EDF's analysis thus provides only a snapshot of facility pollution prevention performance, using data obtained on a particular date. Reported data may reflect different definitions of a facility. A variety of distinct processes may be closely located, though not always at the same address. Some facilities submit separate reports for each operation, while others aggregate wastes from all operations in a single report. EDF aggregated multiple, separate facility reports to the TRI and AIRS databases.
Facilities have different processes and products.
Differences in processes and products create differences in the types and quantities of waste generated. Facilities may have different utilization rates. Utilization rate is equal to actual crude oil processed divided by refinery capacity. The normalized performance indicators used in the ranking are based on refinery capacity, not the actual quantity of crude oil processed, a figure that is much harder to obtain. Because idle capacity costs money, however, refineries try to maximize their utilization rate.