Post-coal planning for one of Australia’s biggest regional economies must include the vast buffer around current mining operations to give the Hunter a chance at future growth, research suggests.

The scheduled closure of Hunter coal mines will free up 130,000 hectares of land over the next 20 years, economic modelling released on Wednesday has found.

Some 17 mines in the Hunter will close, unlocking degraded sites and vast areas of less damaged zones set aside by mining companies, according to the report prepared by consultancy firm EY for the Lock the Gate Alliance of farmers and environmentalists.

Hunter Jobs Alliance coordinator Warrick Jordan told AAP the current shortage of areas zoned for industrial use, called “employment lands” by planners, is a barrier for businesses looking to come to the region.

“Identifying those specific parcels of land that can be used to attract investors and start to test the possibilities – that’s critical.”

He said the region also has some of the best expertise in the nation on land rehabilitation, which could drive jobs and growth in repurposing mine sites and biodiversity restoration projects .

The EY report found the post-mining “bonanza” could be worth $3.7 billion in new economic output from clean industries powered by renewable energy, conservation work to restore biodiversity, and an expansion of agriculture.

Lock the Gate spokeswoman Georgina Woods said the Hunter’s post-mining planning should be expanded to include the “extensive mining buffer lands”, identified by the organisation’s own detailed mapping.

“We also need the new Albanese federal government to work together with NSW to establish a Hunter Valley Authority,” she said.

The new authority, backed by a new long-term rehabilitation fund, could coordinate the release of land and fund jobs in regrowing forests, restoring the water catchment, and monitoring pollution.

Mr Jordan said certainty for investors about when land was available was critical, as was removing complexity around development approvals to release the “rehab land” more quickly.

Communities and governments expect extensive open pits to be filled and land prepared for re-use, with the report assuming mining land will be available for restoration five years after operations cease.

But the economic modelling goes beyond the minimum mandatory requirements for rehabilitation and environmental management.

Extending biodiversity restoration and conservation beyond mine sites and into the buffer lands could increase economic output.

Mining companies are required to rehabilitate land based on their existing approvals.

But under the modelling’s “maximum conservation scenario”, where the buffer lands are restored for conservation or farming, the economic output and new jobs could be twice that of the status quo.

The report said economic returns were largest when the repurposed land is used for renewable energy precincts serving new clean industries.

The “renewable energy precincts scenario” combines extensive biodiversity restoration with industrial development on heavily damaged mining areas.