Sacks and carboard used for packaging are often treated with a fire
retardent these days so you may find sacking burns better if you give it a
rinse first.
I've heard that elephant dung is highly prised as a smoker fuel in Africa
but that's a bit hard to find here in the UK so I generally start with
small ball of newspaper and once thats flaming nicely I stuff in a handful
of semi dry lawn trimmings. If the moisture content is just right they will
burn for hours and produce plenty of smoke.
Joe Trattle
Norfolk
England