The atom economy of a reaction is found from:
The atom economy works out to be 36.7%,
which is not very good! This means that considerably less than
half the mass of reactants ends up in the required product, even
if we assume 100% yield. In practice the yield is more likely
to be in the region of 88%, giving a figure of 32.3%, barely a
third of the reactant mass.
Sodium sulphite has uses in the wood pulp and paper industry,
and in several other processes, but the large amount of waste
produced is one of the reasons why the benzene sulphonation route
is no longer used.