Module 3 · Stump to mill

Chips, sawdust, shavings and bark: how the other half is sold

Level 2 · Working knowledge 11 min read 4 questions

Roughly half of every log leaves the mill as something other than lumber. Each stream has its own buyers, its own unit and its own price, and together they often decide whether the mill is profitable.

This is the lesson that answers the question people usually phrase as 'what happens to the scrap'. The honest answer is that a modern sawmill has almost no scrap. It has four co-products, each with a separate market, and it sells all of them.

The four streams

Why this is not a side business

Residuals are frequently the difference between a sawmill that runs and one that does not. Three reasons:

1. The log is already paid for. The residual arrives at zero marginal raw material cost. Every dollar of residual revenue is close to a dollar of contribution.
2. Disposal is not free. A mill without buyers must still move the material, and paying to dispose of half your input is not survivable.
3. Energy. Bark and wet residuals fire the boilers that run the kilns. Many mills are energy self-sufficient for heat, and some generate electricity. That is a real cost avoided, not a sustainability talking point.

The pellet trade

The newest large buyer of fine residuals is the wood pellet industry, which compresses dried sawdust and shavings - and increasingly roundwood grown for the purpose - into uniform pellets that can be handled like a bulk commodity and burned in converted coal plants and domestic boilers.

Pellets are the clearest case in this course of a residual becoming a traded commodity in its own right, with long-term offtake contracts, dedicated port terminals and ocean shipping. They are also the most contested: whether burning them is genuinely low carbon depends on what was harvested, what regrows, over what period, and what the alternative use of that wood would have been. This course states the trade structure and does not attempt to settle that argument.

What else the world does with the non-lumber half

That last note is the one to carry out of this lesson. Half of all the wood cut in the world is burned, most of it as domestic fuelwood in countries where it is the primary cooking fuel. The industrial chain this course describes - sawmills, panels, pulp, pellets - is the other half.