NH3, N2O and CH4 emissions during passively aerated composting of straw-rich pig manure

Straw-rich manure from organic pig farming systems was composted in passively aerated static piles to estimate the effect of monthly turning on organic matter degradation and NH3, N2O and CH4 emissions. Turning enhanced the rate of drying and degradation. The four-month treatment degraded 57 ± 3% of the initial organic matter in the turned piles, while only 40 ± 5% in the static piles. The turned piles showed low ammonia and N2O emissions, 3.9 ± 0.2% and 2.5 ± 0.1% of total initial nitrogen, respectively. Static piles gave low ammonia (2.4 ± 0.1% Ninitial), but high (9.9 ± 0.5% Ninitial) N2O emissions. Prevalence of anaerobic regions in the static system was supported by the higher CH4 emissions, 12.6 ± 0.6% VSdegraded for the static vs. 0.4 ± 0.0% VSdegraded for the turned system. It was shown, that straw-rich pig manure with very low C/N ratios could be composted directly without significant NH3 and N2O emissions if turned on a monthly basis.