Agricultural by-products are simply materials produced as a result of producing something else. In most cases, that 'something else' is a product we choose to provide ourselves as a convenience or comfort. Each byproduct has certain characteristics which make it valuable as a resource for us. Many contain nutrients which can be safely utilized for agriculture or horticulture. Examples include potato skins and cleanings, processed waste food, etc.
The undigested feed and food that is removed from the first division of the stomach of a ruminant animal, typically cattle, in which most food collects immediately after being swallowed and from which it is later returned to the mouth as cud for thorough chewing.
Pellets are heat dried biosolids that meet the highest standard for use as set forth by the USEPA and CDPH&E. They are 'BB' shaped hard shaped pellets that are used in traditional agricultural and horticultural fertilizer. The material has commonly been used in golf course turf management and has been sold to homeowners for decades as a Trademarked name Milorganite.