Relative reduction index
The above fuel performance at delivery and fuel measurement system provides a) a baseline for the existing fleet (just multiply the fuel consumption by 3.17 to calculate CO2) and b) a method for measuring actual consumption and thus subsequently fuel reduction.
Any fuel and emissions reduction technology must be independently verified (Greenwave's is verified by a leading Classification Society; Lloyds Register).
Thus the technology reduction percentage can be verified by actual performance on voyage.
Ships would be indexed on 100 on their 'ex yard' rating and reduce in percentage for each emsission technology they adopt.