Products undergo production processes that often yield more than just the intended primary output. Alongside the main product, secondary materials or substances are frequently generated, known as by-products. These components play a significant role in various industries, holding potential value beyond their initial production context.
What Defines a By-Product
A by-product is a secondary output arising incidentally during a manufacturing or chemical process, not representing its main goal. Its generation is often unavoidable, produced as an integral part of primary production. Unlike the main product, a by-product is typically minor in quantity or net realizable value.
The distinction between a by-product and waste is important. While waste generally has no further use or commercial value and is often discarded, by-products possess inherent properties allowing for potential use or marketability. If a material loses its potential for direct use without extensive additional processing, it may then be classified as waste.
Common By-Products and Their Origins
Many industries generate familiar by-products. For instance, lumber production, focused on creating wood planks, produces sawdust when logs are cut.
In the dairy sector, cheesemaking separates milk into solid curds (cheese) and liquid whey, which remains after milk proteins coagulate. Similarly, sugar refining from sugarcane or sugar beets leaves behind molasses, a thick, dark syrup remaining after sugar crystals are extracted.
Energy generation contributes by-product streams like fly ash from coal-fired power plants, formed when coal combustion carries fine ash particles with flue gases. The brewing industry generates brewers’ spent grains, residual solids from malted barley after sugars are extracted during mashing.
Transforming By-Products into Value
Historically, many by-products were treated as waste and disposed of, leading to environmental concerns and missed economic opportunities. However, there has been a significant shift towards transforming these secondary outputs into valuable resources. This approach aligns with principles of resource efficiency and sustainability, seeking to keep materials in use for as long as possible.
Sawdust, once a disposal challenge, is now processed into particleboard, animal bedding, or biomass pellets for fuel. Whey, a liquid by-product of cheesemaking, is extensively processed for protein concentrates and isolates in nutritional supplements, or incorporated into food products. Advanced separation technologies have enabled the recovery of high-quality proteins and lactose from whey, adding significant economic value.
Molasses is fermented for ethanol biofuels or used as an ingredient in animal feeds due to its energy content. Fly ash, from coal combustion, is widely utilized as a supplementary cementitious material in concrete, enhancing its strength and durability and reducing the need for virgin cement and improving concrete performance.
Brewers’ spent grains, a nutrient-rich by-product, are primarily used as animal feed but are also explored for human consumption in baked goods due to their fiber and protein content. These transformations reduce disposal costs and create new revenue streams, contributing to a more circular and sustainable industrial system.