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For The Killers album, see Sawdust (album).

Sawdust is composed of fine particles of wood. This material is produced from cutting with a saw, hence its name. It has a variety of practical uses, including serving as a mulch, or as an alternative to clay cat litter, or as a fuel, or for the manufacture of particleboard. Historically, it has been treated as a by-product of manufacturing industries and can easily be understood to be more of a hazard, especially in terms of its flammability. It has also been used in artistic displays and as scatter. It is also sometimes used in bars in order to soak up spills, allowing the spill to be easily swept out the door. Perhaps the most interesting application of sawdust is in pykrete, a slow-melting, much stronger ice composed of sawdust and frozen water.

A sawyer's sawdust pile in Pembroke, Ontario.

The main by-product of sawmills, unless reprocessed into particleboard, burned in a sawdust burner or used to make heat for other milling operations, sawdust may collect in piles and add harmful leachates into local water systems, creating an environmental hazard. This has placed small sawyers and environmental agencies in a deadlock.

-Questions about the science behind the determination of sawdust being an environmental hazard remain for sawmill operators (though this is mainly with finer particles), who compare wood residuals to dead trees in a forest. Technical advisors have reviewed some of the environmental studies, but say most lack standardized methodology or evidence of a direct impact on wildlife. They don’t take into account large drainage areas, so the amount of material that is getting into the water from the site in relation to the total drainage area is minuscule.

Other scientists have a different view, saying the "dilution is the solution to pollution" argument is no longer accepted in environmental science. The decomposition of a tree in a forest is similar to the impact of sawdust, but the difference is of scale. Sawmills may be storing thousands of cubic metres of wood residues in one place, so the issue becomes one of concentration.

Water-borne bacteria digest organic material in leachate, but use up much of the available oxygen. This high "biological oxygen demand" can suffocate fish and other organisms. There is an equally detrimental effect on beneficial bacteria, so it is not at all advisable to use sawdust within home aquariums, as was once done by hobbyists seeking to save some expense on activated charcoal.

But of larger concern are substances such as lignins and fatty acids that protect trees from predators while they are alive, but can leach into water and poison wildlife. Those types of things remain in the tree and, as the tree decays, they slowly get broken down. But when sawyers are processing a large volume of wood and large concentrations of these materials get out into the runoff, they cause toxicity and are toxic to a broad range of organisms. (Source: Canadian Geographic Online)