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      Department of Public Works Bureau of Sanitation

Depending on their composition, products take different lengths of time to naturally break down, also known as "biodegradation." Biodegradation is the decomposition of material by microorganisms.

Biodegradable matter is material that can be biodegraded. For example, most plastic bags are not biodegradable, but paper bags are. This can sometimes be an important difference, because plastic bags stay around forever if left as litter, whereas paper bags eventually decompose. However, in anaerobic landfills, whether a material is biodegradable makes little difference: biodegradable matter usually does not decay, because of the lack of oxygen required by the microorganisms.

In seawater, the following commonly found products biodegrade in these timeframes:

Cardboard:
2 months

Aluminum can:
50 years

Newspaper:
6 weeks

Paper towel:
2-4 weeks

6-pack plastic ring:
400 years

They can also entangle sealife

Polystyrene (Styrofoam) materials:
400 years

Plastic Liter bottle:
450 years

Disposable diaper:
450 years