Examples of biofuels are; fuelwood, ethanol, biodiesel, biogas, bioether, methanol, and biobutanol. They differ from each other slightly in chemical composition and physical properties.
This article discusses the examples of biofuels, as follows;
1). Fuelwood (as one of the Examples of Biofuels)
Fuelwood is a biofuel that occurs in solid phase, and is derived primarily from the woody, fibrous parts of plants.
Examples of fuelwood are; wood chips, firewood (bark, stems, roots, branches, leaves), wood pellets, corn stover, sawdust and straw. These materials all come from plants, and may serve as a source of bioenergy with or without any form of processing.
Fuelwood can be collected deliberately from trees by logging, or may be collected as waste from agriculture, forestry or agroforestry.
In African countries, fuelwood constitutes a very large portion of total available energy that is consumed per annum .
Uses of fuelwood include space heating, water heating, cooking, and electricity generation. These uses span across industrial, commercial and domestic sectors.
The intensive use of fuelwood is due to the fact that it is relatively easy to access in most parts of the world, especially when compared to other biofuels. Globally, at least 2.8 million people depend on fuelwood for various forms of energy, with majority of these located in developing countries .
The main challenge with this example of biofuel is its role in environmental degradation. Using solid biomass as a source of energy can cause air pollution and human respiratory ailments, while contributing to atmospheric greenhouse emission and global warming.
Ethanol is a biofuel that occurs as a colorless, volatile and flammable liquid, and which has the chemical formula; CH3CH2OH .
It is a major example of a renewable fuel derived mostly from plant biomass through biochemical conversion processes like fermentation.
The use of ethanol as a biofuel is achieved by subjecting the fuel to combustion, which may occur in an internal combustion engine. This process converts stored energy in the fuel from chemical potential form, to thermal energy that can be either used directly or further converted to mechanical energy and electric power.
Ethanol from biomass can be alternatively called bioethanol, and it is used as an energy source in biofuel power plants and vehicles.
Compared to fossil fuels and their derivatives like gasoline, the energy density of ethanol is low. Because of this, it is fairly common for ethanol to be used as an additive rather than a sole energy resource, in systems that demand high energy intensity.
In countries where ethanol is used in the transport sector, such as the United States, the ethanol is generally mixed with gasoline, in specific ratios such as 9:1 .
Advantages of ethanol as a biofuel include the fact that it is renewable, less susceptible to pipeline flow-impediment, and high in oxygen content that allows for efficient combustion with less pollution.
Problems of ethanol biofuel are land resource-demand, low energy density, production cost, and excessive fertilizer usage for feedstock cultivation.
The cost of ethanol production can be attributed to the fact that bioenergy is in its developmental stage. In terms of feedstock, ethanol can fall under all types of biofuels (1st, 2nd and 3rd generations), as it can be produced from food crops, organic waste, and even microalgal matter .
3). Biodiesel (as one of the Examples of Biofuels)
Biodiesel is a liquid biofuel that is produced by the conversion of oil-rich biomass through the biochemical process of transesterification.
Feedstock from which biodiesel is produced include; oil palm, soybean oil, and animal fat.
In parts of the world where biofuels are used, biodiesel is usually second to bioethanol in prominence as a (processed) bioenergy source.
While some studies present biodiesel as being different from biofuel, there is in fact no difference between biodiesel and biofuel, since biodiesel is simply an example of biofuels.
Alongside biogas and bioethanol, biodiesel is viewed as a promising alternative in the scheme of energy transition from fossil fuels . The main advantage of this fuel is its low gaseous emission compared to other energy sources.
The possible uses of biogas include industrial/domestic heating and electricity generation.
5). Bioether (as one of the Examples of Biofuels)
Bioether (or bio-ether) is a low-density biofuel that occurs in liquid or gaseous form, and is derived from plant biomass feedstock like sugar beet.
While it is similar in physicochemical characteristics, to ethanol, bioether differs from ethanol by having lower volumetric density, energy content and boiling point.
A common way to produce bioether is through gasification of biomass, which usually results in a mixture of bioether and carbon dioxide, called syngas . This method produces flammable, gaseous dimethyl-ether (DME).
