Detailed in the environmental assessment documentation prepared by consultancy Hansen Bailey and submitted to the Department of Environment, Water, Heritage and the Arts, the modifications are expected to boost the workforce from 230 to 305 full-time employees.

Located near Morisset in the Newcastle coalfield of New South Wales, Mandalong has extracted up to 4Mtpa from the West Wallarah seam through longwall mining since 2005.

The mine already has approval for processing and transportation of up to 8Mtpa of raw coal, at 4Mtpa each from the Mandalong mine services site and the Delta entry site.

Centennial does not require an increase in the approved underground mining area to meet the 6Mtpa target as the ramp-up is expected to be achieved on the back of improved operational efficiencies, better knowledge of the geology and technological advances.

In seeking approval for the extra tonnage, Hansen Bailey said Mandalong would not exceed the 4Mtpa throughput at either its services site or the Delta site.

“As such, it is considered that the surface environmental impacts associated with the handling, processing and transport of the additional coal extracted from Mandalong mine have been approved,” the consultancy said.

Based on ongoing discussions with Australian Gas Light Company, Centennial aims to feed the gas extracted from its existing methane drainage plant into one or multiple gas engines to create total power output of up to 12MW.

“If this modification were not approved, the methane gas extracted from the drainage plant would either be released into the atmosphere or burnt by utilising the approved gas flares without generating electricity for use in the NSW power grid,” Hansen said.

“As such, the construction of the gas engines is expected to result in a considerable reduction in the quantity of greenhouse gas emissions from the site and benefit the wider community through ‘green’ generation of electricity.”

The engines are expected to be the size of a typical shipping container and can be constructed offsite.

Design work is yet to be finalised with AGL yet to complete a feasibility study on the long-term methane flow rates at the mine.

But the move is estimated to cut carbon emissions by about 136,000 tonnes per annum.

Operation of the gas engines and infrastructure is expected to be managed from one central and fully automated, computerised control room.

Centennial has not yet constructed a ballast borehole that has already been approved, but is seeking to relocate it another 1km south of the access site as part of its application.

The proposals will require the clearance of about 5 hectares of disturbed grassland.

The federal application was made to meet the requirements of the Environment Protection and Biodiversity Conservation Act, with a total of 12 threatened flora species and 17 fauna species potentially within a 10km radius of the site.

Although Mandalong could produce 8Mtpa, Centennial views 6Mtpa as a practical alternative to reduce the potential impact on the neighbouring community and to ensure the longevity of the operation.

Mandalong’s run-of-mine coal output was more than 5Mt in 2009 with 4.57Mt from the longwall face and 490,000t from continuous miners.