Evaluation of a solid-liquid manure separation operation
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Field monitoring and laboratory tests were conducted to evaluate the efficacy and practicality of a solid-liquid separation barn for finishing pigs. The solid-liquid separation system included a mechanical scraper and gravity flow system to separate manure into solid and liquid portions. The objectives of this research were to evaluate the performance of a solid-liquid separation finishing barn in improving manure nutrient management, the potential for nutrient/water recycling based on filtration, and barn construction and operating costs. A full-scale barn in Missouri was closely monitored to perform these objectives. Laboratory scale pretreatments and filtrations were conducted to evaluate the practicality of nutrient/water recycling from the separated liquid manure. The daily liquid manure production averaged 885 gallons, and daily solid manure production averaged 299 gallons. The solid separation system removed an average of 61.7%, 41.7%, 74.8%, and 46.2% of nitrogen, ammonium, phosphorus, and potassium, respectively, from the liquid stream. The filtration results indicate that the microfiltration was capable of removing suspended solids, but not the dissolved nutrients. The reverse osmosis process was time and energy intensive, with only minimal nutrient removal, but was probably constrained by the relatively small scale of the operation, small filter surface area, and high dissolved nutrients in the liquid manure. The construction cost of the solid-liquid separation barn in 2010 was $269/pig, which was around 15% higher than that for a deep pit barn. Additional electricity cost was $331 per year for daily operation of the scraper and conveyor systems, which equates to $0.28 per headspace per year. The additional maintenance of the scraper system averaged $1,342 per year. The solid-liquid separation barn was shown to have lower ammonia and hydrogen sulfide emissions when compared with deep-pit barns.