Environmentally friendly fuel is produced from plants and trees and can fix CO2 in a season or yearly depending on the crop yield. The growth of fast food restaurants in the State of Kuwait has resulted in the accumulation of large quantities of partially oxidized vegetable oil used in frying burgers, breaded chicken pieces, and chips. In this publication, kinetics of the transesterification reaction is discussed in great depth to understand the true mechanism and to determine the optimum conditions for the maximum yield for the commercially viable esterification process of used oil/fat with supercritical methyl ethanoate.