Carbon Footprint

You probably know that as humans, we have a massive impact on climate change, also known as global warming. However, a lot of the data we see comes in the form of big, overwhelming numbers and it is hard to relate what we see on the news to our own lives. So how can we, individuals, quantify our impact? Read on to learn more about the carbon footprint, including what it is, how it can be calculated, the causes of its increase, and more.

Carbon Footprint Carbon Footprint

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Table of contents

    Carbon Footprint Meaning

    Carbon footprint is “the sum total of all the greenhouse gas emissions that had to take place for a product to be produced or for an activity to take place.”

    A carbon footprint is a measurement of an entity's total direct and indirect greenhouse gas emissions produced for an activity to take place.

    Greenhouse gases are gases that can absorb infrared radiation from the Earth and reradiate it back. They contribute in this way to increasing the Earth's temperature.

    The entities that emit greenhouse gases may be:

    • Individuals
    • Countries
    • Corporations
    • Occupations
    • And many more.
    Rather than focusing on the greenhouse gas emissions that are associated with production, carbon footprint focuses on the greenhouse gas emission associated with consumption.

    How to Calculate a Carbon Footprint

    A carbon footprint is calculated by adding up the lifetime sum of all greenhouse gas emissions from a given entity.

    Taking into account the differences in GWP (global warming potential) for each gas, we can estimate an entity's carbon footprint in CO2e (carbon dioxide equivalents). CO2e is much more accurate than measuring CO2 because it takes into account all greenhouse gases, not just CO2. Several websites can be used to estimate your own carbon footprint, including this one provided by the United States Environmental Protection Agency.

    Carbon footprints are very hard to calculate mainly because there are a lot of factors to account for. Take for example a flight. The footprint is higher for business class passengers who take up more space. The altitude the plane flies to is also a big factor. And this is an easy calculation compared to calculating the carbon footprint of the production of a car, where all the steps in the process have to be included: from acquiring the materials (like extracting the metals that go into the vehicle parts) to the emissions of each machine that melt, mix and connect these materials to create the final product, plus the emissions from the transport of each material and car piece.

    Carbon Footprint Causes

    There are numerous causes of increased greenhouse gas emissions, such as the burning of fossil fuels, agricultural practices, cattle farming, and more. We will go over these causes in greater detail below.

    Carbon Footprint of Food

    On a global level, livestock contributes approximately 7.1 gigatonnes of CO2 to the atmosphere annually, with beef contributing the greatest amount (Fig. 1) (Table 1). Most of these emissions come from two sources - land conversion/destruction of habitat to make way for cattle grazing, and from cattle flatus. In terms of dietary patterns, it has been found that, unsurprisingly, people who eat a very large amount of meat on average contribute the largest dietary CO2e daily, at over 7 kg CO2e, and vegans contributed the least, at less than 3 kg CO2e.

    Food itemKg of CO2e per kg of food
    Beef (from beef herds)60 kg CO2e per kg
    Lamb24 kg CO2e per kg
    Beef (from dairy herds)21 kg CO2e per kg
    Cheese21 kg CO2e per kg
    Chocolate19 kg CO2e per kg
    Coffee17 kg CO2e per kg
    Farmed prawns12 kg CO2e per kg
    Oil palm8 kg CO2e per kg
    Pork7 kg CO2e per kg
    Chicken6 kg CO2e per kg

    Table 1: Food items by kg CO2e per kg of food.

    Carbon Footprint of Vehicles (Including Electric Cars)

    Vehicles contribute a very large amount of greenhouse gases to the atmosphere, though the amount contributed differs depending on the type of vehicle driven and the type of fuel used. It is estimated that the average vehicle produces 4.6 tonnes of CO2 every year! In the European Union, over 60% of vehicle-based greenhouse gas emissions come from cars, followed by larger, heavy-duty trucks at more than 25%. The lowest contribution comes from motorbikes, at a mere 1% of the vehicle-based total.

    Electric cars can reduce the vehicular carbon footprint drastically, but they do not remove it entirely. In the US, for example, it was found that using an electric car exclusively results in a little over a third of the CO2e emissions compared to those generated by a petrol-powered vehicle (Table 2).

    Another form of vehicular travel that has a major impact on your carbon footprint is air travel. Indeed, for people who travel by air frequently, the largest contributor to their individual carbon footprint (outside of whether they choose to have kids or not, more on that later) is likely to be related to travelling by plane. On a global scale, however, air travel only amounts to around 2.5% of the total carbon footprint. This is largely due to economic inequalities that result in the majority of humans being unable to afford frequent air travel.

