There are four alternatives to immediate disposal, none of which is available to you unless the dead person made provision when they were alive and you give the go-ahead when that person is dead. If the person who has died opted for one of these, you ought to know all about it. These alternatives are:
Donation of the body to medical science: There is no upper limit on the amount of time a body so donated may be retained but in practice it is normally between 3—5 years.
Cryonic preservation: keeping the body frozen in liquid nitrogen until medical science can find a way of reviving it.
Plastination: a process whereby water is drawn out of the body and replaced by polymers which set hard, after which it is posed and displayed in a Bodyworlds exhibition.
Long-term preservation of the body.