Finding power in effluent

STACY SQUIRES/The Press

Making good from gas: Ian Bywater, left, and Peter Stevens in front of the ``digestive tank'', where the effluent is processed, at the pilot biogas plant in Eyrewell.

Relevant offers

Farming

Fonterra taps NZX to run farmer share trading Milk price inquiry to continue LIC earnings rise amid dairy confidence Another shot fired in milk price battle BayWa extends deal for T&G Optimism for booming sheep industry Possum fur prices boost industry BayWa lifts stake in T&G ahead of deadline Kiwifruit IP report 'will be released' Taranaki foreign farms buy-up nearer

A dairying system that is turning effluent into power and fertiliser in Canterbury is expected to revolutionise the way farmers treat cow muck.

Its investors have set up a pilot plant at a Landcorp Farming dairy farm in Eyrewell that is extracting methane and carbon dioxide from effluent with biodigester technology, and using it as fuel in a co-generation plant to make electricity.

The methane would otherwise have gone into the atmosphere and produced greenhouse gases.

The system also turns the effluent into a better fertiliser than what the cow drops on a paddock.

After being left in the heated digester for 20 days, nitrates in the effluent lose their polluting ability and are turned into ammonium nitrate, with acidity levels close to neutral.

The patented technology was developed by Ian Bywater, manager of Natural Systems. It is about to be made commercially available.

Bywater said New Zealand dairy farms could be world leaders in producing stand-alone power generated from a waste product which removed greenhouse-gas emissions and produced better milk and fertiliser.

It was a revolutionary step for dealing with effluent on the farm, he said.

"We pride ourself on having a clean, green image, but it is severely tested by our major export industry. Adopting this as a standard for processing dairy-farm effluent would reap major international accolades."

Effluent is collected after milking and pumped into a tank where a biogas made up of 65 per cent methane and 35 per cent carbon dioxide is produced.

This mixture is used as a fuel for a diesel generator to generate power. Waste heat from the engine heats the digester plant, with electricity used on the farm and surplus power made available to the main grid.

Water is automatically frozen by the computer-controlled BioGenCool technology so milk can be cooled instantaneously.

This is much quicker than conventional sheds, which must cool milk to 7deg within three hours of milking to prevent bacteria building up.

Ice-cold water from an ice tank goes through a heat exchanger to rob the milk of its heat. Warm water from the process is returned to the ice bank to turn ice into cold water.

This also means that the milk can be stored longer and does not have to be collected as often.

"As far as we know, this is an unique system," said Bywater.

"You can find ice banks in dairies for rapid cooling of milk, although it may not be done automatically, and you will find biogas producing electricity on farms, but to my knowledge no-one has integrated the whole system."

Refinements to the demonstration plant built last year have been completed and it is ready for its first full season.

So far, the 750-head dairy herd produces 80 per cent of the power needed to run a generator, hot-water savings of $3000 and 15,000 fewer litres of water a day, as well as big savings in fertiliser costs.

To be self-sufficient in power, the effluent from about 1000 cows is needed.

A biogas unit and milk-cooling system might cost $300,000 for a 1000-cow farm.

The payback from effluent-generated power alone is expected to be 10 years, Bywater said.

The power benefits are at least tripled if the system is attached to a cow housing unit or feed-pad system and Natural Systems has linked with Spanwood Building Systems (SBS) to make this available.

SBS's managing director, Peter Stevens, said the downside of more effluent from housing cows was an advantage when bioplant processing was attached to a confinement system.

"When cows are put into housed-fed situations they will produce 20 per cent more milk, they are healthier and they will last 20 per cent longer."

Stevens plans to incorporate his patented laminated veneer lumber in housing sheds of up to 50m in span.

He has invested $800,000 over the last two years, the same amount Natural Systems has invested in research and development for its technology.

 The thin strips of 3mm pine laminated into 150mm thick, 1.2m wide spans are half the cost of steel.

The BioGenCool technology has attracted interest from Australia and the United Kingdom.

- © Fairfax NZ News