As governments and industries worldwide prioritize sustainability and resource efficiency, re-refining is gaining popularity in the lubricants industry. It serves as a viable strategy for managing waste oils responsibly while supporting circular economy initiatives. But what is re-refining, and how is it done? Re-refining of used lubricating oils is an advanced recycling process that restores spent oils to high-quality base oils suitable for reuse in various applications.
Re-refined base oils are a fourth descendant of crude oil. Initially, crude oil is extracted from various oil wells worldwide and processed in a crude oil refinery through processes such as atmospheric distillation, vacuum distillation, dewaxing, and solvent extraction. The petroleum products from this processing include gasoline, diesel, kerosene, bitumen, Liquefied Petroleum Gas (LPG), naphtha, and virgin base oil, among others.
The virgin base oil produced from the crude oil refinery is blended with additives to produce various grades of finished lubricants. These finished lubricants are used in industrial, automotive, and consumer sectors to protect equipment from premature failure due to friction between moving parts. After many hours of use, the Used Lubricating Oil (ULO) becomes unsuitable for continued use due to contamination and loss of key lubrication characteristics, and it is replaced with new lubricant.
The ULO can be discarded in various ways that are harmful to the environment, causing air, water, or soil pollution. The best practice regarding recovered ULO is to send it to the re-refining plant facilities, where it is processed to become oil that is suitable for blending with additives to become lubricating oil again.
Mduduzi Khanyile is a seasoned professional in the energy, petrochemical, lubricants, and chemicals industries with 25 years of experience. He has worked in technical, strategy and sales roles for major companies in the industry including Sasol, Engen Petroleum and FFS Refiners. His educational background includes MBA from UKZN and Bachelor of Technology in Chemical Engineering.
Acid–Clay Treatment Process
This process is one of the old treatment methods for re-refining used oil, where solid and liquid contaminants are removed from ULO and then treated with sulphuric acid, which acts as a catalyst that promotes polymerization reaction of unsaturated hydrocarbons. The acid reacts conversely with oxygen compounds, sulphur and nitrogen-based compounds, sludge and gum, asphaltic substances, and metallic compounds. These contaminants either precipitate out or form acid sludges, which are later separated. After acid treatment, the mixture is allowed to settle or is centrifuged to separate the acidic sludge (containing impurities) from the oil.
The partially purified oil is then passed through or mixed with activated clay (fuller’s earth or bentonite clay). The clay absorbs colored compounds and any other remaining impurities. The clay, along with absorbed impurities, is filtered out, leaving behind a clearer, decolorized, and cleaner oil.
This process was popular because the cost of setting it up is relatively low, and it requires simple equipment, making it ideal for small operations. The downside, however, is the adverse environmental effects, which are counterintuitive to exploring re-refining. This process produces acidic sludge that is hazardous and difficult to dispose of.
The 3 basic processes that may be used to re-refine ULO to obtain high-quality base oil are acid-clay treatment, solvent extraction, and catalytic hydrotreatment.
Solvent Extraction Process
The acid–clay treatment process was largely replaced by the solvent extraction process, where the acid is substituted by an environmentally friendly solvent that is recycled during the process. This process begins with filtering the used oil to remove large particulates, followed by dehydrating it through heating to remove water content. A selective solvent (such as propane, butanol, MEK, or furfural) is mixed with the dehydrated oil. This solvent selectively dissolves undesirable components (e.g., additives, oxidation products) while leaving the base oil.
The mixture separates into two distinct layers: the solvent-rich layer, which contains contaminants and additives, and the oil-rich layer, containing the purified base oil. Separation can be enhanced by using tanks or centrifuges. The solvent is recovered through distillation and reused in the process, making it a cost-effective and sustainable approach. The oil may undergo clay treatment, hydrotreating, or blending with additives to improve its final quality.
With increasing environmental regulations and demand for high-quality re-refined base oils, solvent extraction is gaining popularity as it strikes a balance between efficiency, safety, and sustainability.
