Re: How long does it take for a plastic fork to decompose?

It depends on what the fork is made of?  Different plastics decay at 
different rates and depending on what the waste bed it is sitting in in 
can take up to several thousand years.  It also depend on the quality of 
the plastic and what impurities are present and whether the plastic is 
exposed to sunlight as most plastics are not UV stable.

I don't think you can associate a half life with this type of 
decomposition processes.  You really need to be talking about radioactive 
decay and if this is the case the half life of a spoon is about 10^100 
years.

Cheers