function turnBack()
  turtle.turnRight()
  turtle.turnRight()
end
function turnForward()
  turtle.turnLeft()
  turtle.turnLeft()
end
while true do

    if turtle.getFuelLevel() < 100 then
      print("Needing refuel in slot 16")
      turtle.select(16)
      turtle.refuel()
      turtle.select(1)
      print("New fuel level: "..turtle.getFuelLevel())
    end
    if turtle.getItemCount(15) > 0 then
      turnBack()
      for i = 1, 15 do
        turtle.select(i)
        turtle.drop()
      end
      turtle.select(1)
      turnForward()
    end
    if turtle.detect() then
      turtle.dig()
    end

end