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.
