The great green ferry dream has turned into a nightmare for islanders and sunk a shipyard in the process. It really wasn't worth the risk, argues Herald columnist Alan Simpson.

It was hailed as the future for maritime vessels, would dramatically reduce carbon emissions and was predicted to spark a boom in Scots shipbuilding as orders would flood in from all over the world.

Except none of that happened, the exact opposite in fact and probably encapsulates the entire sorry saga of Scotland’s current ferry crisis.

In a final indignation, it has been revealed that CalMac’s much-vaunted “eco-friendly” dual-fuel ferry MV Glen Sannox - which is capable of running on gas - has been operating solely on diesel since last July.

So much for all the hype.

The irony of the news should not be lost on anyone as the complex nature of the LNG dual-fuel engines is widely credited with being the main factor in why the MV Glen Sannox and sister ship MV Glen Rosa were delivered late.

Procurement agency CMAL, which owns the ships operated by CalMac, first started looking at LNG as a possible fuel as long ago as 2012.

Two years later, when the procurement for two new ships began, CalMac agreed that the new vessels should be dual-fuel, capable of running on LNG as well as traditional marine oil.

The attraction was that gas burns more cleanly, meaning the ferries would easily comply with new regulations on pollutants and sooty emissions which were soon to come into force.

The Finnish manufacturer of the dual-fuel engines also claimed they would emit up to 25% less carbon dioxide when running on gas.

But the global warming benefits of the LNG engines have been questioned because they also emit methane, itself a powerful greenhouse gas.

A report for CalMac has estimated that the carbon equivalent savings when running the ship on gas are less than 9%  and that figure does not include the methane vented........

© Herald Scotland