Definition
Biofuels can be defined as solid, liquid, or gas fuels derived from biological, renewable sources called biomass. Some examples of biomass that can be
used to produce biofuels today include sugar crops, corn grains, grain byproducts, oil seed crops, trees and grasses.
A Brief History of Biofuels
Renewable biofuels made from vegetable oils and other plant materials were used in some of the first combustion engines in the early 1900s until petroleum
came to the mass market. It wasn’t until the last 30 years that they regained popularity in the U.S. due to oil embargos, rising gas prices, the politics surrounding foreign oil dependency and global warming. Now, the need for carbon-neutral fossil fuel alternatives in the U.S. and beyond is a widely accepted
notion.
How Biofuels are Made
To create biofuels from biomass, the biomass must go through the appropriate chemical reaction, also called an energy conversion route. For example, to create
alcohol-based, advanced biofuels like butanol and isobutanol, the biomass must first be fermented (like beer or wine) using a microorganism to produce the crude biofuel
product. The crude product is then refined to make the fuel and chemical products.
| FUEL |
Energy Density |
Air-FUEL Ratio |
Specific Energy |
Heat of Vaporization |
| Gasoline |
32.0 MJ/L |
14.6 |
2.9 MJ/kg air |
0.36 MJ/kg |
| Butanol |
29.2 MJ/L |
11.2 |
3.2 MJ/kg air |
0.43 MJ/kg |
| Ethanol |
19.6 MJ/L |
9.0 |
3.0 MJ/kg air |
0.92 MJ/kg |
| Methanol |
16.0 MJ/L |
6.5 |
3.1 MJ/kg air |
1.20 MJ/kg |
Why Aren’t We Using Biofuels Already?
First-generation biofuels like bio-diesel and ethanol are still facing several challenges on their path to market, including: production costs, efficiency,
transport and distribution, and costly vehicle modification. That is why Gevo is focused on developing second-generation biofuels like butanol and isobutanol
that can address these roadblocks. The biofuel comparison chart above outlines some of the major benefits of butanol compared to other fuels.