Covered dairy effluent anaerobic ponds could soon appear on
larger dairy farms to generate power from the methane produced. Photo from Niwa.
Dairy effluent could be used as a source of heat and
electricity on Southland dairy farms.
If trials are successful, the dairy farming waste product
could become a valued resource in the future.
Monitoring at two farms in Dacre and Pukerau has shown that
anaerobic digestion of dairy farm effluent in unheated
effluent ponds, is consistently producing large volumes of
methane, even during the cold conditions of the Southland
Another installation at a 900-cow dairy farm at Isla Bank is
under way and is expected to be operational in a couple of
months to make use of the methane full scale for the first
time in Southland.
Niwa research engineer Stephan Heubeck and his team have been
working with Venture Southland for the past three years
researching the biogas conversion system.
Venture Southland's Enterprise and Strategic Projects group
manager Steve Canny said the work up until now had focused on
the quantity and quality of the methane production.
''Methane from dairy farm effluent can provide about 75% of
the farm's electrical requirements as well as all process
heating - hot water requirements - for the farm.''
He said the process could help save water and also removed
the smell from the effluent. Dairy effluent stored in ponds
produces methane and carbon dioxide, a mixture also known as
biogas, and a plastic cover collects the gas and makes it
available for use. The biogas recovered from such a covered
anaerobic pond can be used to fuel a small boiler or
''We realised there is an untapped resource available in
effluent ponds,'' Mr Heubeck said.
''We wanted to see if we can come up with a simple and
low-tech means to recover biogas from effluent ponds.
''We worked with simple, straightforward technology and have
about a dozen of the systems running in New Zealand and
Initially the Niwa team worked with the pork industry to work
out the best way to cut odour from piggery effluent, but many
farms now utilise the energy potential of the recovered
biogas as well.
He said, given the right setting, tens of thousands of
dollars could be saved on farmers' energy bills if covered
anaerobic ponds were installed, but the amounts saved
depended on farm size and the potential to use existing
infrastructure such as an existing pond or generator.
Mr Heubeck envisages a covered anaerobic pond system on every
larger dairy farm, making efficient use of the methane, and
providing the majority of the farm's heat and electricity
''A farm in Taranaki has run a 50kW generator on biogas for
the past four years, so we know that the simple technology
works'' he said.
''Furthermore, we now know that ponds in Southland are as
good at turning effluent solids into biogas as in any other
part of the country.
''Therefore, we will probably see hundreds of systems built
in the next few years on farms from Cape Reinga to Bluff.''
Mr Canny said generally speaking a biogas system would help
the farmer reduce his inputs, as he was using existing
resources on the farm.
A large number of farmers were interested in the work carried
out on biogas systems in Southland.