Answer
1. Biofuels
A biofuel is produced from biological/renewable organic material, such as:
- used cooking oil,
- vegetable oils,
- animal fats,
- agricultural residues,
- forestry waste,
- organic waste.
In marine engineering, they are categorized into generations:
First Generation (FAME - Fatty Acid Methyl Esters): Produced via transesterification of vegetable oils or animal fats.
Engine Concerns: Hygroscopic (absorbs water), risk of microbial growth, poor cold flow properties (cloud point/CFPP), degrade seal materials (NBR/FKM), and potential deposit formation in fuel pumps and injectors.
Second Generation (HVO - Hydrotreated Vegetable Oil): Paraffinic bio-diesel produced by hydroprocessing.
Engine Advantage: Fully drop-in fuel. Chemically similar to conventional MGO, high Cetane number (>70), excellent stability, no microbial growth issues, directly compatible with existing fuel treatment systems.
2. Synthetic Fuels (e-Fuels / Power-to-X)
e-Fuels are synthesized by combining green hydrogen (produced via electrolysis using renewable electricity) with recycled carbon dioxide or nitrogen:
e-Methanol (CH3OH): Stored as liquid at ambient temperature. Requires low flashpoint fuel delivery systems (IGF Code), explosion-proof spaces, and double-walled piping.
e-Ammonia (NH3): Carbon-free fuel (NOx and N2O are primary emissions). Stored refrigerated (−33∘C) or under pressure (∼8.5 bar). Highly toxic; requires selective catalytic reduction (SCR), double-walled piping, nitrogen purging, and toxicity containment/venting systems.
e-Diesel / e-Methane: Direct drop-in substitutes for MGO or LNG requiring zero modification to existing engine technology.
3. Alternate Fuels (Gaseous & Low-Flashpoint)
Alternative fuel is a broad term for a fuel or energy carrier used instead of conventional HFO/MGO, generally to reduce air pollution and/or GHG emissions.
Marine examples include:
- LNG / biomethane / e-methane
- Methanol
- Ammonia
- Hydrogen
- LPG
- Biofuels
- Synthetic/e-fuels