    Vehicle typetonnes of CO2e emitted annually
    Petrol5.2 tonnes of CO2e
    Hybrid2.9 tonnes of CO2e
    Plug-in hybrid2.6 tonnes of CO2e
    Electric1.8 tonnes of CO2e

    Table 2: CO2e emissions by vehicle type in the US.

    Carbon Footprint of Emails

    We may not often think about it, but the electronics we use daily produce greenhouse gases. From electric ovens to video game consoles to even the internet! Residential electricity use contributes significantly to the CO2e in developed countries, particularly the electricity used to power indoor climate control in the form of cooling and heating.

    Even using a smartphone contributes to your carbon footprint, primarily due to its manufacture, less so its actual use. The same is true for laptops, of which nearly 80% of CO2e comes from its manufacture and only 20% from its use over a three-year average. Perhaps one of the most surprising sources of CO2e is the use of email! Yes, every single email you send has an amount of CO2e "attached" to it (albeit extremely small)! Individual emails are estimated to contribute anywhere from 0.03 grams to 26 grams of CO2e, which is very small. Yet, since over 300 BILLION emails are sent annually from roughly 4 billion internet users, the amount contributed is much larger than you may expect. However, even at this level, email's contribution to the worldwide total CO2e is tiny, being well under half of a single percent, and the use of email is vastly superior to sending physical mail in terms of carbon footprint.

    Average Carbon Footprint UK

    On a global scale, anthropogenic CO2e amount to around 50 gigatonnes annually and the average citizen contributes 6.5 tonnes to that total. The average citizen in the United Kingdom contributes around 6.8 tonnes annually, so slightly higher than the global average. Citizens of the United States contribute an average of 18.4 tonnes per person, while the citizens of Brunei contribute the most, at around 38.8 tonnes (Table 3).

    In terms of total emissions, rather than per person, China has by far the largest carbon footprint, at 11.7 gigatonnes of CO2e annually, followed by the US at 5.8 gigatonnes and India at 3.4 gigatonnes. Combined, these three countries account for more than half of all CO2e emitted globally (Table 4). Much further down the list is the UK, at around 0.4 gigatonnes of CO2e.

    CountryCO2e tonnes per person
    Brunei38.8 CO2e tonnes per person
    Qatar35.9 CO2e tonnes per person
    Bahrain31.2 CO2e tonnes per person
    United Arab Emirates27.3 CO2e tonnes per person
    Kuwait27.3 CO2e tonnes per person

    Table 3: Countries by tonnes of CO2e per person.

    Countriesgigatonnes CO2e
    China11.7 gigatonnes CO2e
    USA5.8 gigatonnes CO2e
    India3.4 gigatonnes CO2e
    Russia2.0 gigatonnes CO2e
    Indonesia1.7 gigatonnes CO2e

    Table 4: Countries by gigatonnes of CO2e.

    Carbon Footprint Examples

    Since looking at the total carbon footprint of an individual is time-consuming and involves more variables than we can provide here without it getting too complex, let's instead look at five different individuals' yearly travels.

    Traveller #1: Travels roundtrip in an average petrol car from Los Angeles to San Bernardino, California, USA 320 times per year for work and also takes a roundtrip economy flight to Washington DC to visit family from Los Angeles twice per year.

    Traveller #2: Travels from London, UK to Reading, UK 320 times per year in an average hybrid petrol car for work. They also take a roundtrip flight in economy class to Paris, France three times per year to visit family.

    Traveller #3: Works partially remotely and has to travel in an average petrol car into the office 12 times per year roundtrip, from San Diego, California, USA to Los Angeles, California, USA. They also travel roundtrip on business class to Frankfurt, Germany twice per year for work.

    Traveller #4: Works remotely and never visits the office. Travels roundtrip on economy from Los Angeles, California, USA to Darwin, Australia via Sydney, Australia once per year.

    Traveller #5: Travels from Tokyo, Japan to Singapore roundtrip 5 times per year in business class for work. They also travel from Tokyo to Yokohama 320 times roundtrip in an average hybrid petrol car per year for work.

    Who do you think has the highest carbon footprint?

