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 every time it switches between fuel types.

'Staggering': ScotGov axes Calmac ferry failure fines despite scrutiny vow

Ageing CalMac ferry fleet sees cancellations skyrocket due to ‘technical’ issues

'Staggering': ScotGov axes Calmac ferry failure fines despite scrutiny vow

CalMac 'profoundly sorry' as Glen Sannox ferry out of action until at least Tuesday

Crucially, there is no local supply of LNG, so the gas has to be imported from Qatar and then driven 540 miles by road tanker to Scotland from Kent.

This, of course, means the imported gas has to travel through the Strait of Hormuz, and gas prices have skyrocketed since the US-Israel conflict with Iran.

So complex are the engine spaces on MV Glen Sannox, they have been dubbed the “snake pit” because of the amount of pipework packed into them.

MV Glen Sannox and MV Glen Rosa are the first LNG ships of their type constructed in the UK, and the choice of an LNG propulsion system increased the design challenge for the Ferguson Marine shipyard which built them.

One of the problems the shipyard faced was that the LNG tank and cryogenic pipework added significant weight to the ship and took up a lot of space.

During the building process, Ferguson Marine in Port Glasgow, which has a long and illustrious history building non dual-fuel ferries, went into administration and was nationalised.

From the outset, it was hoped that the ground-breaking dual fuel ferries would give the shipyard a bright future as orders would flood in after the yard built

Instead, they sunk the yard and its future remains uncertain.

Ironically, the two ships remain the only LNG vessels in the CalMac fleet, as CMAL has opted for traditional diesel engines for the new Islay-class ferries, the first of which entered service at the end of March.

Two new freight vessels recently ordered by CMAL for the Northern Isles will also use traditional diesel engines to generate electricity for their propulsion units.

CalMac decided to suspend the use of LPG last last summer after concern that some gas could enter the engine spaces.

Extra safety features were fitted during the vessel’s annual overhaul to address the issue but CalMac then decided not to “re-gas” the ship when it returned in February.

A spokesperson said  it would take at least a week and the priority had been to get the vessel back into service as soon as possible given the shortage of available ferries on its west coast network.

The initial decision to suspend the use of LNG for the main engines followed concern that gases from a vent pipe could enter the engine spaces via an air intake.

Venting into the atmosphere is a standard feature of LNG ships to control pressure and to get rid of “boil off” gas - where the gas deliquefies - as well as gases released when the ship switches between fuels.

Energy Secretary Miliband must approve these North Sea oil fields now

The curious case of the post-Brexit deal that will rename marmalade

Handing taxpayers cash to comedians to perform is no laughing matter

Why Pennan residents need a new local hero and not silly rules about windows

CalMac said refilling the LNG tank was a lengthy process because the engine had to cool down for a week before the refuelling operation could commence.

Given the shortage of serviceable vessels it was facing, the operator decided instead to continue operating the ship solely on marine gas oil, a form of diesel.

CalMac says the cryogenic LNG tank on Glen Sannox cannot be refilled until the engines have been allowed to cool for a week.

CalMac said it planned to resume using LNG once the current network pressures had eased and a suitable opportunity arose to take Glen Sannox out of service for re-gassing.

The spokesperson added: “She was designed to run on either LNG or diesel and has not operated on LNG since July 2025.

“The vessel has been a welcome addition to the CalMac fleet since she joined the service in January 2025.”

In the meantime, MV Glen Sannox is currently doing the Ullapool- Stornoway route because of vessel shortages.

Another ferry service between the Western Isles and the mainland has been cancelled for one month as CalMac r deals with the network disruption.

The service between Mallaig and Lochboisdale on South Uist will not run until May 18, as the Lord of the Isles - the ferry which usually serves that route - will be moved to cover sailings between the mainland and Islay.

CalMac said the move was required to avoid “displacing thousands of bookings”, while a new timetable crossing the Sound of Barra would be put in place to allow passengers to make sailings from Castlebay to Oban.

In recent weeks multiple vessels have been taken out of service as a result of annual maintenance and technical issues.

All of this, of course, is not CalMac’s fault - they just have to play musical ships every day to ensure that as many passengers as possible can sail across the network.

But with most of the ferries being well beyond their operational shelf life and new ones still some way off from being delivered, the network will continue to face severe disruption.

I suspect that every day CalMac staff at the Gourock HQ have their fingers crossed while waiting for a dreaded phone call from a raging skipper after their vessel is hit with another problem.

Even John Swinney has admitted that the state of the network had left him ‘embarrassed’.

Pity his embarrassment took so long to show itself.

One thing is clear - the dual-fuel ferries were a risk that was not worth taking and the knock-on effects has been disastrous for passengers, crew and the island communities they serve.

Not to mention a shipyard that appears to have been sunk in the process.

© Herald Scotland