Page 28 - Advances in Eco-Fuels for a Sustainable Environment

Introduction to sustainable and alternative ecofuels 5

depleting total oil reserves as well as future fuel security. The fuel price has also been
increasing over the last few decades in a long-term comparison. However, the oil price
has been quite stable in recent years. The largest share of fossil fuel is mainly con-
sumed by the fast-growing transport sector (including aviation, road transport, etc.)
around the world. The huge consumption of fossil fuel by the transport sector creates
serious environmental pollution. One of the key tools to tackle this situation is an
alternative fuel for the transport sector that is renewable, biodegradable, and, impor-
tantly, low pollutant-emitting. It follows that the use of aviation biofuel and biodiesel
could be a promising solution for future energy security and environmental
sustainability.

1.2 Is ecofuel a possible solution for future energy
security and environmental sustainability?

Ecofuels are renewable biofuel produced from biological resources such as
vegetable oil, animal fat, or green wastes, which are mainly composed of fatty acid
methyl esters and fulfill the requirements of the ASTM D6751 biodiesel standard
[10, 17]. In other words, ecofuels are liquid fuels that can be extracted from lignocel-
lulosic biomass and waste, including animal fats. The ecofuels are of different types
that include bioethanol [18], renewable methanol [19], aviation biogasoline [6], bio-
diesel [20, 21], biogas [22], biobutanol [22], and biohydrogen [23]. These fuels can
replace and serve as alternatives to fossil fuels. There are some excellent benefits
in using ecofuels because they are nontoxic, biodegradable, have low emissions,
and are safer and environmentally acceptable fuels [24, 25]. In addition, environmen-
tal carbon can be recycled through plants from which it can be extracted as fuel to
produce energy. It can also be described as carbon recycling renewable energy.
Fig. 1.5 illustrates the lifecycle of ecofuels, showing different steps for carbon
recycling.
As shown in Fig. 1.5, the ecofuel lifecycle involves steps such as feedstock prep-
aration, processing, transportation, and usage in the transport sector, including the avi-
ation sector. Compared to fossil fuels, the use of ecofuels produces lower GHG
emissions, which can also be recycled by regrowing the feedstock plants. The sum-
mation of carbon emissions from cultivation machines, processing equipment, trans-
portation, and combustion is almost equivalent to the amount extracted by the
feedstock plants from the environment as they regrow. For this reason, ecofuels are
also called carbon neutral, renewable biofuel. There are some other benefits in using
ecofuels, namely that they are a sulfur-free fuel that can reduce GHG emissions by up
to 60% compared to fossil fuels, as reported by Hoekman and Robbins [26] and
Mofijur and Rasul [27]. Another benefit of using ecofuels from second-generation
feedstocks is to remove pressure from food and land usage, as discussed by Azad
and Rasul [28]. Therefore, ecofuels have a strong sense of balance between agricul-
ture, the environment, and economic development, as reported by Demirbas [8] and
Meher and Vidya Sagar [29].