A “green” ferry recently built in Scotland is set to produce a larger carbon footprint than the older diesel-powered vessel currently serving the route between the mainland and Arran. Despite using liquified natural gas (LNG), the dual-fuel ferry Glen Sannox will produce 10,391 equivalent tonnes of CO2 emissions annually compared to 7,732 for the MV Caledonian Isles. The new ferry requires larger engines to carry 127 cars, and these bigger engines emit methane, a greenhouse gas with a more significant global warming effect than CO2. Some experts have argued that with poor upstream Qatar emissions and the ship’s size, it would be better to use diesel instead.
CMAL, the ferries procurement agency, claims that the comparison between the two ships is inaccurate as the Glen Sannox vessel is larger. The addition of LNG technology came with its technical complexity, and the Ferguson shipyard faced several challenges during its development, resulting in the project running over time and budget. Moreover, its size means it cannot sail into the mainland harbour at Ardrossan until a significant redevelopment takes place.
CalMac’s emissions analysis of the ferry shows that Glen Sannox’s primary carbon footprint is due to significant decisions made by CMAL, ferry operator CalMac, and Transport Scotland when outlining the contract for the vessel. Glen Sannox has bigger engines that produce more emissions and require more fuel to carry a higher top speed. Furthermore, the lack of a local LNG supply in Scotland means the fuel must be brought up from a terminal in Kent using diesel road tankers, which releases a higher annual CO2 equivalent than transporting MGO-fuelled ships.
Environmentalists and academics have urged companies to consider a “well to wake” comparison of fuels to give a clearer picture of the climate impact rather than comparing emissions solely during engine operation. It has been suggested that CalMac could run the Glen Sannox ferry on biogas, which is considered carbon neutral since the gas used is produced from organic waste and by-products from whisky industries. Alternatives could be to retrofit potential future fuels like ammonia for the four more large CalMac ferries under construction in Turkey. Alternatively, catamarans could be an option that is more fuel-efficient than single-hulled ships. The chartered catamaran Alfred is considered the most environmentally-friendly large ferry in Scotland as it has low fuel consumption
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