The latest technology to achieve the best base oil qualities of the dehydrated ULO is a hydrogenation process. It involves treating the oil with hydrogen gas under high pressure and temperature in the presence of a catalyst to remove impurities and improve oil quality.
Hydrogenation Process
The latest technology to achieve the best base oil qualities of the dehydrated ULO is a hydrogenation process. It involves treating the oil with hydrogen gas under high pressure and temperature in the presence of a catalyst to remove impurities and improve oil quality. The ULO is first cleared of solid contaminants and water through filtration and distillation, respectively. The pre-treated oil is mixed with hydrogen gas. The mixture is passed through a reactor containing a metal catalyst (commonly cobalt-molybdenum or nickel-based catalysts). The conditions for the reactor are usually a temperature of 300–400°C and a pressure of 100–300 atmospheres.
Hydrogen reacts with and removes harmful impurities, such as Sulfur, Nitrogen, Oxygen compounds, and Chlorinated compounds. It also saturates unsaturated hydrocarbons, improving the stability and oxidation resistance of the oil. After hydrogenation, gases and by-products are separated. The resulting oil is then filtered, cooled, and blended with additives as necessary to meet the desired specifications. Hydrogenation is increasingly favored due to the growing demand for high-performance, eco-friendly lubricants and stricter environmental regulations. It allows re-refiners to produce Group II and Group III base oils, which are suitable for modern engines and industrial applications.
Re-refining has long-term benefits, which, if executed effectively, can significantly reduce environmental impact. Amongst many reasons for re-refining, a few worth mentioning are:
• Prevents or limits air, water, and soil pollution.
• Saves natural resources since 159 Liters of crude oil yield 1.89 liters of base oil compared to 159 liters of ULO, which yield 128.7 liters of base oil.
• Consumes approximately two-thirds less energy than producing virgin base oil.
• Reduces the carbon footprint compared to virgin base oil processing.
• Achieves a 40% savings with single-use and up to 70% with multiple-use of ULO.
• Reduces reliance on external oil supplies, reduces the delivery period, and excessive transport emissions for the regions that have no crude oil supply.
In Africa, the following countries have companies already re-refining ULO.
Egypt
MASAFEE
Established in 2016 and headquartered in Suez, Egypt, MASAFEE processes up to 24,000 tons of waste lube oil annually, producing high-quality regenerated base oils. Their product range includes SN150, SN300, SN600, and SN1200 base oils. MASAFEE is ISO 9001 and ISO 14001 certified, and it has also achieved REACH compliance, allowing it to export products throughout Europe. MASAFEE leverages Egypt’s trade agreements to facilitate efficient exports to clients across the Middle East, Africa, Europe, Asia, and South America.
EgyOil
EgyOil is a privately held Egyptian company specializing in the re-refining of used lubricating oils into high-quality base oils and finished lubricants. Established in 2007, the company operates under a license from the Egyptian General Petroleum Corporation (EGPC). EgyOil’s initial operations focused on recycling used oil as a preparatory phase before transitioning to a full-scale re-refining process.
Al Thurya Oil Refining Company (TRC)
TRC is a prominent Egyptian firm specializing in the re-refining of used lubricating oils into high-quality base oils. Established in 2017, TRC holds a unique export license from the Ministry of Industry and the Ministry of Oil for the re-refining of used and waste oil in Egypt. The company has a daily production capacity exceeding 100 tons, utilizing technologies such as vacuum distillation and hydrogenation to produce a range of base oils, including SN 100, SN 150, SN 300, and SN 500.
Alexandria Petroleum Company (APC)
As a subsidiary of the Egyptian General Petroleum Corporation (EGPC), APC operates a dedicated Re-refining Spent Oil Unit designed to process used oils into base oil. APC established its Spent Oil Re-refining Unit in 1997. This facility was designed with a processing capacity of 30,000 tons per year.
Apart from the above companies refining the ULOs in Egypt, other companies are playing supporting roles, such as collecting used oil and delivering it to refiners. One of these companies is Misr Petroleum. It collaborates with the Cooperation Petroleum Company in collecting used oil from various distribution companies. The collected oils are typically supplied to specialized re-refining facilities for processing and reuse.
