Hydrogen (and LNG, CNG)

• At sea level water vapour is harmless, so a way of reducing CO2 emissions is to burn Hydrogen (so creating H2O or water) rather than the carbon (which creates CO2).
  
• Natural gas has a higher proportion of hydrogen then oil, particularly heavy fuel oil. So using natural gas rather than oil as a fuel reduces the CO2 emissions created for a unit of energy. (Being free of sulphur, it also reduces SOx emissions).
  
• For shipping, the high value of natural gas, whether compressed (CNG) or liquefied (LNG) is likely to be attractive only in special circumstances, but, as the value of carbon reductions increases, the scope will expand.

INDEPTH
Ultimately, hydrogen as a fuel creates no CO2 emissions. It also enables use of fuel cells, which provide a direct chemical conversion from fuel and air to electricity. So this is a very attractive aspiration for the longer term, as several challenges have yet to be overcome.

There are no natural sources of hydrogen as a fuel. It has to be created from other sources.

So one challenge is to develop sources of hydrogen that do not themselves create CO2. Most energy visionaries see renewable energy, such as wind, wave, tidal and solar as being the likely sources, but most developments will, for some time, be directed at the electricity markets.

Hydrogen is also difficult to store. It is not yet clear how hydrogen as a marine fuel would best be handled and stored.