Pig poo is powering clean, green plan

Pig manure in Hamilton has been developed as an alternative energy source. Photo / Christine Cornege

There's a new, unlikely energy source that can power farms while reducing greenhouse gas emissions - pig poo.

A team of scientists at the National Institute of Water and Atmospheric Research in Hamilton has developed a system that stores greenhouse gases from pig manure in a deep pond, from where it can be used as an energy source.

Niwa research engineer Stephan Heubeck said the system cut greenhouse gases in the atmosphere while giving an alternative energy source.

"The manure is introduced into a deep pond and it's an oxygen-free environment," he said.

There, anaerobic bacteria breaks down the manure into biogas; methane and carbon dioxide, the two main greenhouse gases.

"That is producing odour problems. The big driver for many of the pig farms is to intercept the gas before it reaches the atmosphere, reducing odour emissions."

A large cover traps the gases in the ponds. Farmers can use the biogas by connecting it to a gas boiler or electricity generator, all for a low cost.

"We had great deal of support from the New Zealand Pork Industry Board. They were interested in finding a way of reducing odour emissions from the pig farms and were very helpful."

The Niwa team also worked with the Energy Efficiency and Conservation Authority (EECA). At Steve Lepper's piggery in Taranaki, where the first system was built, a 7000cu m pond had to be dug, a pond-cover built and an electricity generator bought.

The system provides heat and power, and the waste heat from the generator is used for a heating system which keeps piglets warm.

The total cost was $120,000, including an EECA grant of $30,000, but Mr Lepper expects to recoup his investment within three years.

The project has also attracted interest in Australia, where four systems are under construction.

Mr Heubeck said the industry there was embracing a "spirit of development", after the Australian Government introduced the Carbon Farming Initiative, which rewards farmers who reduce their gas emissions.

"Australian Pork Limited has been very, very supportive in getting this message out there."