The direct burning of used oils in conventional combustion devices can create serious pollution problems, such operations produce large quantities of heavy metal emission particles, toxic gases (SO2, NOx, HCI) and residue products, which are ranked among the most toxic in comparison with other environmental particles and, although this can be reduced by fitting pollution abatement equipment, this is not, in most cases, very practicable. The burning in specially designed waste incinerators can diminish these problems; however, the process is very expensive, particularly if they do not provide for energy recovery.
Most of the re-refining units in the small scale sector in India use the acid--clay process. This classical process, which once used to be the basic one all over the world, has the disadvantage of resulting in the generation of large quantities of hazardous and toxic acid sludge and clay contaminated with oil and heavy metals. For this. reason, the acid--clay process is not an environment friendly process and has been given up for some years in most countries including the USA, the European Union and other industrially advanced countries. Since this sludge contains a significant amount of oil and has fuel value, it is presently also used in India as a fuel, e.g. in brick manufacturing units. Though this is a reuse of a resource, burning of acid sludge in brick kilns creates environmental problems by generating hazardous gaseous emissions, as the kilns are not properly equipped with air pollution control devices.
The bulk of used motor oil generated in India generally goes into undesirable applications and only a very small amount is currently re-refined. A large number of roadside garages, for example, drain used oils from automobile engines and there is no record of the next destination of such oils. Used motor oil is also burned, generally inlnadequate equipped installations.
Improperly refined used oils are often also used as spurious oil or as duplicates of branded oils. They are often sold in the market to truck and two-wheeler owners at cheaper rates. The use of improperly re-refined or spurious oil in automobiles could not only damage them faster, but would also lead to increased pollution load.
Burning or dumping of used oil is a luxury and a country like India, already crippled by a heavy import oil bill. Lubricant never wears out. It only gets dirty due to contaminants and the bulk of the hydrocarbons in it remain unchanged. Additives in oil are mainly degraded, re-refining of used lubricating oil is an intelligent strategy and the best disposal option. This not only provides the solution to the environmental problems, but also helps in conservation of an increasingly expensive, non-renewable petroleum resource.
The Waste Oil Management Rules 2000 the notification which mandates buy-back of re-refined oil by major oil companies. It draws a distinction between waste oil and used oil, and seeks to permit the import of used oil, provided it meets parameters given in a schedule.