Riding a green wave and loving it

When Leighton Minnell bought the former Wanganui Mushrooms property he didn't know it had the only state-of-the-the-art Dutch compost making system in New Zealand.

Having spent six months and more than $500,000 getting the place going, he's amazed at its potential.

Mr Minnell, best known in Wanganui for his motor racing and race organising, said he was now "riding the green wave". He's not involved with the Cemetery Circuit this year, and is engrossed in making his new 2.1ha property work.

He has companies as far away as New Plymouth wanting him to compost their green waste - Affco Imlay wanting him to compost paunch waste, schools wanting to see how the compost is made and people queuing to buy trailer loads of the finished product.

And he hopes to have a first crop of mushrooms ready by around Christmas, and sell them at the Whanganui River Traders' market.

He bought the property in 2007, from Gerry Jonker.

"I just thought I had a four-car flash garage with some timber doors," he said.

But those "garages" were all set up for growing mushrooms, and across the yard was a Euro $1.3 million Gicom In Vessel composting complex built in the early 1990s. When he rang the makers in The Netherlands they told him its four tunnels was capable of turning green waste into organic compost in 10 days, with no mess and no smell.

With today's drive to keep waste out of expensive landfills, there's no shortage of green waste.

Mr Minnell already had a huge pile there, sourced from both of Wanganui's waste transfer stations. Taranaki people want to add some of theirs as well.

"I've had calls from waste companies as far away as New Plymouth wanting to bring their stuff, because they've got nothing," he said.

Mr Minnell and his one staff member first separate potential firewood, rubbish and reusable plants from the green waste, then grind it into small pieces. Then they mix it with fertiliser such as super phosphate and lime, to provide the nitrogen and other nutrients needed as it decomposes.

After that it's moved into one of the computer-controlled composting tunnels on the property. There the temperature is raised to 65C and any leachate is collected in tanks.

The computer adds air or liquid leachate to keep the mixture exactly moist and warm enough. The heat broke down inorganic fertiliser and hormone sprayed into organic compounds, Mr Minnell said, and it killed seeds and tubers.

After 10 days the compost is ready. It's screened to remove any small pieces of inorganic rubbish that remain, and ready to sell.

The tunnels can make 240 tonnes of compost a week. It is bought by market gardens, a berry farm and home gardeners. Mr Minnell can't keep up with demand.

He has also just bought a bagging machine, so that the compost can be bagged and back-loaded to the transfer stations for sale.

As a side business, he is stockpiling wood chips supplied by Wanganui arborists and selling them to gardeners for mulch.

The compost will also be ideal for growing mushrooms, and Mr Minnell plans to start his first batch any day.