If you know the flue gas composition you should know all of those emissions seeing as they would be part of it. If you don't actually know the complete composition then you will not be able to calculate these emissions.
What you can do though is assume all of the nitrogen and sulphur gets fully oxidized. This will give you worst case scenarios for both those components. CO is impossible to calculate as CO2 emissions probably assume all carbon is oxidized leaving none for CO. PM cannot be calculated but you could possibly assume that all of the ash goes out the stack, or at least to some sort of emission controls. This will probably give you a figure that is too high since biomass boilers have bottom ash.
These methods will all give you worst case scenarios, best bet is to find someone where you work who can provide a set of typical figures.