The oily sludge from crude oil contains hazardous BTEX (benzene, toluene, ethylbenzene, xylene) found in the bottom sediment of the crude oil tank in the petroleum refining plant. This study uses microwave treatment of the oily sludge to remove BTEX by utilizing the heat energy generated by the microwave. The results show that when the oily sludge sample was treated for 60 s under microwave power from 200 to 300 W, the electric field energy absorbed by the sample increased from 0.17 to 0.31 V/m and the temperature at the center of the sludge sample increased from 66.5 °C to 96.5 °C. In addition, when the oily sludge was treated for 900 s under microwave power 300 W, the removal rates were 98.5% for benzene, 62.8% for toluene, 51.6% for ethylbenzene, and 29.9% for xylene. Meanwhile, the highest recovery rates of light volatile hydrocarbons in sludge reached 71.9% for C₃, 71.3% for C₄, 71.0% for C₅, and 78.2% for C₆.

The sludge in this study was obtained from refinery crude oil storage tanks. It contained a high proportion of hydrocarbon composition and harmful substances (such as polycyclic aromatic hydrocarbons and benzene). Through the microwave irradiation treatment process, the harmful substances were removed from the sludge which was then recycled and combined with agricultural waste mushroom substrates to produce refuse derived fuel (RDF). The results showed that the calorific value of RDF was 7279 cal/g when the blending ratio (wt/wt) of oil sludge and mushroom substrates was 5:5. On the other hand, when the portion of the mushroom substrates was increased, the sludge became easier to ignite with better combustion reaction. When the blending ratio (wt/wt) was changed from 8:2 to 5:5, the ignition index and comprehensive performance index were increased by 51.9 and 50.2%. Therefore, mixing the sludge with agricultural waste mushroom substrates is in line with the concept of waste recycling and circular economy.