Council staff say they have been encouraged by results from four bores sunk at the landfill. Since March, they have been sucking up methane at a steadily increasing rate.
Dunedin City Council solid waste manager Ian Featherston said the results showed a consistent supply of methane, even as the bores' suction was gradually stepped up.
Gas recovery had increased by 20% since March, to a flow of 175cu m an hour, and another two gas bores were to be installed within months, he said.
At present, the methane was being burnt by a flare to convert it to carbon dioxide, which was 20 times less environmentally damaging.
However, the volume of methane being harvested was expected to increase for the next decade, as new bores went in, and attention had turned to potential uses for the gas, he said.
Council staff were exploring piping the gas to the nearby Green Island wastewater treatment plant, where it would be used as a power source. Any power not needed could be transported to the electricity grid, and, hopefully, a small profit made, he said. Both initiatives could help reduce the pressure on rates increases in Dunedin, he believed.
"I'm hoping we can save on the power bill, which, ultimately, is saving money. If we are able to export a bit... then that acts as a revenue stream."
Council energy manager Neville Auten said gas from the Green Island wastewater treatment plant's digesters would also feed into the supply being collected, and together could amount to energy each year, which if converted into cash, could be worth $415,000 - more than covering the wastewater treatment plant's $340,000 annual power bill.
The figures were a "best guess" at the moment, as a feasibility study was not expected to be completed until late next month, and this week's closure of the Green Island fellmongery complicated matters.
The fellmongery's wastewater was piped to the Green Island wastewater plant, and contributed to gas produced, so the plant's closure would reduce the volume available to be harvested, Mr Auten said.
It was expected to cost about $1.5 million to install pipes and other infrastructure needed to convert the gas to power and cash, he said. The cost could, in part or full, be covered by the Government's Crown loan scheme, with savings generated initially used to pay back the loan.
If approved, the scheme would have a life expectancy of up to 20 years after the landfill was capped, making it "quite exciting" for the city, Mr Auten said.
