The post about how BP is recycling the oil booms in the Gulf oil disaster got me to thinking about how oil is actually recycled and how pure it is afterwards. This is what I found out:
Industrial and automotive used oils are recycled at what are called “re-refineries”. These re-refineries receive the used oil in bulk, usually via large tanker trucks. After it is received, the oil is tested to determine suitability for re-refining. Once a shipment of used oil is deemed suitable, the water is removed in the first processing step. This dehydrating process also removes light fuels from the oil. These light fuels are actually used to power the refinery. After this process, ethylene glycol is removed for re-use in recycled antifreeze.
Then vacuum distillation is used to remove the fraction suitable for reuse as lubricating oil. This is referred to as the “Lube Cut”. This leaves other heavier oils and other combustion by-products for use in roadpaving. The lube cut next undergoes hydro treating to remove residual polymers and other chemical compounds, and to saturate carbon chains with hydrogen for greater stability.
The final oil separation, or “fractionating”, separates the oil into three different oil grades. The first are light viscosity lubricants suitable for general lubricant applications, then low viscosity lubricants for automotive and industrial applications, and finally high viscosity lubricants for heavy-duty applications.
The final production step involves blending detergent and anti-friction additives into these three grades of oil products. Then each product is tested again for quality and purity before releasing it to the public for resale.
So, how good is it? Experts agree that the re-refining process produces products indistinguishable from products produced by conventional refining. In some cases, it might be argued that recycled oil is even a little better.