An incidental product deriving from a manufacturing process or chemical reaction, and not the primary product or service being produced. A by-product can be useful and marketable, or it can have negative ecological consequences.

US EPA, 2015, Terminology Services. U.S. Environmental Protection Agency, accessed 4 December 2023.

Source category: Agency Documents

A secondary product; a substance of more or less value obtained in the course of a specific process, though not its primary object.

Oxford English Dictionary, accessed 04 December 2023

Source category: Dictionaries

A secondary product which is made incidentally during the production of something else. Example: Sawdust when sawing timber.

ISO 16559:2014(en) Solid biofuels — Terminology, definitions and descriptions

Source category: Standards

A substance or object, resulting from a production process, the primary aim of which is not the production of that item, may be regarded as not being waste referred to in point (1) of Article 3 of the Directive 2008/98/EC but as being a by-product only if the following conditions are met:

(a) further use of the substance or object is certain;

(b) the substance or object can be used directly without any further processing other than normal industrial practice;

(c) the substance or object is produced as an integral part of a production process; and

(d) further use is lawful, i.e. the substance or object fulfils all relevant product, environmental and health protection requirements for the specific use and will not lead to overall adverse environmental or human health impacts.

Directive 2008/98/EC of the European Parliament and of the Council of 19 November 2008 on waste and repealing certain Directives

Source category: EU Legislation