Processing of Feedstock in Context of Biodiesel Production

Abstract

A feedstock is a type of raw material that is used in the production of biodiesel. It is an alternative to fuel in today's market (petroleum and diesel). Two types of feedstocks are used in biodiesel production: edible and non-edible. Examples of edible feedstock are coconut oil, palm oil, and soyabean oil and non-edible feedstock are neem, mahua, etc. Extraction of biodiesel from oil is practiced in many countries by using different processing methods. Different extraction methods are used for the extraction of oil from the feedstock. They include old traditional methods, solvent extraction, mechanical extraction, microwave-assisted, and ultrasonic-assisted methods. Old traditional methods consist of a simple process but are regarded as inefficient due to the lesser oil yield and recovery. Conventional methods are the most widely used methods. The solvent extraction method is more efficient and produces good quality oil. The most common solvent used is hexane because it is highly reactive, has a low cost, and is easily available. The limitation of this method is time-consuming and very tedious. Many innovative techniques are also used to overcome the limitations of conventional methods. Microwave-assisted and ultrasonic-assisted are some of the new techniques which include the pretreatment of raw material using either ultrasonic waves or radio waves, which helps in increasing the efficiency of the extraction of oil and improves the final quality of the oil. Transesterification is the most commonly used process for the commercial production of biodiesel. In this technique, the oil is heated at the desired temperature in the presence of alcohol and catalyst. It is a reversible reaction, where a catalyst is used for obtaining a conversion rate. Based on the rate of reaction, different catalysts (acid or alkali) are used. Nowadays, researchers are focusing on assisted transesterification as it speeds up the reaction process and increases product yield. Commonly used assisted transesterification methods are microwave-assisted (microwave irradiation is used for activating the reacting molecules) and ultrasound-assisted (sound energy is used for rarefaction and compression of reacting molecules). Numerous benefits stem from biodiesel like it helps in reducing air pollution, improves the rural economy, is readily available, and reduces dependence on fossil fuels. Many technical challenges are being faced in biodiesel production like the presence of a higher amount of water and free fatty acids in feedstock, which leads to problems in the processing of biodiesel as cheaper energy source, etc.