The Independent Planning Commission (IPC) is hearing speakers this week regarding Glencore's proposal to run the mine until 2030 and extract a further 52 million tonnes of coal.

The company argues it would most likely cease production in 2025 if the plan is rejected despite an approval extending to 2029. It estimates early closure would cost NSW $408 million.

While numerous written submissions support the plan based on economic factors, many speakers on Wednesday pointed to greenhouse gases and environmental impacts in their opposition.

Felice Quach argued in favour of the plan based on "a strong track record of environmental performance ... particularly in their rehabilitation work".

Wybong resident Margot White told the meeting she believed planners' arguments of limited effects on residents were an "absolute misunderstanding of everything we have been saying for the last decade".

Paul Vincent said he lived five kilometres from the mine, but the extension would cut that to 2.5 kilometres. The Department of Planning, Industry and Environment's assessment found the project to be in the public interest and approvable with comprehensive conditions.

"The department has given no weight to the concerns of the community," Ms White said. "This little bit extra leaves a very large, forever negative legacy."

The meeting also heard from Wybong resident Alan Nightingale, who raised concerns regarding noise and risks to water including a bore that he said had helped his property survive the drought.

Speaker Nic Clyde argued for complete offset of certain types of emissions as a bare minimum if the plan was approved.

Denman Aberdeen Muswellbrook Scone Healthy Environment Group's Wendy Wales said she was addressing the meeting "with disbelief" after objecting to the mine as Anvil Hill in 2007.

"With clear and present danger of climate change now being explained to us by children, we have to listen and act," she said.

Muswellbrook Shire Council has voiced its opposition to the coal mine, a position that Glencore said had been surprising and disappointing.

"We take the issues raised by council very seriously and will be providing a detailed response for the IPC, noting that the council's report does not appear to have taken into account the Project's entire Environmental Impact Statement (EIS) or the detailed technical assessments," a spokesman said.

Hearings are scheduled to continue on Thursday.