BIOFUEL PRODUCTION TYPES & SOURCES
Biofuels can be classified in two ways, firstly by the state at which the fuel exists in their natural form which are mainly gas, liquid or solid. And secondly by the sources they have been produced from and the technology used to produce them. In this literature review, biofuels have been classified according the second way.
FIRST GENERATION – (food crops)
First generation biofuels are derived from food crops such as starch, sugar and vegetable oil using conventional techniques discussed later on. Several types of first generation biofuels are discussed briefly below.
Biodiesel
Biodiesel is probably the most common and most popular type of biofuel in the world because it also is the easiest to produce from ordinary vegetable oil. Biodiesel is produced very simply by combining any type of oil or biomass with methanol and sodium hydroxide[1]. It can be used on any diesel engine without any changes to it by mixing with mineral diesel as was described earlier in the “History of Biofuels” section.
There has a been great interest shown by European countries and the USA, the graphs below show a rising trend of biodiesel production is USA and many countries of Europe.
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Figure 7 - Source: National Biodiesel Board
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Figure 8 - Source: European Biodiesel Board
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Biogas & Syngas
Biogas is produced from organic materials by anaerobic digestion. Waste materials which are biodegradable can also produce biogas if they are fed into anaerobic digesters[2]. The resulting biomass can be used as fertiliser for agricultural usage. Biogas is rich in methane gas which can be recovered and used as burning fuel. Methane gas is also produced by the natural decay of garbage dumps over time. Another process to produce Syngas or biosyngas is by gasification of biomass into carbon monoxide and hydrogen. Hydrogen can be recovered from syngas or the syngas can be converted to diesel fuel using Fischer-Tropsch process[3].
Bioalcohols (bioethanol)
Enzymes and micro-organisms are used to produce alcohols through the process of fermentation of starches and sugar[4]. Ethanol being the most common of those bioalcohol as in bioethanol produced from sugar cane in Brazil. A significant amount of ethanol is also produced from sugar beets and corn by fermentation in other parts of the world.
SECOND GENERATION (non food crops)
Second generation of biofuels had been developed to use biomass left from the non-food parts of current crops such as stems, leaves and husks left behind after the important parts of the crop has been taken. It also includes biomass from non food crops such as Jatropha plant (which are toxic), switch grass and industrial waste such as wood chips, skin and pulp from fruit pressings. This generation of biofuels is not cost competitive with existing fossil fuels, do not threaten food supplies and biodiversity[5].
THIRD GENERATION (algaculture)
Third generation biofuels is obtained from algae and this is also called advanced biofuel. Algae is easy to grow and it is a high-yielding feedstock for the production of biofuel as it produces 30 times more energy per acre of land than traditional crops such as corn or soybean[6]. They are biodegradable so it is environmentally friendly. Similar to obtaining the oil from vegetation, algae contains almost 40-50% oil which is squeezed out and the remaining biomass can be used as fertilizer or high protein animal feed. The oil from algae can be converted to biodiesel.
FOURTH GENERATION (biodiesel to gasoline)
Last but not least is fourth generation biofuels which is still undergoing research at the highest levels. The main aim is to convert biodiesel into gasoline similar to the one obtained from petroleum but it will be much cleaner with less harmful emissions. This is similar to how natural gas or methane is converted to petrol. However there is much more study required in this part and will probably not be available in 10-20 years time.
[1] Biofuel Organisation: http://biofuel.org.uk/first-generation-biofuels.html
[2] Biofuel Organisation: http://biofuel.org.uk/first-generation-biofuels.html
[4] Biofuel Organisation: http://biofuel.org.uk/first-generation-biofuels.html
[5] RenewableEnergy.com News Article: Next generation of biofuels; http://www.renewableenergyworld.com/rea/news/story?id=49099
[6] Washington Post News Article; http://www.washingtonpost.com/wp-dyn/content/article/2008/01/03/AR2008010303907.html
Follow up with this four part series on BIOFUELS by clicking the link below:
Part I, Part II , Part III, Part IV
Follow up with this four part series on BIOFUELS by clicking the link below:
Part I, Part II , Part III, Part IV
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