Bay 12 Games Forum

Use wood furnace and make charcoal with wood.  For future forts, consider bringing a few pieces of bituminous coal.  They are only cost 3 points a piece and they each yield 9 coal when smelted. 
    I have made a self sustaining fort before with no traders and migrants.  It lasted several years.  I just left the migrants outside to die.  I didn't make any kind of traps (in retrospect I wish I had) so they took really long for them to starve to death and go berserk.  From the wiki, I knew they should stop coming once enough dwarves had died at my fort.  Apparently however having a low population and high wealth will attract more anyway.  Every time one batch of migrants died off, another would come  because of the lowered population.  Eventually I dropped a pick from my tower so with with good mining and burrows I could get the migrants to kill themselves off faster.  This just made the new waves spawn more frequently so I started allowing them to live by foraging off the terrain and then planting the seeds from the foraging.  Eventually one of them got a fell mood so I dropped the materials from my tower and they made an artifact.  I figured with some tricky burrows I could let just the artifact maker and the artifact in, but all the migrant trash pathed in to my fort despite the burrows.  I abandoned in disgust.  I was having difficulty making enough slabs to keep off the ghosts anyway.  And wow that story turned dark just answering a simple question. 
    Anyway to answer your question all it took was a few irrigated farms and some pets and I had plenty of food for my entire fort (of only 20 or so).  With a small but continuous production of leather and cloth you can keep them all clothed too.  If you want to get fancy dig an aqueduct from a stream and with the right combination of floodgates and depressurization tricks (diagonal connections)  you can have underground fishing, and plenty of water for wells/mist generators/water reactors.