Environmental Engineering Reference
In-Depth Information
Technically, biodiesel can be obtained from any vegetable oil. Therefore, the choice of feedstock
mainly depends upon the country and its climate. This is evident from the fact that soybean oil
(Kaieda et al. 1999; Samukawa et al. 2000; Watanabe et al. 2000; Wei et al. 2004; Noureddini
2005) is the most commonly used vegetable oil for biodiesel production in the United States,
whereas rapeseed/canola (Korbitz 1999; Lang et al. 2001; Massimo et al. 2003; Chang et al. 2005)
is the major feedstock in Europe and Canada. Regions with tropical climates utilize tropical
oils such as coconut and palm oil (Crabbe et al. 2001; Fukuda 2001; Sulaiman 2007). Cotton
seed, peanut, and sunflower oils are also commonly used as source for biodiesel (Soumanou and
Bornscheuer 2003; Knothe and Dunn 2005; Orcaire et al. 2006; Sulaiman 2007; Demirbas 2008;
Joshi et al. 2008; Keskin and Guru 2008; Sagiroglu 2008). A comparison between the physical
and chemical properties of biodiesel fuels (Fukuda et al. 2001; Knothe and Dunn 2005) indicated
that palm oil has the highest yield (4,000 kg/ha) as compared with other vegetable oils leading to
substantial gains in worldwide production of palm oil. Other vegetable oils that have been studied
for the production of biodiesel include sesame oil (Sydut et al. 2008), olive oil (Sanchez and
Vasudevan 2006), tobacco seed oil (Giannelos et al. 2002), rubber seed oil (Ikwuawgu et al. 2000),
coffee oil (Oliveira et al. 2008), jatropha (Foidl et al. 1996; Shah and Gupta 2006; Berchmans and
Hirata 2008), and other nonconventional oils or oils from novel sources (Munavi and Obhiambo
1984; Park et al. 2005, 2007; Holser and Harry-Okuru 2006; Kesari et al. 2008; Naik et al. 2008;
Rashid et al. 2008; Razon 2008; Ruan et al. 2008; Santos et al. 2008; Sinha et al. 2008).
18.1.3 S
Econd
-g
EnEration
B
iofuElS
The first-generation biofuels are limited in their wide scale production and utility in many ways.
The issues of producing enough biofuel without compromising the food supply, disturbing the
ecosystem, creating a noncompetitive product in terms of cost, and increasing fossil fuel related
emissions generate the need for second-generation fuels. First-generation biodiesel is made mainly
from edible vegetable oil crops such as soybeans, rapeseed, sunflowers, and palm. The increase
in the demand of these vegetable oils has put pressure on valuable ecosystems such as rainforests
and has decreased the area available for food crops. There are examples where old forest land has
been burned to cultivate oil palms. Burning of old growth forests not only leads to deforestation
and reduces biodiversity but also releases large amounts of carbon dioxide in the air. Because very
high quantities of vegetable oil will need to be produced to replace diesel and gasoline, the required
methods of cultivation may lead to greater harm of natural resources.
To counter such threats, some experts recommend using jatropha seeds for a vegetable oil supply.
Compared with the four most common plant oils suitable for fuel production (soybean, sunflower,
rapeseed, oil palm), jatropha is drought resistant and tolerant of high humidity and temperature. It
is a non-food crop, bears seed for almost fifty years, and performs very well as a low-input crop on
marginal land. Considering its current yield of 5 tons of seed/ha per year with a potential for a much
larger production, it can easily provide sustainable environmental solutions for biofuel production.
The only major limitation to its large scale production is the current labor-intensive extraction
methods used for oil extraction of jatropha seed. With research and improvement of traditional
extraction techniques such as the Bielenberg hand press which is used in Tanzania, it is likely that
oil extraction time and cost can be reduced to make such seeds more valuable (Benge 2006).
Another improvement for first-generation biofuels lies in the cost-effective and efficient production
of vegetable oil on a mass scale. This can be attained by harvesting particular types of algae which
contain almost 50% vegetable oil. The process is known as algaculture and can produce much
more oil per unit area than current farming methods (Sheehan et al. 1998). Experts are certain that
algaculture can produce quantities of vegetable oil sufficient to replace petrodiesel (Christi 2007).
It can, therefore, be concluded that production of vegetable oil from algae might just be the solution
to a wide range of issues including deforestation and high cost of production. Because scientists and
engineers are mostly concerned about replacing petroleum and diesel with vegetable oil, it may be
