Alternatives to capital punishment

I came across to this blog which attempts to prove that capital punishment actually costs more than lifelong imprisonment. There is quite a debate going on worth going through them, I recommend it.

Question came to my mind is not which one is more costly, as you can prove anything with statistics. The question is…

What are the alternatives?

Bear in mind prisoners mentioned here are all guilty and deserve capital punishment.

My girlfriend suggests an island where all the prisoners are abandoned for life is a better solution. There are many complications with this approach, but for now let us ignore how doable it is. The island will be a rubbish bin for humans. Prisoners will be just dropped in the island with no supply and will have to survive on what is available from nature for the rest of their lives.

My suggestion is, however, to use them as donors for blood, kidneys. Well, basically for anything human body can be useful in the name of medicine and saving a life. Another way is to use them instead of monkeys for testing new drugs. Or they could be forced to work in dangerous places.

I would also add that prisoner should always have a chance/option to commit a suicide.

Now, if we consider from which one of these suggested alternatives is more humane, obviously the first one is, as they are given the opportunity to live again. For me, it is a waste of valuable resource that can be used to save lives (and money?)