**1. Introduction**

320 Recent Trends for Enhancing the Diversity and Quality of Soybean Products

Tulcan, O. E. P., Performance of a stationary engine using different biofuels and emissions

van Dam, J.; Faaij, A.; Hilbert, J.; Petruzzi, H. & Turkenburg, W. (2009). Large-Scale

1364-0321

Brazil, November 2009

1733, ISSN 1364-0321

*Sustainable Energy Reviews*, Vol. 14, Issue 9, (December 2010), pp. 2748-2759, ISSN

evaluation (in portugues), *Ph.D. Thesis*, Federal Fluminense University, Niterói, RJ,

Bioenergy Production from Soybeans and Switchgrass in Argentina: Part A: Potential and Economic Feasibility for National and International Markets. *Renewable and Sustainable Energy Reviews*, Vol. 13, Issue 8, (October 2009), pp. 1710-

> According to the predictive studies of the World Energy Outlook 2009, the global demand of energy is expected to increase till 2030 of about 1.5 percentage points per year. Fossil fuels are expected to remain the main energy source in the world, but in the meantime renewable energy sources (wind, solar, geothermal, bioenergy) will be characterized by a rapid growing rate. Their use and development is strongly encouraged by most of the recent regulations. For instance, as reported by the European Environment Agency Transport (EEA), 2009, the European Union required in the same year to achieve by 2020 at least 10% of mixture of hydrocarbons from renewable and conventional sources for what concerns the energy employed for the transports. In addition, the increase in oil price and the growing interest in environmental issues have recently given a considerable impetus to the research for cleaner and renewable energy sources, in order to ensure a sustainable future.

> Biodiesel (BD) is a renewable energy source in liquid form that has many advantages over normal diesel, including lower emissions of gases harmful to humans and environment. The UE directive 2003/30/EC, defines the Biodiesel as "a methyl ester produced from vegetable or animal oil, of diesel quality, to be used as biofuel". Moreover, the National Biodiesel Board (NBB), 1996, responsable for biodiesel ASTM standards, define biodiesel as "the mono alkyl esters of long chain fatty acids derived from renewable lipid feedstock's, such as vegetable oils or animal fats, for use in compression ignition (diesel) engines."

> The processes for BD production are well known. According to the NBB, 2007, there are three main routes to BD production from oils and fats:


At the present BD is mainly produced through the base-catalyzed transesterification for many different reasons:


Soybean Oil De-Acidification as a First Step Towards Biodiesel Production 323

Soybean oil 0.1 10.6 - 4.8 22.5 52.3 8.2 15.5 Palm oil 1.2 47.9 - 4.2 37 9.1 0.3 53.3

oil - 6.0 - 4.2 18.7 69.3 - 10.2 Lard 1.7 17.3 1.9 15.6 42.5 9.2 0.4 34.6

Table 1.Typical FFA composition of soybean oil and others raw materials for BD production. As already discussed in the introduction, the chemical transformation of these lipids into

Nowadays BD is industrially obtained using alkaline homogeneous catalysts, such as sodium and potassium methoxides and hydroxides. Other possible routes to obtain biodiesel through transesterification and exploiting different catalytic systems are reported in a recent review (Vyas et al., 2010). These include: 1) homogeneous acid catalysis, 2) heterogeneous alkali or acid catalysis; 3) enzymatic catalysis, 4) supercritical conditions without catalyst, 5) microwave or ultrasound assisted reactions. All these methods will be

Any TG or FFA source (vegetable oil, animal fat or waste grease) may be potentially used as source for biodiesel production through alkali or acid-catalyzed transesterification reaction. In spite of this, a feedstock characterized by a low impurities level and low water and FFA content is required to obtain a valuable, marketable product. In particular, the basecatalyzed transesterification requires high purity reactants (FFA < 0.5wt%, water< 0.1-0.3 wt%), having demonstrated to be very sensitive to the impurities contained in the feedstock

As a matter of fact, the raw material contributes 60-70% to the final manufacture cost of BD obtained from soybean oil. As a consequence, the utilization of expensive raw materials is

In paragraph 2.1 different methods of performing the transesterification reaction are described, while in paragraph 2.2 various processes to lower the acidity content of the oil are

Synthesis of biodiesel via homogeneous acid catalysis: the homogeneous acid-catalyzed reaction rate is reported to be about 4000 time slower than the homogeneous one (Srivastava and Prasad, 2000). Nevertheless, adopting this technology it is possible to perform TG transesterification of not refined oils. Sulphuric acid is reported to be the best performing catalyst. Other homogeneous catalytic systems, such as HCl, BF3, H3PO4 and organic sulphonic acids have also been studied (Liu, 1994). Homogeneous systems require a large molar ratio alcohol to oil (30:1 at least) to reach acceptable reaction rates. On the other hand,

**2.1 Non alkali-catalyzed transesterification for BD production from feedstock with** 

responsible for the lack of economic competitioness of BD with fossil fuel.

by increasing the alcohol amount, the separation costs increase as well.

biodiesel involves the transesterification of glycerides with alcohols to alkylesters.

2.4 23.2 3.8 13 44.3 7.0 0.7 38.6

1.7 22.8 3.1 12.5 42.4 12.1 0.8 37.0

Palmitoleic 16:01

Fatty acid Myristic

Sunflower

Yellow grease

Brown grease

14:00

presented in the paragraph 2.2.

(Strayer et al., 1983).

**high FFA content** 

reported.

Palmitic 16:00

Fatty acid composition, wt%

Stearic 18:00

Oleic 18:01

Linoleic 18:02

Linolenic 18:03

Sat. (%)


According to the base-catalyzed process, BD is produced through the transesterification of triglycerides contained in oils or fats, with methanol and in the presence of an alkaline catalyst, also yielding glycerin as a by-product (Fig. 1).


Fig. 1. Transesterification of a triglyceride for biodiesel production.

Although food-grade oils with low acidity can be employed with few practical problems, their use is strongly discouraged to avoid interference with the human food requirements, besides being not cost-wise competitive with the petroleum-based diesel.

To overcome this problem, waste materials, such as waste cooking oils or animal fat, can be employed.

The use of not refined or waste oils as a feedstock represents a very convenient way in order to lower biodiesel production costs. Crude vegetable oil, waste cooking oils and animal fat are examples of alternative, cheaper, raw materials. The main problem associated with the use of this type of low-cost feedstock lies in its high content of FFA, leading to the formation of soaps during the final transesterification step.

The presence of soaps during the transesterification complicates the reaction resulting in hindering the contact between the reagents and causing difficulties in products separation

Not refined or waste fats require therefore to be standardized by the reduction of the acidity prior to be processed through the transesterification reaction (Bianchi et al., 2010).

However, while BD (pure or mixed) as an alternative fuel to diesel for use in diesel engines is a reality in many states (in France it is usually used in a 5% blend with diesel fuel, in Germany pure, in the USA in the "fleet"), the same cannot be stated for what concerns the use of biofuels as boilers in small, medium or large size plant.

The EU has also published some very restrictive parameters in collaboration with the CEN (*European Committee for Standardization*) to ensure an adequate performance and consequently a higher quality of the BD as biofuel. The required limits for biodiesel properties are listed in the paragraph 4 (European Standard EN 14214).
