The generator is also recycled. It originally ran on compressed natural gas and powered a Wellington hospital.
Even the heat and hot water the generator creates while converting the methane is not wasted — it is diverted to two large water cylinders in the cow shed.
The pilot methane conversion plant at Fairfax — the first in Southland — was commissioned last week after more than two years of planning and design.
It is expected to generate about 50kW of electricity annually —enough to power about 75% of the farm’s electricity needs and equivalent to the requirements of about 10 urban households.
The pilot is a collaboration between Venture Southland, Invercargill dairy engineering consultancy Dairy Green Ltd and Glenarlea Farms Ltd, with support from the Energy Efficiency and Conservation Authority (EECA).
Dairy Green consultant engineer John Scandrett said the concept of gas recovery from waste was not new, but until now it had been thought Southland’s temperatures were too cool to produce enough methane to make a conversion plant viable.
EECA business project manager Dinesh Chand, who visited the farm on Friday, said there were already two methane conversion plants operating on North Island farms with another under construction in Canterbury.
‘‘This is the the farthest south, and as the temperature gets colder the [biogas] bugs don’t work as well. So if we can get the bugs to work and produce methane here, it shows dairy farmers in the rest of New Zealand it could be done anywhere.’’
Venture Southland enterprise and strategic projects group manager Steve Canny said creating energy from waste was an ‘‘elegant solution’’ for dairy farmers, and relatively speaking, not a capitalintensive solution.
It was hoped the pilot would encourage other farmers to install similar systems, he said.
‘‘Once you have got [a pilot] nailed, as these guys are doing, then you can repeat that, with confidence. The trailblazers make it easier for farmers in the future to embrace the technology.’’