Chaff (; ) is dry, scale-like plant material such as the protective seed casings of cereal grains, the scale-like parts of flowers, or finely chopped

straw Straw is an agricultural byproduct consisting of the dry wikt:stalk, stalks of cereal plants after the grain and chaff have been removed. It makes up about half of the crop yield, yield by weight of cereal crops such as barley, oats, rice, ry ...

. Chaff cannot be digested by humans, but it may be fed to livestock,

plough A plough or ( US) plow (both pronounced ) is a farm tool for loosening or turning the soil before sowing seed or planting. Ploughs were traditionally drawn by oxen and horses but modern ploughs are drawn by tractors. A plough may have a wooden ...

ed into soil, or burned.

Etymology

"Chaff" comes from

Middle English Middle English (abbreviated to ME) is a form of the English language that was spoken after the Norman Conquest of 1066, until the late 15th century. The English language underwent distinct variations and developments following the Old English pe ...

, from

Old English Old English ( or , or ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the Early Middle Ages. It developed from the languages brought to Great Britain by Anglo-S ...

, related to

Old High German Old High German (OHG; ) is the earliest stage of the German language, conventionally identified as the period from around 500/750 to 1050. Rather than representing a single supra-regional form of German, Old High German encompasses the numerous ...

', "husk".

Grain chaff

grass Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family (biology), family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and spe ...

es (including cereals such as

rice Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...

barley Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikele ...

, oats, and

wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...

), 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. In wild cereals and in the primitive domesticated einkorn,Potts, D. T. (1996) ''Mesopotamia Civilization: The Material Foundations''

Cornell University Press The Cornell University Press is the university press of Cornell University, an Ivy League university in Ithaca, New York. It is currently housed in Sage House, the former residence of Henry William Sage. It was first established in 1869, maki ...

. p. 62. . emmer and spelt wheats, the husks enclose each seed tightly. Before the grain can be used, the husks must be removed. The process of loosening the chaff from the grain so as to remove it is called " threshing" before " drying" – traditionally done by milling or pounding, making it finer like "

flour Flour is a powder made by Mill (grinding), grinding raw grains, List of root vegetables, roots, beans, Nut (fruit), nuts, or seeds. Flours are used to make many different foods. Cereal flour, particularly wheat flour, is the main ingredie ...

". 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 uses a broad, plate-shaped basket or similar receptacle to hold and collect the winnowed grain as it falls back down. Domesticated grains such as durum and common wheat have been bred to have chaff that is easily removed. These varieties are known as "free-threshing" or "naked". Chaff should not be confused with

bran Bran, also known as miller's bran, is the component of a Cereal, cereal grain consisting of the hard layersthe combined aleurone and Fruit anatomy#Pericarp layers, pericarpsurrounding the endosperm. Maize, Corn (maize) bran also includes the p ...

, which is a finer, scaly material that is part of the grain itself.

Straw chaff

Chaff is also made by chopping

(or sometimes coarse hay) into very short lengths, using a machine called a chaff cutter. Like grain chaff, it is used as animal feed and is a way of making coarse fodder more palatable for livestock.

Coffee chaff

''Coffee chaff'' is produced from the so called ''silverskin'', the thin inner-parchment layer on dried coffee beans, in the process of grinding coffee beans.

Botany

botany Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...

, chaff refers to the thin receptacular bracts of many species in the sunflower family

Asteraceae Asteraceae () is a large family (biology), family of flowering plants that consists of over 32,000 known species in over 1,900 genera within the Order (biology), order Asterales. The number of species in Asteraceae is rivaled only by the Orchi ...

and related families. They are modified scale-like

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

surrounding single

floret This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary ...

s in the flower-head.

Metaphor

Chaff as a waste product from grain processing leads to a

metaphor A metaphor is a figure of speech that, for rhetorical effect, directly refers to one thing by mentioning another. It may provide, or obscure, clarity or identify hidden similarities between two different ideas. Metaphors are usually meant to cr ...

ical use of the term, to refer to something seen as worthless. In the

Bible The Bible is a collection of religious texts that are central to Christianity and Judaism, and esteemed in other Abrahamic religions such as Islam. The Bible is an anthology (a compilation of texts of a variety of forms) originally writt ...

, such use is found in Job 13:25, 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.

Use

Hungarian engineer László Schremmer has discovered that the use of chaff-based filters can reduce the

arsenic Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...

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 An aquifer is an underground layer of water-bearing material, consisting of permeability (Earth sciences), permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The s ...

.Newspaper article
(in Hungarian) published by Magyar Nemzet on April 15, 2012.

References

{{Wheat Plant morphology Fodder Waste ca:Espícula#Glumel·les