Exploiting synergy in animal co-product bisolids processing: the cactus project



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The current project is a feasibility study prepared for the Dumas Economic Development Corporation in Cactus, Texas for the purpose of evaluating the feasibility of constructing a facility that processes leather wastes to produce useful products. The project aims at developing a zero discharge strategy by fully utilizing the wastes from the leather making industry and converting them into value-added products. The model of the comprehensive animal co-product biosolids processing facility consists of six processing units namely the tannery, the keratin unit, the collagen unit, the biodiesel unit, the modular agriculture unit, and the biogasification unit. All the above units are linked to each other in such a way that the waste produced by one unit is used as input to another unit, leading to zero waste discharge. Simulation models of all the units were developed using the SuperPro Designer software.

The tannery processes raw goatskins and converts them into wet blue leather. In the process, the tannery generates wastes like hair pulp, fleshing grease, wastewater, and waste biosolids. The hair sludge and fleshing grease produced from the sanitization of hides in the tannery are sent to the keratin unit and biodiesel unit to obtain useful products like keratin and bio-diesel, respectively. The collagen unit is used to produce gelatin, protein, and basic chrome sulfate from wet blue shavings. The chrome sludge produced in this process is sent to the tannery to enable sanitization of the hides. The wastewater produced from all the above processes is sent to a modular agriculture unit, to grow duckweed and baitfish. Virtually all the waste biosolids are sent to a biogasification unit to produce power, steam, and ash.

The annual operating costs for all the units in the facility were determined based on current prices of equipment, raw materials, labor, and utilities. The revenues obtained from the product sales of each unit determined the profitability. The profítability of the entire facility was determined based on the economics of the individual units. The total capital investment on the facility was approximated at $8,890,000. The total annual operating costs were estimated to be $7,466,000. The total annual revenues were found to be $9,581,000. The total gross profit obtained from the entire facility was estimated to be $2,115,000. The total net profit was found to be $1,763,000. The payback time is just 5 years. The results of the study indicate that the Cactus facility provides economic benefits and reduces environmental impact by eliminating the discharge of wastes.