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Title: AN ECONOMIC ASSESSMENT OF ALGAL TURF SCRUBBER TECHNOLOGY FOR TREATMENT OF DAIRY MANURE EFFLUENT

Author
item PIZARRO, CAROLINA - UMD, COLLEGE PARK
item Mulbry, Walter
item BLERSCH, D - UMD, COLLEGE PARK
item KANGAS, P - UMD, COLLEGE PARK

Submitted to: Ecological Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2005
Publication Date: 7/31/2006
Citation: Pizarro, C.X., Mulbry III, W.W., Blersch, D., Kangas, P. 2006. An economic assessment of algal turf scrubber technology for treatment of dairy wastewater. Ecological Engineering. 26:321-327.

Interpretive Summary: The vulnerability of ecosystems and groundwater to pollution has forced increasingly stringent environmental regulations to be imposed on dairy farms. However, harnessing solar energy to grow algal biomass on wastewater nutrient could provide a holistic solution to nutrient management problems at livestock operations. Since anaerobic digestion increases the availability of manure nutrients, the combination of anaerobic digestion followed by algal production could be synergistic. In addition, energy recovered from manure by digestion can be used for drying the biomass and carbon dioxide from burned biogas can be directly recycled back into the algal ponds. The purpose of this paper is to assess the economics of ATS treatment technology at the farm-scale for a hypothetical 1000-cow dairy. The majority of capital costs were due to land preparation, installation of liner material, and engineering fees. The majority of operational costs were due to energy requirements for water pumps, biomass drying, and to labor costs. On farms using anaerobic pretreatment, waste heat from burning of biogas could be used to offset approximately 90% of the energy requirements of biomass drying. Under the best case (algal treatment system coupled with anaerobic digestion pretreatment), the yearly operational costs per cow, per kg of nitrogen, per kg of P, and per kg of dried biomass were $404, $5.50, 27.60, and $0.68, respectively. The estimated costs per animal are particularly sensitive to the daily amount of total nitrogen in the solids-separated manure effluent. Improvements in nitrogen removal during solids separation would decrease the size of the required algal treatment system and consequently, would decrease the per animal treatment costs.

Technical Abstract: Controlling the input of nitrogen (N) and phosphorus (P) from dairies and other livestock operations into the surrounding air- and watersheds poses both technical and economic challenges to the agricultural community. The purpose of this paper is to assess the economics of ATS treatment technology at the farm-scale for a hypothetical 1000-cow dairy. Costs were developed for farms with and without anaerobic pretreatment. The majority of capital costs were due to land preparation, installation of liner material, and engineering fees. The majority of operational costs were due to energy requirements for water pumps, biomass drying, and to labor costs. On farms using anaerobic pretreatment, waste heat from burning of biogas could be used to offset approximately 90% of the energy requirements of biomass drying. In addition, biogas combustion exhaust gas could then be recycled back to the algal system to supply dissolved inorganic carbon for optimal algal production and pH control. Under the best case (algal treatment system coupled with anaerobic digestion pretreatment), the yearly operational costs per cow, per kg of nitrogen, per kg of P, and per kg of dried biomass were $404, $5.50, 27.60, and $0.68, respectively. The estimated costs per animal are particularly sensitive to the daily amount of total N in the solids-separated manure effluent. Improvements in TN and TP removal during solids separation would decrease the size of the required algal treatment system and consequently, would decrease the per animal treatment costs.