BIO-DIESEL: A FUEL FOR THE FUTURE
Biodiesel, A form of Biofuel refers to those solid, liquid, or gaseous fuels which could be synthesized from biomass. In this highly advancing socio-political state, an infinite supply of energy is in demand. Finite fossil fuel supplies of coal and petroleum would not be able to meet this surge for a longer period. Herein the search for a viable source of a renewable and sustainable source of energy started to meet the upcoming demand. Biofuel fulfills all these criteria being an alternative, renewable, and sustainable energy technology, thus reducing petroleum dependency. Moreover, this would also help to solve the fuels supply issue in rural areas along with the urban ones.
Biofuels include bioethanol, bio-methanol, vegetable oils, biodiesel, biogas, bio-synthetic gas (bio-syngas), bio-oil, bio-char, Fischer-Tropsch liquids, and biohydrogen. Most traditional biofuels are synthesized by photosynthetic organisms (micro and macroalgae) followed by a biochemical, physical, and thermochemical method. Ethanol from corn, wheat, or sugar beets, and Biodiesel from oilseeds are a few such examples. Here we are going to analyze BioDiesel in terms of its feasibility, challenges and constraints, production along with its commercialization.
Technically, Biodiesels are the alkyl esters of fatty acids which are produced by the transesterification of oils and fats derived from plant’s biomass with short-chained alcohols like Ethanol or methanol and also sometimes Glycerols. In 1911, German inventor Rudolf Diesel designed and presented a model of a compression-based engine, known as The diesel Engine today. At that time there was no special fuel for this newly designed engine and he used groundnut oil as its feed. This was the first use of Biodiesel in the history of fuel technology. In the preface of the book Thermodynamics, (Chalkey, 1911),1 Rudolph Diesel wrote that the diesel engine could be fed by vegetable oils and that this possibility could help the agricultural development in the countries where this engine would be used.
Esters from vegetable oils are the main component of biodiesel and turn out as the best substitutes for conventional diesel as they have a high energetic yield. Biodiesel is produced when oils extracted from feedstock are subjected to dilution, micro-emulsification, pyrolysis, catalytic cracking, and transesterification. These processes reduce the viscosity which makes them operational even in conventional diesel engines without further alteration or modification of their design.
There are two practical methods of preparation of Biodiesel:
1. Lipase-catalysed transesterification of biodiesel: This method is conducted with Lipase enzyme as a catalyst. Lipase is can be extracted from papaya latex, oat seed, and castor seed. But in the production of Biodiesel, bacterias like Candida antarctica, and Candida rugosa are used as lipase sources. Candida rugosa, obtained from yeast, is the most used microorganism for lipase production. The process is conducted in two steps, which involve hydrolysis of the ester bond followed by esterification with the second substrate.
2. Synthesis using Supercritical Fluids: A supercritical fluid is a compound, mixture, or element above its critical pressure and critical temperature but below the pressure required to condense it into a solid. The “SAKA-DADAN method of Biodiesel synthesis “ is based on this theory. Ethanol, Methanol, Methyl acetate, and Dimethyl carbonate have been recognized as ideal SCFs for the synthesis of Biodiesel.
The above two schematic diagrams explain the reaction process and methods of synthesis of biodiesel with the help of SCFs.
The advantages of vegetable oils as diesel fuel are :
(1) liquid nature-portability,
(2) heat content (80% of diesel fuel),
(3) ready availability, and
(4) renewability.
The disadvantages are :
(1) higher viscosity,
(2) lower volatility, and
(3) the reactivity of unsaturated hydrocarbon chains.
All research focusing on the use of vegetable oils to feed diesel engines showed coking and trumpet formation on the injectors to such an extent that fuel atomization does not occur properly or is even prevented. Numerous hindrances are associated with using vegetable oils directly in diesel engines, problems such as a decrease in power output and thermal efficiency of the engine; carbon deposits; oil ring sticking; thickening or gelling of the lubricating oil as a result of contamination by vegetable oils .
Yet overall these factors, Biofuel still has to overcome a lot of hindrances to reach the point of being successfully commercialized efficiently. Biofuel technology would improve consequently, in the next few decades it would be at par with petroleum-based fuels hence dependency on fossil fuels would decrease which would lead to a vital impact on a country’s economy and environment.
