There are all kinds of sites with emission and emission intensity factors, what value do those numbers have?

The emission factors are often region-specific. It is good to see which organizations are behind them, and how old the figures are.

This is even more true for emission intensity factors. There are all kinds of factors floating around for which it is difficult to find out what the basis is, how they were determined, how old they are, and what assumptions lie behind them. With some research it is possible to find out, but it takes time and attention.