Although it is part of our everyday vocabulary, the term "carbon footprint" is not well understood by most people who use it. What it actually refers to is the total Greenhouse Gas (GHG) emissions, represented as tons of carbon dioxide equivalent (tCO2e), of a person, action, event, product, service or others. By definition, carbon footprint has to include GHG emissions from all sources.
Carbon footprint assumes great significance today with the alarming rate of global warming and climate change. The cause-and-effect relationship between GHG emissions and global warming is well established and accepted. Therefore, carbon footprint represents a direct measure of human contribution to global warming and climate change.
Carbon footprint is the key metric on which corporate emission reduction plans are built and managed.
The Paris Climate Agreement reached in 2015 aims to limit global warming to below 20C above the pre-industrial average temperature. The Agreement represents the recognition of climate change as the biggest threat of the century and our attempt to avoid the possible disastrous outcomes of it. Staying within the 20C global warming target requires steep cuts in GHG emissions. Carbon footprint, being the measure of GHG emissions, therefore becomes the key tool to manage global warming.
Reducing GHG emissions starts with carbon accounting or carbon footprinting, which involves identifying relevant GHGs, their sources, and calculating the carbon footprint over a period. The GHG Protocol of the World Business Council for Sustainable Development (WBCSD) is typically followed in calculating the carbon footprint. The Intergovernmental Panel on Climate Change (IPCC) has identified several GHGs including CO2, methane and N2O, among others. Of these, CO2 is the most abundant and constitutes nearly 75% of the anthropogenic GHG emissions. Therefore, it is not uncommon to find the term GHG emissions used interchangeably, with CO2 emissions, carbon emissions or simply carbon.
Based on the nature and source of GHG emissions, they are categorized into Scope 1, Scope 2, or Scope 3 emissions. The total carbon footprint should include all relevant scopes of emissions.
- Scope 1 emissions represent the direct emissions caused by the entity for which it is being calculated. These typically include emissions from the combustion of fuels that the entity has paid for—such as for DG sets, boilers, own vehicles, etc.
- Scope 2 emissions represent indirect emissions from the use of electricity (produced using fossil fuels) supplied from outside.
- Scope 3 emissions represent all other indirect emissions, such as those from transport of raw material and products, business travel, employee commutes, etc.
When reporting the carbon footprint of a product, it is important to understand the terms life cycle carbon footprint and embodied or embedded carbon footprint or emissions. Most products have three phases in their life: the production phase, the use phase, and the post-use phase. All three phases contribute to their lifecycle carbon footprint. When comparing products on the basis of carbon footprint, it is important to compare their lifecycle carbon footprints. The term embodied or embedded carbon footprint of a material or a product refers to the emissions that have already occurred in producing the material or the product. The lifecycle carbon footprint includes the embodied carbon footprint.
Today, carbon footprint calculation and reporting have become a part of mainstream corporate activities. Many companies report their carbon footprint through sustainability reports and/or the Carbon Disclosure Project (CDP). Carbon footprint is the key metric on which corporate emission reduction plans are built and managed. Many large companies have extended their emission reduction plans to their supply chains as well. In the coming decade, carbon footprint accounting and management is expected to become universal as the fight against global warming and climate change intensifies in our efforts to stay within a 20C temperature rise.