What is Biodiesel?
‘Biodiesel’ refers to diesel produced from bioresource. Biodiesel is similar to diesel in fuel properties. but But diesel is a fissile fuel like coal and natural gas and is produced by natural processes such as by anaerobic decomposition of organisms over millennia. While it is nature that converts the dead biomass into diesel taking long course of time, in the case of biodiesel it is done by chemical processes which converts the plants and animals oil/fat into (bio) diesel.
Is Biodiesel Renewable?
Yes. As biodiesel is produced from renewable crops, it is a renewable fuel. Unlike Traditional fossil diesel, Biodiesel (Fatty Acid Methyl Easters) is non-toxic and biodegradable.
What is the meaning of transesterification?
The first step in the biodiesel production process is the extraction of oil. In the subsequent steps the extracted oil is subjected to a chemical process known as transesterification. Transesterification is essential as the plant and animal oil is highly viscous as compared to the fossil traditional diesel fuel. Transesterification process reduces the viscosity of the oil and making its physical characteristics closer to those of fossil diesel fuels.
Why methanol is used in transesterification?
The answer lies in the chemical composition of fats and oils. Chemically the oil and fats are triglyceride which means that these are made up of long chain fatty acids and glycerol. Glycerol is responsible for making it viscous. When methanol replaces the glycerol under the controlled conditions (transesterification) long chain fatty acid methyl esters (FAME) are produced. These are much smaller compound and with much less viscosity. In terms of chemistry biodiesel is, therefore, a mixture of different fatty acid methyl esters. This can be used as a fuel after blending with diesel.
Biodiesel Fuel Sources
The first requirement of the biodiesel production is the oil. The various sources utilized for making biodiesel are:
- Vegetable oil,
- Animal oil/ fats
- Waste cooking oil
Oil crops used for Biodiesel Production
Rapeseed, palm and soybean, sunflower, are considered the most suitable oil source for biodiesel production. However, they all need fertile land for cultivation. It mans that they directly compete with the food crops for land.
There are certain other oil crops such as canola, Jatropha, mustard, coconut Camelina (alse false flax) hemp, pennycress and Salicornia bigelovii (dwarf saltwort) which appears promising to be developed as biodiesel feedstock.
Among these Jatropha, Camelina, Salicornia bigelovii are able to grow in the marginal land.
Raw oil is expensive and therefore the biodiesel produced from raw oil cannot compete with fossil diesel fuel. The cost benefit analysis restricts the direct use of edible oil as biodiesel feedstock. On the other hand using / waste vegetable oil is much more cost effective and can be used as biodiesel feedstock after removing impurities. Therefore, most biodiesel produced at present is produced from waste vegetable oil which can be sourced from restaurants and industrial food producers etc.
If vegetable oil is used directly as “virgin” oil, then the biofuel produced will fall under first generation biofuel. The vegetable oil becomes a second generation biofuel feedstock if used after it is no longer fit for cooking.