There are four stages to the production of milled peat -
1: MILLING
2: HARROWING
Milling
- 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
3: RIDGING
4: HARVESTING
Harvesting
- this is the final stage of milled peat production
- each individual ridge is lifted mechanically by a machine called a harvester
- 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
The 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 emptied 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 following months
- peat is stored in these stockpiles until loaded into wagons and transported by narrow gauge railway to power station or factory
In brief:
The milled peat production harvest is similar in many ways to agricultural harvesting, and like farming, is highly weather dependent.
Production requires the good drying conditions offered by anticyclonic summer weather and can commence anytime from mid-April onwards.
A typical milled peat bog is divided up by drains 15 m apart into long parallel production fields, each around one kilometre in length.