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The Tug Lyttelton Preservation Society is considering new options to power the 115-year-old boat, one of the oldest operating steam-powered vessels in the world.
Society president Mike Bruce said up to 60-tonne of coal is used a year to run the vessel.
"We’ve got to change, we want to run the ship for another 100 years, we won’t do that on coal," he said.
But the cost of converting from coal to a more environmentally-friendly fuel option are high.
"We are well aware we have got to do something but we are not self-sustainable," Bruce said.
"We can’t fund ourselves through the year from passenger sales so need to go and get grants from Rata, pub charities, the heritage society, and others."
Bruce said the society is looking into a range of options, one of which is bio-fuel.
Bruce estimates the conversion costs of moving from coal to bio-fuel will be about $40,000.
He said double the amount of wood would be needed to achieve the same amount of energy as coal.
Another option, which could be run in conjunction with bio fuel, is to use an electric pre-heater to pre-heat the boiler. But this would cost another $80,000.
If they turn to battery power, it will be the “oldest vessel in the world running the newest technology,” Bruce said.
Whatever decision is made will be based on the funding available.
"We’ve got to get off coal, but we’re not going to get off coal without funding."