the average retail price of natural gas per thousand cubic feet in their region to come up with the amount of natural gas used and then multiply by the emission factor for total CO2 emissions. The average retail price of residential natural gas for: the US comes from the Energy Information Administration's Short-Term Energy and Winter Fuels Outlook, the EU from Eurostat, Canada from IEA's Key World Energy Statistics and Australia from the Department of Treasury and Finance’s Competition Index.

Heating Oil

Heating oil emissions are calculated based on an emission factor in kilograms of CO2 per gallon found in the EPA’s Inventory of U.S. Greenhouse Gas Emissions and Sinks. We then converted the quantity to gallons if it was in liters and multiply by the emission factor to get total CO2 emissions.

For users who enter the cost of their monthly heating oil bill, we divide the bill by the average retail price of heating oil in their region to come up with the amount of heating oil used and then multiply by the emission factor for the total CO2 emissions. The average retail price of residential heating oil for: the US comes from the Energy Information Administration's Short-Term Energy and Winter Fuels Outlook, the EU as well as Canada from IEA's Key World Energy Statistics and Australia from the Department of Primary Industries, Water and Environment’s Home Heating booklet.

Transportation

Annual car usage

Passenger vehicle based emissions are calculated based on the fuel efficiency that is determined by the type of car selected. Different types of car models are grouped together into 4 broad categories and attributed a fuel efficiency rating:

1. Suvs, trucks, luxury and full-size cars
2. Station wagons, vans, sports and mid-size cars
3. Hatchbacks, compact and small cars
4. Hybrid cars

If you know the fuel efficiency of your vehicle you can enter it instead of selecting a category. If you enter this in litres/100 km or British miles/gal, it is then converted to US miles/gal. Input for the distance is converted to miles if necessary. Total number of miles driven is then divided by miles per gallon to determine the total number of gallons of fuel that are used which is finally multiplied by the fuel emission factor. The emission factor is from the EPA's fact sheet, Emission Facts: Average Carbon Dioxide Emissions Resulting from Gasoline and Diesel Fuel.

Annual air travel

CO2 emissions caused by air travel vary considerably because a significant amount of fuel is used for take-off. Therefore large amounts of emissions are created at the beginning of the flight which will have a big effect on emissions per miles if the length of the flight is shorter. This is why we have created 3 types of flight lengths:

1. Short (2 hours or less)
2. Medium (3-5 hours)
3. Long (6-8 hours)

Flight lengths are then converted to miles using the OAG’s Flight Duration Finder. The total number of flights for each type is then multiplied by its respective average flight lengths and emission factors to get total CO2 emissions. The different emission factors come from the UK Department for Environment, Food and Rural Affairs’ guidelines for calculating CO2 emissions.

Waste

Landfills are a major source of methane emissions. All of the previous emission calculations were with respect to carbon dioxide so we will use carbon dioxide equivalency to add waste related emissions to our total. The carbon dioxide equivalent for a gas is derived by multiplying the amount of the gas by its global warming potential.

The per capita household waste emissions and the resulting emission savings caused by recycling different types of materials come from the EPA’s Solid Waste Management and Greenhouse Gases report. It is assumed that if you say that you recycled a specific type of material that you did not throw away any of that material in the regular garbage.

Results

Your greenhouse gas emissions are the sum of all the above calculations, resulting in an estimate of the greenhouse gases that are caused by transportation of produce and products, home energy use, personal transportation and waste. Greenhouse gas emissions are calculated using metric units like kilograms and metric tons. Carbon dioxide emissions are calculated from the weight of carbon.