A carbon footprint of products (goods and services), or a product’s GHG inventory, is the compilation and evaluation of the inputs, outputs, and potential GHG impacts of a product system throughout its life cycle (WRI and WBCSD, 2011). 

 

Firstly, the life cycle stages are listed and interrelated. These key stages include the extraction and transformation of raw materials, provisioning, manufacturing and packaging of the product in question, its use and ultimately its end of life management (reuse, recycling and disposal).

The GHG emissions that arise from these stages are then compiled and expressed in terms of a functional unit determined by the function of the studied product. The quantified emissions are then translated to an impact on climate change through their respective global warming potential (GWP). The final results represent the product’s carbon footprint, or GHG inventory.

The links between the carbon footprint and LCA

The carbon footprint of a product, or the inventory its life cycle GHG emissions, represents its impact on climate change. Hence, it is a subset of the life cycle assessment.

In fact, the LCA measures the potential environmental impacts of a product, process or service over its life cycle. In addition to GHG, the LCA takes into account all other material and energy inputs and environmental releases and assesses their potential impact on the environment.

The spectrum of impact categories is broad and includes: human health, ecosystem degradation, climate change and natural resource depletion. LCA is therefore a "multicriteria" analysis that assesses multiple impacts.

The carbon footprint is essentially "monocriterion" as it focuses on a single environmental impact, climate changes.
Both methods rely on functional approaches for impact assessment. In fact, a "functional unit", or quantified performance of a studied product, serves as the basis for analysis and enables comparability between products with similar functional units.