By-product

A secondary product or consequence arising incidentally from producing something else or carrying out an activity, rather than being its primary aim.

Chemical reaction: A process in which substances are transformed into other substances through rearrangement of atoms. Side reactions can generate substances alongside a reaction’s intended product.
Bagasse: The fibrous residue left after juice is extracted from sugarcane or sorghum. Sugar production leaves this residue, which can fuel boilers or supply paper and board.
Main product: The primary output that a production process is designed to make. A by-product is secondary to this intended output.
Greenhouse gas: A gas that absorbs and emits infrared radiation, contributing to the greenhouse effect. Some production by-products, especially carbon dioxide and methane, contribute to climate change.
Side reaction: A reaction pathway that occurs alongside a desired reaction and produces an unintended or secondary product. It is a direct chemical route by which an unwanted by-product forms.
Glycerol: A three-carbon alcohol used in foods, medicines, and personal-care products. Biodiesel production can generate glycerol as a secondary product of transesterification.
Co-product: One of two or more outputs from a process that are regarded as having significant economic value. Unlike a by-product, a co-product is treated as a purposeful, valuable output.
Acid rain: Precipitation made unusually acidic by atmospheric pollutants, especially sulfur dioxide and nitrogen oxides. These emissions can be by-products of burning fuels and industrial activity.
Metabolic byproduct: A substance produced during metabolism that is not the main product of the process. Living systems generate these secondary outputs as they transform nutrients and release energy.
Blast furnace slag: A glassy material formed when mineral impurities separate from iron during blast-furnace smelting. Ironmaking produces slag that can be processed into cement and construction materials.

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