By-product

A '''by-product''' or '''byproduct''' is a secondary product derived from a production process, manufacturing process or chemical reaction; it is not the primary product or service being produced.

A by-product can be useful and marketable or it can be considered waste: for example, bran, which is a byproduct of the milling of wheat into refined flour, is sometimes composted or burned for disposal, but in other cases, it can be used as a nutritious ingredient in human food or animal feed. Gasoline was once a byproduct of oil refining that later became a desirable commercial product as motor fuel. The plastic used in plastic shopping bags also started as a by-product of oil refining.<ref> {{cite book | last1 = Muthu | first1 = Subramanian Senthilkannan | last2 = Li | first2 = Yi | chapter = Manufacturing Processes of Grocery Shopping Bags | title = Assessment of Environmental Impact by Grocery Shopping Bags: An Eco-Functional Approach | url = https://books.google.com/books?id=D8fEBAAAQBAJ | series = Environmental Issues in Logistics and Manufacturing | location = Singapore | publisher = Springer Science & Business Media | publication-date = 2013 | page = 7 | isbn = 9789814560207 | access-date = 27 July 2019 | quote = Plastic is obtained as a by-product from the oil refining process [...] }} </ref> By-products are sometimes called '''co-products''' to indicate that although they are secondary, they are desired products. For example, hides and leather may be called co-products of beef production. There is no strict distinction between by-products and co-products.

== In economics == In the context of production, a by-product is the "output from a joint production process that is minor in quantity and/or net realizable value (NRV) when compared with the main products".<ref>Wouters, Mark; Selto, Frank H.; Hilton, Ronald W.; Maher, Michael W. (2012): ''Cost Management: Strategies for Business Decisions'', International Edition, McGraw-Hill, p. 535.</ref> Because they are deemed to have no influence on reported financial results, by-products do not receive allocations of joint costs. By-products also, by convention, are not inventoried, but the NRV from by-products is typically recognized as "other income", or as a reduction of joint production processing costs when the by-product is produced.<ref>World Trade Organization (2004): ''United States – Final dumping determination on softwood lumber from Canada'', WT/DS264/AB/R, 11 August 2004.</ref>

The International Energy Agency (IEA) defines ''by-product'' in the context of life-cycle assessment by defining four different product types: "'''main products''', '''co-products''' (which involve similar revenues to the main product), by-products (which result in smaller revenues), and '''waste products''' (which provide little or no revenue)."<ref>{{Cite web |url=http://www.ieabioenergy-task38.org/systemdefining/biomitre_technical_manual.pdf# |title=BIOMITRE Technical Manual, Horne, R. E. and Matthews, R., November 2004 |access-date=2011-02-16 |archive-url=https://web.archive.org/web/20110726171133/http://www.ieabioenergy-task38.org/systemdefining/biomitre_technical_manual.pdf# |archive-date=2011-07-26 |url-status=dead }}</ref>

== In chemistry == While some chemists treat "by-product" and "side-product" as synonyms in the above sense of a generic secondary (untargeted) product, others find it useful to distinguish between the two. When the two terms are distinguished, "by-product" is used to refer to a product that is not desired but inevitably results from molecular fragments of starting materials and/or reagents that are not incorporated into the ''desired product'', as a consequence of conservation of mass; in contrast, "side-product" is used to refer to a product that is formed from a competitive process that could, in principle, be suppressed by an optimization of reaction conditions.<ref>{{cite journal | author = Watson, Will |title = On Byproducts and Side Products| journal = Org. Process Res. Dev. | year = 2012| volume = 16 | pages = 1877–1877| doi = 10.1021/op300317g | issue = 12| doi-access = free}}</ref>

==Common byproducts== *bagasse and molasses from sugar production *bran and germ from flour milling *buttermilk from butter production *distillers grains from ethanol production *fly ash and bottom ash from coal combustion *glycerol from soap or biodiesel production *lanolin from wool processing *lees from wine fermentation *pomace from fruit juice or olive oil production *saw dust from lumber production *slag from smelting ore *straw from grain harvesting *trub from beer fermentation *vinasse from sugar or ethanol production *whey from cheese production

== See also == * Main product * By-product synergy * Circular economy * Side reaction

== References == {{Reflist}}

Category:By-products