By-product

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

Animal sources

 * dried blood and blood meal - from slaughterhouse operations
 * chicken by-product meal - clean parts of the carcass of slaughtered chicken, such as necks, feet, undeveloped eggs, and intestines.
 * chrome shavings - from a stage of leather manufacture
 * collagen and gelatin - from the boiled skin and other parts of slaughtered livestock
 * feathers - from poultry processing
 * lanolin - from the cleaning of wool
 * manure - from animal husbandry
 * meat and bone meal - from the rendering of animal bones and offal
 * poultry byproduct and poultry meal - made from unmarketable poultry bones and offal
 * poultry litter - swept from the floors of chicken coops]
 * whey - from cheese manufacturing
 * fetal pigs

Vegetation

 * acidulated soap stock - from the refining of vegetable oil
 * bran and germ - from the milling of whole grains into refined grains
 * brewer's yeast - from ethanol fermentation
 * corn stover - residual plant matter after harvesting of cereals
 * distillers grains - from ethanol fermentation
 * glycerol - from the production of biodiesel
 * grape seed oil - recovered from leftovers of the winemaking process
 * molasses - from sugar refining
 * orange oil and other citrus oils - recovered from the peels of processed fruit
 * pectin - recovered from the remains of processed fruit
 * sawdust and bark- from the processing of logs into lumber
 * straw- from grain harvesting

Minerals and petro chemicals

 * asphalt - from the refining of crude oil
 * fly ash - from the combustion of coal
 * slag - from ore refining
 * gypsum - from Flue gas desulfurization
 * ash and smoke - from the combustion of fuel
 * mineral oil - from refining crude oil to produce gasoline
 * salt - from desalination

Other

 * sludge - from wastewater treatment