The rate of Bioremediation of ex-situ crude oil contaminated soil to which Palm Bunch Ash was added has been studied in this work, based on Total Petroleum Hydrocarbon content. Four samples each were contaminated with 100g, 200g and 300g respectively of crude oil and 0g, 100g, 200g and 500g of Palm Bunch Ash were added respectively to the four samples to produce twelve samples. The samples were analyzed for TPH at two weeks interval after pollution for eight weeks, and the experimental data fit a rational model. Results reveal that the rate of PBA enhanced Bioremediation can be modeled as a second order process with the difference between the contaminant concentration at any time and the ultimate contaminant concentrations as the driving force. PBA enhances the rate of Bioremediation especially at low levels of crude oil contamination, because at higher levels of crude oil contamination, the reduction in the ultimate contaminant concentration it achieves is almost nullified due to a corresponding decrease in the Bioremediation rate constant.