Gaseous emission during the composting of pig feces from Chinese Ganqinfen system

The Ganqinfen system - a process of manually cleaning animal feces by means of a shovel - is a widely used manure separating method in Chinese pig farms. Ganqinfen pig feces and chopped corn stalks were mixed at the ratio of 7:1, and composted in 1.5 m(3) rotting boxes for 70 d. Evolution of CH(4), N(2)O and NH(3) during composting, and the effects of turning and covering, were studied in this research. Results showed that 20-39% and 0.5-4% of total nitrogen were lost in the form of NH(3) and N(2)O respectively, and 0.1-0.9% of initial organic carbon was emitted as CH(4). Turning enhanced air exchange in the piles, thus decreasing CH(4) emission by 83-93% and shortening the maturing period. When trials were finished, all non-turned piles were separated to three layers by moisture content. This structure caused the N(2)O losses of non-turning treatments to be 6-12.7 times higher than that of turning treatments. Covering materials reduced air exchange at the surface of the pile, thus decreasing the O(2) supply and consequently increasing CH(4) production by 33-45%. Covering also reduced NH(3) emission by 4-34%. For the composting of Ganqinfen pig feces, we suggest that a program of turning twice weekly without covering will result in compost that is sufficiently matured after 6 wk with the lowest resultant greenhouse gas emission.