Councillors adopted the new roadmap on Tuesday night in its first major strategy announcement since declaring a "climate emergency" none months ago.

All councillors voted through the roadmap, despite some fears the plan could one day expose the shire to a bill of between $50,000 and $500,000.

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The concerns centre on one part of the roadmap, which allows for the council to "offset" emissions if zero emissions cannot be reached in five years.

The council would purchase the offsets from other groups already working on projects to suck carbon dioxide out of the atmosphere, like those planting trees, for example.

Councillor Dave Petrusma said it was a "real unknown cost factor.

"The market changes all the time. I have real concerns about the council at that time and whether it will need to pay money to achieve the target."

About the plan: Everything you need to know about how Mount Alexander Shire wants to slash emissions to zero

Fellow councillor Stephen Gardner shares his worries that a future council could be saddled with huge bills.

"I've never really been keep on the proposition ... but the reality is, it's not our problem and it's not the next council's problem either. It's the one after," he said.

"Hopefully, by then, it (reaching zero emissions) has happened."

The roadmap does not assume the council will reach zero emissions by 2025, though it does anticipate huge cuts through green energy purchases, street lighting upgrades and other efficiency upgrades..

The shire will still need to offset 1615 tonnes of carbon dioxide equivalent each year after 2025, according to the roadmap, council officers believe.

More than half the remaining greenhouse gases will likely come from methane seeping out of the closed Castlemaine landfill, with the rest from a depot plant, any remaining fleet vehicles not replaced with electric cars and gas use in buildings.

Both councillors stressed that they were not opposed to the roadmap.

"I think it's a wonderful aspiration," Petrusma said.

Cr Gardner acknowledged that some in the community were skeptical about climate change but said the roadmap made financial sense.

"I know people can get a bit historical about climate change, that it is going to cost the world an everything," Cr Gardner said.

"Most of this is about the council adopting (new practices) to the way it operates, so it should save us money in the long term."

Councillor Tony Cordy said one way of addressing the risks of a huge offsets bill would be to work with the community on plans.

"That would allow us to see what we could achieve locally before we go outside (the shire)," he said.