Chaff (//; also UK: //) is the dry, scaly protective casing of the seeds of cereal grains or similar fine, dry, scaly plant material (such as scaly parts of flowers or finely chopped straw). Chaff is indigestible by humans, but livestock can eat it. In agriculture it is used as livestock fodder, or is a waste material ploughed into the soil or burned.
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In grasses (including cereals such as rice, barley, oats, and wheat), the ripe seed is surrounded by thin, dry, scaly bracts (called glumes, lemmas and paleas), forming a dry husk (or hull) around the grain. Once it is removed it is often referred to as chaff.
The process of loosening the chaff from the grain so as to remove it is called threshing – traditionally done by milling or pounding. Separating remaining loose chaff from the grain is called winnowing – traditionally done by repeatedly tossing the grain up into a light wind which gradually blows the lighter chaff away. This method typically utilizes a broad, plate-shaped basket or similar receptacle to hold and collect the winnowed grain as it falls back down.
Chaff should not be confused with bran, which is finer scaly material that is part of the grain itself.
Chaff is also made by chopping straw (or sometimes coarse hay) into very short lengths, using a machine called a chaff cutter. Like grain chaff this is used as animal feed, and is a way of turning coarse fodder into a form more palatable to livestock.
In botany, chaff refers to the thin receptacular bracts of many species in the sunflower family Asteraceae and related families. They are modified scale-like leaves surrounding single florets in the flower-head.
Chaff as a waste product from grain processing leads to a metaphorical use of the term, to refer to something seen as worthless. In the Bible, such use is found in Job 15:25, Isaiah 33:11, Psalm 83:13-15, and other places. Chaff also lends its name to a radar countermeasure, composed of small particles dropped from an aircraft.
Hungarian engineer László Schremmer has discovered that by the use of chaff-based filters it is possible to reduce the arsenic content of water to 3 microgram/litre. This is especially important in areas where the potable water is provided by filtering the water extracted from an underground aquifer.
- Daniel Jones (2006). Peter Roach; James Hartman; Jane Setter (eds.). Cambridge Pronouncing Dictionary. Cambridge University Press.
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- Vaughan, J. G. & P. A. Judd. (2003) The Oxford Book of Health Foods. Oxford University Press. p. 35. ISBN 0-19-850459-4.
- "What Is Chaff: Learn How To Winnow Seeds From Chaff". Gardening Know How. Retrieved 2022-10-07.
- "The Chaff cutter". Archived from the original on 2006-01-03. Retrieved 2005-09-06.
- Cutting chaff by hand: detail of painting by David Teniers the Younger
- A Victorian chaff cutter Archived March 21, 2008, at the Wayback Machine
- Ronald Jones (25 March 2005). Plant Life of Kentucky: An Illustrated Guide to the Vascular Flora. University Press of Kentucky. pp. 751–. ISBN 0-8131-7194-6.
- "Job 13:25 Would You frighten a windblown leaf? Would You chase after dry chaff?". biblehub.com. Retrieved 2022-10-07.
- "Bible Gateway passage: Isaiah 33:11 - New International Version". Bible Gateway. Retrieved 2022-10-07.
- "Bible Gateway passage: Psalm 83:13-15 - New International Version". Bible Gateway. Retrieved 2022-10-07.
- Newspaper article Archived 2012-04-17 at the Wayback Machine (in Hungarian) published by Magyar Nemzet on April 15, 2012.