Quicklime Stabilization of Belt-separated Swine Mnaure
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Date
2005-08-16
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Abstract
Quicklime may be used to raise the pH of manure solids, thus initiating a stabilizing effect of killing pathogens, reducing vector attraction, and controlling odors. A range of 5% to 15% quicklime doses was tested on separated manure solids. The largest dose (15 %) yielded higher stabilization temperatures, a higher initial pH increase during mixing, and lower residual moisture in the stabilized product. Solids treated with doses of 10 % and 15 % quicklime can produce a stabilized product meeting the same requirements as Class-A biosolid defined in Part 503 of the CFR 40. Manure treated with 10 % quicklime lost through volatilization approximately 80% of the original ammonia over a period of 7 days. An additional 10% was liberated over the next 21 days.
Stabilization pH occurs above 12 and nearly all ammoniacal nitrogen is in the form of ammonia. Consequently, ammonia volatilization was increased from approximately 0.005 μg / min g dry solids for the raw manure to a maximum of 45 μg / min g dry solids for a one liter stirred reactor following addition of 10% quicklime on a wet weight basis. This volatilization rate was not maintained after mixing due to limitations on diffusion of aqueous ammonia through the manure solids. Under steady state operation of a 15' X 6" auger reactor the maximum amount of ammonia removed was less than 20% of the original ammoniacal nitrogen in separated manure solids over a three minute period and less than 1% of the total nitrogen in the swine waste.
Continuous belt operation will produce the highest moisture manure possible for the belt system. With respect to quicklime utilization and product temperatures, the most efficient systems will combine this belt removal technique with a constantly warm in-house treatment scheme. A quicklime stabilization process such as studied here, using a 10 % quicklime dose, assuming an average solids output of 2 lbs / pig / day and a quicklime cost of $ 100 / ton, would have a material cost of one cent per pig per day.
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Keywords
belt, pH, quicklime, Calcium oxide, swine, manure
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Degree
PhD
Discipline
Biological and Agricultural Engineering
