A prototype methane recovery system is capturing biogas gas from an effluent pond on a 900-cow Southland dairy farm and converting it into electricity.
It took local agricultural engineering firm Dairy Green nearly three years to plan and install the system that now provides enough power to run the dairy shed, as well as heating all the water required for processing and wash-downs.
'Methane is 21 times worse off in the atmosphere than carbon dioxide so we burn the methane through the generator and the motor and it returns back to the atmosphere as carbon dioxide again," says Dairy Green engineering consultant Quinton Scandrett.
The system demonstrates the commercial viability of this technology in a cool climate. Until now it had been thought Southland's temperatures were too cool to produce enough methane to make a conversion plant viable.
Quinton says performance has exceeded forecasts and cow manure now provides 30KW electrical power and 60KW hot water per hour.
"The exciting thing is that we've shown we can do it. We're gathering a lot of data and monitoring and from there it's going to help us to really build on it and create a lot more of these around Southland or even New Zealand."
The methane process does not remove any nutrients from the effluent. Once the methane has been captured, the liquid effluent is spread slowly onto paddocks. The sludge is then removed from the pond using a slurry tanker and is spread onto the land."