Chapter 5 - Biodiesel and green diesel

Abstract

The production and use of renewable fuels have been intensified to reduce the dependence upon fossil fuels and ensure the sufficiency of energy production, mainly for countries dependent upon imported oil. Conventional diesel is an important fuel for the world's transport sector, especially for heavy-duty vehicles and several alternative fuels have been tested as a possible substitute for this fossil fuel. These substitutes must be technically and economically viable and the feedstock should be sustainable and not compete with food chain. Biodiesel and green diesel are two such candidates which can be readily blended with petro-diesel. Green diesel, one of alternative, is a second-generation biofuel, which has a similar molecular structure as petroleum diesel but provides better diesel properties. Whereas, biodiesel is a mixture of alkyl esters of fatty acid, green diesel is a mixture of hydrocarbons with a similar carbon number range to that of petrochemical diesel and is free of aromatic compounds. Biodiesel, both conventional and green, can be made from triglycerides (lipids) which may be plant or of animal origin adopting a process of transesterification for conventional and hydrotreating for green diesel. Green diesel can also be produced from biomass by thermos-chemical route of from biomass sugars. The high similarity to fossil fuels confers several benefits to the use of green diesel. The main advantages of green diesel over biodiesel are the possibility of using it at a much higher proportion in mixtures with conventional diesel and it can be produced using the existing infrastructure used in the production of diesel in a petroleum refinery.