For a given environmental issue, life cycle assessment comprehensively encompasses all processes and environmental releases beginning with the extraction of raw materials and the production of energy used to create the product through the use and final disposition of the product.
Keeping in mind that the product/system that is being talked about in the video is Energy and the functional unit is CO2/unit energy, in our case, the following explains how exactly LCA works:
To know more about how LCA is used to compare the various energy sources, read the Special report published by the World Energy Council below: ( Recommended Pages: 3, 6(E), 13, 19, 34, 55(7.2) )