In order to generate results, GaBiwas used to perform a balance
of flows, which is a function that takes into account all the relevant
flows into the different processes in the life cycle and all the relevant
flows out of those processes before computing the net environmental
impact. The functional unit for LCA was one roll of
asphalt roofing product (1 roll ¼ 1 square ¼ 100 ft2), which weighs
49.9 kg. The results have been normalized by taking the overall
mass in each category and dividing by the total number of rolls
produced in a year, which was 60,000 rolls in 2010. It may be noted
that, although 60,000 rolls were produced, only 43,563 rolls were
delivered as shown in Table 3.