Foam peanuts, also known as packing peanuts or packing noodles, are a common loose-fill packaging and cushioning

Cushioning

Package cushioning is used to help protect fragile items during shipment. It is common for a transport package to be dropped, kicked, and impacted: These events may produce potentially damaging shocks. Transportation vibration from conveyors, trucks, railroads, or aircraft can also damage some...

 material used to prevent damage to fragile objects during shipping. They are shaped to interlock when compressed and free flow when not compressed. They are roughly the size and shape of a peanut

Peanut

The peanut, or groundnut , is a species in the legume or "bean" family , so it is not a nut. The peanut was probably first cultivated in the valleys of Peru. It is an annual herbaceous plant growing tall...

 (in its shell) and usually made of expanded polystyrene

Polystyrene

Polystyrene ) also known as Thermocole, abbreviated following ISO Standard PS, is an aromatic polymer made from the monomer styrene, a liquid hydrocarbon that is manufactured from petroleum by the chemical industry...

 foam.

Usually two to three inches (50 – 75 mm) of peanuts are used for cushioning applications.

Polystyrene foam peanuts

Polystyrene-based packing peanuts were introduced circa 1965 by Dow Chemical. Originally made from 100% virgin polystyrene resin, peanuts made from 100% recycled polystyrene have been commercially available since the mid-90s. The color and shape sometimes indicate what it is made of and who made it. Often green is 70% or more recycled polystyrene, white is 70% or more virgin resin and pink means anti-stat has been applied; although there are some variations. The most common shapes are similar to a "S", "figure 8" or "W" . Foam peanuts are very light (usually around 3 grams per litre/0.17 to 0.2 lb per cu ft) and easy to use.

Polystyrene peanuts may be used and reused many times with little or no loss in protection for the product shipped. They may be reused and recycled at many packing and shipping stores.

Starch-based packing peanuts

In the early 1990s, starch-based packing peanuts were developed as a more environmentally friendly alternative. The starch

Starch

Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

 in the peanuts comes from crop-based sources rather than petroleum-based polystyrene, and is non-toxic. One of the first brands of biodegradable peanuts, Biofoam, is made from the grain sorghum

Sorghum

Sorghum is a genus of numerous species of grasses, one of which is raised for grain and many of which are used as fodder plants either cultivated or as part of pasture. The plants are cultivated in warmer climates worldwide. Species are native to tropical and subtropical regions of all continents...

; 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 safe for humans and pets to ingest accidentally. However, they are not produced in food-safe conditions, and are not recommended for eating. Also, during the manufacturing process, the nutritional value is removed from starch-based packing peanuts. This removes edible components, such as sugars, that would otherwise attract rodents and bugs. Their main drawbacks compared with polystyrene are lower resilience, higher weight (6.5 to 13g per litre/0.4 to 0.8 lb per cubic foot), dust creation, and higher price. Starch-based peanuts are soluble in water, and polystyrene peanuts are soluble in acetone

Acetone

Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...

, but not vice versa.

Chemical properties

Because polystyrene peanuts are non-soluble in water, they are also used as a light-weight aggregate in hydroponics

Hydroponics

Hydroponics is a method of growing plants using mineral nutrient solutions, in water, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel, mineral wool, or coconut husk.Researchers discovered in the 18th...

. They are also sometimes used to fill beanbag chairs and in a variety of crafts.

General references

• Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, ISBN 978-0-470-08704-6