A carbon footprint is generally the amount of carbon or greenhouse gas emissions associated with something.
In this guide, we outline in greater depth what makes up a carbon footprint, how it’s measured, how it might be used, and more.
Summary – What Is A Carbon Footprint
Most things we do and consume in life have a carbon footprint – food, a product, a service, an activity
Footprints can also apply to things such as individuals, a household, a business, a sector or industry, or even a country
A true carbon footprint takes into account the total quantity of direct and indirect greenhouse gases emitted over a specified time period, or over the lifecycle of something
The total lifecycle of a product or service might involve totalling the emissions from the different stages of the product or service lifecycle – in sourcing, making, transporting and distribution, buying, using/consuming and disposing of that thing.
The different greenhouse gas types can be combined to come to one measurement – expressed as CO2e (carbon equivalent).
For example, a gasoline car while in operation will emit greenhouse gases from the burning of gasoline, but there is also greenhouse gases that were emitted in the manufacturing process of that car.
These are the direct and indirect emissions to consider with each product or service we use.
A car may also principally emit CO2, but also emit nitrous oxide and methane in smaller amounts (all 3 are greenhouse gases)
With cars in particular, we can measure CO2e per kilometer or mile, but also per passenger in the vehicle (as ride sharing or public transport can be more efficient per passenger)
With food, CO2e can be measured in terms of CO2 per pound of food, per gram of protein, per gram of fat, per calorie, per dollar of economic value produced, and more
In general for different products and things, emissions might be measured in total emissions annually, emission intensity, and also other measurements
So, there’s different ways to measure or express the carbon footprint for different things
Carbon footprints can also be measured as a single greenhouse gas rather than CO2e i.e a singular carbon dioxide footprint, a singular methane footprint, a singular nitrous oxide footprint
But, carbon dioxide is the main gas that most researchers and people are concerned about in regards to a changing climate, so this is the one that is usually expressed
It helps us to get an idea of the emission footprint of different things, and how they might affect climate change and other environmental issues
Something to note about the transport of goods is that local isn’t always better.
The type of transport used (road vs sea freight for example) matters, as well as packing efficiency, how clean the fuel is, and so on
On a society wide scale, some sources indicate that population size, economic output (and industrialization), rate of consumption, and the type of energy source used (fossil fuel vs cleaner fuels), can all significantly affect a country’s carbon footprint
*What should be noted is that there are limitations to calculating and using carbon footprints.
They aren’t a perfect concept, or a definitive measurement.
The total carbon footprint cannot be exactly calculated for a lot of products and services because of inadequate knowledge, a lack of data, differing production and lifecycle processes, different geographic weather and conditions, and so on.
At each stage, there are different variables (different types of freight/transportation used is one variable) to account for.
So, carbon footprints might be more of a general discussion point, rather than a definitive measurement that can be used for solid conclusions.
This is in a similar vein to water footprints – they are just one tool or factor among many.
What’s A Carbon Footprint?
In general – a carbon footprint is the total sum of emissions caused by something, and is often expressed as tonnes of CO2e (carbon dioxide equivalent).
CO2e is a measurement that combines all greenhouse gases emitted in the one measurement, and allows different carbon footprints to be compared to each other as well (different GHGs have different potential for global warming- so, if they are combined into one measurement, they can be compared like for like)
A true carbon footprint takes into account the total quantity of direct and indirect greenhouse gases emitted over a specified time period (such as the production stage only, or the operation/consumption stage only), or over the entire lifecycle of something (i.e. from sourcing and production all the way through to waste or re-use)
A carbon footprint … is calculated by summing the emissions resulting from every stage of a product or service’s lifetime (material production, manufacturing, use phase, and end-of-life disposal).
CO2e is calculated by multiplying the emissions of each of the six greenhouse gases by its 100 year global warming potential (GWP).
A carbon footprint considers … Carbon dioxide (CO2), Methane (CH4), Nitrous oxide (N2O), Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs) and Sulphur hexafluoride (SF6).
Examples Of A Carbon Footprint
As an example, the true carbon footprint of driving a car includes not only the emissions that come out of the exhaust pipe (direct), but also all the emissions (indirect) that take place when oil is extracted, shipped, refined into fuel and transported to the petrol station, not to mention the substantial emissions caused by producing and maintaining the car.
Growing, rearing, farming, processing, transporting, storing, cooking and disposing of the food – all has a carbon footprint (greeneatz.com)
[a food carbon footprint might involve] production and application of fertilizers, pesticides and other materials used to grow crops through to the processing, transportation and disposal of unused food at the retail, institutional and household level (static.ewg.org)
Context Of Using A Carbon Footprint
The carbon Footprint is [only] one part of the ecological footprint, along with other footprints like a water footprint or a land footprint
However, a carbon footprint is obviously more relevant when discussing the issue of climate change.
