Mould needs four things: a food source, oxygen, a temperature between roughly 4 and 38 °C, and moisture above about 20% in the wood. You cannot remove the first three. Moisture is the whole game.
Where the water comes from
Rarely rain. Usually condensation — a cold pallet moved into warm humid air, or a shrink-wrapped stack that traps overnight dew. Wrap is the quiet villain: it seals moisture against wood and holds it there in the dark.
Three changes that fix most of it
- Store off the ground and under cover, with airflow on at least two sides. Concrete wicks.
- Do not wrap damp. If a stack comes in wet, let it break and dry before it goes under film.
- Rotate stock properly. Mould is a time problem as much as a water problem; FIFO starves it.
If it has already bloomed
Surface mould on a structurally sound pallet is usually cosmetic and can be brushed or, for food programmes, kiln-dried out. Blue stain is a fungus that discolours without weakening. Soft, crumbling, punky wood is decay, and that pallet is finished — send it to the grinder and let it become mulch.
Written by the Pallets Recycle yard crew, Richmond VA. Corrections welcome — tell us if we have this wrong.