Fertilizer Production From Wheat Straw Pulping: Spent Ammonium Sulfite Liquor, 1997 Pulping Conference Proceedings

Wheat straw is an alternative fiber source currently being investigated which can be pulped using ammonium sulfite. The spent cooking liquor from wheat straw pulping may prove to be a marketable fertilizer byproduct, thus enhancing the economic feasibility of ammonium sulfite pulping of wheat straw. The spent liquor provides valuable nitrogen and sulfur sources needed by the agricultural industry to replenish the soil nutrients used during the growing cycle. Using a liquor oxidation system, multiple effect evaporators, and a spray drying unit, the spent cooking liquor can be dried to form a marketable solid pellet fertilizer which can be easily stored and transported. Assuming that an ammonium sulfite mill already exists, and that the fertilizer will be sold weekly to a distributor, the payout time on the fixed capital required is 1.5 years with a present worth of $32 million at 15% for 8 years, and a DCFROI of 56%. If the fertilizer is to be sold directly to the farmer the payout time on the fixed capital required is 2.0 years with a present worth of $6.5 at 15% for 8 years and a DCFROI of 18%.