Work with the venue onsite waste.

Be accountable for waste volumes, change how you and the venue approach waste collection onsite - set targets, measure how many skips or unreasonable waste you are charged for each event and cut that by a % next time

Push culture change - aisles full of waste encourage aisles full of waste!

Bring in a waste specialist. 

Look at the optimum price point for correct waste disposal vs a contractor not using it because it's too expensive. Ops responsibility should not be over when the waste leaves the building on a contractors truck.