[COLOR=#949494 said:
I think it's a dustbin; even in those days one already started thinking of environmental friendly warfare.[/COLOR]
Not a dustbin but indeed a fuel tank - these are photos of another Renault tank in a French collection showing both sides of the drum (it may be the same tank before repainting, as, if I remember well, the original FT of the Invalides museum was stuck under the main stairs and had an overall drab paint - this one was on display at the armistice memorial in Compiegne).


Whether the fuel drum was used in this way in operational conditions is another issue, though some tanks of the interwar period and early WW2 had ...fuel trailers (the Skoda Pzkpfw 38t for instance, and also the Pzkpfw III and IV in the North African campaign).
BTW most French dustbins of the period had very typical looks, made of zinc, often with longitudinal ribs, and, above all, a couple of handles, diametrically opposed, near the top, and a separated lid. Earlier (the first dustbins, around the turn of the century, were wooden with a inner lining of galvanized "white" metal and roughly cubic)
Pzkpfw 38t with towed 200l fuel trailer:

Pzkpfw IV with dual 200l drum fuel trailer

and of course the French tracked combat support vehicle Lorraine 37L with its 565l fuel trailer


....showing what happens in combat conditions:

