The human population has grown beyond Earth’s sustainable means. We are consuming more resources than our planet can regenerate with devastating consequences.

By 1Muhammad Talha Aslam, 1Dr. Rizwan Maqbool, 1Dr. Imran Khan, 1Dr. Umer Chattha, 1Dr. Umair Hassan, 2Ahsan Shabbir

The increase in world population is increasing the demands for fossil fuels; however, these resources (crude oil, gas, and coal) are continuously diminishing. According to the CIA World Factbook, we will finish all of the known reserves of crude oil by 2052, gas by 2060, and coal by 2088. Due to the ever-diminishing fossil fuels and increasing fuel demands combined with environmental pollution concerns, the world has been focusing on the development of alternate renewable and cleaner energy resources that would save the environment for future generations. Human unsustainable practices have put earth resources to the extent of the danger of extinction.

We have to address all the issues to meet the demand of the population by alternating means. Biodiesel is a cleaner form of fuel and it consists of long-chain alkyl (methyl, ethyl, or propyl) esters. It is commonly produced from biological-based resources such as vegetable oils and animal fats with an alcohol producing fatty acids esters.

Biodiesel production is a natural, biodegradable, non-toxic, and environment-friendly source of energy.

The utilization of biodiesel as a vehicle fuel amplifies energy security, recovers air quality and thus environment safety occurs, which provides other safety advantages.

Crude oil or fat is used for biodiesel production which is obtained by utilizing natural vegetable oil and animal fat. These oils usually have free fatty acids, phospholipids, and other molecules which affect the quantity and quality of biodiesel production.  Animal fats and different plant-based oils including palm oil, soybean oil, coconut oil, sunflower oil, rapeseed oil, and Tung oil can be used in biodiesel production.

“Biodiesel produced at the domestic level is clean that is a renewable replacement for the petroleum”.

The developed world has made significant progress in biodiesel production over the last two decades. It was estimated that World had produced approximately 3.8 billion liters of Biodiesel in 2005 and about 85% of total production was in the taken place in the European Union, which is about one-third of the total annual diesel requirement of Pakistan. Biodiesel is generally produced by three methods namely;

  1. Supercritical method
  2. Microwave-assisted method
  3. Ultrasound-assisted method

Supercritical method

Supercritical method biodiesel production

It is a novel method to produce biodiesel without the use of catalysts. Water, carbon, and alcohol are used as a supercritical fluid that spread at both temperature and pressure above their critical point.  Such fluids are environmentally and economically beneficial to use.

Figure 1.

Biodiesel production by continuous supercritical alcohol process 

Microwave-assisted method

 In this technique, the raw material used in biodiesel production is heated by heating coils.  Microwave provides a lot of assistance by microwave irradiations that stimulate the smallest degree of polar molecules and ions with continuously altering the magnetic field (Azcan and Danisman, 2007).

Microwave-assisted method biodiesel production


Figure 2

Microwave-assisted transesterification process schematic diagram 

Ultrasound-assisted method

High-pitched sound waves named Ultrasonic waves are used in this process which vibrates more than 20,000 per second.  This process is involved; 1) Mixing vegetable oil with alcohol and catalyst, 2) Heating the mixture, 3) The heated mixture is sonicated inline, and 4) Glycerin separation by centrifugation.

Ultrasound-assisted method biodiesel production

Figure 3

Scheme of biodiesel production process via an ultrasound-assisted method


Biodiesel produced from Vegetable oils has a high viscosity that hinders its proper combustion in the engine and causes numerous problems such as coking, carbon deposition, sticking of oil ring, thickening and gelling of lubrication. Micro-emulsion techniques may be employed to solve high viscosity problems. Solvents (such as methanol, ethanol, and 1-butanol) have been used in the micro emulsion technique. Through this technique, optically isotropic fluid microstructure, dispersed with the dimension generally in the 1-150 nm range and formed spontaneous mixture from two immiscible liquids.

The diesel obtained from this type of technique has a low octane number and energy. Thermal cracking makes use of pyrolysis to produce biodiesel from vegetable oils and animal fats.  In pyrolysis, vegetable oils and animal fats are heated at a temperature between 450-850 ⁰C in an oxygen/air-free environment in the presence of a catalyst (SiO2/ Al2O3). 450-850 ⁰C which cleavage the chemical bonds and yields small molecules. The remaining (methyl ester) may directly be used as fuel. This technique was used during World War 1 for the production of diesel, gasoline, and kerosene from the Tung oil. Trans-esterification is the process by which the fat and oil react with the alcohols (methanol and ethanol) and the ester and glycerol are produced. The maximum ester may be produced with the ratio of (1:3) reactant triglyceride and alcohol.

Alkalis, acids, and enzymes are used as a catalyst to enhance the reaction rate. Alkali catalysts comprised of NaOH, KOH, carbonates, sodium methoxide, sodium ethoxide, and sodium peroxide. Whilst; sulfuric acid, sulfonic acid, and hydrochloric acid are usually used as an acid catalyst. Lithium may also be used as a catalyst in Trans-esterification. Glycerides and alcohols must be anhydrous when alkali catalysts are used because the presence of water may shift the reaction toward saponification, a process by which soap is produced. This process is completed in a series of reactions.

saponification biodiesel production

A mole of the ester is liberated at each step during this process. This ester is used as biofuel. During this process, the glycerides should have pH less than one and an anhydrous environment if it has moisture then there will be the formation of soap which affects the catalytic activity. The molar ratio should be 3:1 for vegetable oil and 6:1 for animal fats respectively.

Moreover, there are numerous methods of producing biodiesel from natural renewable resources; however, Trans-esterification produced high quality and quantity biodiesel with desired qualities of low viscosity and, high combustion power. Biodiesel is a cleaner energy source that would also reduce our reliance on ever diminishing fossil fuels. 

Concluding remarks:

By using biodiesel, we can not only improve our environment but also enhances the efficiency of the vehicle and extends the life of diesel engines as it has better lubricant properties than petroleum products. Thus, the developing countries should adopt such policy, research, and development activities that would enable them to start biodiesel production ensuring fuel security and environmental stewardship. 

Authors 1Muhammad Talha Aslam, 1Dr. Rizwan Maqbool, 1Dr. Imran Khan, 1Dr. Umer Chattha, 1Dr. Umair Hassan, 2Ahsan Shabbir
1Department of Agronomy, University of Agriculture, Faisalabad 2Department of Plant Pathology, University of Agriculture, Faisalabad

By Muhammad Talha Aslam

Master of Science (Hons.) Scholar Weed Science Laboratory, Department of Agronomy, University of Agriculture, Faisalabad, Pakistan