Peat accumulates at about 0.5-1 mm a year in ideal conditions, so replacing a 10 cm layer takes 100-200 years and a 2 m bog 2,000-4,000 years. A household that cuts 15-24 m³ a year takes more than the whole accumulation of a hectare of bog, and a replaced turf cap restores the living surface, not the fuel beneath it.
Part of Peat Harvesting
The arithmetic of how fast a bog rebuilds, set against how fast a household cuts it, and what regrowth does and does not mean.
The Rate And Where It Comes From
The parent article gives accumulation as roughly 0.5-1 mm a year in ideal conditions and says peat is effectively non-renewable on human timescales. That is the only rate this article uses. It is an upper estimate: it is the ideal case, accumulation in a drained or disturbed bog is slower or negative, and a bog’s rate varies from place to place. No independent source for the figure was checked here.
Worked Example: Replacement Times
Inputs: accumulation rate 0.5-1 mm/yr (parent).
- A 10 cm block layer is 100 mm: 100 ÷ 1 = 100 years to 100 ÷ 0.5 = 200 years.
- A 60-100 cm bank (the working height): 600 ÷ 1 = 600 years to 1,000 ÷ 0.5 = 2,000 years.
- A whole 2 m deposit: 2,000 ÷ 1 = 2,000 years to 2,000 ÷ 0.5 = 4,000 years (the parent’s figure).
Worked Example: One Household Against One Hectare
Inputs: 1 ha = 10,000 m²; household cut 15-24 m³/yr (5,000-8,000 blocks of 3 L).
- Accumulation per year over a hectare = 10,000 m² × 0.0005 m to 10,000 m² × 0.001 m = 5-10 m³ a year.
- A household’s yearly cut = 15-24 m³.
- Cut ÷ accumulation = 15 ÷ 10 = 1.5 to 24 ÷ 5 = 4.8.
One household cuts 1.5 to 4.8 times what a whole hectare of bog grows in a year. And that compares fresh cut volume to fresh volume, which is fair: both are measured wet in the ground.
Turf Replacement Is Not Peat Replacement
Replacing the turf cap, as the parent advises, helps the living surface re-establish. That is worth doing, but the layers you removed beneath it do not come back in any time that matters for fuel. Rest cycles of 20-30 years (parent) at 0.5-1 mm a year restore 10-30 mm (20 × 0.5 mm to 30 × 1 mm), about a centimetre or three: surface recovery, not replacement.
Common Mistakes
- Reading “regrowth” as “renewable”. The moss grows back; the peat does not.
- Assuming a faster rate. If you want to use a different rate, find a measurement for your own bog.
- Counting only the fuel layer. The water and carbon in the bog go too.
Safety
Cut-over bogs are unstable and flammable
A bog cut repeatedly is a mosaic of soft ground, water-filled cuts and drying peat ridges. Keep to firm paths, probe before you step, and keep fire away from dry cut surfaces (Environmental Considerations).
What’s Next
- Learn next: Sustainable Harvesting Limits — setting a budget
- Combine with: Carbon Implications — what the loss means for carbon