According to PlasticsEurope The ?carbon footprint` is an unreliable indicator of environmental sustainability.
In recent years, the ?carbon footprint` has become a popular way of comparing the relative environmental impact of goods, services or industrial activities. Companies have seized on it as a way of building a competitive advantage ("our product has a smaller footprint than yours"), or measuring improvement ("a smaller footprint means a better product"), while environmentally conscious procurers and consumers use it to decide between competing offers. And yet, in practice, simply comparing carbon footprints is rarely fair or scientific. Indeed, as a measure of environmental impact or sustainability, it can be quite misleading. There are three main problems.
The first problem is that many people have only a vague idea of what a carbon footprint is, or means. A carbon footprint measures the amount (expressed in units of CO2 equivalents) of greenhouse gases that enter the atmosphere as the result of a given activity or product. As such, there is nothing wrong with it, and sound environmental accounting methodologies are available for calculating it (ISO 14040, 14044 and 14064).
But the carbon footprint tells us only about carbon emissions; it says nothing about total environmental impact. To get an all-round picture, many other factors - acidification, ozone depletion, energy consumption, soil and water pollution, and more - need to be considered.
Unfortunately, many people simplistically tend to equate carbon emissions with overall environmental impact, although there is no direct correlation between the two. As a result, if people are invited to compare products purely on the basis of their carbon footprints, those who want to "do the right thing" for the environment may be led to make precisely the wrong choices.
The second problem is that the scope of the carbon footprint is usually too narrow. Any genuine measure of a product`s or an activity`s environmental impact needs to encompass its total impact over time, i.e., throughout its entire lifecycle. It also needs to consider the wider context. All too often, however, the calculation of the carbon footprint is limited to the production phase, and takes little or no account of the subsequent use and disposal phases. It also neglects contextual effects.