In the movie Sunshine the Captain of the first space ship Icarus I survived for almost 7 years. How did he survive this long in space without any backup or support? Also, he was severely burnt, so how did he survive for seven long years? There was oxygen on Icarus I but no sign of food and medical facilities, so how did he survive?
Danny Boyle makes the point in the directors commentary that the inclusion of Corazon's garden was not just that they would have a self - replenishing supply of oxygen - it is indeed shown in the film that carrots, among other foodstuffs were being grown there. He also suggests that food sources such as fish could be used on such flights in a similar manner.
With the Icarus I' s oxygen garden having got so completely overgrown it is not difficult to imagine that there was enough vegetation to at least feed Pinbacker on his own...
... but to be honest one has to really suspend their disbelief when acknowledging that Pinbacker had not only survived but was so severly burned that one can not even see him straight due to the amount of radiation surging back out of his body all of the time. I love the film and love the premise of the character, but he has been transformed into something that crosses the border into supernatural, Bruce Banner-esque territory.
"(Danny Boyle) also described the potentially unrealistic presence of Pinbacker as an example of something that breaks the pattern of realism, similar to his scene in Trainspotting (1996) in which Ewan McGregor's character dives into a toilet."
(Quoted from https://web.archive.org/web/20090107144715/http://www.luminomagazine.com/mw/content/view/2074/1 ) - interview with Danny Boyle, LuminoMagazine 2007.