Ann: Receipt of Initial Payment of Federal Government Grant Funds, page-34

Spot on @osr1986.

I have always thought the feedstock was likely to be either the spent sodium aluminate liquor from the Bayer process circuit after precipitation of aluminium hydrate (i.e. before it is recycled to the fresh ore digestion stage) OR the actual aluminium hydrate itself which is removed before it goes to the calciners (which converts it to alumina).

For some reason I had it in my mind that A4N took a liquid stream as feedstock, which could only have been the sodium aluminate, but the 35% aluminium content you describe is consistent with the molecular formula of the hydrate (100*26.98/78 = 35%) - whether this is delivered as a slurry or dewatered product I am not sure, but use of hydrate makes sense as it is a high concentration source with relatively low impurities, which still has the lowest embedded energy as it is pre-calcination.

BTW @piwi33, this is by no means a "waste" stream as you often put it - it an intermediary product stage.