Page 158 - Advances in Eco-Fuels for a Sustainable Environment

Microwave-assisted fast pyrolysis of hazardous waste engine oil into green fuels 129

them can be subjected to microwave pyrolysis (MP) for conversion into valuable
products.
About 75% of the weight of the vehicles is recycled every year and the remaining
25% is known as auto shredder residues (ASR). The ASR is obtained from the auto-
mobile after the separation of iron and steel particles through magnetic separation
[49]. These solid ASR materials cannot be disposed of through a landfill due to their
complexity. The ASR materials mostly consist of heavy metals such as zinc-lead and
copper. A Canadian ASR sample consists of 6% moisture, 18% metals, and 37% fines
as well as some other particles in small fractions such as plastics, woods, textiles, and
fiber materials. Because of complex chemical composition and diversity in the mate-
rials, heat treatment is emphasized by minimizing the mechanical recycling.
Thecurrent trendisformicrowavepyrolysisandplasmaarc thermaldestructionpro-
cess for low treating ASR for reducing costs. Donaj et al. [50] have developed a process
in which microwave pyrolysis and high-temperature gasification have been combined
to be used in ASR waste management. This method can be applied to automobile waste
(tires, wire tubes, oils), construction and demolition waste, residues from oil refineries,
and petrochemicals. In this method, metals can be preserved and organic wastes can be
converted into valuable products. The MP process occurs in molecular level thermal
decomposition at temperatures ranging from 275°C to 300°C [51]. The solid and liquid
products after microwave pyrolysis of ASR could be further subjected to high-
temperature steam gasification (HTSG) for fuel gas production [24].
Due to the fast depletion of fossil fuels, there is a need to search for alternate fuels
for internal combustion engines. Moreover, there is a requirement to discover new
alternative fuels due to a drastic increase in energy demand and regulations in emis-
sion norms. One of the methods to derive alternate fuels is the conversion of a waste
substance to energy. On the other hand, we have a large number of vehicles that offer a
significant amount of used engine oil every year. It is easy to derive usable and valu-
able products rather than to dispose of waste oil. The waste engine oil can be converted
into highly potential fuel through the pyrolysis method. This waste engine oil is envi-
ronmentally hazardous, and when mixed with nature it will cause pollution. Globally,
nearly 24 million metric tons of waste oil are generated every year. This high-quantity
waste is difficult to dispose of and to treat due to the presence of elements such as
polycyclic aromatic hydrocarbons (PAHs), soot, and impurities from additives such
as polychlorinated biphenyls (PCBs) and chlorinated paraffin [24, 52].
Recent studies have proved that the best disposal method for waste oil is pyrolysis.
The aim of recycling waste lubricant oil is through conversion into reusable products
such as gasoline and oil. It has been discovered that through microwave pyrolysis, they
can recover most of the commercially valuable products from waste engine oil [52].
Pyrolysis of waste oil can be carried out by mixing of excellent microwave receptor
materials such as particulate carbon [32]. More particularly, they understood the
potential for recovering gaseous hydrocarbons with liquid hydrocarbon oils con-
taining benzene derivatives, BTX, and light olefins. When compared with conven-
tional pyrolysis processes, the microwave pyrolysis process showed improved
cracking reactions [24]. However, there is a considerable effect of temperature on
the formation and overall yield of the recovered pyrolysis liquids and gases.