Can an arm fat be used for brazilian butt lift?

Definitely. I do this all of the time. this area alone is not likely to provide enough fat to make a significant enhancement for your buttocks, but it can be added to the fat obtained from elsewhere. We can take fat from just about any area of your body that you would like to have it removed from, just like we would with normal liposuction, and use this fat to transfer to your buttocks. The only area I will not use fat from is the breast. Even though breasts are mostly made up of fat, when liposuction of the breast is performed, breast cells can be removed as well, and we don't want to transplant these to your buttocks.

Hello dear!!
Thanks for the question and provided information as well. 
Yes, you can harvest fat from different areas of your body, including your arms. l recommend you to make an appointment with a board certified plastic surgeon to talk about your goals and anything you need to know.
Good luck :)

Thank you for your question. Definitely, yes it is possible, I would suggest to be treated by board certificated plastic surgeon with experience in this procedure, to get the best desired results.
Kind Regards,Dr. Emmanuel Mallol Cotes.-