Petroleum and natural gases are currently the main energy source used in the world, but the amount of viable fossil fuels are slowly depleting. Also, research is being done to produce more environmentally friendly fuels to combat greenhouse gas emissions produced from petroleum. Scientists have turned to biofuels as an effective alternative to fossil fuels. Until now, bioethanol has been the primary biofuel, because it is economically favorable to produce and easy to manufacture. It is also a renewable fuel that is made from agricultural feedstock. However, biobutanol is proving to be much more advantageous than bioethanol.
Compared to bioethanol, biobutanol has more energy per gallon, thus more miles per gallon. Biobutanol has 110,000 BTUs per gallon, while bioethanol only has 84,000 BTUs per gallon. Butanol can also be blended with gasoline at much higher levels than bioethanol without any necessary engine alterations, because its physical attributes are more similar to gasoline. It has lower vapor pressure, which makes it safer to store, and handle. Because biobutanol is a better biofuel than ethanol, this project has designed a process to create this solvent. This new plant will hopefully replace ethanol plants, so it was mirrored as closely as possible to the ethanol process.
Traditionally, an Acetone-Butanol-Ethanol (ABE) process is used for biobutanol production. This one stage batch process uses a Clostridium strand (generally C. beijerinckii or C. Acetobutylicum) to produce a mixture of butanol, acetone and ethanol.
First, fermentation produces a mixture of butyric, lactic and acetic acid. Later, the culture pH drops and butanol, acetone and ethanol are produced in a 6:3:1 by mass ratio respectively. The main problems with this process are the low conversion of glucose to biobutanol, and the large amount of undesired solvents produced. Also, the process is very complicated and difficult to control, so its use has dramatically declined since the 1950s. Now, butanol is mostly produced via petrochemical routes, which is not eco-friendly.
David Ramey of Butyl Fuel, LLC, has created a process that uses two-stage anaerobic fermentation to produce green butanol with higher specificity and efficiency than the ABE process. Up until now, there have only been laboratory-scaled productions of butanol using this process. The objective of this project is to design a scaled up process that can produce at least 50 million gallons per year of butanol at 99.5% pure with less than 10ppm acetone. It will be a challenge to create a high yield of butanol. The separations process must also be able to handle a much larger amount of undesired solvents and water when the process is scaled up. Also, sterility will be a main concern for any stream entering and coming out of the fermenters.
The main reason for the production of biobutanol is to have an eco-friendly fuel for the future. As seen above, butanol is made from a biological material, thereby reducing greenhouse gas emissions. Also when burned, it produces no SOx or NOx, making it very environmentally beneficial.