Charles Duane Fulhage

Characteristics of Low-Profile Cross-Ventilated Freestalls

The ventilation characteristics in a low-profile cross-ventilated freestall building were monitor in May and August 2006. Three different ventilation rates were evaluated in an 800 cow facility located in North Dakota. The high, medium and low ventilation rates selected were based on exchanging the air inside the building every 60, 120 and 240 seconds, respectively. The particle concentrations from the three samplers were 78.2 µg/m3 near the east end, 74.8 µg/m3 in the center and 94.8 µg/m3 near the west end. Hydrogen sulfide measurements were 14, 8 and 7 ppb at the low, medium and high ventilation rates respectively. Gases emitted from the LPCV were predominately nitrogen-based gases (NH3, NO2, NO) during the spring and summer testing periods. Ammonia concentrations and emission rates were higher during the springtime at the lowest ventilation rate. No statistical differences were found between NH3 concentration and emission rates at the high ventilation rate during springtime, low ventilation rate during the summer, and high ventilation rate during the summer. No statistical differences in NH3 concentrations were observed during the medium ventilation rates of both seasons. Average concentrations of NH3 observed were 1219 +/-5 ppb during the spring and 1117 +/- 4 ppb during summer. The NH3 emissions rate at the low ventilation rate was 856 mg/h/500-kg live weight during the spring and 678 mg/h/500-kg live weight during the summer. The indoor and outdoor temperature and indoor relative humidity were found to be significant factors contributing to the prediction of the maximum NH3 concentration within the LPCV dairy barn during the spring.

Design criteria and operational guidelines for a pilotscale anaerobic digester

Abstract Design considerations for constructing a pilot anaerobic digester are presented. A 4.34 m3 pilot digester was constructed using these criteria. Operational guidelines are presented. Also included is an iterative technique for sizing an internal heat exchanger, suggestions for selecting pumps, meters, and other equipment, and an electrical control system that permits automation of the entire system. The pilot digester operated successfully for more than 4 years with swine manure as a feedstock at a loading rate of 4 kg volatile solids per m3 per day with a 15-day detention time at 35°C. Energy balances indicate that the overall energy efficiency of the digester is a function of ambient temperature surrounding the digester, amount of agitation, and amount of insulation.