Abstract
Waste engine oil contains hydrocarbons which are potentially carcinogenic. The objective of this study was to determine if organic
wastes, specifically cow dung (T1) and poultry manure (T2) can improve the microbial degradation of the hydrocarbons. A
questionnaire survey to determine generation, management and disposal of waste engine oil was carried out. A Complete
Randomized Design, with two treatments and three replications was used to set up plots at Makerere University Agricultural
Research Institute Kabanyolo (Uganda). Plots were intentionally contaminated with 2 Litres (L) of waste oil and after seven days
the treatments were applied at a rate of 50 tons/ha each. The control plots (T0) were not treated. Soil samples (0–30 cm) were
collected after 30 days and analyzed for pH, nitrogen, phosphorous, potassium, organic carbon, bacterial characterization and the
residual total hydrocarbon content. The obtained results showed that waste engine oil was poorly managed and disposed off to the
environment. There was an increase in soil pH, carbon, phosphorous, potassium and a decreased in nitrogen in the order T2 > T1 >
T0. There was no significant difference (p ≤ 0.05) between T1 and T2 which recorded average bacterial count of 7.62×107 cfu/g and
6.51×107 cfu/g respectively as compared to T0 with a count of 3.24×107 cfu/g. This implied that the organic wastes increased the
degradation of the hydrocarbons as compared to the control. Based on the results of this study, T1 and/or T2 may be considered by
regulatory agencies as treatment methods for waste oil pollutions.