Page 29 - Advances in Eco-Fuels for a Sustainable Environment

6 Advances in Eco-Fuels for a Sustainable Environment

Fig. 1.5 Ecofuel lifecycle
for feedstocks regrown as
environmental carbon Feedstocks
recyclers.
Carbon
recycling Transport

Ecofuel
lifecycle
GHG
emission Processing

Uses Transport

1.3 Prospective ecofuel feedstocks

Biofuel feedstocks are broadly categorized as edible or first generation (1G) [30, 31],
nonedible or second generation (2G) [30, 32], and microorganism or third generation
(3G) [33]. Some examples are given here for each category. This study is mainly
focused on the prospect of aviation biofuel and biodiesel feedstocks from available
sources, considering a broad range of technical issues.
Edible sources or 1G biofuels are produced from edible biomass such as food crops
and vegetable oils, as reported by Lee and Lavoie [33]. Food crops include wheat, bar-
ley, rice, whey, sugar beets, etc., which are marginally used in biofuel production [34].
Vegetable oil feedstocks for biodiesel production include soybean oil [35], sunflower
oil [36], olive oil [37], palm oil [38], coconut oil [37], macadamia [39], and rapeseed oil
[40]. In addition, corn waste and sugarcane are widely used feedstocks for bioethanol
production [41]. A few more feedstocks are listed in Table 1.1. Currently, more than
50% of ecofuel produced from edible sources is facing some socioeconomic challenges
such as food versus fuel debt and use of fertile land to grow the feedstock.
Nonedible sources or 2G biofuels can be produced from a wide array of feedstocks
such as nonfood crops, animal fats, and lignocellulosic solid waste [33, 45, 46]. The
nonedible oil seed includes jatropha curcas [17], pongamia glabra [38], castor oil [47],
beauty-leaf oil [48], crambe, borage, waste cooking oil [49], and animal fats such as
beef tallow [50], as shown in Fig. 1.6. A few more nonedible feedstocks are listed in
Table 1.2. The nonedible feedstocks can overcome the main economic, social, and
environmental challenges of 1G biofuel feedstocks without creating any pressure
on land use and hindering the food supply because they are nonedible and can grow
on marginal land.