Page 400 - Advances in Eco-Fuels for a Sustainable Environment

354 Advances in Eco-Fuels for a Sustainable Environment

particulate matter (PM), oxides of nitrogen (NO x ), carbon dioxide (CO 2 ), and carbon
monoxide (CO), which are the main contributors to environmental pollution and
global warming [2]. In addition, fossil fuel depletion, an increase in global warming,
and stringent emissions norms have stimulated research interest in alternative renew-
able energy. The major renewable sources are solar energy, wind energy, tidal energy,
and biofuels. Among all those sources, biodiesel is a predominant alternative fuel
because it is renewable, nontoxic in nature, free from sulfur, and environmentally
friendly [3]. Biodiesel is a methyl or ethyl long chain fatty acid ester derived from
edible and nonedible oil, animal fats, and waste frying oil (WFO) [4]. Edible and non-
edible oils are sunflower, palm, soybean, jatropha, pungamia, etc. WFO-based biodie-
sel is cheaper than virgin oil-based biodiesel because of low feedstock cost and the fact
that it avoids water and soil pollution by reusing the WFO in the form of biodiesel [5].
Chen et al. [6] observed that the direct disposal of WFO causes water pollution and
blockage in water drainage system. Hence, WFO should be pre-treated before dispos-
ing to the environment. The cost for the pre-treatment process is quite high. WFO can
be used as a feedstock for biodiesel production to avoid this problem. Moreover, WFO
based biodiesel partially replace the petroleum diesel fuel and also it solve the problem
of energy shortage and environmental pollution. The major WFO sources are from
restaurants and domestic use. It has been found that nearly 10 million tons of WFO
are generated from the United States every year. Salad oil and animal fat have gen-
erated 4.5 million tons per year in China [7]. WFO, including rapeseed and sunflower
oil, accounts for about 0.7–10 million tons per year in Middle East and European
countries [8].
Diesel engines have the problem of injector choking and piston ring sticking due to
using vegetable oil as a fuel, because it has low volatility, high density and viscosity.
Engine modification or fuel modification is required to achieve better engine perfor-
mance and lower emissions as noticed by Jaichandar et al. [9]. Thus, raw vegetable oil
viscosity should be reduced to get normal combustion in diesel engines. The trans-
esterification process, the esterification process, pyrolysis, and the microemulsion
and dilution methods were employed to diminish the viscosity of raw vegetable
oil. Pyrolysis is the process of thermal decomposition of vegetable oils, which reduces
the viscosity of the oil. Gaseous products, alkanes, alkenes, aromatics, and carboxylic
acids are produced during the pyrolysis process. Direct blending of oil with diesel and
emulsification of fuel on the diesel engine causes coking, thickening, gelling of lubri-
cating oil, oil ring sticking, and carbon deposits, which reduces the diesel engines per-
formance characteristics and combustion characteristics, as noticed by Demirbas [10].
Kulkarni and Dalai [8] investigated the biodiesel synthesis from WFO using a KOH
catalyst. The reaction conditions of methanol to oil ratio 7:1, 50°C temperature, and
0.75wt% of catalyst concentration achieved 90% biodiesel yield. Babu and Anand [5]
conducted the experiment on biodiesel production from WFO through the trans-
esterification process with reaction conditions of 55°C reaction temperature,
150min of time, 6:1molar ratio, 1.5wt% of catalyst, and 975rpm of stirrer speed; they
obtained the maximum yield of 97.4%. Al-Hamamre and Yamin [11] observed that
the biodiesel yield of 98% was obtained from WFO using KOH as a catalyst. Abdullah
et al. [12] extracted the biodiesel from palm oil sludge using KOH catalyst through