基于生物炭的生物有机质堆肥及其土地利用的温室气体排放研究

Biochar can be used as a promising amendment material in composting for improving properties of compost mixture, enhancing nutrient retention, and increasing benefits of biochar-based compost applied in soils, because of the good physico-chemical properties, sustainability, and renewability. The effects of biochar on the greenhouse gas (GHG) emission during the processes of organic waste composting and biochar-based compost (BOWC) utilization in soils may directly influence the acquisition of comprehensive benefits of biochar application. However, the systemic studies on this aspect is still scare and the underlying mechanisms are also unclear. Therefore, this proposal aimed to investigate the effects of biochar addition on the GHG emission during chicken manure composting under different conditions (e.g., different feedstocks, pyrolysis temperatures, and the application rate) and reveal the underlying mechanisms through distinguishing the relationships among the changes of properties of biochar and compost mixture and the characteristics of GHG emission. Moreover, the effects of BOWC application on the dynamics of carbon pool and GHG emissions in soils will be also studied and the underlying mechanisms will be clarified through distinguishing the relationships among the changes of BOWC properties, soil properties and the characteristics of soil carbon pool and GHG emission. In addition, a comprehensive technical system of BOWC will be established and the life cycle assessment model will be employed to assess the reduction potential of GHG emission for the BOWC system. Furthermore, the optimized GHG emission technical model of BOWC and its product application can be proposed.

生物炭由于其良好的理化特性和可再生性，作为改进剂应用到堆肥中，在改善堆肥基质特性、提高养分保持、增加土壤应用效益等方面具有巨大的潜力。生物炭对堆肥过程、及其复合产品（BOWC）利用过程中温室气体排放的影响直接关系到其利用综合效益的获得。然而，目前对这方面的研究还比较匮乏，内在的影响机制亦不清楚。本项目拟研究在不同原料、热解温度和添加量等条件下，生物炭对鸡粪堆肥过程中温室气体排放的影响，通过探究生物炭特性、堆肥基质特性和温室气体排放特征等变化之间的内在联系，揭示生物炭影响堆肥过程温室气体排放的内在机制；研究BOWC对土壤碳库和温室气体排放的影响，通过探究BOWC特性、土壤特性与土壤碳库、温室气体排放特征等变化之间的内在联系，揭示BOWC对土壤碳库、温室气体排放等影响的内在机制；最后，利用生命周期评估方法，定量评估BOWC技术系统的温室气体减排潜力，提出优化温室气体排放的技术模式。

近年来，我国有机废弃物（如城市污水污泥、家畜粪便等）年产生量巨大，它们的不当处置和低效利用成为当前我国城市和区域所面临的主要废弃物管理和环境问题。同时，这些有机废弃物中蕴含大量的营养物质，如何回收和利用营养物质以替代矿物肥使用成为研究的热点问题。生物有机质堆肥被认为是一种理想的技术模式，但是在堆肥过程中，较高的氮损失和温室气体排放（如CH4和N2O）导致低效的资源利用和环境污染问题。因此，本项目通过联合生物炭（biochar，BC）应用，研究BC对堆肥过程中温室气体（greenhouse gas，GHG）排放的影响，并阐明BC的GHG减排机制；探究BC或BC基有机废弃物堆肥（biochar-based organic waste compost，BOWC）土壤利用过程中对土壤有机碳矿化和稳定、GHG排放与减排等方面的影响，并揭示其主要机制；在此基础上，通过建立系统的生命周期评估模型，对BOWC利用系统的GHG减排和环境影响缓解潜力进行定量评估。研究表明：1）通过矿物离子溶液处理、固体无机矿物共热解等方式能够以简易和低成本的方式制备高矿物负载量的BC；通过选择纤维素和木质素含量高的有机原料作为添加剂与污水污泥共热解，能够显著提高污水污泥BC的理化特性和养分特性，提高养分回收利用潜力。2）通过污水污泥堆肥中试实验发现，BC单独或者与锰矿联合使用能够显著减少N2O和CH4排放6.60%-46.0%和33.6%-71.2%，总气候变暖潜值减少16.3%-42.1%。3）通过土壤培养矿化实验发现，矿物负载BC（Fe和Ca）能够显著抑制土壤有机碳的矿化速率和降低总矿化量；土壤团聚体稳定性提高及其促使的土壤有机碳在稳定的大颗粒团聚体中的分布，以及降低土壤微生物丰富度等是矿物负载BC促进土壤有机碳稳定和累积的主要机制。4）以小麦为典型农业种植系统的代表，通过对小麦种植不同施肥策略情景的全生命周期评估揭示，BOWC施肥策略能够减少小麦种植系统的全球变暖潜值36.9%-48.2%。本项目可为我国建立高效的、良好环境效益的有机废弃物资源化利用模式提供重要的基础数据和理论依据。