Please describe the minimum age for kidney donation?

Varies. I assume you are asking about living donation. Most kidney transplant programs will consider you if you are 21 years of age or older. Some will even consider patients who are 18 years of age. A lot depends on how emotionally mature the potential donor is and whether he/she understands the potential risks of living kidney donation.
18 yrs and above. Living donors should be in good overall physical and mental health and older than 18 years of age.Please see this link for more info http://www.Unos.Org/docs/living_donation.Pdf.