Considering that the unprincipled disposal of engine oil waste can pollute surface and underground water up to one million times its volume, the Iranian researchers produced an asphalt mixture based on this waste. According to the researchers, based on the results of the tests, the pollutant emission of this final product was less than the maximum allowed limit.

Alireza Ali Akbari, a PhD graduate of the Faculty of Civil and Environmental Engineering of Amir Kabir University of Technology, who has implemented this project titled “Production of an additive to improve the rheological and mechanical properties of asphalt mixture from engine oil refining waste” under the supervision of Dr. Ali Khodaei and Dr. Pourya Haji Karimi, faculty members of Amirkabir University of Technology, said: “Every year, about 20 thousand tons of waste materials known as ‘acidic sludge’ are produced from refining engine oil, which consist of sulfuric acid, vehicle engine chips, burned polymers and some used oil engine.”

Emphasizing that due to the excessive concentration of heavy metals and its acidity, acid sludge is classified as hazardous waste, he said: “Based on the studies, if this waste is disposed of improperly, it can contaminate surface and underground waters more than a million times its volume, which is considered a threat to the environment due to the volume of its production.”

Ali Akbari considered the principled and hygienic disposal of this waste to be accompanied by exorbitant costs and reminded: “Providing a suitable solution that can minimize the relevant costs in addition to the sanitary disposal of this waste can be a suitable solution to the challenge in the engine oil refining industry, and the use of this waste in the production of asphalt mixture is considered among the suitable solutions for the sanitary disposal of engine oil refining waste.”

This researcher of Amirkabir University of Technology emphasized: “Since the sanitary disposal of the waste produced from the refining of engine oil is accompanied by exorbitant costs, and this sanitary disposal is also very important from an environmental point of view, making the production of refined engine oil economical along with meeting the environmental standards is very important. By making the process of disposing the waste created from engine oil refining economical through providing a simple and efficient method, this research, in addition to solving the problem of engine oil refining industry, is a great contribution to improving the properties of asphalt mixture against rutting damage, humidity sensitivity and low-temperature cracking by replacing the obtained product as a part of asphalt mixture production materials.”

This graduate of Amirkabir University of Technology pointed out: “Considering the complex and unknown structure and function of engine oil refining waste, this study took a step by step approach, using the findings of the previous step in order to determine the path and approach of the next step. The first step identified and determined the main engine oil refining centers, the amount of annual waste production, the variety of waste and the identification and separation components of this waste, and the behavior of the samples was identified and determined through appropriate planning and using chemical and functional tests.”

Ali Akbari emphasized: “Due to the impossibility of using this waste directly in the asphalt mixture, methods applicable in the industry were used to modify the waste and by adding the product obtained from these methods to bitumen and asphalt mixture, its impact was measured based on engineering criteria. According to the results, the best method for this purpose was identified and its product, which is modified waste, was evaluated using more advanced and complementary tests.”

He added: “The obtained results were promising and led to the production of a valuable product for improving the properties of asphalt mixture. In the final step, in order to ensure the sanitary disposal of this waste in the road structure, pollutant emission environmental tests were used, and the emission values were lower than the maximum permissible limits with a significant confidence interval.”

The researcher of this project considered the selection of a simple and accessible method of acid waste neutralization by lime and the use of the obtained neutralized product as a substitute for stone materials in the production of asphalt mixture as one of the achievements of this research and said: “This achievement can be applied in oil refining factories as the producers of this waste.”