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المجلد الثالث و ال
Re-refining of Used Lubricating Oil and its Economic and Environmental Implications
52
Likewise, re-refining represents an environmental benefit over primary production of
virgin base oil from crude oil. As illustrated Figure 28, the benefits of re-refining are not
limited to displacing atmospheric pollutants but extend to resource conservation.
Primary production of lubricants contributes significantly to oil depletion. At least 600
tons of lubricating base oil can be recovered from each 1000 tons of used oil, whereas
6000 tons of crude oil is required to produce this amount of lubricating base oil
(Bridjanian et Al, 2006). Moreover, environmental issues such as global warming,
acidification, fine particulates emission, etc, are attenuated, but not eliminated, when re-
refining is used in lieu of primary production.
6.1
Environmental implications of used oil burning
When used lubricating oil is burned as a fuel for energy recovery, the benefits are
limited. In a controlled combustion process such as in steel mills or cement kilns, used
lubricating oil can be burned in order to recover its heating value. According to EPA
(1996), one gallon of used oil processed for fuel contains about 140,000 BTUs of energy.
The heat recovery option certainly provides valuable energy, but the product is
destroyed and cannot be recycled again as in re-refining. This alternative, however, is
not without problems for burning of used oils generate toxic emissions and non
degradable products. According to US EPA, potential pollutants include carbon
monoxide, sulfur oxides, nitrogen oxides, particulate matter, toxic metals, organic
compounds, hydrogen chloride and global warming gases (carbon dioxide, methane).
Moreover
, if burned at low temperatures, it releases a range of toxic compounds directly
into the atmosphere. Thus, for each ton of used oil burned, 2.9 tons of CO2 are released
into the environment. What´s more, the used lube oil which is burned produces a
carbon footprint eight times greater than re-refining (Gray, 2014). It is estimated that
every one hundred million gallons of re-refined used oil consumed avoids over 650
million metric tons of greenhouse gas emissions- that´s equal to the carbon sequestrated
by growing over 19 million trees for 10 years in an urban area (Knapp, 2013). In short,
uncontrolled burning results in significant levels of hazardous emissions to the
atmosphere.
6.2
Unsafe disposal of used oil
When used oil cannot be re-refined or recycled as fuel, it is often disposed of in landfills
or burned without heat recovery. In both cases, the heating value is lost. If improperly
disposed of (i.e. illegal dumping), used lube oils can pollute the environment to a point
of no return. It is estimated that each volume of used oil can pollute at least 250000
volumes of water (Bridjanian et Al, 2006), hence its disposal in landfills can pose serious
environmental problems. Studies have shown that it takes up to 20 years for a