Except for hydroelectricity and nuclear energy, the majority of the present-day world’s energy needs are fulfilled by fossil fuels such as petrochemical fuels, coal and various natural gases. These fossil fuels sources are finite and judging from the current usage rates are in danger of depleting shortly.
Also the two renewable sources used currently i.e. hydroelectricity and nuclear energy cannot be used as fuels in transport vehicles majority of which are run using fossil fuels. Because of the large and increasing levels of energy requirement demands in both the industrial and domestic sector, as well as the increased pollution problems because of using fossil fuels have made it necessary to develop renewable energy sources that would last limitlessly and would cause less harm to the environment than the traditional fossil fuels.
This requirement has fueled the interest in alternative sources to petroleum-based fuels. One such alternative is to use oils of plant origin which is known as biodiesel. Biodiesel is a biodegradable and non-toxic fuel and has low emission profiles as compared to petroleum diesel (Meher, Vidyasagar & Naik, 2004:249-250).
Using converted vegetable oils and animal fats as an alternative to Petrol-Diesel fuel has been around for decades. In fact the use vegetable oil for diesel engines is almost as old as the diesel engine itself. The original Diesel engine was designed to run on cheap vegetable oils.
The engine was commonly demonstrated running on peanut oil. Most of the present day diesel engines can in fact run on biodiesel without using any special equipment. The importance of biodiesel as an attractive fuel is increasing due to the depletion of fossil fuel resources (Knothe, Dunn & Bagby, n.d:1).
This dissertation is a study into the use of biodiesel as an alternative to petroleum-based fuels by focusing on the various aspects of biodiesel and its use.
The study will focus on understanding the various reasons for going in for alternative fuels in detail, study the engine performance using biodiesel fuels, assess the compatibility of biodiesel and fossil fuels, study the production process of biodiesel in detail, analyze the emission levels using biodiesel as fuel, and study the advantages and limitations of using biodiesel.
What is Biodiesel?
Biofuels can be defined as liquid fuels produced from biomass for either transport or burning purposes. They can be produced from agricultural and forest products, and biodegradable portion of industrial and municipal waste.
It is generally held that biofuels offer many benefits, including sustainability, reduction of greenhouse gas emissions, and security of supply. Various scenarios have led to the conclusion that biofuels will be in widespread use in the future energy systems. Biofuels can be converted into liquid and gaseous fuels through thermo-chemical and biological methods.
Hence, a variety of fuels can be produced from biomass resources including liquid fuels such as methanol, biodiesel and Fischer-Tropsch diesel, and gaseous fuels such as hydrogen and methane. Biofuels are primarily use din vehicles but can also be used in engines or fuels cells for electricity generation. The figure below shows the types of biofuels.
The term biodiesel is a combination of two terms: the Greek word for life ‘bio’ and ‘diesel’ from the last name of the inventor Rudolf Diesel. The term refers to the diesel equivalent, processed fuel derived from biological sources. It is a cleaner-burning diesel replacement fuel made from natural and renewable sources such as new and used vegetable oils and animal fats. Biodiesel is the name for a variety of ester-based oxygenated fuels from renewable biological sources. It can be made from processed organic oils and fats.
Chemically, biodiesel is defined as the monoalkyl esters of long-chain fatty acids derived from renewable biolipids. In general terms, biodiesel may be defined as a domestic, renewable fuel for diesel engines derived from natural oils like soybean oil that meets the specifications of ASTM (American Society for Testing & Materials) D 6751.
While in technical terms, biodiesel is a diesel engine fuel comprised of monoalkyl esters of long-chain fatty acids derived from vegetable oils or animal fats, designated B100 and meeting the requirements of ASTM D 6751 (Demirbas, 2008:114; Shrivastava & Jain published in Kumar & Nehar 2007:32).
Properties of Biodiesel
Biodiesel is a clear amber-yellow colored liquid with a viscosity similar to that of petrodiesel. Biodiesel is non-inflammable and in contrast to petrodiesel is non-explosive, with a flash point of 423K for biodiesel as compared to 337K for petrodiesel. Unlike, petrodiesel, biodiesel is biodegradable and non-toxic and also significantly reduces toxic and other emissions when burned in a fuel.
However, it is more expensive than petrodiesel, which appears to be the primary factor in preventing its more widespread use (Demirbas, 2008:115). The figure below shows the main technical properties of biodiesel.