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Biofuel in a simplistic definition is a substance produced biotechnologically and used as combustible. This definition matches several gaseous and liquid substances (bioethanol, biobutanol, biomethane, biohydrogen, biodiesel), produced by microorganisms, bacteria, yeasts, fungi, algae, etc.

This review could be a starting point

https://doi.org/10.3390/fermentation9090813

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Yes, While methane and ethanol are two of the most well-known biofuels produced through fermentation, there are several others that have been developed or are under investigation:

1. Butanol:

• Source: Can be produced from a variety of feedstocks, including agricultural residues, food waste, and lignocellulosic biomass.
• Advantages: Higher energy content than ethanol, better compatibility with existing gasoline infrastructure, and lower water solubility.
• Challenges: Higher production costs compared to ethanol.

2. Hydrogen:

• Source: Produced by fermentative bacteria through a process known as dark fermentation.
• Advantages: Clean-burning fuel with high energy density.
• Challenges: Storage and transportation challenges due to its gaseous state.

3. Biodiesel:

• Source: Produced through the transesterification of vegetable oils or animal fats.
• Advantages: Can be used as a direct replacement for diesel fuel.
• Challenges: Competition with food production for land and resources.

4. Isobutanol:

• Source: Produced through a similar process to butanol but from different feedstocks.
• Advantages: Higher energy content and better compatibility with gasoline infrastructure than ethanol.
• Challenges: Higher production costs compared to ethanol.

5. Biogas:

• Source: Produced through the anaerobic digestion of organic matter.
• Advantages: Can be upgraded to biomethane, which is a cleaner-burning alternative to natural gas.
• Challenges: Requires specialized infrastructure for collection, storage, and upgrading.

6. Biojet Fuel:

• Source: Can be produced from a variety of feedstocks, including algae, agricultural residues, and waste cooking oil.
• Advantages: Can be used as a direct replacement for conventional jet fuel.
• Challenges: Higher production costs and limited commercialization.

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