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Animal and Poultry Waste Management Center
A candidate technology of the North Carolina Agreements Project:
Development of Environmentally Superior Technologies
per Agreements Between the Attorney General of North Carolina
and Smithfield Foods, Premium Standard Farms and Frontline Farmers

Solids Separation/Combustion
for Energy and Ash Recovery

picture of FAN Screw Press Separator, Feed Tanks and Tangential Flow Separation System
FAN Screw Press Separator, Feed Tanks and Tangential Flow Separation System

Picture of Filtramat Separator, Lift Station and Tangential Flow Separation System
Filtramat Separator, Lift Stations and Tangential Flow Separation System

This project includes two systems designed to separate the solid portion of the waste stream coming from pig barns, while the separated solids are then combusted to produce energy, and the ash that remains following combustion was evaluated for use as fertilizer.

The technology provider is Biomass Energy Sustainable Technology (BEST). Dr. Garth Boyd, director of environmental technology for Smithfield Foods, Inc., developed and manages the project in cooperation with Doug Miller of QED Occtech. The two solids separation systems are located at Corbett Farm, a Murphy-Brown farm near Rose Hill in Duplin County, North Carolina.

Corbett Farm Unit 1, screw-press separator
This system is treating waste from five finishing barns, which contain 3,320 pigs when full. Manure flushed from the barns flows first to a collection pit, then to an above-ground feed tank, then to a screw press separator (FAN® Separator (USA), Inc.) on a raised platform. The separator has a screen with .25 millimeter openings. The liquid that flows through the screw press separator screen flows to a second feed tank, then to two tangential flow gravity settling tanks sited parallel to each other. Each tangential flow settling system consists of a 2.2-meter diameter tank with a cone bottom followed by a 1.2-meter diameter sludge thickening tank, also with a cone bottom. Tangential flow in the first tank causes solids to concentrate in the center of the tank and settle to the bottom. This settled slurry is then pumped to the second tank for sludge thickening. The tangential flow settling system is manufactured by QED Occtech of Australia. For about 10 minutes every hour the settled slurry from the second tangential flow settling tank is pumped back to the tank that feeds the screw press separator, where the settled slurry is combined with the flushed manure that is being pumped to the screw press separator.

Corbett Farm Units 3 and 4, Filtramat separator
A second separation system is located at Corbett Farm Units 3 and 4, which include a total of four finishing barns that house 4,048 pigs when full. This system employs a Filtramat™ separator made by Denitral of France and marketed in North America by Environgain of Quebec, Canada. The separator consists of sloping concave screens and a hydraulic screw press. The screen has .5 millimeter openings. Separated solids migrate down the screen into a hopper. A wiper moves across the screen periodically to clean it. The solids that drop to the hopper are fed to a chamber to be dewatered by a hydraulic screw press. The liquid that leaves the Filtramat flows to a tangential flow settling system identical to the system used at Corbett Farm Unit 1. Settled solids from the sludge thickening tank are periodically returned to the screw press.

Solids collected from both systems along with turkey litter were trucked to Coeur d' Alene, Idaho, during the evaluation period. In Idaho, the solids and turkey litter were combusted at a test facility/pilot combustion plant operated by Energy Products of Idaho (EPI). The combustion and emissions characteristics of turkey litter, swine manure solids and various mixtures of the two were evaluated in an atmospheric bubbling fluidized bed system maintaining minimum bed temperature above 1,300° F. The ash that remains after combustion was sent to Alabama, where it was evaluated by Applied Chemical Technology for its fertilizer value.

Technology Evaluation
Dr. Phil Westerman
Department of Biological and Agricultural Engineering
North Carolina State University, Raleigh, NC
Phone: 919.515.6743

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