To serves two functions - relation-expressor (like prepositons normally do) and infinitive marker (really more like articles).
an innovative approach to reducing pollution ...
To is used to express a relation between the noun "approach" and "reducing pollution..." - that relation is "directing efforts toward X, X being a goal or desired result".
Objects of prepositions like other objects have to be a noun role - gerunds do that.
allowed the company to reduce
To here is just an infinitive marker. To reduce more or less "hangs" off of the verb "allowed" as something like an indirect object (to reduce answers "what?" for the verb "allowed"), though I'm sure it's precise grammatical function is something much more complicated and involves the word "complement".