In DNV we have segment directors for the various ship types; tank, bulk, container, and special ships. I had the pleasure of having dinner with all of them earlier this week, and I asked them “which are the marine fuel alternatives for the future?” Here’s the top ten list, in debatable order of expected future market share:
- Heavy Fuel Oil with exhaust cleaning
- Distillate fuels
- Hydrogen (as energy carrier)
- Battery (as energy carrier)
LNG is currently a cheap energy source, with vast reserves compared to oil. Natural gas is the cleanest of the fossil fuels, so as long as combustion engines is the way ships are propelled, natural gas will offer the best environmental performance. The drawback with LNG is that it much prefers to return to gas phase, so keeping it liquid adds challenges to both the distribution chain, and the storage onboard the ships. It also requires more tank volume to achieve the same sailing distance as conventional fuels.
Heavy Fuel Oil will still be in this contest for many years to come. There is an established distribution system, and the fuel is available everywhere around the planet. With proper exhaust cleaning systems, it will also comply with currently planned environmental requirements. The drawback is that the ability to comply with further strengthening of requirements may be limited, and the exhaust cleaning systems also need energy, leading to overall reduction in fuel efficiency.
Distillate fuels, i.e. oil based fuels refined to meet the environmental requirements. Obvious benefit is that these fuels require only minimal changes to the ships engine design and fuel supply systems. On the negative side, analysts seem to expect fairly steep prices for these products. There is also uncertainty about refineries’ capacity to meet the demand for these fuels.
LPG, i.e. heavier hydrocarbon gases than methane (LNG), is an alternative. The benefit is that it is liquid at higher temperatures than LNG. The negative side is that LPG is more expensive, available in smaller volumes, and it comes with more severe safety concerns; it has different flammability characteristics and it is heavier than air so it will not dissolve and disappear, like LNG will.
GTL is transport mode for natural gas, competing with LNG. Benefits of GTL is that it is liquid at atmospheric temperature, so it is easier to transport and distribute. On the negative side, the GTL process consumes a large share of the energy (some 40%).
CNG is another transport mode for natural gas. It would be easier to distribute to the ships than LNG because it could be extracted from existing gas distribution grids. However, it would require twice the tank volume as LNG to offer the same sailing distance, and it would complicate distribution where a natural gas grid doesn’t already exist nearby.
Biogas might become available in the future. At least this is what politicions tell us. The shipping industry would need so much of it, that it is doubtful that biogas will penetrate any significant share of shipping. For in-city ferry routes or other short sea trades, though, it might be an environmentally friendly alternative. And the systems would be identical to those for LNG – after all we are talking about methane, CH4, in both cases – the engine doesn’t know whether it’s clean or dirty CH4.
Hydrogen is a potential energy carrier. Hydrogen can be produced in land-based plants and then utilised in fuel cells or combustion engines in ships. Efficient production of hydrogen is one challenge. The volume occupied by hydrogen is another, requiring about 6 times the space of LNG.
Battery is another way of carrying energy from land-based plants to ship, this time in the form of electricity. Battery technology and lifecycle efficiency are key challenges.
Nuclear is the wild card in this list of future fuels. The potential is tremendous, and the environmental benefits are strong as long as the waste is handled correctly. Safety concerns and perceived risk, though, may just be insuperable obstacles.
A conclusion to this list is not necessary. There should be room, small or large, for a large selection of the above fuels. And maybe even more to come.
Next week, I’ll be reporting from San Francisco, with some interesting news on LNG. Stay tuned.