BC Ferries is continuing its move toward liquefied natural gas with an upgrade of its two Spirit Class vessels.

The operator has pulled the first of two ships from service for upgrades, which will be done in Gdansk, Poland. The vessels will be converted to operate on liquefied natural gas or ultra-low sulphur marine diesel.

BC Ferries projects the switch to natural gas will cut carbon emissions by 12,000 tonnes annually — akin to removing about 2,500 vehicles from the road each year.

The Spirits are the two largest ships in BC Ferries' fleet — servicing the Tsawwassen-Swartz Bay route. They're also its biggest fuel guzzlers.

The ships ate up about 15 per cent of BC Ferries' $100 million fuel bill last fiscal year.

"By converting to natural gas, we can cut that fuel bill in half. That's a significant benefit for the fare payer," BC Ferries CEO Mark Collins told All Points West guest host Jason D'Souza.

Listen to the full interview below.

Upgrades to the Spirit of British Columbia will be completed by spring of 2018. BC Ferries will then pull the Spirit of Vancouver vessel next fall.

Both vessels will operate during peak traffic in the summer.

"We're looking for another 20 to 25 years for these ships," Collins said.

Passengers will also notice new carpeting, refurbished washrooms, an expanded gift shop and a new coffee bar.

Fixing the doors

Earlier this summer, BC Ferries introduced its three new Salish Class vessels, which also operate on liquefied natural gas.

But what drew the most attention were the vessels' automatic doors, which customers complained were slow and difficult to operate.

"If you had asked me two years ago what I'd be worrying about on these ships, I wouldn't have told you doors," Collins said.

"The beepers are loud and annoying, so we're trying to get those turned down," he said.

"We've sped the doors up so they open and close more rapidly. And we're trying to make the sensors less sensitive."

Collins said customers have also complained about the steep stairways, although there are two elevators on each ship.

"In the main, the ships have been very well received," he said.

"People really like the artwork on them. People like the fact that they're quiet and powered by LNG."

The Polish shipyard contracted to build the Salish vessels will also perform the upgrades on the Spirit Class due to their expertise in natural gas propulsion.

"That gives us the confidence that the job will be done correctly," Collins said.

With files from CBC's All Points West