M. P. Dorado

4.1 Introduction

The present energy scenario is undergoing a period of transition, as more and more energy consumers understand the inevitability of exhaustion of fossil fuel. The era of fossil fuel of nonrenewable resources is gradually coming to an end, where oil and natural gas will be depleted first, followed eventually by depletion of coal. In developing countries, the energy problem is rather critical. The price paid for petrol, diesel, and petroleum products now dominates over all other expenditures and forms a major part of a country’s import bill. In view of the prob­lems stated, there is a need for developing alternative energy sources. Alternative fuel options are mainly biogas, producer gas, methanol, ethanol, and vegetable oils. But biogas and producer gas have low energy contents per unit mass and can substitute for diesel fuel only up to 80%. Moreover, there are problems of storage because of their gaseous nature. Methanol and ethanol have very poor calorific value per unit mass, apart from having a low Cetane number. Therefore, these are rather unsuitable as substitutes for high-compression diesel engines. Experimental evidence indicates that methanol and ethanol can be substituted up to only 20-40%. There exists a number of plant species that produce oils and hydrocarbon substances as a part of their metabolism. These products can be used with other fuels in diesel engines with various degrees of processing. The development of veg­etable oils as liquid fuels have several advantages over other alterna­tive fuel options, such as

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1. The technologies for extraction and processing are very easy and simple, as conventional equipment with low energy inputs are needed.

2. Fuel properties are close to diesel fuel.

3. Vegetable oils are renewable in nature.

4. Being liquid, these oils offer ease of portability and also possess sta­bility and no handling hazards.

5. The by-product leftover after extraction of oil is rich in protein and can be used as animal feed or solid fuel.

6. Cultivation of these oilseeds is adaptable to a wide range of geo­graphic locations and climatic conditions.

7. Biodiesel can be used directly in compression ignition engines with no substantial modifications to the engine.

8. Biodiesel contains no sulfur, and there is no production of oxides of sulfur.

Hence, biodiesel is considered an alternative fuel for internal combus­tion engines derived from oils and fats from renewable biological sources; it emits far less regulated pollutants than the standard diesel fuel [1—10]. It entails minimal reduced engine performance as a result of a slight power loss and increase in specific fuel consumption [8, 11—29]. However, one main concern in further usage of biodiesel is the economic viability of producing biodiesel.

The main economic criteria are manufacturing cost and the price of raw feedstock. Manufacturing costs include direct costs for oil extrac­tion, reagents, and operating supplies, as well as indirect costs related to insurance and storage. Fixed capital costs involved in the construc­tion of processing plants and auxiliary facilities, distribution, and retail­ing must also be taken into consideration [30].

Several authors have found that biodiesel is currently not economi­cally feasible unless tax credits are applied [23, 31]. Peterson [23] has found that diesel fuel costs less than biodiesel, and an emergency or diesel shortage would be required to provide a practical reason for using biodiesel. Some authors have stated that biodiesel could compete with diesel fuel if produced in cooperatives [31, 32].

To promote biodiesel consumption, several countries have exempted biodiesel from their fuel excise tax. Among them, the European Union (EU) approved the biodiesel tax exemption program in May 2002. The financial law funded biofuels through excise exemption over a period of 3 years (Art. 21, Finance Law 2001). The U. S. Senate Finance Committee also approved an excise tax exemption for biodiesel in 2003. Moreover, the legislation provides a 1% reduction in the diesel fuel excise tax for each percentage of biodiesel blended with petroleum diesel up to 20%. Also, among some other countries, the Australian Senate approved an excise exemption on biofuels in 2004. However, the tax exemption will one day come to an end; in order to continue to promote the social inclusion and economic attraction of biodiesel, other steps will be needed. This could be facilitated by the selection of low-cost raw materials, such as nonedible oils, used frying oil, or animal fat, and the use of a lower-cost transes­terification process.

A lower-cost biodiesel production can be achieved by the optimization of the process. Because the chemical properties of the esters determine their feasibility as a fuel, the intent of the optimization is to investigate and optimize the involved parameters maximizing the yield of ester, to develop a low-cost chemical process, and to ensure appropriate oil chemical properties for both the transesterification and the engine performance.

Although it is a well-known process since, in 1864, Rochleder described glycerol preparation through the ethanolysis of castor oil [33], the pro­portion of reagents affects the process, in terms of conversion efficiency [34]; this factor differs according to the vegetable oil. Several researchers have identified the most important variables that influence the trans­esterification reaction, namely, reaction temperature, type and amount of catalyst, ratio of alcohol to vegetable oil, stirring rate, and reaction time [20, 35-42]. In this sense, it is important to characterize the oil (i. e., fatty acid composition, water content, and peroxide value) to determine the correlation between them and the feasibility to convert the oil into biodiesel [39, 43].

However, several studies have identified that the price of feedstock oils is by far one of the most significant factors affecting the economic viability of biodiesel manufacture [30, 44-46]. Approximately 70-95% of the total biodiesel production cost arises from the cost of the raw material [44, 45]. To produce a competitive biodiesel, the feedstock price is a factor that needs to be taken into consideration. Edible oils are too valuable for human feeding to run automobiles. So, the accent must be on nonedible oils and used frying oils.