Foam peanut

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Foam peanuts, also known as packing peanuts, are a common loose-fill packing material used to prevent damage to fragile objects during shipping. They were introduced circa 1970. They are roughly the size and shape of a peanut (in its shell) and usually made of polystyrene.

In the mid-1990s, a more environmentally friendly starch-based alternative was developed. One of the first brands of biodegradable peanuts, Biofoam, is made from grain sorghum; other brands are made from corn starch. Biodegradable foam peanuts have no electrostatic charge, another benefit over polystyrene. Being biodegradable and nontoxic, they are also edible. Two of their main drawbacks are a lesser resilience and higher weight relative to polystyrene.

Starch-based peanuts are soluble in water, and polystyrene peanuts are soluble in acetone, but not vice versa. Because polystyrene peanuts are non-soluble in water, they are also used as a light-weight aggregate in hydroponics.