What’s Makes Up A Carbon Footprint? (Direct & Indirect Emissions)
A true carbon footprint account for all:
indirect greenhouse gas emissions
… for the entire lifecycle of the of a thing i.e. from sourcing through to waste (dumping, recycling, or re-use).
For entire cities:
For the footprint of entire cities, you not only have to consider the direct emissions that go on within the city boundary, but also the indirect emissions that happen outside the city boundaries for things such as products that are produced elsewhere, and imported into the city for consumption.
Sectors like agriculture, industrial activity, residential and commercial, and even transport when considering electric cars, all have their own direct emissions, but also indirectly use electricity from power generation, which has an indirect emission footprint
Energy sources can emit greenhouse gases not only directly at the combustion stage, but indirectly also across the whole lifecycle of sourcing and using the energy source.
One example of this the potential for indirect methane leaks when mining oil or gas, in addition to direct emissions when burning oil or gas products when using them for energy a the operation stage
Mobility (driving, flying & small amount from public transit), shelter (electricity, heating, construction) and food are the most important consumption categories determining the carbon footprint of a person
For individuals … Transport, housing and food have the three largest carbon footprints at a household level
For products generally:
Production Emissions – emissions before the product leaves the production stage e.g. before food leaves a farm, or before a good leaves a factory.
Post Production Emissions – emissions after [a] product leaves production stage. e.g. for food – processing, transport, retail cooking, waste disposal.
You should also look at the materials used in a product too, such as for packaging:
For example, a juice carton is made of an aseptic carton, a beer can is made of aluminum, and some water bottles either made of glass or plastic.
Indirect emissions can outweigh direct emissions for a product’s carbon footprint, so, it’s important they are included:
Most of the carbon footprint emissions for the average U.S. household come from “indirect” sources, e.g. fuel burned to produce goods far away from the final consumer.
These are distinguished from emissions which come from burning fuel directly in one’s car or stove, commonly referred to as “direct” sources of the consumer’s carbon footprint.
Carbon Footprint Of Businesses
Businesses might have different footprints to measure and assess:
Emissions from all the activities across an organisation, including buildings’ energy use, industrial processes and company vehicles.
Includes emissions which are outside an organisation’s own operations. This represents emissions from both suppliers and consumers, including all use and end of life emissions.
Emissions over the whole life of a product or service, from the extraction of raw materials and manufacturing right through to its use and final reuse, recycling or disposal.
Emissions from the raw materials and services that are purchased by an organisation in order to deliver its service(s) and/or product(s).
How To Calculate A Carbon Footprint
Do a LCA (Life Cycle Assessment) – This is the best way of trying to estimate direct and indirect emissions
Carbon Accounting – can be a personalised or custom accounting of carbon emissions
Use Online Carbon Calculators (a shortcoming of these calculators though is that some of them only calculate direct emissions and not indirect) – google carbon calculators for individuals, households, businesses, farmers etc.
Reporting Of Carbon Footprints – Inclusions & Omissions
An individual carbon footprint calculation may also include and omit certain data.
You have to look to the actual report and check what data was included and excluded from the final report numbers.
The data they did and didn’t include for the carbon footprint of different foods was…
“LCAs included GHG emissions associated with the following processes:
Production and transport of “inputs,” the materials used to grow crops or feed animals (fertilizers, pesticides and seed for crop production; feeds for animal production)
On-farm generation of GHG emissions (e.g., the enteric fermentation digestive process of cows, sheep and other ruminants; manure management; soil emissions from fertilizer application; etc.)
On-farm energy use (fuel and electricity, including energy used for irrigation)
Transportation of animals and harvested crops
Processing (slaughter, packaging and freezing)
Refrigeration (retail and transportation)
Retail and consumer waste (waste before and after cooking, including served but uneaten food that is thrown away)
Due to lack of data, the LCAs did not consider the following processes related to food production:
Consumer transport to and from retail outlets
Home storage of food products
Production of capital goods and infrastructure (typically excluded from most LCAs and is currently excluded from standards such as PAS 2050)
Energy required for water use in growing livestock feed (irrigation is included for alfalfa but not for corn and soybeans)”
Limitations & Problems With Using A Carbon Footprint
In most cases, the total carbon footprint cannot be exactly calculated because of various reasons such as inadequate data available, inadequate knowledge of full processes to produce and eventually consume or dispose of a product, lack of transparency with the production process, conditions and environments differing around the world (weather, farmland, and laws and regulations in different regions and countries, and so on), different processes and methods being used to produce products (factory farmed vs open range farming just as one example), and so on.
It’s hard to get both a fully accurate, but also comparable carbon footprint final number.
For this reason … there are suggestions to define the carbon footprint as:
A measure of the total amount of carbon dioxide (CO2) and methane (CH4) emissions of a defined population, system or activity, considering all relevant sources, sinks and storage within the spatial and temporal boundary of the population, system or activity of interest. Calculated as carbon dioxide equivalent using the relevant 100-year global warming potential (GWP100).
