Manure belts for harvesting urine and feces separately and improving air quality in swine facilities

Modern swine facilities have not been designed to maximize manure value nor to minimize NH3 emission. These benefits can possibly be achieved by harvesting urine and feces separately using a conveyor belt placed at a 4° angle beneath the slats. Urine drains from this belt into a gutter leading to a closed storage vessel while feces remain on the belt for up to 24 h. Such a belt was evaluated in a partially slatted swine facility housing 80-100 grower pigs in five separate experiments. Fecal DM was determined as a function of both belt residence time and collection time-of-day. The driest feces were obtained with daily collections at 0600 h. Collections at this time of day resulted in a 9.8±5.0% increase in DM over collection at 1500 h (P=0.07). Under steady state conditions, feces were collected at 49±5% DM and output was 0.26±0.05 kg DM pig−1 d−1 suggesting an apparent feed DM digestibility of 82.8±2.1%. Urine collected was 1.3±0.2 L pig−1 d−1, equivalent to 33±6% of the water intake. Emissions from this facility were for ammonia 1.03±0.20 kg pig−1 yr−1 or 5.9±1.0% of the intake N and for methane 1.05±0.29 kg pig−1 yr−1 or 0.64±0.18% of the feed energy. Odor emission at the ventilation fan was 1.9 OU animal−1 s−1. All three emission parameters were substantially less than literature values for conventional houses. In conclusion, the belt system was easy to operate and allowed for the separate collection of urine and feces resulting in reduced odor nuisance. Technically, it resulted in feces that could be harvested at 49% DM, and emissions of only 1 kg NH3 and CH4 pig−1 yr−1.