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Continuing with the alternative energy series, this week’s blog examines a popular idea in green alternatives with biofuel, a type of fuel energy that is created through biological carbon fixation. This can include fuels derived from biomass conversion, solid biomass, liquid fuels and various biogases. Carbon fixation is the process through which an inorganic compound, such as carbon dioxide, is converted to an organic compound by a living organism. A common example of this is photosynthesis. The most common biofuels are bioethanol and biodiesel. Bioethanol is produced through fermentation of carbohydrates found in sugars and starches and is widely used in both the US and Brazil. Biodiesel is made from animal fats and vegetable oils, and in its purest form can be used as fuel for modified vehicles. More commonly however it is used as an additive to diesel to reduce levels of carbon monoxide and hydrocarbon particulates. The process by which biodiesel is produced is known as transesterification and is common in Europe. The International Energy Agency has a goal of biofuels supplementing more than a quarter of the world’s demand for transportation fuels by 2050.
How Does it Work
While Ethanol is currently the most common biofuel, it lacks certain qualities to make it the most desirable. For example, ethanol produced from biomass in the US has a high production cost and just 2/3 the energy density of gasoline, causing cars running on E85 (which is 85% ethanol and 15% gasoline) to get about 30% lower gas mileage.i Therefore, the most prevalently researched method of creating biofuel is using bacteria to convert plant matter directly into isobutanol. Isobutanol is beneficial because it can be used in regular car engines due to its higher heat capacity and similar consistency to gasoline.ii While isobutanol is produced through fermentation, there are many other methods that can lead to the formation of biofuel such as catalysis, cellulosis, hydroprocessing and synthetic biology. Catalysis is a reaction which is only made possible by catalysts, which lower the activation energy required for a chemical reaction. By lowering the activation energy a catalyst in turn increases the rate of the reactions; this leads to reliability and large production volumes. Cellulosis has a large advantage over other processes because it has an abundance of possibilities in terms of raw materials; however a larger amount of energy is required to produce ethanol through cellulosis than through fermentation. The two main methods of creating biofuels using cellulose are gasification and acid hydrolysis. Gasification is the process by which a solid biomass is deconstructed through a high temperature, high pressure system and converted into smaller particles. Recent achievements in the gasification processes have lead to eliminating more harmful impurities, such as carbon dioxide, which results in a cleaner and more efficient synthetic gas. Hydrolysis is a water based chemical reaction which converts polysaccharides into many simple sugars. Acids are used to catalyze reactions in which one fragment of the polysaccharide gains a positive hydrogen ion and the other group collects the remaining OH- ion. Hydroprocessing is not a single phase, but a generalized term for any chemical engineering process which breaks down heavy hydrocarbons into light fractions with the addition of hydrogen. Hydroprocessing is most commonly used for breaking down animal fats, such as beef tallow and chicken fat, that can produce a wide variety of fuels. Lastly, synthetic biology is a new form of biofuel creation which refers to biological components and systems that do not exist in the natural world and the redesign of existing biological systems.iii
The long term goal for all alternative energy sources is to replace our dependence on fossil fuels and move toward a sustainable and environmentally friendly society. With current advancements in biofuel energy engineering, it is likely to assume that vegetable and animal fats could become a main source of power. Even though retrofitted cars can currently be powered by biofuels, new advancements will soon allow all cars to be powered by both gasoline and biofuels. When oil is no longer abundant or necessary it will be the other energy sources that are called upon to produce the energy that we need, and if biofuels production continues to improve we may have little concern.