Swamp mining for peat

It’s an industry redolent of colonial Ireland – picture sodden peasants hewing the stuff from bogs – but peat mining is a well-established, though shrinking business in New Zealand.   BY HUGH DE LACY

The family-owned Gamman Mining of Ngatea on the Hauraki Plains is typical of the cluster of companies specialising in turning partly decomposed sphagnum moss into a range of horticultural products that battle for market-share with green waste and bark, and with imported peat and coir (coconut) fibre.

It’s a battle that the local industry has been slowly losing, with output slumping from 60,000 million cubic metres a year in the mid-1990s to about half that today, but the Gamman family – Jackie and Russell and their sons Kerry and Paul – are hoping the decline has bottomed out despite the pressure from imports and alternatives remaining high.

The Gamman’s Ngatea peat mine is one of only five – three of them in Southland – still operating in New Zealand, though peat has been quarried (or mined) here since the early colonial times. The Gammans have a licence covering 180 hectares of the 10,200 hectares Kopuatai peat dome, which rises in the middle of an area bounded by SH27 in the west, SH2 in the north and east, and SH26 in the south.

Auckland-based NZ Peat holds the licence for another corner of the Kopuatai peat dome, while its subsidiary, NZ Peat (Southland), quarries a bog at Tussock Creek, north-west of Winton. NZ Growing Media (NZGM) mines at Browns, while the fifth player in the game is Scobies Peat of Wyndham.

New Zealand is not particularly well endowed with peat resources, having only 0.6 percent or 1660 square kilometres of its land area – about the size of Stewart Island – under peat bogs, compared to a global total of two percent, or 3,000,000 square kilometres. Most of the global resource is in the Northern Hemisphere, with Canada, Finland and eastern Europe accounting for 80 percent of it.

Peat is the midway fossilising stage between vegetation and coal. New Zealand peat is derived from sphagnum moss, which is classified geologically as High Moor peat. It grows on a clay base that has raised itself above the surrounding landforms into an extended dome-like structure, of which the Kopuatai is typical.

Because of its impermeability and elevation, no water actually flows into the Kopuatai, so it’s a silt-free environment that delivers a particularly pure grade of sphagnum peat, whose commercial value lies in its ability to absorb up to 26 times its own weight in moisture. This gives it immediate application to potting mixes, compost, mushroom growing media, organic fertilisers, nursery plant production and soil conditioners. It also makes it ideal as a medium for absorbing and cleaning up oil and chemical spills.

It can be prepared for these roles by a range of processes from kiln-drying and milling to chopping, screening and mixing.

The Gamman family has been operating its Ngatea mine since 1990, supplying bulk peat to about 20 clients in the upper half of the North Island for bagging, nursery and potting mixes. Hauraki peat is darker than the “blonde” Southland type, and includes rotted-down ferns and rushes as well as the basic sphagnum.

The production cycle of the Gammans’ peat quarry is based on a two-year timeframe, beginning with drainage of a 30-40 hectare block, for which a water right is required. After sediment is removed by a settlement pond, the water is drawn off into local waterways and eventually into the Firth of Thames by way of the Waihou River. V-shaped drains a metre deep are cut in the swamp by a Dondai implement that spreads the peat over five metres either side.

The swamp is owned by state farmer Landcorp, and the licence, issued under the Coal Mining Act, requires the Gammans to block the drains and restore the sphagnum cover to its original condition after quarrying. This isn’t so difficult to do, not just because they’re able to collaborate with state-owned Landcare Research in the restorative process, but because their method of harvesting usually involves taking just the top centimetre of the peat with a standard agricultural forage harvester.

The Gammans have four such machines, drawn by Massey Ferguson 100-120hp four-wheel-drive tractors. The harvested peat is stockpiled for a year to dry, with most of the distribution work carried out over the winter months.

Harvesting can take place only from about Labour Weekend to April, and rainy seasons have delayed starts till as late as Christmas. As many as 20 passes a season can be made over the same block of bog. If the peat’s not dry enough – and in it’s natural state it comprises 80 percent water - it won’t lift into the trailer, but instead clogs up the harvester.

All four harvesters operate during the season, with two or three local casuals assisting as weather permits. During the winter the bulk supply cuts the labour force to just one, with the rest of the Gamman family occupied with machinery and business maintenance.

A second means of harvesting, representing the most recent technology and sidestepping the problems of the peat being too wet for the harvesters, is to ridge it into a windrow, then pick it up with a belt or a digger. The drawback with this latter system is the propensity for the digger to break through the surface peat and get itself well and truly bogged, so the Gammans have to keep winching equipment handy to rescue it.

With plenty of resource remaining under their licence, the Gammans are not too worried about their own business in the long term, but Russell Gamman believes that planning requirements are contributing to the wider industry’s decline. Licences to harvest sphagnum peat are issued by the Department of Conservation to whom quarrying and mining, if not anathema, is at least not the preferred use of any such natural resource.

At least as big a threat to the industry are the imports and alternatives. The days of foresters just bulldozing tree prunings and offcuts into windrows to rot are passing, with more and more of the residue of forest harvesting being ground up for either bio-fuel to power pulp and paper factories, or mulch for the same horticultural markets that used to be the more-or-less exclusive preserve of peat-miners.

Competitive pressures are pushing peat-miners into greater diversification of their products, particularly fertilisers and soil conditioners, and it’s this process that Gamman believes will be the industry’s eventual saviour.

Giving some basis to his confidence in peat-mining’s future was the acquisition a year ago by the big Ravensdown farm fertiliser co-operative of NZGM, formerly known as Australasian Peat. NZGM mines at Browns in Southland, and Ravensdown has sunk money into expanding its product line to include organic fertilisers.

NZGM manager and long-time peat miner Oz Harvey told Q&M that although the company already has a solid client base in the mushroom and lily-bulb sectors, he was delighted Ravensdown had decided to “have another crack at the garden market.”

Rival company NZ Peat has been producing peat-based organic fertilisers under its BioBoost brand for most of the nine years it’s been operating in both Hauraki and Southland, but Gamman believes Ravensdown’s involvement suggests the long-term outlook for peat quarrying is now better than it’s been in years.