ARS | Publication request: Effect of solid separation and composting on the energy content of swine manure

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: May 25, 2007
Publication Date: June 17, 2007
Citation: Cantrell, K.B., Bauer, P.J., Ro, K.S. 2007. Effect of solid separation and composting on the energy content of swine manure. In: Proceedings of American Society of Agricultural and Biological Engineers Annual International Meeting, 17-20 June, Minneapolis, Minnesota. Paper Number 07-4157, 9 p. CDROM

Technical Abstract: Animal manure represents a significant source of renewable bioenergy. In order to utilize current thermochemical energy conversion processes, a dry material (more than 90% total solids) is recommended. Solid-liquid separation can serve as a useful pretreatment of animal manure as a dewatering tool. Analyses were conducted to determine the effects of solid-liquid separation techniques and biological processing on the characteristics and energy content of swine manure. Specifically, four swine manure materials were examined: 1) homogenized house effluent, 2) separated solids from a belt, screen, and rotary press solid-liquid separators, 3) anaerobic lagoon sludge, and 4) biologically processed solids from a composting facility. In addition to dewatering the aqueous waste stream, solid-liquid separation generated solids with similar volatile solids content yet different in fixed carbon, ash, and higher heating value (HHV). Rotary press separation with polymer flocculation produced a solid with the largest dry basis HHV, 9470 Btu/lb, followed by belt separation (8782 Btu/lb), and screen separation (7191 Btu/lb). All of these solids had larger HHV than the homogenized house effluent solids HHV (6441 Btu/lb). The increase in HHV is partially attributed to solid-liquid separation reducing the ash content of dried solids between 48 to 80%. Biological processing of swine manure, whether anaerobically digested sludges or aerobically stabilized composts, generates solids (on a dry basis) similar in ash, volatile, and fixed carbon content with an average HHV of 5700 Btu/lb. These dried solids contain 60 to 80% of total energy available in separated solids.