Chaff (; ) is the dry, scaly protective casing of the seeds of

cereal grain A cereal is any grass cultivated for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, germ, and bran. Cereal grain crops are grown in greater quantities and provide more food ...

s or similar fine, dry, scaly plant material (such as scaly parts of

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanis ...

s or finely chopped straw). Chaff is indigestible by humans, but

livestock Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to ani ...

can eat it. In

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people ...

it is used as livestock fodder, or is a waste material ploughed into the

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...

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 Englis ...

''chaf'', from

Old English Old English (, ), 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 was brought to Great Britain by Anglo-Saxon settlers in the mid-5th ...

, related to

Old High German Old High German (OHG; german: Althochdeutsch (Ahd.)) is the earliest stage of the German language, conventionally covering the period from around 750 to 1050. There is no standardised or supra-regional form of German at this period, and Old Hig ...

''cheva'', "husk".

Grain chaff

grass Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns a ...

es (including

cereal A cereal is any grass cultivated for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, germ, and bran. Cereal grain crops are grown in greater quantities and provide more food ...

s such as

rice Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...

barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley p ...

, oats, and

wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

), the ripe seed is surrounded by thin, dry, scaly

bracts In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or ...

(called

glume In botany, a glume is a bract (leaf-like structure) below a spikelet in the inflorescence (flower cluster) of grasses (Poaceae) or the flowers of sedges (Cyperaceae). There are two other types of bracts in the spikelets of grasses: the lemma and ...

lemma Lemma may refer to: Language and linguistics * Lemma (morphology), the canonical, dictionary or citation form of a word * Lemma (psycholinguistics), a mental abstraction of a word about to be uttered Science and mathematics * Lemma (botany), ...

s 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; currently housed in Sage House, the former residence of Henry William Sage. It was first established in 1869, making it the first university publishing enterprise in ...

. 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'' – 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. Domesticated grains such as durum wheat and

common wheat Common wheat (''Triticum aestivum''), also known as bread wheat, is a cultivated wheat species. About 95% of wheat produced worldwide is common wheat; it is the most widely grown of all crops and the cereal with the highest monetary yield. T ...

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

Straw chaff

Chaff is also made by chopping straw (or sometimes coarse hay) into very short lengths, using a machine called a

chaff cutter A chaff cutter is a mechanical device for cutting straw or hay into small pieces before being mixed together with other forage and fed to horses and cattle. This aids the animal's digestion and prevents animals from rejecting any part of their ...

. Like grain chaff this is used as animal feed, and is a way of turning coarse fodder into a form more palatable to livestock.

Botany

botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...

, chaff refers to the thin receptacular

of many species in the sunflower family

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae ...

and related families. They are modified scale-like leaves 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 o ...

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 often compared wi ...

ical use of the term, to refer to something seen as worthless. Like in Job 15:25, Isaiah 33:11, Psalm 83:13-15, among other things.

Use

Hungarian engineer László Schremmer has discovered that by the use of chaff-based filters it is possible to reduce the

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, b ...

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, permeable rock, rock fractures, or unconsolidated materials ( gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characte ...

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

References

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