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{{short description|Byproduct or waste product of woodworking operations (sawing, sanding, milling, etc.)}}{{Other uses}}File:Saw dust (Zaagsel).jpg|thumb|Sawdust made with hand sawhand sawFile:Ogatan(JapaneseBriquetteCharcoal).jpg|thumb|(:ja:オガ炭|Ogatan), Japanese charcoal briquettebriquetteFile:Sawdust vendors. Kashgar markets.jpg|thumb|Sawdust vendors in KashgarKashgarSawdust (or wood dust) is a by-product or waste product of woodworking operations such as sawing, sanding, milling and routing. It is composed of very small chips of wood. These operations can be performed by woodworking machinery, portable power tools or by use of hand tools. In some manufacturing industries it can be a significant fire hazard and source of occupational dust exposure.Sawdust, as particulates, is the main component of particleboard. Research on health hazards comes from the field of occupational safety and health, and study of ventilation happens in indoor air quality engineering. Sawdust is an IARC group 1 Carcinogen.

Formation

Two waste products, dust and chips, form at the working surface during woodworking operations such as sawing, milling and sanding. These operations both shatter lignified wood cells and break out whole cells and groups of cells. Shattering of wood cells creates dust, while breaking out of whole groups of wood cells creates chips. The more cell-shattering that occurs, the finer the dust particles that are produced. For example, sawing and milling are mixed cell shattering and chip forming processes, whereas sanding is almost exclusively cell shattering.IARC 1995. Wood Dust. In IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Vol. 62: Wood Dust and Formaldehyde. Lyon, France: World Health Organization International Agency for Research on Cancer, p. 70.

Uses

A major use of sawdust is for particleboard; coarse sawdust may be used for wood pulp. Sawdust has a variety of other practical uses, including serving as a mulch, as an alternative to clay cat litter, or as a fuel. Until the advent of refrigeration, it was often used in icehouses to keep ice frozen during the summer. It has been used in artistic displays, and as scatter in miniature railroad and other models. It is also sometimes used to soak up liquid spills, allowing the spill to be easily collected or swept aside. As such, it was formerly common on barroom floors.Felman, David (2005) “Why Did Bars Used to Put Sawdust on the Floor? Why Don’t They Anymore?” Do Elephants Jump? HarperCollins, New York, page 118, {{ISBN|978-0-06-053914-6}}, quoting Christopher Halleron, bartender and beer columnist. It is used to make Cutler’s resin. Mixed with water and frozen, it forms pykrete, a slow-melting, much stronger form of ice.Sawdust is used in the manufacture of charcoal briquettes. The claim for invention of the first commercial charcoal briquettes goes to Henry Ford who created them from the wood scraps and sawdust produced by his automobile factory.Green, Harvey (2006) Wood: Craft, Culture, History Penguin Books, New York, page 403, {{ISBN|978-1-1012-0185-5}}

Food

(File:Wood Shavings from a Chainsaw.jpg|thumb|Wood shavings made from a chainsaw in wet wood)Cellulose, fibre starch that is indigestible to humans, and a filler in some low calorie foods, can be and is made from sawdust, as well as from other plant sources.NEWS, Nassauer, Sarah, Why Wood Pulp Makes Ice Cream Creamier, 4 May 2011,www.wsj.com/articles/SB10001424052748703834804576300991196803916, The Wall Street Journal, While there is no documentationPacking houses formerly purchased large quantities of sawdust for the cutting room floors, and still purchase sawdust for use as a fuel and flavoring in the smoking process. for the persistent rumor, based upon Upton Sinclair’s novel The Jungle, that sawdust was used as a filler in sausage, cellulose derived from sawdust was and is used for sausage casings.WEB,www.fao.org/docrep/003/x6556e/X6556E03.htm, Savic, I. V., Small-scale sausage production: Sausage Casings, Food and Agriculture Organization of the United Nations (FAO), Rome, 1985, Sawdust-derived cellulose has also been used as a filler in bread.NEWS, Bread Labels on Wood Fiber Draw Attack, 9 October 1985, Los Angeles Times,articles.latimes.com/1985-10-09/news/mn-16819_1_high-fiber-bread,articles.latimes.com/1985-10-09/news/mn-16819_1_high-fiber-bread," title="web.archive.org/web/20100916223613articles.latimes.com/1985-10-09/news/mn-16819_1_high-fiber-bread,">web.archive.org/web/20100916223613articles.latimes.com/1985-10-09/news/mn-16819_1_high-fiber-bread, 16 September 2010, live, When cereals were scarce, sawdust was sometimes an ingredient in kommissbrot. Auschwitz concentration camp survivor, Dr. Miklós Nyiszli, reports in Auschwitz: A Doctor’s Eyewitness Account that the subaltern medical staff, who served Dr. Josef Mengele, subsisted on “bread made from wild chestnuts sprinkled with sawdust”.BOOK, Nyiszli, Miklos, Auschwitz: A Doctor’s Eyewitness Account, 3, 2011, New York: Arcade Publishing, 34, Sawdust is a primary ingredient in many types of processed chicken.NEWS, John, Smith, 2023-01-06, Chicken Preparation and How to,www.theguardian.com/lifeandstyle/2005/may/15/foodanddrink.shopping3,

