A few weeks ago a new meeting of the United Nations treaty on climate change culminated in Glasgow. A new meeting and a new disappointment. The governments of the main countries of the world still do not take the demanding measures that society demands to mitigate global warming.
However, we must not lose sight of the fact that these measures will have an impact on our daily habits. Citizen consumption is the main responsible for greenhouse gas emissions (GHG): between 60 and 75% of GHGs are linked to our transportation, food, clothing or air conditioning.
The connection between global and individual emissions can be made through a better understanding of the carbon footprint (HC). In this article I intend to explain how it is calculated, what are the main factors that explain it and what impact it has on the mitigation of climate change.
What is the carbon footprint?
The carbon footprint of a certain product or activity measures the amount of GHG emissions that can be assigned to that consumption or activity. As in any other dimension of the environmental impact that we generate, it is necessary to consider these emissions throughout the life cycle of the product.
In this sense, two types of scopes are usually distinguished:
The so-called “from the cradle to the door” (cradle to gate The business to business, B2B) includes emissions linked to the production, transport and storage of the product until its acquisition by the consumer or by another company.
The reach “from the cradle to the grave” (cradle-to-grave The business to consumer, B2C) also includes the processes linked to the use phase and their eventual reuse or recycling (which may partially offset previous emissions).
Since the carbon footprint is aimed at measuring our impact on climate change, its calculation involves considering all the greenhouse gases that have been emitted as a result of the activity or product that we are considering.
The most prominent GHGs are carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O). In order to have a common scale of emissions and to simplify its analysis, the HC is usually expressed in mass (grams, kilograms, tons…) of CO₂ equivalent (CO₂e). In this way, all the emissions that a mass of CO₂ with a similar global warming potential (GWP) would suppose are converted.
This concept, which is sometimes also called radiative forcing potential, indicates the ability of a given gas to increase the greenhouse effect compared to that of carbon dioxide, considering a given period of time (generally 100 years). For example, according to data from the Intergovernmental Panel on Climate Change (IPCC), methane has 28 times more GWP than CO₂ and NO 265 times more.
How is it calculated?
The carbon footprint of any activity or product is the result of the sum of the emissions of all the greenhouse gases used to obtain it multiplied by their corresponding global warming potential. All this expressed in kilograms of CO₂.
HC is usually expressed in kg of emissions per kg of product mass (for example: 1.2 kg of CO₂e per kg of bread consumed), in kg per km traveled (for air travel, for example) or in kg per area (CO₂e emitted per km² deforested).
Emissions are calculated by adding those produced in the life cycle that we are considering. For example, to calculate the carbon footprint of a food we should add the emissions that have been produced in the cultivation, transformation, transport, storage and distribution of the product, until it is purchased by a customer in the supermarket. This involves estimating the emissions produced by all the inputs and energy required in plowing, sowing, fertilizing, etc.
In addition, it must be taken into account that some phases of the life cycle may involve absorption of CO₂. In that phase, it would not be an issuer but a sink, including itself with a negative value in the total calculation.
Carbon footprint of organizations, products or services
The European Union has been betting on the development of methodologies that allow the calculation, certification and standardized communication of the carbon footprint of products and organizations, as shown in the pilot projects executed in recent years.
The standards or regulations for the calculation of the HC are usually distinguished according to their scope of application. On the one hand, those that apply to organizations and, on the other, those that apply to products, services or events.
Ideally, the HC calculation would be accessible to any consumer who wants to know the climate impact of what he is buying: food, clothing, transport, etc., but currently this information is only available on some products. It is routinely incorporated in airline tickets, while in food it is very rare.
If consumers had carbon footprint data, those with the greatest environmental commitment could use it to make more informed decisions. Those producers that have more energy efficient procedures could prevail, either because they are in closer places (proximity trade) or because they use low-emission energies.
How to know and reduce your carbon footprint
Another way to be more aware of our emissions is to calculate the carbon footprint of our specific activity, over a long period of time (generally one year). This allows us to get a better idea of the climatic impact of our habits, knowing the sectors where it can be much superior compared to other people with similar conditions to ours (type of work, age, income, etc.).
To this end, different HC calculators, freely available on the internet, which provide a quantitative estimate of personal emissions, as well as of the effectiveness of different climate change mitigation measures. Recently, we have developed a HC observatory, which includes an example of this type of calculator.
In a recent study Regarding the factors of the carbon footprint in Spain from a sample of 1 000 people, we observed that the HC of consumption accounted for 73% of the total emissions of the country. The most important sectors are transport and food, which account for 78% of the total.
The main determinants of the carbon footprint were age (lower for the youngest and the oldest), income level (higher income, higher HC) and type of work (with higher footprint for rural jobs) . The internal factors (knowledge, level of commitment) were not so explanatory, except for CH linked to food.
Interestingly, we observed that the level of climate activism was not linked to the personal carbon footprint, which may indicate a disconnect between commitment and habits or a lack of information on HC associated with specific activities.