Product carbon footprints are published to show the overall climate impact of a product. Usually the calculation methods follow the principles of a life cycle assessment (LCA2 (ISO 14040: 2 . An LCA covers many more aspects than just the climate impact and is used to document the overall sustainability of a product. We will only focus on the aspect of climate relevance, which is of major attention today. It should be noted however, that other aspects of an ecological assessment of products must not be neglected, and focusing only on climate impact can lead to overall misleading conclusions.
Some development of standardization initiatives is underway to harmonize and render more precisely the methods and procedures of carbon footprint calculations, for example, a Publicly Available Specification, PAS2050 , from the British Standards Institution. We distinguish two major scopes of PCFs; the cradle - to - gate and the cradle - to - grave scope. A cradle - to - gate scope covers all upstream activities, logistics, and production processes. The last step covered is the production unit for the respective product, potentially including a supply and distribution step to the point of sale. The cradle-to-grave approach also includes all steps downstream of the production. That involves supply logistics, downstream processing, packaging and particularly the use of the product and what happens to it at the end of life. Some cradle 2 to 2 grave footprints of various products can be found in  with explanations.
Many polymers and chemicals are intermediates and have their end use in manifold applications. For example window frames, cable coatings, toys, construction materials, electronic devices are all made of PVC. If we wanted to prepare a cradle-to-grave PCF for PVC we now have also to include downstream production and logistics, the different use phases and the question of end of lifetime, whether it will be recycled, incinerated or deposited. Lifetime and use 2phase vary from one-way products with a very short lifetime (e.g., food packaging) up to construction materials that might be in use for more than 100 years. We could use a representative subset of applications and use phases of some major routes. This expansion into multiple product lines is typical for intermediates and can lead to ambiguous results (Figure 1.4).
Raw Upstream Chemical Production DistributionProduct Material Processing Processing
Upstream: Unique identification of production route distinct footprint
Downstream: Manifold product & lifecycle routes Assumptions and vague approximations
More ambiguous footprint
Figure 1.4 Schematic contributions for cradle-to-gate and cradle-to-grave approaches for a typical chemical intermediate.
This can be avoided if the definition of a functional unit is used that determines the application.
Extensive literature on the topic is available elsewhere, for example, [9, 12-14]-We would like to highlight some important aspects for PCFs and focus on example illustrations.
The sections below make frequent use of the term -product - Here we focus mostly on a product defined in the conventional way as a tangible matter. However, one finds PCFs applied in a similar way to immaterial products like financial products, logistic services, consulting services, and so on.
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