A biofuel is defined as any fuel whose energy is obtained through a process of biological carbon fixation. That definition serves to make our understanding of biofuels as clear as mud, so let’s unpack it a bit.
Biological Carbon Fixation
Carbon fixation is a process that takes inorganic carbon (in the form of things like CO2) and converts it into organic compounds. In other words, any process that converts carbon dioxide into a molecule that would be found in a living organism is carbon fixation. If this process occurs in a living organism, it is referred to as ‘biological carbon fixation’.
The next part of the definition of a biofuel involves fuel. A fuel is nothing more than something from which we humans can get energy. Carbon fixation can lead to a number of different compounds, like proteins, fats, and alcohols (just to name a few). If any of those molecules can be used to provide energy in a mechanical setting, we call it a fuel.
The Real Definition of a Biofuel and the Practical Definition
A biofuel is a hydrocarbon that is made BY or FROM a living organism that we humans can use to power something. This definition of a biofuel is rather formal. In practical consideration, any hydrocarbon fuel that is produced from organic matter (living or once living material) in a short period of time (days, weeks, or even months) is considered a biofuel. This contrasts with fossil fuels, which take millions of years to form and with other types of fuel which are not based on hydrocarbons (nuclear fission, for instance).
What makes biofuels tricky to understand is that they need not be made by a living organism, though they can be. Biofuels can also be made through chemical reactions, carried out in a laboratory or industrial setting, that use organic matter (called biomass) to make fuel. The only real requirements for a biofuel are that the starting material must be CO2 that was fixed (turned into another molecule) by a living organism and the final fuel product must be produced quickly and not over millions of years.
Biofuel versus Fossil Fuel
Biofuels are not new. In fact, Henry Ford had originally designed his Model T to run on ethanol. There are several factors that decide the balance between biofuel and fossil fuel use around the world. Those factors are cost, availability, and food supply.
All three factors listed above are actually interrelated. To begin, the availability of fossil fuels has been of concern almost from day one of their discovery. Pumping fuel from the ground is a difficult and expensive process, which adds greatly to the cost of these fuels. Additionally, fossil fuels are not renewable, which means they will run out at some point. As our ability to pump fossil fuels from the ground diminishes, the available supply will decrease, which will inevitably lead to an increase in price.
It was originally thought that biofuels could be produced in almost limitless quantity because they are renewable. Unfortunately, our energy needs far out-pace our ability to grown biomass to make biofuels for one simple reason, land area. There is only so much land fit for farming in the world and growing biofuels necessarily detracts from the process of growing food. As the population grows, our demands for both energy and food grow. At this point, we do not have enough land to grow both enough biofuel and enough food to meet both needs. The result of this limit has an impact on both the cost of biofuel and the cost of food. For wealthier countries, the cost of food is less of an issue. However, for poorer nations, the use of land for biofuels, which drives up the cost of food, can have a tremendous impact.
The balance between food and biofuel is what keeps the relatively simple process of growing and making biofuels from being substantially cheaper than fossil fuel. When this factor is combined with an increased ability (thanks to advances in technology) to extract oil from the ground, the price of fossil fuel is actually lower than that of biofuel for the most part.