Methanol is a liquid biofuel derived mainly from woody biomass, by thermochemical conversion.
As a biofuel, methanol is used mainly by blending it with biodiesel, so that the derived flammable mixture can be used as an energy source in combustion engines.
Methanol is more suitable than ethanol for blending with biodiesel in engines, because of its low cost, minimal emissions, and its role as in transesterification. Some studies have reported improved energy efficiency and performance in vehicles when methanol as an additive in biodiesel .
Methanol can be used in the production of biodiesel, by reacting it with glycerol .
7). Biobutanol (as one of the Examples of Biofuels)
Biobutanol is another alcoholic liquid biofuel that is produced by microbial fermentation of cellulosic biomass. This biomass could come from plant matter or microalgae.
Based on physical and chemical characteristics, biobutanol is very similar to bioethanol. It is viewed as a promising alternative to bioethanol in gasoline blends due to these similarities .
Compared to other biofuels, biobutanol performs optimally as a fuel .
Examples of biofuels are;
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2). Beschkov, V. (2017). "Biogas, Biodiesel and Bioethanol as Multifunctional Renewable Fuels and Raw Materials." Frontiers in Bioenergy and Biofuels. Available at: https://doi.org/10.5772/65734. (Accessed 9 March 2023).
3). Bharathiraja, B. (2016). "Biobutanol – An impending biofuel for future: A review on upstream and downstream processing tecniques." Renewable and Sustainable Energy Reviews 68(1):788-807. Available at: https://doi.org/10.1016/j.rser.2016.10.017. (Accessed 9 March 2023).
4). Brahma, S.; Nath, B.; Basumatary, B.; Das, B.; Saikia, P.; Patir, K.; Basumatary, S. (2022). "Biodiesel production from mixed oils: A sustainable approach towards industrial biofuel production." Available at: https://doi.org/10.1016/j.ceja.2022.100284. (Accessed 9 March 2023).
5). Bušić, A.; Kundas, S.; Morzak, G.; Belskaya, H.; Marđetko, N.; Ivančić Šantek, M.; Komes, D.; Novak, S.; Šantek, B. (2018). "Recent Trends in Biodiesel and Biogas Production." Food Technol Biotechnol. 2018 Jun;56(2):152-173. Available at: https://doi.org/10.17113/ftb.56.02.18.5547. (Accessed 9 March 2023).
6). Bušić, A.; Marđetko, N.; Kundas, S.; Morzak, G.; Belskaya, H.; Ivančić Šantek, M.; Komes, D.; Novak, S.; Šantek, B. (2018). "Bioethanol Production from Renewable Raw Materials and Its Separation and Purification: A Review." Food Technol Biotechnol. 2018 Sep;56(3):289-311. Available at: https://doi.org/10.17113/ftb.56.03.18.5546. (Accessed 9 March 2023).
7). Chang, J.; Fu, Y.; Luo, Z. (2011). "Experimental study for dimethyl ether production from biomass gasification and simulation on dimethyl ether production." Biomass and Bioenergy 39. Available at: https://doi.org/10.1016/j.biombioe.2011.01.044. (Accessed 9 March 2023).
8). Deka, T.; Osman, A. I.; Baruah, D. C.; Rooney, D. W. (2022). "Methanol fuel production, utilization, and techno-economy: a review." Environmental Chemistry Letters. Available at: https://doi.org/10.1007/s10311-022-01485-y. (Accessed 9 March 2023).
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11). Iodice, P.; Amoresano, A.; Langella, G. (2021). "A review on the effects of ethanol/gasoline fuel blends on NOX emissions in spark-ignition engines." Biofuel Research Journal 8(4):1465-1480. Available at: https://doi.org/10.18331/BRJ2021.8.4.2. (Accessed 9 March 2023)..
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14). Obergruber, M.; Hönig, V.; Procházka, P.; Kučerová, V.; Kotek, M.; Bouček, J.; Mařík, J. (2021). "Physicochemical Properties of Biobutanol as an Advanced Biofuel." Materials (Basel). 2021 Feb 15;14(4):914. Available at: https://doi.org/10.3390/ma14040914. (Accessed 9 March 2023).
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