Julien’s expertise was built up through managing part of the French GHG and air pollution inventory system. This expertise is now applied in other countries in order to support them in developing sustainable inventory systems, QA/QC procedures, applying up-to-date requirements of MRV as a base of P&M and projection determination. The organization of Trainings and Workshop is key to develop exchange between experts from the same team or from different countries. The development of inventory data management tools is also part of the activity carried out and allowing maintaining Inventory systems over time.