:By-product
{{Short description|Secondary product of an item or process}}
{{Redir|Side product|similar uses|Side effect (disambiguation)}}
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.
{{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 [...]
}}
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".Wouters, Mark; Selto, Frank H.; Hilton, Ronald W.; Maher, Michael W. (2012): Cost Management: Strategies for Business Decisions, International Edition, McGraw-Hill, p. 535. 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.World Trade Organization (2004): United States – Final dumping determination on softwood lumber from Canada, WT/DS264/AB/R, 11 August 2004.
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)."{{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 }}
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.{{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}}
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