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.

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.

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

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.