I second Cough's figures, most flight plans allow for about 42-44kg per min fuel burn (trip fuel) so about 1200kg per engine per hour. Fuel flow at idle during taxi is about 400 ish. I recently had a 50 min taxi (no I did not get lost but I did use up my daily allowance of enthusiasm. Net result was 700kg of fuel gone. On the fms2 aircraft, certainly on the IAE equipped ones on the fuel page you can see the fuel flow in kg per min.