A carbon footprint is the total amount of greenhouse gas (i.e., carbon dioxide, methane, nitrous oxide and fluorocarbons) that is generated by a person, organization, activity or product during every stage of the product's, project's or service's lifetime. This includes its raw materials procurement, manufacturing, shipping at all stages, use, and final disposal.
Carbon footprints are measured in metric tons of carbon dioxide equivalent (CO2e), which multiplies each type of emission by its greenhouse effect relative to carbon dioxide. Thus, for example, because methane is about 80 times more potent at causing global warming than carbon dioxide, each ton of methane emitted would be weighted the same as 80 tons of carbon dioxide, i.e., 80 tons of CO2e.
There is no simple method and no single method for calculating carbon footprints. Rather, they are estimated on the basis of criteria defined by the scientific community along with various statistical data. Fortunately, a number of online carbon footprint calculators have been developed which greatly simplify estimates.
There are several reasons that it is important to measure carbon footprints. One is that it helps individuals, businesses and countries in their decision making and to know if they are making progress towards environmental goals. Also, it can provide a competitive advantage for products or businesses that can show that they are more environmentally friendly.
As important as the concept of carbon footprints is, it needs to be stressed that this is only one aspect of environmental issues and does not include such things as habitat destruction, loss of biodiversity, loss of topsoil, ground water depletion and ocean acidification.
In fact, there can be conflicts with regard to both the environment and other concerns. For example, constructing a dam on a river can generate electricity to replace electricity produced by burning fossil fuels and thus could lower the carbon footprint for an electric power generating company, a region, or a country. But it could also damage habitat for fish and other wildlife along the river and possibly result in the extinction of some species.
Likewise, replacing internal combustion engine automobiles with electric automobiles could result in a reduced carbon footprint, at least if the electricity were not generated by burning fossil fuels. However, the production of electric automobiles is leading to the increased mining of rare metals in developing countries, which is causing severe ecological damage there. Electric automobiles also have a variety of additional disadvantages that are not included in carbon footprint calculations, including requiring massive allocation of resources for new infrastructure and creating more particulate matter from the abrasion of roads and road markings, because of their much greater weight, which can float in the air and be inhaled and can also enter water bodies and eventually enter the food chain.
Although the concept of the carbon footprint is without doubt an extremely important tool and a major step forward in dealing with climate change, it needs to be kept in context and regarded as just one measure of the environmental (and health and other) effects of products, projects and services. Hopefully, similar tools will be developed for estimating other forms of environmental damage.