Biocontained mortality compost using liquid manure
During disease outbreaks, composting has been used to safely dispose of carcasses and infectious solid manure. However, optimized methods have not been established to use liquid manure (> 80% water content, WC) from dairies as the substrate for mortality composting. In April of 2007, a 3x2 factorial study was conducted in wooden compost bins (240 x 240 x 140 cm) lined with 0.5 mm plastic to a height of 50 cm. Three levels (LO, 95 kg; MED, 236 kg; HI, 606 kg wet wt.) of liquid manure (91% WC) were applied to barley straw containing a single calf mortality (avg. wt 130 kg). Compost temperature and carcass degradation were evaluated in each bin over 52 d. As an indication of compost efficiency, viability of 4 types of weed seeds (wild buckwheat, Polygonium convolvulus L, BW; dandelion, Taraxacum officinale, DL; stinkweed, Thlaspi arvense L., SW; and wild oat, Avena fatua, WO) was determined from seeds retained at the laboratory (Control) or from those placed in sealed nylon bags (50 µm pore size) embedded at 3 locations in each bin. Initial C: N ratios ranged from 58:1 (HI) to 68:1 (LO), while initial WC was 64, 52 and 42% for the HI, MED and LO treatments, respectively. Rate of compost heating and peak temperature (58.6 vs. 46.5°C) was increased (P < 0.05) for HI as compared to LO. Rate of temperature decline was lower (P < 0.05) and calf decomposition was visibly superior for HI as compared to LO. Viability of WO was eliminated by all compost treatments, but that of BW increased (P < 0.05) in MED and LO as compared to Control. Although HI did not eliminate WO viability, this treatment showed the the most promise for incorporating liquid manure as a substrate in contained mortality compost.