Pathogen contamination of waterways is a serious concern in dairy farming areas where livestock waste is applied to agricultural fields. As an alternative, a biodrying composting system dries collected livestock waste, reduces the strong odors, and has been proposed as a means of reducing, and even eliminating pathogens present in the waste. Therefore, the survival of pathogens in a biodrying composting system was investigated. Dairy farm livestock waste was piled in a biodrying storage shed where forced aeration and natural decomposition processes heated a major portion of the waste pile to temperatures exceeding 55 degrees C. Ascaris suum eggs were used as the surrogate species and inoculated into special chambers and placed at three different elevations at different intervals along the length of the pile. Control chambers were stored in water at 4 degrees C in the laboratory. Both compost and control chambers were removed at Day 4, 8, 12, 16, and 20. The eggs were extracted from the chamber medium and analyzed for viability. No viable eggs were recovered from any of the chambers removed from the compost pile, while >or=90% viability was observed in the control chambers. High temperatures and continued drying were the major contributing factors to the inactivation of the helminth eggs. The complete inactivation of A. suum eggs by the biodrying process encourages the storage and treatment of manure to high temperatures and reduced moisture conditions before field spreading to reduce the risk of harmful pathogens contaminating waterways and potential drinking water supplies.

A comprehensive and fundamental mathematical model that predicts energy requirements to operate a plug-flow anaerobic digester at a specified temperature was developed. This information is supportive to designers as they determine heating requirements and energy use by the digester system. The model accounts for heat loss/gain by the influent and effluent flows, the digester floor, top-covering material and walls. Also, the model accounts for frozen ground surrounding digester walls, thus increasing heat loss through the walls. Solar energy transmitted through the top-covering material was also accounted for in the model. Predicted heat was validated against experimental data and the results agree reasonably well. The model can be used to estimate energy requirements to operate a plug-flow anaerobic digester on a daily, monthly or yearly basis. Low energy was required to operate the digester in June through August, the lowest being in July, and more energy was required in November through March. Considerable energy could be saved if the effluent manure heat was used to pre-heat the influent manure.

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