Freshly cut peat is 80-90% water by weight and has to be dried to below 30% before it burns well, which means each block must lose roughly 71-86% of its weight as water. Spread the blocks, then stand them in small stacks, then build them into covered clamps; in good weather this takes 6-8 weeks.
Part of Peat Harvesting
Why cut peat needs weeks of drying, the three stages it passes through, and how to tell when it is ready.
Moisture Is Stated On A Wet Basis Here
Moisture can be given as water over total weight (wet basis) or water over dry weight (dry basis), and the two differ greatly at high moisture. In this article, “80-90% water by weight” and “below 30% moisture” are wet-basis: the water is that percentage of the block’s total mass. On a dry basis, 90% wet-basis would be 900%.
Worked Example: How Much Water Must Leave
Inputs: fresh peat at 80-90% water, wet basis; target 30% wet basis. Take 1 kg of dry peat matter.
- Fresh at 90%: total mass = 1 ÷ (1 − 0.90) = 10 kg, so 9 kg is water.
- Dried to 30%: total mass = 1 ÷ (1 − 0.30) = 1.43 kg, so 0.43 kg is water.
- Water lost = 9 − 0.43 = 8.57 kg, which is 8.57 ÷ 10 = 86% of the original mass.
- At 80% start: total 5 kg, loss = 5 − 1.43 = 3.57 kg, which is 71% of the original mass.
So a 3 kg fresh block at 90% ends near 0.43 kg. The same arithmetic shows why drying is the bulk of the work.
The Three Stages (Parent Article)
Weeks 1-2, spreading. Lay the blocks flat in a single layer, spaced apart, and turn them every 2-3 days. The surface crusts while the inside stays wet (Drying Timeline).
Weeks 3-4, footing. Stand 4-6 blocks upright, leaning against each other. Air then reaches all faces. Blocks must not sit in water (Footing & Stacking Stages).
Weeks 5-8, clamping. Build criss-crossed stacks with gaps for air and cover the top with sod or a tarp. In good weather peat is ready after 6-8 weeks in total.
Common Mistakes
- Stacking soft blocks. They squash and stay wet.
- Leaving the blocks flat in rain. They reabsorb water.
- Burning peat that is only crusted. Drying is from the outside in: the centre is still wet.
Safety
Wet peat smokes badly, and large peat stacks can heat
Peat that is not dry gives dense, irritating smoke and carbon monoxide (Carbon Monoxide Risks). Large, tightly packed stockpiles of peat, especially dust, can heat themselves and ignite, so keep clamps open in texture and check them.
What’s Next
- Learn next: Footing & Stacking Stages — the work in the middle weeks
- Combine with: Weather Dependency — timing the season