The tsunami of 2020 is just the tip of the iceberg. The Paris Agreement mandates a dramatic reduction of CO2 emissions. Now, shipping, the primary transporter of world commerce, has attracted everybody’s attention. Future economy will be multi-fueled. It is critical to make the right choice; drivers will be the cost, technology, availability, and of course regulations. Also, it is important to recognize that shipowers without motivation will not go to exotic, alternative fuels. It is just fair to compensate them for the risks taken by them due to uncertainties in price, immature technology, and availability.


So many predictions and studies nominate ammonia and hydrogen to be the queen and king of the future fuels. Ammonia for example is one of the most energy dense non-fossil fuels. A big advantage of ammonia is that it is easier to store than LNG. Of course there is no free-lance, ammonia is toxic, but it has calorific value about half of diesel and it is three times cheaper than gasoline. It causes stress corrosion in steels and needs fuel for ignition.


Methanol complies with 2020, it has relatively low CO2 emissions, it is not cryogenic like LNG, and has a lot of problems. It is costlier than LNG and LPG, corrosive and has low energy density which means we need a lot of volume. It can be used like natural gas, it is toxic and has low-flashing point. At this point, I would like to remind of the Stena experiment; the ship Stena Germania never went ahead with methanol from initial stages.


Welcome to the fuel of the zeppelin and its developed counterpart, the space shuttle: Hydrogen. Hydrogen is probably one of the most abundant elements in nature, it can be produced from natural gas, coal, biomass, but we need to look at the life-cycle of hydrogen production. Ideally, we want to produce hydrogen utilizing renewable sources of energy. It is a sustainable fuel, but it is flammable and has low energy density. It is stored at very low temperatures, minus 253 degrees Celsius, so one idea is to burn it immediately after production. Stepping stones are:

  • Infrastructure;
  • Production cost;
  • Storage;
  • Low energy density;
  • Flammability.

Fuel Cells

Hydrogen is used in a fuel cell, where we get thermal and electrical energy due to the pairing of hydrogen with oxygen. But why do we want to use fuel cells? Because they are much more efficient than diesel generators. So what are their stumbling blocks?

  • High catalyst cost;
  • High footprint;
  • System complexity;
  • Low power density;
  • Sensitivity of the electrodes. Now we have fuel cells of 100 KWs. Imagine how many fuel cells we need for an Aframax tanker.


Biofuels are made from animal fats and vegetable oils.  They are able to satisfy the 2020 requirements, but they do compete with the food-chain. We would need two times the UK in expands, in order to get what we need in bio-fuels. One of them, biodiesel, is a very safe fuel, with high-flash point, but it has its problems, for example price comparable to diesel, high cloud point meaning that it clogs the filters and attacks seals, gaskets and rubber hoses. And more importantly it degrades, it does not like prolonged storage.

Micro-algae Fuel

This is fuel from micro-algae, like botryococcus braunii, which is three birds with one stone. We get fuel, we absorb carbon dioxide due to its photosynthetic production and it works day and night.


Of course, a very hopeful candidate is LNG and its cousin LPG. LNG is utilized in high and low pressure dual fuel engines. Right now there is a stumbling block with its availability. But we can utilize the Otto cycle and the diesel cycle and the highest expense is related to its storage in membrane and C-Type tanks. Maybe some of these problems can be removed with LPG which is easier to store at -48 degrees for propane and also it has higher availability. LNG is an excellent bridge fuel and I would have to mention that you do not have to shoot the dual fuel engines with methane slip because the break-even point with HFO, for example, is 4.3% methane slip, which is slightly higher than the low pressure engines.

Propulsion modes, a key feature for the future

However, not only the fuels, but also the propulsion modes will change in the future. We are going to go back to the age of the clippers, we are going to see wind utilization, we are going to see the Teslas of the seas; many different modes of propulsion.

In the end, there is a very promising solution: the carbon-neutral fuels. Fuels that are made with renewable sources of energy from carbon capture, having a net CO2 emissions of zero. If we capture the produced CO2 we get carbon negative that, the tally is negative. Thus, we remove CO2 from the equation which makes it very promising.

Shipping industry will also welcome the carbon dioxide scrubbers. If you think that you are going to end up with SOx scrubbers, you are wrong. We are going to see carbon dioxide scrubbers which is not considered as a bad solution.

Concluding, some take away points would be:

  • Synthetic fuels - bio-fuels are options;
  • Ammonia and hydrogen are “sine qua non”;
  • Carbon neutral/carbon negative fuels;
  • Nuclear power plants are ideal for ships;
  • The most important would be renewable energy sources.

Above text is an edited version of Dr. John Kokarakis’s presentation during the 2019 GREEN4SEA Conference.

You may view his presentation herebelow

The views presented hereabove are only those of the author and not necessarily those of  SAFETY4SEA and are for information sharing and discussion  purposes only.

Dr. John KokarakisChairman, Greek Section, SNAME

John Kokarakis is a graduate in Naval Architecture & Marine Engineering from National Technical University of Athens (1979). He also holds graduate degrees from the University of Michigan (MSE 83, MSE 84 and PhD 86). He worked in various projects worldwide as a consultant/technical investigator of maritime accidents. The most notorious were the explosion of  Space Shuttle Challenger, the grounding of Exxon Valdez, the explosion and fire of Piper Alpha, the capsize of drillship Sea-Crest and others. Furthermore, he was a consultant for numerous aspects on containership design, operation and repair.  He has extensive experience in ship design and operations, spanning over forty years. He is currently working at Bureau Veritas in charge of technical development and troubleshooting. He focuses on the implementation of the “green” regulations, fuel saving techniques, energy efficiency, speed and hydrodynamic optimization, resistance and propulsion, performance monitoring, ship design, machinery and safety, education and training, asset integrity management and alternative fuels.