畜禽粪便堆肥中CH4和N2O排放及其微生物学机制研究

Agricultural wastes, such as manure, is the considerable emission source of CH4 and N2O, which are important atmospheric greenhouse gases (GHGs). Manure composting reveals significant mitigation potential of CH4 and N2O emission in agriculture. This study will investigate the emission patterns of CH4 and N2O and the related microbial mechanisms during composting of different organic substrates by closed-chamber method and molecular techniques. This study will address the following items as listed: (i) The emission patterns and intensity of GHGs (CH4 and N2O) during the composting of different organic substrates (chicken manure, pig manure, and dairy manure). (ii) The effects of different mitigation measures (application of biochar and azotobacterin) on the emission of GHGs during manure composting and the mitigation potential. (iii) The microbial community structure and gene functions associated with the effects of substrates type and mitigation measures on GHGs emission during manure composting. The results of this study will provide data support for assessment of the emission intensity of CH4 and N2O and the mitigation potential during manure composting, and offer scientific evidence for revealing the microbial-driven mechanisms associated to GHGs emission during composting.

畜禽粪便等农业废弃物是大气温室气体甲烷（CH4）和氧化亚氮（N2O）的重要排放源，畜禽粪便等农业废弃物综合利用对减缓CH4和N2O农业源排放具有较大的潜力。本项目拟以不同有机物料的堆肥为对象，采用静态箱法与分子手段相结合，研究堆肥过程中温室气体CH4和N2O排放及其微生物学机制。项目将完成：（1）不同有机物料（鸡粪、猪粪及牛粪）堆肥过程中的温室气体（CH4、N2O）排放特征及其排放强度；（2）碳氮调控（生物质炭及固氮菌剂施用）对畜禽粪便堆肥中温室气体排放通量的影响规律及其减排潜力；（3）不同有机物料及碳氮调控措施对堆肥过程中温室气体排放影响的微生物群落结构及其基因功能。研究结果将为合理评估畜禽粪便堆肥中CH4和N2O排放量及其减排潜力提供数据支撑，为揭示堆肥过程中温室气体排放的微生物学驱动机制提供科学依据。

畜禽粪便好氧堆肥是实现废弃物稳定化、无害化和资源化的重要途径，然而在堆肥过程中会产生大量温室气体，造成环境污染。目前有关堆肥过程中温室气体排放特征的观测、减排潜力评估和具体微生物学驱动机制的报道还很少。本项目以工厂化条垛式畜禽粪便堆肥为研究对象，围绕其温室气体排放强度及驱动机制开展研究，获得了以下主要结果：（1）通过原位工厂化堆肥实验，利用静态暗箱-气相色谱法测定了堆肥全过程的CH4与N2O排放速率，堆肥过程中的CH4与N2O排放趋势与稻田中类似，呈现出此消彼长（trade-off）的关系。CH4的排放主要集中在堆肥过程的前期，而N2O的排放主要在堆肥成熟期，即堆肥温度与氧气含量均出现下降的后熟阶段。通过定量PCR微生物功能基因丰度同步检测技术，揭示了堆体理化特性与微生物功能基因丰度变化相互作用共同调控有机肥堆制过程中CH4与N2O排放的动态变化的微生物学机制。微生物功能基因丰度与CH4和N2O排放通量呈显著相关关系。逐步回归拟合结果表明，CH4排放通量动态主要由堆体温度、mcrA基因丰度以及NH4+变化得以解释；而N2O排放通量动态主要取决于nirk、nosZ和pmoA基因丰度变化。（2）研究了生物质炭的使用对堆肥过程中N2O的排放趋势的影响及相关的微生物学机制。实验结果表明，生物质炭的添加能显著降低N2O的排放通量主要原因是因为生物质炭对nirK基因（亚硝酸还原酶）丰度的抑制。相关性分析表明，N2O的排放通量与堆肥过程中nirK基因的丰度呈显著正相关关系，而与nosZ基因呈显著负相关关系。本实验结果说明生物质炭的添加可以作为减少温室气体N2O排放量的途径之一。（3）比较了农业废弃物常规堆置与条垛式堆肥温室气体排放差异。与常规堆置相比,农业废弃物条垛式分别增加了226.2%和374.6%的CO2和CH4排放,但能够减少72.5%的N2O排放。本项目明确了农业废弃物条垛式堆肥CH4及N2O的排放系数，并揭示了其排放机制，该研究结果为合理评估畜禽粪便堆肥中CH4和N2O排放量及其减排潜力提供数据支撑，为揭示堆肥过程中温室气体排放的微生物学驱动机制提供科学依据。