碳氮比对鸡粪堆肥腐熟度和臭气排放的影响

为确定鸡粪堆肥最优碳氮比（C/N比），该研究以新鲜鸡粪为堆肥原料，添加玉米秸秆调节初始C/N比为14、18和22进行好氧堆肥，研究不同C/N比对鸡粪堆肥腐熟度和臭气排放（NH3和H2S）的影响。结果表明：C/N比为14的处理堆肥产品未腐熟，C/N比为18和22的处理均达到腐熟。C/N比为18的处理NH3累积排放量和总氮（TN）损失率最高；C/N比为18～22时，C/N比越高，NH3累积排放量和TN损失率越低。C/N比为14的处理H2S累积排放量和总硫（TS）损失率最高；C/N比为18和22的两个处理，H2S累积排放量显著降低，且无显著差异。此外，C/N比为18处理的微生物群落多样性在整个堆肥过程中显著高于C/N比为14和22处理。堆肥的理化指标、臭气排放与微生物群落之间的相关性分析表明，高温、高pH和缺氧环境会增加Firmicutes丰度，进而促进NH3和H2S的排放，相反地，低温、低pH和氧气充足的环境更有利于Actinobacteria增殖，有利于减少NH3和H2S的排放。综合考虑堆肥产品腐熟度和臭气减排效果，建议低C/N比鸡粪堆肥的初始C/N比为18～22。当秸秆资源不足时，建议初始C/N比为18；秸秆资源充足时，建议初始C/N比为22。

Effects of C/N ratio on maturity and odor emissions during chicken manure composting

Abstract: With the growing demand of chicken meat and eggs, the number of chicken manure dramatically increased in China. Untreated manure will not only pollute the environment but also harm the human health. Nevertheless, composting is an effective, sustainable and economic approach for manure treatment prior to land application. And there are usually lots of odor emissions during nitrogen-rich chicken manure composting. Actually, the compost maturity and the odor emissions during composting were markedly affected by the C/N ratio of raw materials. At present, there were lots of studies focusing on the effect of C/N ratio on the compost maturity and quality, while few reports paid attention to the odor (NH3 or H2S) emissions during chicken manure composting. In order to study the comprehensive effect of C/N ratio on maturity and odor emissions (NH3 and H2S) during chicken manure composting, chicken manure and cornstalks as the bulking agent were co-composted at different C/N ratio (14, 18 and 22) to improve the compost quality and decrease the odor emissions. The aeration method was intermittent (aerated 30 min, stopped 30 min) and the rate was 0.2 m3·h-1. The composting lasted 35 days and was turned and sampled on day 0, 3, 7, 14, 21, 28, 35, respectively. The basic physicochemical and maturity indexes were measured, including temperature (T), oxygen (O2), inorganic nitrogen content (NH4+-N, NO3--N), pH value (pH), electrical conductivity (EC), C/N ratio, germination index (GI) and the element content (C, N and S). Odor emissions (NH3 and H2S) were continuously monitored daily. Besides, the microbial community composition and their correlation with physicochemical indexes and odor emissions were also analyzed using Canonical Correspondence Analysis (CCA). The results showed that the final compost with C/N of 14 was not mature, while both the treatment with C/N of 18 and 22 reached the maturity standard. In terms of odor emissions, the C/N of 18 treatment had the highest NH3 emission because of the higher degradation of organic matter. When the C/N ratio ranged from 18 to 22, the NH3 emission and total nitrogen (TN) loss decreased with the C/N ratio increase. In addition, the cumulative H2S emission and total sulfur (TS) loss were highest in the C/N of 14 treatment, while that in the C/N of 18 and 22 treatments greatly decreased and had no significant differences. Moreover, microbial community diversity analysis indicated the C/N of 18 treatment had the highest microbial diversity compared with other two treatments during the whole composting period. Furthermore, the microbial community composition in the C/N of 14 and 18 treatments (Firmicutes) were significantly different from the C/N of 22 treatment (Actinobacteria and Firmicutes). More importantly, CCA showed high temperature, high pH and hypoxic environment was beneficial to the proliferation of Firmicutes and promoted the emission of H2S and NH3. In the opposite case had higher Actinobacteria abundance and could decrease the H2S and NH3 emission. Comprehensive consideration, the recommended C/N ratio during co-composting of chicken manure and cornstalk is 18-22. Specifically, the appropriate ratio can be determined according to the number of cornstalks.