PRELIMINARY-STUDY OF THE EFFECT OF CONTINUOUS AND INTERMITTENT AERATION ON COMPOSTING HOG MANURE AMENDED WITH SAWDUST

The effects of using intermittent aeration during composting on ammoni a emissions and dry matter loss were determined during composting of h og manure amended with sawdust. Composting trials lasted three weeks a nd used pilot-scale 200 liter vessels (four). The experimental design used replication of two treatments, continuous aeration (CA) and inter mittent aeration (IA), in two series of experiments (total of eight te sts). In the CA sequence, compost temperatures were controlled at 60 d egrees C using feedback control on high and low air flow fans while th e IA sequence consisted of five minutes of air flow followed by 55 min utes of rest. Mixing ratios of hog manure to sawdust were 1:1.1 and 1: 1.7 dry weight basis with resulting C:N ratios of 18.2 +/- 1.2 and 23. 7 +/- 2.2 for the two series of tests. Airflow reduction was 63 percen t for LA compared to CA. Percent nitrogen loss between treatments were moderately statistically different (alpha = 0.14) with average percen t nitrogen loss at 29.7 percent for CA and 23.0 percent for IA. Nitrog en loss as ammonia-N was higher for CA than IA (25.9 versus 14.3) but was not statistically different. No significant differences existed in dry solids loss between treatments and the physical and chemical prop erties of the compost produced from IA were similar to that from CA fo r each series. Results showed that IA compared to CA may be a practica l way to reduce nitrogen loss and ammonia emissions during composting of swine manure with sawdust.