Biogas system starting to pay its way
Knowing the potential power of methane might have saved former National MP and farmer Shane Adern some grief after he drove a tractor up the steps of Parliament in 2003, protesting against proposed legislation targeting the biogas.
Southland-based company Fortuna Group is leading the charge in a different way, turning biogas into a significant power source on Glenarlea Farms, Isla Bank.
The system is one of the ﬁrst on a New Zealand dairy farm. The project has been a labour of love for more than 10 years for its brainchild, Fortuna Group chief executive David Dodunski.
The project evolved into a collaboration between Dairy Green, the Energy Efficiency and Conservation Authority, the National Institute of Water and Atmosphere and Venture Southland.
It was, however, the vision between Dave Dodunski and Dairy Green owner John Scandrett, that brought the project to life. Fortuna Group senior operations manager Pete Bruce has overseen the development and installation of the system on Glenarlea.
It was initially unknown if it would produce enough biogas, especially during cooler temperatures, however the drop in output during winter conveniently coincides with the dairy off-season.
“There was a lot of unknowns,” Pete says. The system is now on the cusp of being commercially viable and produces electricity at Glenarlea for six to eight hours a day, he says.
Fortuna Group has an over-arching goal to provide New Zealand’s dairy farms with a biogas recovery plant, eventually at a cost of $100,000 – at that amount costs would be recouped in about ﬁve years – but the present cost is higher.
John Scandrett says the system, which has been operational for three seasons, powers a diesel engine converted for natural gas and produces enough biogas on average to create 30kWh (kilowatts of power an hour) for the dairy shed.
It heats two water cylinders with a total capacity of 700 litres as well as providing electricity to the shed. “It produces about 210 kilowatt hours of electricity per day and about another 140 kilowatt hours of hot water per day.”
The shed uses about 450 to 500kWh a day, so 70% of the energy needs are provided by the system. The biggest variable in the generation of energy is the makeup of the efﬂuent fed into the biogas pond, which is separate to the main efﬂuent pond.
The outﬂow from the biogas pond goes into the main pond and an advantage is that the solids have been partially biodegraded in the process which makes nutrients more bio-available when
efﬂuent is applied to pastures.
John is currently working on a version two prototype with the intention to create a turn-key system which can be widely distributed to dairy farms. He believes the system would currently suit about 30% of the 12,000 dairy farms operating in New Zealand.
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