适量通风显著降低鸡粪好氧堆肥过程中氮素损失

【目的】研究不同通风量对鸡粪好氧堆肥过程中温度、含水率、种子发芽指数 (GI) 及氮素形态转化的影响,以期在达到鸡粪无害化要求的前提下,为减少鸡粪好氧堆肥过程中的氮素损失、提高堆肥成品品质、优化通风曝气工艺参数和节省能耗提供参考。【方法】试验在山东某有机肥厂好氧堆肥车间开展,以鸡粪和稻壳为原料,按照1∶1(质量比) 混合均匀之后作为堆肥初始物料。在间歇性强制通风和翻抛条件下,设置低、中、高3个通风水平,即通风量依次为0.1、0.2和0.3 m3/(m3·min),好氧堆肥周期为28 天。通过现场定期采样,测定温度、全氮、NH₄+-N、NO₃–-N、pH、含水率和发芽指数等指标,研究不同堆肥阶段各指标的变化和氮素形态的转化。【结果】在整个好氧堆肥周期内,堆体温度呈现先升高后降低的趋势,低、中和高通风量的最高温度分别达到68.3℃、71.8℃和68.6℃,高温 (≥ 50℃) 持续时间均超过12 天,达到了畜禽粪便无害化卫生要求;含水率逐渐下降,各通风量处理分别由最初的63.2%、62.1%和64.5%降低到32.4%、30.1%和29.2%;pH先升高后降低,至好氧堆肥结束时,各通风处理的pH均处于7.5～8.0 之间;种子发芽指数 (GI) 均大于80%,说明经过28 天的好氧堆肥后,三个通风处理条件下的鸡粪堆肥成品均达到了腐熟度要求。NH₄+-N含量均呈现先增长后逐渐降低的趋势;NO₃–-N含量呈现明显的增加趋势;总氮 (TN) 含量在整个好氧堆肥周期内整体上呈现先降低后增加的趋势;经过28 天的好氧堆肥结束之后,低、中、高通风处理的氮素损失率分别为19.8%、20.2%和29.6%,低通风量与中通风量之间差异不显著,高通风量显著高于低通风量和中通风量 (P ≤ 0.05)。【结论】在鸡粪进行好氧堆肥过程中,通风量为0.1、0.2和0.3 m3/(m3·min) 下,堆肥成品均能达到腐熟度和无害化要求,其中采用中通风量0.2 m3/(m3·min) 时的氮素损失较少,且种子发芽指数较高。综合以上指标及实际工厂化运行过程的影响因素,在鸡粪好氧堆肥过程中建议采用的通风量为0.2 m3/(m3·min)。

Moderate intensity of ventilation can significantly reduce nitrogen loss during aerobic composting of chicken manure

【Objectives】The study was focused on effects of different ventilation intensities on nitrogen transformation in chicken manure composting. The objectives were to optimize the operating parameters of ventilation, reduce the loss of nitrogen, and improve the quality of the final chicken manure.【Methods】The experiment was conducted at the composting site of an organic fertilizer factory in Shandong Province, with the chicken manure and rice husks mixed at 1∶1 as the initial material. Under the condition of forced aeration and turning, aerobic fermentation of composting was carried out for a period of 28 days. Mild, moderate and strong ventilation intensities of 0.1, 0.2 and 0.3 m3/(m3·min) were setup during the composting. Samples were taken at different time during the process of composting.Temperature, pH and moisture content were monitored, and the contents of total nitrogen, NH₄+-N and NO₃–-N were determined throughout the overall period. The germination index of the compost products was tested using rape seeds at last.【Results】During composting, the windrow temperature under mild, moderate and high ventilation intensities rapidly reached up to 68.3℃, 71.8℃ and 68.6℃ respectively. The temperature of ≥ 50℃ lasted over12 days, and then declined to the environment temperature. The moisture content of windrow reduced from the initial 63.2%, 62.1%, and 64.5% to 32.4%, 30.1% and 29.2%, respectively. The pH of the windrow varied from 7.5–8.0 under all the ventilation treatments. At the end of the composting process, the seeds germination index (GI) was more than 80% in all the treatments. The content of NH₄+-N decreased gradually after the slight increasing at early period. The content of NO₃–-N kept increasing significantly. The content of total N showed a trend of decreasing and then increasing gradually during entire composting. The nitrogen loss in mild, moderate and strong ventilation were 19.8%, 20.2%, and 29.6% respectively. The rates of nitrogen losses were not significantly different between mild and moderate ventilation, but both of them were significantly lower than that of strong ventilation (P ≤ 0.05).【Conclusions】During the chicken manure composting, ventilation intensity does not affect the process, and all could produce qualified products that meet the safety and hygiene requirements of manure. Among three ventilation intensities, moderate intensity of 0.2 m3/(m3·min) of the material leads to the least nitrogen loss and high germination index, making it the recommended ventilation for chicken manure composting.