Page 149 - Advances in Eco-Fuels for a Sustainable Environment

120 Advances in Eco-Fuels for a Sustainable Environment

difficult to recycle. The utilization of these fractions for energy purposes should be
further investigated (Statistical Review of World Energy, June 2016) [3]. According
to certain studies, the energy has been utilized from gas approximately next 150 years
and coal for long period [4]. Consequently, the researchers and the analysts of the
whole world currently endeavour to find a new alternative energy for the future, while
seeking to develop innovations allowing to re-use the substantial surpluses like a
source of vitality.
Waste materials can be of many types, mainly biodegradable such as biomass and
nonbiodegradable such as plastics, waste oils, metallic wastes, and many more. Many
research works have addressed the application of discarded lubricating oils from waste
oil for the diesel engine as a source of energy [5, 6]. The surplus lubricating oils can be
reclaimed as fuel or finished into diesel-like fuel. Every year, about 40 million metric
tons of waste engine oil are generated, and around 60% of the waste is particularly
misused. Less than 45% of the available surplus oil was gathered universally in
1995 [7].
Waste lubricating oil is hazardous and toxic as it contains additives such as lead,
zinc, phosphorous, magnesium, etc. [8]. The methods adopted to recycle and reuse the
waste oil vary from one country to another. There are various thermochemical
methods available for the conversion of waste lubricant oil to some useful energy.
The thermochemical conversion processes are combustion, gasification, and
pyrolysis.
Pyrolysis occurring in the absence of oxygen is thermal decomposition to extract
liquid oil, gaseous fuel, and solid char. The yield of these three products varies
according to the variation of the operation parameter [9, 10]. There are various
methods available for heating the waste lubricant oil. Among them, conventional
heating and microwave heating have been carried out previously. Real world wastes
can be treated very efficiently in the microwave pyrolysis process as compared to the
conventional pyrolysis process. In the traditional pyrolysis technique, the heating
mechanism is less efficient and slower as it is based on conduction and convection,
whereas in microwave pyrolysis it heats all the substances equally due to the diffuse
character of the electromagnetic field. Thus, microwave pyrolysis provides equal dis-
tribution of heat and efficient heat transfer, and heating methods can be controlled
easily. Microwaves penetrate and create the hotspot only on dipole materials. So,
the hotness created substantially on the pyrolysis feed causes higher process efficiency
than conventional heating [11].
Huang et al. [12] states that microwave heating is better than conventional heating
because of various advantages. Hotspots, which form under microwave irradiation,
would have a significant influence on the return and features of microwave processing
products. The solid goods of microwave pyrolysis at proper microwave power levels
can have high heating values and specific surface areas with higher gas and solid
yields but lower liquid yield than conventional pyrolysis. By using microwave pyrol-
ysis, almost half the lignocellulosic biomass can be converted into a gas product,
which is mainly composed of H 2 ,CH 4 , CO, and CO 2 , with more bioenergy because
of its high H 2 and CO yields. The addition of proper catalysts provides a substantial
influence on the product selectivity of microwave pyrolysis. The gas and liquid yields