Effect of aeration method on organic matter degradation and ammonia emission of composting in a laboratory-scale reactor

Maintaining proper aerobic conditions is a crucial factor in composting. Positive aeration (PA, blowing) has been widely applied but diffuses the odorous exhaust gas to the atmosphere. Negative aeration (NA, suction) enables to minimize the gas diffusion, but NA has scarcely been applied mainly because there has been no clear answer about the advantage in the organic matter degradation rate in this system. The air in the PA flows from the higher temperature zone (inside the pile) to the lower temperature zone (the top of the pile), while the air in the NA flows in the opposite direction. We hypothesized that the water vapor and NH₃ gas produced in the high-temperature zone of PA was more likely to be transported and absorbed/adsorbed in the lower temperature zone than that of NA, which could influence microbial activity during composting. This study quantitatively evaluated the effect of two aeration methods on organic matter degradation during composting. We examined the effect of absorption/adsorption of NH₃ on the compost by preventing the compost from drying. We found that PA indeed tended to accumulate more NH₃ than NA but did not show large differences, consequently having little influence on the organic matter degradation.