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 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 refinery 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.[
] 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
. 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)."
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.
Common byproducts
-
bagasse and molasses from sugar production
-
bran and cereal 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
