Abstract
The objective of this research was to evaluate the chemically coagulated swine manure solids as biofuel and/or compost feedstock. Three coagulants, namely agricultural lime [CaCO3], hydrated lime [Ca(OH)2], and lime slurry [Ca(OH)2], were added to fresh swine manure to coagulate manure solids. Four levels, i.e., 0.00 (0.0X), 4.89 (0.5X), 9.77 (1.0X), and 19.77 (2.0X) gm Ca⋅liter-1, were tested, in triplicates. Increasing the coagulant concentration increased the total solids, ash content, and pH of solid manure samples, whereas it decreased their volatile solids, chemical oxygen demand, and heating value. At the coagulant level of 2.0X rate, heating values of samples coagulated by agricultural lime, hydrated lime, and lime slurry were 2.64, 4.48, and 4.54 MJ⋅kg-1, respectively. The heating value of raw manure solids was as high as 13.49 MJ⋅kg-1. Increasing the coagulant concentration increased the O/C atomic ratio for all the studied coagulants. Accordingly, the high coagulant concentrations might reduce the acceptability of the feedstock as a biofuel that can be co-combusted with other feed stocks. The C/N ratio and the pH values of the solid separated swine manure increased by increasing agricultural lime and hydrated lime concentrations. The former might increase satisfactoriness for composting these solids, whereas the latter might hinder their use in the composting process. The maximum coagulant concentrations that allowed pyrolyzing the final product, based on the net energy values, were 48.80 (2.0X), 18.06 (1.0X), and 18.06 (1.0X) gm⋅liter-1 for agricultural lime, hydrated lime, and lime slurry, respectively. The maximum acceptable coagulant concentrations that allowed composting the final product, based on the pH values, were 48.80 (2.0X), 0.00 (0.0X), and 9.03 (0.5X) gm⋅liter-1 for the same three coagulants.
Highlights
The total number of pigs in the United States had reached 65.9 million head, as recently published in the quarterly inventory report by the USDA [1]
Evaluation of the coagulated swine manure solids, as biofuel and/or composting feedstock, requires comprehensive analyses that determine the acceptable levels of the concentrations of each coagulant
Riano and Garcia-Gonzalez [3] found that the total solids produced from swine manure solids separated by a screw press and a coagulation-flocculation unit reached 73.3% and 85.4%, respectively
Summary
The total number of pigs in the United States had reached 65.9 million head, as recently published in the quarterly inventory report by the USDA [1]. The total amount of swine manure generated annually is more than 110 million metric tons. Land application of excessive volumes of swine manure creates environmental issues associated with nutrient loss to water bodies following manure application on fields [3]-[5]. Land application of swine manure is considered the most common practical and economical utilization method [6]. Repeated manure land application on the same field to meet crop N requirements results in elevated P concentrations, which may lead to P loss to the environment through surface runoff or leaching [9] [10]. Regulatory agencies require strict application plans based on soil nutrient content (N, P) before issuing permits for manure land application [11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
