Peat forms wherever plant growth outpaces decay in waterlogged, acidic ground. Blanket bogs, usually 1-5 m deep, and raised bogs fed only by rain, which can exceed 10 m, give the best fuel, while fen peat from groundwater-fed wetlands is richer in minerals and typically too wet and crumbly.
Part of Peat Harvesting
The three main kinds of peatland, how each forms, and which ones make usable fuel.
Waterlogging Is The Mechanism
Where the ground stays under water, the oxygen needed for rot is missing, and plant remains pile up instead of decaying. In bogs the water is also acid and poor in nutrients, which suits sphagnum moss and slows decay further. The parent article’s rule of thumb is that peat forms wherever growth exceeds decomposition.
| Type | Water source | Setting | Depth (parent article) | Fuel value |
|---|---|---|---|---|
| Blanket bog | Rain | Flat or gently sloping uplands in wet, maritime climates | Often 1-5 m | Good; common in Ireland, Scotland, western Norway |
| Raised bog | Rain only | Dome-shaped lowland deposits | Can be 10 m or more | Good; across northern Europe and North America |
| Fen | Groundwater | Groundwater-fed wetlands | Varies | Poorer: more nutrient-rich and mineral, often too wet and crumbly |
“Raised” describes the shape: the centre of a rain-fed dome stands higher than the edge, because it is lifted by the peat it has itself accumulated. Because a raised bog is fed only by rain, it is low in minerals, and its peat tends to leave less ash.
Why It Matters For Fuel
The type tells you what the peat will do:
- Rain-fed bogs give fibrous top layers and denser, darker peat lower down; the quality grades are covered in Testing Peat Quality.
- Fens hold more mineral matter from the groundwater; expect more ash and a crumbly block.
- Depth decides how long a supply lasts: see Depth Assessment.
Rates Of Formation
The parent article puts accumulation at about 0.5-1 mm a year in ideal conditions. At that rate a 2 m deposit took 2 m ÷ 1 mm per year = 2,000 years to 2 m ÷ 0.5 mm per year = 4,000 years. Cutting a bog therefore spends a store that took millennia to build: see Regrowth Rate.
Common Mistakes
- Assuming all peat is alike. The type changes the fuel.
- Judging a bog by the surface. Fibrous surface peat is the worst fuel; the best lies deeper.
Safety
Soft margins and floating mats
The edges of a bog and the zones around pools can be floating mat that will not bear a person. Probe first, and never walk onto an unproven surface. See Finding & Identifying Peat Bogs.
What’s Next
- Learn next: Testing Peat Quality — grading what you find
- Combine with: Environmental Considerations — what taking it costs