Studies undertaken by an American consulting firm Hart Energy and Dutch CE Delft both showed that ETBE offered an additional CO2 saving versus ethanol; typically 24kg of CO2-equivalent/GJ. In effect, replacing directly blended ethanol with ETBE can save 4 million tons per year of CO2 emissions.
The saving occurs because blending ETBE results in more pronounced modifications of the refining operations as it provides the petrol pool with more octane barrels than ethanol alone. This more than compensates for the energy consumed by the additional processing step.