Biofuels are mixtures of organic compounds derived from biomass , which have an energy value that can be used by internal combustion engines. For example :bioethanol, biodiesel and biogas.
The use of biofuels significantly reduces carbon dioxide emissions into the atmosphere compared to traditional fossil fuels . Even so, biofuels are often blended with fossil fuels to maximize their efficiency. In many countries, however, there is a desire to replace the use of fossil fuels with alternative fuels, such as biofuels.
Bioethanol and biodiesel are the most widely used biofuels. Bioethanol is obtained through the alcoholic fermentation of sugars from plants such as sugarcane and beets. Biodiesel is obtained from vegetable oils, which can even be recycled. It is produced through the esterification and transesterification processes of plant lipids, as well as animal fats.
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Advantages and disadvantages of using biofuels
The main advantages and disadvantages of using biofuels are:
- Its use results in lower carbon dioxide (CO 2) emissions into the environment. While it’s true that in many cases, producing biofuels requires the use of fossil fuels, which emit CO 2 , the quantities of this gas produced during biofuel production are still lower than if fossil fuels were used as fuels for consumption.
- Biofuel production often uses plant-based raw materials, which creates competition with plant-based raw materials used in food production.
- In the case of biofuels produced from forest plants, it is believed that their massive consumption could be a major environmental problem.
There is currently a tendency to refer to biofuels as agrofuels. The reason is that the prefix “bio-” is often used to refer to agricultural products obtained naturally, without any synthetic process. In the case of agrofuels, synthetic processes may be involved.
Biofuels can be obtained from agricultural crops, such as corn and cassava, from oilseed plants, such as soybeans and palm trees, and from forest species, such as pines.
Examples of biofuels
- Biodiesel. It is one of the most in-demand biofuels in Europe. It is obtained from vegetable oils, animal fats , or microalgae oils, and once mixed with mineral diesel, it can be used in any diesel engine . Its emissions are less harmful than those of conventional diesel, as it emits less carbon dioxide and does not produce sulfur emissions.
- Bioethanol. It is produced by the fermentation of sugars or starches in organic matter through the action of microorganisms and enzymes during the alcoholic fermentation process. It is used primarily for vehicle operation due to its lower greenhouse gas emissions.
- Green diesel.It was developed to address some of the problems faced by biodiesel, such as its poor cold-weather performance and oxidation stability. Both of these problems are related to biodiesel.They are solved by applying hydrotreatment and isomerization reactions, which ultimately generate green diesel.
- Biofuel gasoline. There are numerous alternative gasoline projects underway. In 2013, glucose molecules were transformed into a type of biogasoline that did not require mixing using certain strains of the Escherichia coli bacteria . While these experiments still require significant work to become profitable in quantity, it is estimated that there will be surprising results in this area in the coming decades.
- Bioether. Also called oxygenated fuel, it is used to increase the octane number and improve engine performance.
- Biogas. It is a gas obtained from methane through the anaerobic (oxygen-free) decomposition of organic matter. It can also be obtained in anaerobic digesters from biodegradable waste, such as manure, and agricultural residues, where a solid product called digestate is also generated, which can be used as biofuel or fertilizer.
- Syngas. This is a mixture of gaseous hydrocarbons with carbon monoxide and hydrogen, obtained through the partial combustion of organic matter and prior drying and polarization processes. The resulting gas is a highly efficient combustible gas that can be used to produce other, more complex biofuels or burned in an internal combustion engine.
- Biomethanol. It’s an alternative fuel for internal combustion engines currently used in China and the racing car industry. Produced from biomass, it’s cheaper than ethanol, but more polluting and has a lower energy density.
- Mycodiesel. This is a biofuel under development. It is produced by the fungus Glocladium roseum from the northern Patagonian forests, which is capable of converting cellulose into medium-length hydrocarbons, very similar to those in conventional diesel.
- Cellulose ethanol. This is also a biofuel under development. It is obtained from the decomposition of cellulose contained in non-edible raw materials, which is an advantage because the raw material used in its production does not compete with human and animal food sources. Its production is expensive, so new methods are being explored using microorganisms capable of processing cellulose more easily and quickly.
- Algal biobutanol. This is a biofuel produced from algae and solar energy . It has a very low current yield, so methods for its development are being sought.
- Biohydrogen. It is hydrogen produced by algae, bacteria , and archaea, whose photosynthetic process is capable of producing the element instead of oxygen, in the presence of the enzyme hydrogenase . Hydrogen can be used as a chemical in laboratories, but it also holds great potential as a biofuel. Research is currently underway to control this process and produce the quantities of hydrogen needed for use in a combustion engine.
- Hydrobiokerosene. It is produced from hydrobiodiesel, which undergoes further treatment (isomerization and fractionation) to isolate the hydrocarbon stream at its appropriate crystallization and distillation rates .
- DMF (dimethylfuran). It is a substance with 40% more energy than ethanol. It is insoluble in water, which prevents it from absorbing moisture and reducing its performance in an engine. It can be obtained from six-carbon sugars found in inedible plant species. It is being developed as a biofuel, but it is predicted to be as efficient as gasoline.