Sawdust

Sawdust

Overview

Sawdust is a by-product of cutting lumber
Lumber
Lumber or timber is wood in any of its stages from felling through readiness for use as structural material for construction, or wood pulp for paper production....

 with a saw
Saw
A saw is a tool that uses a hard blade or wire with an abrasive edge to cut through softer materials. The cutting edge of a saw is either a serrated blade or an abrasive...

, composed of fine particles of wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

. It can present a hazard in manufacturing industries, especially in terms of its flammability.

Sawdust has a variety of practical uses, including serving as a mulch
Mulch
In agriculture and gardening, is a protective cover placed over the soil to retain moisture, reduce erosion, provide nutrients, and suppress weed growth and seed germination. Mulching in gardens and landscaping mimics the leaf cover that is found on forest floors....

, as an alternative to clay cat litter
Litter box
A litter box, sometimes called a sandbox, sand box, litter tray, litter pan, dirt box, catbox, or cat box, is an indoor feces and urine disposal box for cats that are permitted free roam of a home but who cannot or do not always go outside...

, as a fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

, or for the manufacture of particleboard. Until the advent of refrigeration, it was often used in icehouses
Icehouse (building)
Ice houses were buildings used to store ice throughout the year, prior to the invention of the refrigerator. Some were underground chambers, usually man-made, close to natural sources of winter ice such as freshwater lakes, but many were buildings with various types of insulation.During the...

 to keep ice frozen during the summer.
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Encyclopedia

Sawdust is a by-product of cutting lumber
Lumber
Lumber or timber is wood in any of its stages from felling through readiness for use as structural material for construction, or wood pulp for paper production....

 with a saw
Saw
A saw is a tool that uses a hard blade or wire with an abrasive edge to cut through softer materials. The cutting edge of a saw is either a serrated blade or an abrasive...

, composed of fine particles of wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

. It can present a hazard in manufacturing industries, especially in terms of its flammability.

Sawdust has a variety of practical uses, including serving as a mulch
Mulch
In agriculture and gardening, is a protective cover placed over the soil to retain moisture, reduce erosion, provide nutrients, and suppress weed growth and seed germination. Mulching in gardens and landscaping mimics the leaf cover that is found on forest floors....

, as an alternative to clay cat litter
Litter box
A litter box, sometimes called a sandbox, sand box, litter tray, litter pan, dirt box, catbox, or cat box, is an indoor feces and urine disposal box for cats that are permitted free roam of a home but who cannot or do not always go outside...

, as a fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

, or for the manufacture of particleboard. Until the advent of refrigeration, it was often used in icehouses
Icehouse (building)
Ice houses were buildings used to store ice throughout the year, prior to the invention of the refrigerator. Some were underground chambers, usually man-made, close to natural sources of winter ice such as freshwater lakes, but many were buildings with various types of insulation.During the...

 to keep ice frozen during the summer. It has been used in artistic displays
Art
Art is the product or process of deliberately arranging items in a way that influences and affects one or more of the senses, emotions, and intellect....

, and as scatter
Scatter
In ordinary English, to scatter is to distribute randomly. Scatter also has the following meanings:*In physics, scattering is the study of collisions, especially of waves and particles...

. It is also sometimes used to soak up liquid spills, allowing the spill to be easily collected or swept aside. It is used to make Cutler's resin
Cutler's resin
Cutler's resin is a synthetic resin made of pine pitch, beeswax, and sawdust or carnauba wax used for centuries to attach knife handles. It is used as both an adhesive and for waterproofing. The word cutler means "one who makes knives"....

. Mixed with water and frozen, it forms pykrete
Pykrete
Pykrete is a composite material made of approximately 14 percent sawdust or some other form of wood pulp and 86 percent ice by weight. Its use was proposed during World War II by Geoffrey Pyke to the British Royal Navy as a candidate material for making a huge, unsinkable aircraft carrier...

, a slow-melting, much stronger form of ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

.

Science of sawdust


The main by-product of sawmill
Sawmill
A sawmill is a facility where logs are cut into boards.-Sawmill process:A sawmill's basic operation is much like those of hundreds of years ago; a log enters on one end and dimensional lumber exits on the other end....

s, 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 leachate
Leachate
Leachate is any liquid that, in passing through matter, extracts solutes, suspended solids or any other component of the material through which it has passed....

s 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
Wildlife
Wildlife includes all non-domesticated plants, animals and other organisms. Domesticating wild plant and animal species for human benefit has occurred many times all over the planet, and has a major impact on the environment, both positive and negative....

. 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
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 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 lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...

s and fatty acid
Fatty acid
In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...

s 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
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...

and are toxic to a broad range of organisms.