South Africa
Flexilube
Established in 1984, the company re-refines used lubricating oils back into good-quality base oils. It collaborates with its associate company, Environmental Waste Oil Recycling (EWOR) (Pty) Ltd, which specializes in collecting waste lubricating oil. EWOR ensures that collected oils are managed and transported in compliance with environmental regulations. In 2023, Flexilube was honored with the National Processor of the Year award by the ROSE Foundation, acknowledging its exceptional service and significant contributions to used oil recycling in South Africa.
FFS Refiners
Established in 1974, Fuel Firing Systems (FFS) has developed a national footprint with five manufacturing sites and nine ULO collection points. FFS employs advanced technologies, including high-pressure hydro-treaters, to process collected ULO into base oils that meet or exceed Group I international standards.
FFS promotes the responsible collection and processing of used lubricating oils. The company also collaborates with various stakeholders to enhance the efficiency and reach of its ULO collection network.
Another company in South Africa involved in re-refining is Motolube, which specializes in collecting and processing used lubricating oils, transforming them into high-quality base oils suitable for blending into new lubricants.
The competition for used lubricating oil as an alternative fuel poses one of the biggest challenges for the re-refining sector. ULO is used as a heating fuel, as it is the most cost-effective liquid fuel alternative compared to diesel for cement, brick, or textile industries.
When discussing South Africa’s lubricant re-refining landscape, the discussion would not be complete without talking about the ROSE Foundation. The company was formed in 1994 in South Africa as a voluntary organisation funded by oil majors and importers of lubricants. The main duties of the ROSE foundation are:
• Encourage collection, transportation, storage, and disposal of ULO through safe and environmentally best practices.
• Provide incentives and training to collectors and processors.
• Reliably record and maintain ULO collections for future reference and accountability.
Tunisia
Tunisia’s re-refining industry primarily focuses on recovering base lube oil from used lubricating oils. A company like New Lubricants Company (NLC), for example, collects used motor oils, re-refines them, and sells the re-refined base oil to local oil blenders. NLC commenced production in July 2020. Another company in this country is SOTULUB. The Société Tunisienne de Lubrifiants (SOTULUB) was established in the late 1980s, and it operates a re-refining facility in Bizerte, which was initially commissioned with a capacity of 16,000 tons per year and later expanded to 20,000 tons per year by 1999. The company produces regenerated base oils, such as HR150 and HR350.
Challenges facing re-refining in Africa
While in the countries highlighted above re-refining is already happening, it still faces major challenges outlined below that must be overcome.
The competition for ULO as an alternative fuel poses one of the biggest challenges for the re-refining sector. ULO is used as a heating fuel, as it is the most cost-effective liquid fuel alternative compared to diesel for cement, brick, or textile industries. This undercuts re-refiners who need the same oil as a raw material for higher-value products.
Secondly, many African countries lack an organized system for ULO, leading to widespread improper disposal (e.g., dumping or burning). This affects the volume and quality of feedstock available to re-refiners. Thirdly, re-refining plants require significant upfront investment in technology and environmental controls. Operating costs can also be high due to the need for skilled labor, imported equipment, and chemicals. Such high investment commitments may only materialise on the back of a guaranteed contracted offtake of the base oil for a long term to achieve the return on investments.
Lastly, re-refined base oils often face stigma as being inferior, despite meeting quality standards, and hence should be sold at a very low price. The lubricant blenders regard re-refined base oil as a distinct product class and would opt for the re-refined base oil option if it is of a very high-quality and priced significantly lower than the virgin base oil option.
Conclusion
While the challenges are prevalent, there is still room for growth in this sector. It will take the effort of the Private and Public sectors to collaborate and develop policies that will support re-refining as well as investing to set up processing plants. To ensure re-refining takes root in Africa, all hands from the different quarters related to the lubricants industry will have to be on board. The future for re-refining waste oils is promising.