Carbon footprint

A carbon footprint the amount of carbon dioxide released into the atmosphere as a result of the your activities.

However there are problems with the accuracy of the measurement.

There are also indirect emissions that an individual or business generates but these are not included in the carbon footprint measurement.

Carbon footprints are normally measured annually. Essential data includes energy bills, transport costs and waste generation.

A recent Science News report from Carnegie Mellon University shows there is a large uncertainty in carbon footprint calculating.

So when a business declares itself ‘carbon neutral’ it can never really be 100% correct.

If you type “carbon footprint calculator” into Google you will see that some of the calculators are quite complex and require a lot of information. They ask how many people are vegetarian, how much they recycle and compost etc. The equation can get quite involved.

The Institute suggests that a better way is to devote a percentage of profits to cover their carbon footprint. Carbon footprints are normally measured annually. Here is an example of a Carbon Footprint Calculator.

However it may not be wise to spend a lot of time working out measurements which are based on averages and not particularly accurate.

Nevertheless calculating a carbon footprint is a good way to raise awareness about emissions generated by activities

You can create a list that details your emissions sources covering a 12 month period. Bills from energy suppliers often show the amount of carbon emitted by your usage or you can get the information from their website.

The amount of emissions produced by your vehicle could be gained from the manufacturer however it is easier and still perfectly valid to use figures produced by the bodies such as the US Environmental Protection Agency (detailed below).

According to the UN Environment Program about 45% of emissions are direct ones, such as driving a car or using a heater. Approx. 20 percent are caused by the creation, use and disposal of products we use. 25 percent comes from powering workplaces and 10 percent from maintaining public infrastructure.

The final element involves a carbon offset, “an emission reduction credit from another organization’s project that results in less carbon dioxide or other greenhouse gases in the atmosphere than would otherwise occur,” says the David Suzuki Foundation, which promotes “ways for society to live in balance with the natural world.” You can purchase credits from a renewable energy company, for instance, to offset the amount of carbon emissions you can’t eliminate through other measures.

There are benefits for companies. Consumer buying preferences that favour companies with lower emissions of greenhouse gases than their competitors. There are economic rewards for displaying a “green” social responsibility towards your customers. There are advantages such as reduced production costs due to the application of energy saving practices, reduced inputs, and minimization of the production of waste. Government regulations and pressure from shareholders and investors means companies with a high carbon footprint may not be competitive in the low carbon economies of tomorrow.

This is where offsetting, i.e. buying carbon credits comes in. Buying carbon credits compensates for the unavoidable emissions you create today by financing projects that reduce or absorb carbon emissions in the world.

Accreditations from internationally recognised standards give you the assurance that the projects producing your credits deliver positive environmental and social impacts.

Average Emission Calculations from the EPA

Electricity Reductions (kilowatt-hours)

The Greenhouse Gas Equivalencies Calculator uses the AVoided Emissions and geneRation Tool (AVERT) U.S. national weighted average CO2 marginal emission rate to convert reductions of kilowatt-hours into avoided units of carbon dioxide emissions.

Most users of the Equivalencies Calculator who seek equivalencies for electricity-related emissions want to know equivalencies for emissions reductions from energy efficiency (EE) or renewable energy (RE) programs. Calculating the emission impacts of EE and RE on the electricity grid requires estimating the amount of fossil-fired generation and emissions being displaced by EE and RE. A marginal emission factor is the best representation to estimate which fossil-fired units EE/RE are displacing across the fossil fleet. EE and RE programs are not generally assumed to affect baseload power plants that run all the time, but rather marginal power plants that are brought online as necessary to meet demand. Therefore, AVERT provides a national marginal emission factor for the Equivalencies Calculator.

Emission Factor

1,558.8 lbs CO2/MWh × (4.536 × 10-4 metric tons/lb) × 0.001 MWh/kWh = 7.07 × 10-4 metric tons CO2/kWh
(AVERT, U.S. national weighted average CO2 marginal emission rate, year 2018 data)


  • This calculation does not include any greenhouse gases other than CO2.
  • This calculation includes line losses.
  • Regional marginal emission rates are also available on the AVERT web page.


  • EPA (2019) AVERT, U.S. national weighted average CO2 marginal emission rate, year 2018 data. U.S. Environmental Protection Agency, Washington, DC.