Health hazards

(File:Particle size distribution of hardwood dust.jpg|center|thumb|upright=2.0|Particle size distribution of hardwood dust (0-9 microns) produced from different processes. Measured by mass only, not numerical measures (PNC))Airborne sawdust and sawdust accumulations present a number of health and safety hazards.WEB,safeatworkca.com/wood-dust-exposure/, Wood Dust Exposure, State Compensation Insurance Fund, 30 April 2012, Wood dust becomes a potential health problem when, for example, the wood particles, from processes such as sanding, become airborne and are inhaled. Wood dust is a known human carcinogen.WEB,ntp.niehs.nih.gov/ntp/roc/content/profiles/wooddust.pdf, Report on Carcinogens, Twelfth Edition, Wood Dust, 12 July 2014, dead,ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/WoodDust.pdf," title="web.archive.org/web/20130217080608ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/WoodDust.pdf,">web.archive.org/web/20130217080608ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/WoodDust.pdf, 17 February 2013, WEB,ntp.niehs.nih.gov/ntp/newhomeroc/roc10/wd_no_appendices_508.pdf, FINAL Report on Carcinogens Background Document for Wood Dust, 12 July 2014, Certain woods and their dust contain toxins that can produce severe allergic reactions.WEB, Meier, Eric, Wood Allergies and Toxicity, The Wood Database,www.wood-database.com/wood-articles/wood-allergies-and-toxicity/, The composition of sawdust depends on the material it comes from; sawdust produced from natural wood is different from that of sawdust produced from processed wood or wood veneer.Breathing airborne wood dust may cause allergic respiratory symptoms, mucosal and non-allergic respiratory symptoms, and cancer.United States Department of Labor: Occupational Safety and Health Administration. Wood Dust. In the US, lists of carcinogenic factors are published by the American Conference of Governmental Industrial Hygienists (ACGIH), the Occupational Safety and Health Administration (OSHA), and the National Institute for Occupational Safety and Health (NIOSH). All these organisations recognize wood dust as carcinogenic in relation to the nasal cavities and paranasal sinuses.Baran, S., & Teul, I. 2007. Wood Dust: An Occupational Hazard Which Increases the Risk of Respiratory Disease. Journal of Physiology and Pharmacology 58, Suppl. 5, pp. 43-50.(File:Japanese handplane (kanna) with wood shavings.jpg|thumb|Wood shavings made with a Japanese handplane)People can be exposed to wood dust in the workplace by breathing it in, skin contact, or eye contact. The OSHA has set the legal limit (permissible exposure limit) for wood dust exposure in the workplace as 15 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday. The NIOSH has set a recommended exposure limit (REL) of 1 mg/m3 over an 8-hour workday.WEB, CDC - NIOSH Pocket Guide to Chemical Hazards - Wood dust,www.cdc.gov/niosh/npg/npgd0667.html, www.cdc.gov, 2015-11-28, Water-borne bacteria digest organic material in leachate, but use up much of the available oxygen. This high biochemical 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 carbon.

Explosions and fire

Sawdust is flammable and accumulations provide a ready source of fuel. Airborne sawdust can be ignited by sparks or even heat accumulation and result in dust fire or explosions.

Environmental effects

At 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 do not 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.{{citation needed|date=November 2014}}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.{{citation needed|date=November 2014}}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 are broken down. But when sawyers are processing a large volume of wood and large concentrations of these materials permeate into the runoff, the toxicity they cause is harmful to a broad range of organisms.canadiangeographic.ca, Canadian Geographic Online {{webarchive |url=https://web.archive.org/web/20060428075135www.canadiangeographic.ca/magazine/SO05/indepth/environment.asp |date=2006-04-28 }}

Wood flour

(File:A waste wood powder.jpg|thumb|Wood powder as a waste product)Wood flour is finely pulverized wood that has a consistency fairly equal to sand or sawdust, but can vary considerably, with particles ranging in dimensions from a fine powder to roughly that of a grain of rice. Most wood flour manufacturers are able to create batches of wood flour that have the same consistency throughout. All high quality wood flour is made from hardwoods because of its durability and strength. Very low grade wood flour is occasionally made from sapless softwoods such as pine or fir.

Applications

Wood flour is commonly used as a filler in thermosetting resins such as bakelite, and in linoleum floor coverings. Wood flour is also the main ingredient in wood/plastic composite building products such as decks and roofs. Prior to 1920, wood flour was used as the filler in ¼-inch thick Edison Diamond Discs.Edison Diamond Disc information from Tim GracykWood flour has found a use in plugging small through-wall holes in leaking main condenser (heat exchanger) tubes at electrical power generating stations via injecting small quantities of the wood flour into the cooling water supply lines. Some of the injected wood flour clogs the small holes while the remainder exits the station in a relatively environmentally benign fashion.Because of its adsorbent properties it has been used as a cleaning agent for removing grease or oil in various occupations. It has also been noted for its ability to remove lead contamination from water.JOURNAL, Tan, Yi, Wang, Kaili, Yan, Qian, Zhang, Shifeng, Li, Jiangzhang, Yong, Ji, Synthesis or Amino-Functionalized Waste Wood Flour Adsorbent for High Capacity PB(II) Adsorption, American Chemical Society, 2019, 6, 4, 10475–10484, 10.1021/acsomega.9b00920, 31460144, 6648050, Wood flour can be used as a binder in grain filler compounds.

Sources

Large quantities of wood flour are frequently to be found in the waste from woodworking and furniture companies. An adaptive reuse to which this material can be directed is composting.Wood flour can be subject to dust explosions if not cared for and disposed of properly.

Respirable particulates

As with all airborne particulates, wood dust particle sizes are classified with regard to effect on the human respiratory system. For this classification, the unit for measurement of particle sizes is the micrometre or micron (μm), where 1 micrometre = 1 micron. Particles below 50 μm are not normally visible to the naked human eye.Yuanhui Zhang, 2004. Indoor Air Quality Engineering. Boca Raton, Florida: CRC Press, p. 14. Particles of concern for human respiratory health are those