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Milled Peat Harvesting

Milled peat is the term used to describe peat in granulated or crumb form which has been mechanically harvested from the surface of a bog. Here are the four stages the milled peat harvesting.

Milling

  • A typical milled peat bog is divided up by drains 15 m apart into long parallel production fields, each around one kilometre in length
  • The top 10-15 mm of the surface of each field is broken into peat crumbs by powered milling drums towed behind agricultural tractors
  • This layer of crumbed or milled peat is called a crop
  • This ‘crop’ has a moisture content of about 80% when milled

Milling

  • A typical milled peat bog is divided up by drains 15 m apart into long parallel production fields, each around one kilometre in length
  • The top 10-15 mm of the surface of each field is broken into peat crumbs by powered milling drums towed behind agricultural tractors
  • This layer of crumbed or milled peat is called a crop
  • This ‘crop’ has a moisture content of about 80% when milled

Harrowing

  • After milling, solar energy from the sun and wind dries the peat crop
  • To assist in this drying, the loose peat is harrowed, or turned over, to place the lower layers of the crop on top
  • In this way the entire crop is exposed to the drying action of the sun and wind
  • The harrow consists of a series of spoons which are towed behind an agricultural tractor

Ridging

  • When the milled peat has dried to 45-55% moisture content it is gathered into ridges in the centre of each field
  • The ridger consists of a pair of blades towed in an open V behind an agricultural tractor
  • The open V blades rest on the bog and channel the loose crop into a triangular ridge in the centre of each field
  • This ridge is now ready to be harvested

Ridging

  • When the milled peat has dried to 45-55% moisture content it is gathered into ridges in the centre of each field
  • The ridger consists of a pair of blades towed in an open V behind an agricultural tractor
  • The open V blades rest on the bog and channel the loose crop into a triangular ridge in the centre of each field
  • This ridge is now ready to be harvested

Harvesting

  • This is the final stage of milled peat production
  • Each individual ridge is lifted mechanically by a machine called a harvester
  • Under the Peco system of milled peat harvesting each ridge is lifted, transferred and dropped on top of the adjoining field’s ridge, until 5 ridges have been accumulated into a single large ridge
  • This ridge forms the final lift into the peat storage stockpile

Peco Stockpile Field

  • This field receives the crops from 10 fields i.e. 5 fields on either side
  • Weather permitting, the miller follows the harvester and the production cycle recommences in the harvested fields
  • Each production cycle is known as a harvest
  • In a year with average weather conditions approximately 12 harvests are saved
  • When the production season is over, the stockpiles are covered to keep the peat dry, unless the peat is scheduled for sale in the immediately following months
  • Peat is stored in these stockpiles until loaded into wagons and transported by narrow gauge railway to power station or factory

Peco Stockpile Field

  • This field receives the crops from 10 fields i.e. 5 fields on either side
  • Weather permitting, the miller follows the harvester and the production cycle recommences in the harvested fields
  • Each production cycle is known as a harvest
  • In a year with average weather conditions approximately 12 harvests are saved
  • When the production season is over, the stockpiles are covered to keep the peat dry, unless the peat is scheduled for sale in the immediately following months
  • Peat is stored in these stockpiles until loaded into wagons and transported by narrow gauge railway to power station or factory

The Haku System

Under the Haku system of milled peat harvesting, the ridged crop on each individual field is lifted by the milled peat harvester directly into tractor-drawn trailers that haul the peat for storage in a large stockpile at the edge of the bog.