Page 50 - Advances in Eco-Fuels for a Sustainable Environment

Ecofuel feedstocks and their prospects 27

Table 2.7 Main feedstock for biodiesel production and oil content [26]

Type of oil Feedstock Oil content %
Edible Soybean 15–20
Rapeseed 38–46
Sunflower 25–35
Peanut oil 45–55
Coconut 63–65
Palm 30–60
Nonedible Jattropha seed 35–40
Pongamia Pinnata 27–39
Neem oil 20–30
Castor 53
Other sources Rubber seed 40–50
Sea Mango 54
Cotton seed 18–25
Microalgae 30–70

Ethanol (CH 3 CH 2 OH) is one of the most promising alcoholic biofuels available on
the market today. It is a biomass-based renewable fuel produced by alcoholic fermen-
tation of sugars. As a first-generation fuel, its main feedstocks are sugarcane in trop-
ical areas (i.e., India, Brazil, Colombia) while corn is preferred in other areas (United
States, EU, and China) [29]. Ethanol can also be produced as a second-generation fuel
with lignocellulosic feedstock after milling, pretreatment, hydrolysis, and possible
detoxification prior to feeding to the biofermenters. For fermented sugar production
from starchy materials, processes such as milling, liquefaction, and saccharification
are used [30].
Although its energy equivalent is 68% lower than fossil fuel, its combustion is
cleaner because it contains oxygen. Ethanol is frequently used for blended gasoline,
in different concentrations: E15 (15% ethanol, 85% gasoline) and E85 (85% ethanol,
15% gasoline), but also as fuel for direct ethanol fuel cells (DEFC) and biofuel cells.
Reasons for its use as an alternative fuel are multifold: (i) it is produced from
renewable agricultural products; (ii) it is less toxic than other alcoholic fuels;
(iii) byproducts of its incomplete oxidation (i.e., acetic acid and acetaldehyde) are less
toxic than byproducts formed from other fuel alcohols [31]; and (iv) enables a semi-
closed carbon cycle because part of the CO 2 generated by its production and combus-
tion is reabsorbed by plants.

2.3.2.2 Biobutanol

Butanol is a promising renewable fuel with great advantages for use in internal com-
bustion engines, although it is still less known than ethanol and biodiesel [32]. Bio-
butanol can be produced by fermentation of biomass feedstock [4], and for its
characteristics not only can it be easily mixed with gasoline, but it could also be a