How biofuel is made

This post originally appeared on TriplePundit and is part of a series on biofuel sponsored by Novozymes.

The biofuel story can be a confusing one, since there are so many different types from so many different sources that are used in so many different ways. Let’s see if we can make some kind of sense of all this while gaining some understanding of where they come from and how they are produced.

Biofuel producers often speak in terms of generations, which are really more of a historical classification than a functional one. First generation biofuels are the ones that have been around for a while. They generally come from the starches and sugars found in food crops, along with animal fats and vegetable oils. Like most biofuels, they can be divided into two types: biologically derived material that can fermented to produce alcohol (starch), and natural oils that can be processed to create biodiesel (lipids).

Alcohol-based biofuels are produced in much the same way as liquor, though, of course with different emphasis. In fact, ethyl alcohol, or ethanol, which is the most commonly used bio-alcohol, is the same type of alcohol that is found in whiskey, vodka, gin, etc.  All of these are based on the fermentation of starches and sugars. The ingredients are gathered, ground up, mixed with water and left to ferment with the help of yeast or other organisms for some period of time (three years for Scotch whiskey!) before it is finally distilled into the final product. Whiskey is made from barley. Vodka was traditionally made from potatoes, though various grains are often used now. Bourbon contains 51 percent or more corn. Tequila is made from agave. Rum is made from molasses, and gin comes from juniper berries. Brandy and cognac both come from grapes. All of these are fermented to produce alcohol. In the case of biofuel, which primarily uses corn, because of the quantities required, the emphasis is on productivity, which is why enzymes are often used to accelerate the breakdown of starches into sugars.

Biodiesel, on the other hand, is derived from plants that produce vegetable oils or from animal fat. The most common oil-rich plants used include palm and soybeans, though many other feedstocks can be used including recycled grease and vegetable oil from restaurant deep fryers. In some cases, cooking oil can be burned directly in diesel engines, though it doesn’t flow well at cold temperatures, which is why it is generally converted into diesel first.

These fats can be converted into fuel through a process called transesterification. This is a long word to describe a chemical process in which glycerine is removed from vegetable oil (or grease) to produce biodiesel, which is otherwise known as methyl ester. The process consists of mixing the oil with methanol and sodium hydroxide and then removing the glycerine. It is really a fairly straightforward process which is why people are able to do it at home.  Generally speaking, fairly pure feedstocks must be used to ensure a usable product, but the range of inputs can be expanded through the use of enzymes to allow for lower purity and lower cost inputs.

Other first generation biofuels include biogas, which is made by anaerobic digestion of vegetable matter and syngas, which is made from wood. Biogas generally takes the form of methane. It is being produced successfully in conjunction with both landfills and farming operations. Syngas is produced in a process called pyrolysis, in which wood or other biomass is heated in an oxygen-deprived environment. The byproduct of this process is called biochar, which is being hailed as a potential climate change solution, since, when produced as described above and added to the soil, it has a carbon negative impact, pulling net carbon out of the atmosphere and sequestering it in the ground, where it will remain for centuries.