非生物导电材料介导的好氧堆肥温室气体调控机制研究

The emission of greenhouse gases (GHGs) during the composting process is a serious problem, which results from the comprehensive microorganism activities coupled by the electron transfer between various electron donors and electron acceptors. Abiological conductive materials can facilitate direct interspecies electron transfer (DIET) between anaerobic and aerobic microbial cells, as well as affect the emission of methane (CH4) and nitrous oxide (N2O) during composting process. To mitigate the GHGs emission from composting, this project selects three eco-friendly and cost-effective abiological conductive materials (biochar, nano zero-valent iron and magnetite) as external additives, aiming to explore their effectiveness in influencing the GHGs emission during composting of livestock manure. By integrally analyzing the migration and transformation rule of nitrogen and carbon during the whole composting process, along with observing the coupled relationship of the GHGs emission patterns with the community succession patterns of the functional genes, functional microorganisms and key enzymatic activities, it is expected to reveal the mechanism of conditioning GHGs emission from composting with conductive materials supplement and screen out the favourable abiological conductive material. Further objective of this project is to optimize the addition dosage and time of the favourable conductive material, aiming to find out the optimum proposal of conditioning GHGs emission from composting based on the oriented reinforcement of DIET process between composting microorganisms. This project is expected to provide theoretical foundations and optimized practical method for mitigating the GHGs emission during composting of livestock manure.

好氧堆肥过程中亟待解决的温室气体排放问题，是多种微生物通过不同的电子供体、电子受体和电子传递传递过程综合作用的结果。非生物导电材料能够促进厌氧和好氧微生物细胞间直接种间电子传递(DIET)，并影响堆肥过程中CH4和N2O的排放。为实现堆肥过程中温室气体调控，本项目拟选取三种环境友好、廉价易得的非生物导电材料：生物炭、纳米零价铁和磁铁矿作为外源添加剂，分别研究其对畜禽粪便好氧堆肥过程中温室气体排放的影响；通过综合分析堆肥全过程中氮素和碳素迁移转化规律，功能基因、功能菌群、关键酶活性和微生物群落演替规律与温室气体排放的耦联关系，揭示导电材料调控堆肥过程中温室气体排放的机制，并筛选出较优的非生物导电材料。进一步优化较优导电材料添加量和添加时间，得到以定向强化堆肥物料内微生物DIET过程为基础的堆肥化温室气体排放调控优化方案，以期为调控畜禽粪便好氧堆肥温室气体排放提供理论依据和优化方案。

温室气体排放是好氧堆肥过程中亟待解决的问题。非生物导电材料被证明能够促进微生物直接种间电子传递，并影响堆肥过程中CH4和N2O的排放。为实现堆肥过程中温室气体调控，本项目选取了生物炭、纳米零价铁和磁铁矿三种典型非生物导电材料作为外源添加剂，添加量均为2.5%, 5%和7.5%，分别以不添加非生物导电材料作为对照。主要结论如下：（1）堆肥过程有机质降解随着生物炭添加比例增加而增加，较高比例的生物炭会抑制堆肥胡敏酸形成；生物炭能够提高堆肥总氮含量，促进堆肥过程中氨氮转化，显著降低堆肥过程中碳损失。生物炭添加了和固氮和碳代谢相关的Psychrobacter和Actinomadura相对丰度， 5%生物炭添加效果最优。（2）纳米零价铁作为添加剂，能显著促进有机质降解，促进胡敏素降解而抑制富里酸降解，但不能促成腐殖质形成；显著增加NH3和N2O累积排放量并促进堆肥NO3--N累积，提高木质素降解相关微生物细菌相对丰度，促进堆肥生物脱毒。堆肥内添加纳米零价铁能加速堆肥C、N周转过程并提高堆肥温室气体排放。（3）堆肥内添加不同比例磁铁矿能降低堆肥EC值，且随着堆肥添加比例增加而增加；磁铁矿能显著增加有机质、富里酸降解和胡敏素降解，5%和7.5%磁铁矿处理能分别显著提高胡敏酸/富里酸 25.70%和17.32%，5%磁铁矿处理能显著显著降低NH3排放，促进堆肥硝化反应。磁铁矿能提高堆肥高温期类芽孢杆菌相对丰度，进而提升有机质降解；也能提高腐熟期Nonomuraea和Ruminofilibacter相对丰度，促进堆肥后期半纤维素降解；磁铁矿还能促进相关氨基酸的代谢，提高物质跨膜运输以促进养分传递。总体而言，5%生物炭对堆肥过程中腐殖化和氮保存效果最佳，能有效降低堆肥温室气体排放。通过不同含水率，不同通风速率和生物炭梯度进行正交实验发现，生物炭最优添加量为5%，堆体含水率为65%，通风速率为800 L/(h·t dry weight)。本项目为清洁好氧堆肥添加剂的开发奠定了良好的理论基础，后续可根据本项目揭示的机制进行不同非生物导电材料组合、沉淀、负载后介导好氧堆肥研究。