If you take food as an example:
Predicting GHG emissions with absolute certainty is difficult.
Actual GHG emissions associated with a given product will vary depending on:
1) the extent to which best practices are implemented along the entire supply chain;
and 2) differences in input data as a result of regional and/or production system differences for a for a given meat/crop production system.
There are also uncertainties associated with IPCC emission factors.
Uncertainties arise from the variability of activity data used to model specific production systems as well as assumptions related to background processes.
For example, the specific input data used for modelling beef production systems could be different in Idaho and Nebraska than in Kansas, or the length of time in the feedlot might vary.
Similarly, there may be differences in inputs and transportation distances between one production system and another.
A carbon footprint might be better used to give a general sense of the magnitude of GHGs associated with a particular product or activity, as opposed to providing a specific and absolutely certain number.
Again with food…
In general, there is significant variability and uncertainty with respect to greenhouse gas emissions from agricultural systems
Actual emissions may vary considerably depending on particular conditions, compared to estimates
A recent study’s results … found that the calculation of carbon footprints for products is often filled with large uncertainties.
The variables of owning electronic goods such as the production, shipment, and previous technology used to make that product, can make it difficult to create an accurate carbon footprint
The dilemma (in measuring a carbon footprint) is that it is also impossible to pin down accurately.
We don’t stand a hope of being able to understand how the impact of our bananas compares with the impact of all the other things we might buy instead unless we have some way of taking into account the farming, the transport, the storage and the processes that feed into those stages.
Do the best job you can, despite the difficulties, of understanding the whole picture … make the most realistic estimates that are possible and practical, and be honest about uncertainty [in estimations and stats].
What Increases The Average Person’s Carbon Footprint?
The foods we eat
The buildings we live in
The energy sources and electricity we use
The vehicles we use
The products and services we use, and the industries in a given economy
… can all add up and increase or decrease our carbon footprints.
Some specific things that might increase the average person’s carbon footprint might be:
Meat, Dairy Products, & Poultry, Fish, Seafood and Eggs are all responsible for a large majority of the greenhouse gases [in the average diet]
Vegetables, fruits, grain products, sugars, sweeteners, oil, fats, and other food groups make up less than 20% of the average food consumption’s greenhouse gases
… [In terms of electricity] Coal releases 2.2 pounds, petroleum releases 2.0 pounds, and natural gas releases 0.9 pounds. Nuclear, solar, wind, and hydroelectric release no CO2 when they produce electricity, but emissions are released during upstream production activities (e.g., solar cells, nuclear fuels, cement production).
Space heating with wood emits the least CO2e (31.4 tons per million BTU) followed by 64.2 for natural gas, with the highest being 210.5 for electric heaters.
Refrigerators are one of the largest users of household appliance energy; in 2015, an average of 726.9 pounds of CO2e per household was due to refrigeration
Passenger cars and trucks make up about 17% of total greenhouse gas emissions in the US (as of 2016). So, they are a major emitter in the transport sector.
Apart from that:
Of the roughly 126,000 pounds of CO2e emitted in a car’s lifetime (assuming 120,000 miles for a 1995 mid-sized sedan), 86% is from burning fuel.
Gasoline releases 19.6 pounds of CO2 per gallon when burned, compared to 22.4 pounds per gallon for diesel. However, diesel has 11% more BTU per gallon, which improves its fuel economy.
Greenhouse Gas & Carbon Footprint Calculators
You can calculate carbon per kilowatt hour of electricity with:
Emission rates of different energy sources (wikipedia.org)
You can calculate carbon per mile or kilometre of a standard vehicle, or other modes of transport with:
Pounds of CO2 per passenger mile (transit.dot.gov)
Environmental impact of transport (wikipedia.org)
There’s also general guides on how to calculate the GHG emissions of products:
Carbon footprinting guide (carbontrust.com)
A Note About Transport Of Goods In Relation To Carbon Footprints
What is generally assumed about carbon footprints by many sources is that locally produced or grown products and services are better (or have a lower footprint).
This is not always the case:
The type of transport used to move a product matters – sea freight can be much more eco friendly than road freight in terms of emissions.
Just as one example, there can be less GHG emissions manufacturing in China and sea freighting to an Australian city port, rather than manufacturing in Australia and road freighting within Australia (whogivesacrap.org)
So, this goes to show that presumptions can’t be made, and each carbon footprint must be calculated individually, and specifically looking at each step of the entire process that sources, produces and delivers a product or service to market (and even the consumption and disposal or re-use stages if you want to go that far).
Resources On Different Types Of Carbon Footprints
Read More About Climate Change
If you’re interested in reading more about climate change, this guide outlines some of the basic information to consider, and this guide outlines some of the general solutions that have been proposed to address it