The effect of different particle sizes of biochar on ammonia mitigation during pig manure/wheat straw aerobic composting process

Abstract. A large number of biochar readily produced from straw was availably used in the large-scale aerobic composting process to reduce nitrogen loss and improve the fertilizer efficiency. In this study, pig manure and wheat straw were used as main material for aerobic composting experiment in laboratory-scale aerobic composting reactor system. To comparatively analyze the effect of biochar particles scale on ammonia production, three groups were considered, respectively were control group, with 10% addition in powder biochar (ɸ < 1 mm) and with 10% addition in granular biochar (10 cm > ɸ > 4 mm). During the experiment, it found that two biochar groups significantly increased the total volume of composting piles. The results showed that biochar could reduce ammonia emissions during the high temperature phase and improved the pH value of compost samples. In perspective of emissions cumulation, the small particle size group had more positive effect on ammonia emissions reduction than other two groups. But after the end of high temperature period the ammonia concentration increased in the two biochar addition groups, due to the ammonium saturation in composting piles resulting in ammonia spilled out. Thus, this study could provide feasible method support for the selection of biochar in the aerobic composting process.