    Traveller #1: 12.55 tonnes CO2e annually


    Traveller #2: 22.47 tonnes CO2e annually

    Traveller #3: 16 tonnes CO2e annually

    Traveller #4: 6.35 tonnes CO2e annually

    Traveller #5: 46.6 tonnes CO2e annually

    Did you guess correctly? As you can see, business class travel, combined with a job that requires frequent commutes, adds significantly to an individual's carbon footprint. Also, you may notice that remote work diminishes levels significantly, even for a person that took a very long roundtrip flight (from the USA to Australia!) This may make you think about how much of a positive impact on the environment the popularity of exclusively remote work has become in the wake of the COVID-19 epidemic.

    How Can We Reduce our Carbon Footprint?

    There are several things an individual can do to reduce their carbon footprint.

    As shown above, the vehicles you drive and the food you eat have a large impact on greenhouse gas emissions. Changing to a hybrid or an electric vehicle can help some, though choosing to use public transportation and eschewing vehicle ownership entirely is much better. Note that switching cars when your old car is still functional (and safe!) increases greenhouse emissions significantly since the CO2e from car manufacturing are really high.

    In terms of diet, the less meat-based your diet is, the better. Choosing to remove beef from your diet entirely can be particularly helpful, though eating an entirely plant-based vegan diet is best.

    Other things you can do to reduce your carbon footprint related to food include eating food that is in season, especially regional food, since this avoids the CO2e of long-distance food transportation.

    On top of this, you can also try avoiding too many long flights (such as transatlantic flights), using more sustainable forms of energy (such as solar), recycling, heating your house in winter to a slightly lower temperature, taking colder showers, air-drying your clothing, etc.

    However, there is one thing you can do that has a greater impact on your carbon footprint than all other things combined: choosing not to have children or having one less child (Fig. 2). In doing so, you remove one entire greenhouse gas producing organism from adding to your carbon footprint. We are more than 8 billion people on this planet already!

    This is why, despite having lower per capita emissions, China, the US, and India have the highest overall emissions: due to their massive population sizes. Lifestyle factors do make a difference, which is why the US ranks higher than India, despite having a smaller population. But, ultimately, the number of individuals makes the greatest difference.


    Hopefully, you now know more about carbon footprints. Maybe you could even calculate your own!

    Carbon Footprint - Key takeaways

    • A carbon footprint is a measurement of an entity's total direct and indirect greenhouse gas emissions. These entities may be individuals, countries, corporations, occupations, and much more.
    • A carbon footprint is calculated by adding up the lifetime sum of all greenhouse gas emissions from a given entity. Taking into account the differences in GWP for each gas, we can estimate an entity's carbon footprint in CO2e (carbon dioxide equivalents).
    • On a global level, livestock contributes approximately 7.1 gigatonnes of CO2 to the atmosphere annually, with beef contributing the greatest amount. Most of these emissions come from land conversion for cattle grazing and from cattle flatus.
    • The average citizen in the United Kingdom contributes around 6.8 tonnes annually, slightly higher than the global average of 6.5.
    • In order to reduce your carbon footprint, you can have one less child, forgo personal vehicle use, forgo transatlantic flights, use sustainable energy, become a vegan, and more.
    Frequently Asked Questions about Carbon Footprint

    What are some examples of carbon footprints?

    The carbon footprints of the top 5 CO2e emitters are 11.7 gigatonnes (China), 5.8 gigatonnes (USA), 3.4 gigatonnes (India), 2.0 gigatonnes (Russia), and 1.7 gigatonnes (Indonesia). 

    Which country has the highest carbon footprint?

    China

    What is a carbon footprint?

    A carbon footprint is a measurement of an entity's total direct and indirect greenhouse gas emissions.

    How to calculate a carbon footprint?

    A carbon footprint is calculated by adding up the lifetime sum of all greenhouse gas emissions from a given entity. Taking into account the differences in GWP for each gas, we can estimate an entity's carbon footprint in CO2e (carbon dioxide equivalents).

    Why should we be concerned about our carbon footprint?

    Anthropogenic climate change is driven by greenhouse gas emissions. 

    What causes a carbon footprint?

    Many (or even most) activities we engage in produce a carbon footprint. What we eat, the vehicles we drive, the amount of children we have, the electronics we use, etc. all contribute to our carbon footprint.

    Is carbon footprint good or bad?

    Bad

    What foods have the largest carbon footprint?

    Meats, specifically beef from beef herds. 

    Test your knowledge with multiple choice flashcards

    Earth's atmospheric greenhouse gases are- 

    Anthropogenic climate change is largely driven by two of these gases- ______ & ______.

    True or False- CO2e is much more accurate than measuring CO2 because it takes into account all greenhouse gases, not just CO2.

    Next
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