纤维质原料跨季节贮存过程及理化特性对其厌氧产甲烷效能的影响机理

Trans-seasonal storage and high-efficient production of methane are always the most prominent issues for the biogas large-scale utilization of plant lignocellulosic biomass, such as agricultural wastes and food processing by-products (AWFPB). It has been shown that wet-storage via ensiling can preserve the methane yield of AWFPB for up to one year or longer. However, there are large differences in physicochemical properties after different storage process and method, which lead to the directly or indirectly influence on the specific methane production efficiency. Up to now no confirmed knowledge is available about the information on influence mechanism of storage process and physicochemical properties on the specific methane yields or methane production efficiency for AWFPB biomass, it is necessary to explore in a systematical approach. Taking into full account the correlations of storage and anaerobic digestion process, the inherent connection between storage process and methane production efficiency during anaerobic digestion for lignocellulosic biomass, such as maize straw, Jerusalem artichoke residues and distillers grains, are explored in this project. The physicochemical properties contain the constitution and content of organic components (carbohydrate, fat, protein), lignocellulosic compounds (cellulose, hemicelluloses and lignin), organic elementary compositions (C, H, O, N, etc), storage fermentative quality elements (Lactic acid, volatile, fatty acids and alcohols, etc) and physical structure (the crystalline structure, polymerization degree, available surface area, etc). The purpose of the research is to elaborate the interrelated influence mechanism of storage process and physicochemical properties on the specific methane production efficiency by the means of anaerobic fermentation dynamics analysis and anaerobic microbial communities diversity analysis. Moreover, the transfer and conversion mechanism of matter and energy during trans-seasonal storage and anaerobic fermentation process were illuminated. Furthermore, the coupled biological pretreatment and reinforcement method during storage process, that facilitates the subsequent breakdown of lignocellulosic biomass into its constituent sugars, were studied to enhance hydrolysis conversion rate of holocellulose and further favor methane formation efficiency. The research results not only can solve some practical problems encountered in large and medium-sized biogas projects, such as high-quality trans-seasonal storage and high-efficient methane production of lignocellulosic biomass, but also provide theoretical foundation for the correlation and integration of storage process and anaerobic digestion.

植物纤维原料的跨季节贮存和高效产甲烷是规模化沼气工程面临的重要课题。跨季节贮存的过程和方法不同会使贮存后的原料理化特性存在差异，并对厌氧产甲烷效能产生不同影响。本项目以玉米秸秆、菊芋渣、酒糟等纤维质原料为研究对象，充分考虑原料贮存和产甲烷过程的物质联系基础与能量转换路径，从有机营养成分、有机元素组成、贮存发酵品质构成要素、木质纤维组分及其物理结构等理化特性角度出发，探寻不同贮存过程及理化特性与产甲烷效能之间的联系机制，通过厌氧消化动力学分析和厌氧微生物菌群多样性解析，阐释贮存过程及理化特性对其产甲烷效能的影响作用，揭示贮存和产甲烷过程中物质与能量的传递与转换机理。同时，探索贮存发酵过程“蕴藏”的生物预处理作用规律并进行强化，提高木质纤维原料的水解速率和产甲烷效能。本项目研究成果不仅能解决纤维质原料沼气化利用过程中的保质贮存和高效产甲烷等实际问题，还为贮存、产甲烷过程的紧密衔接奠定理论基础。

植物纤维原料的跨季节贮存和高效产甲烷是规模化沼气工程面临的重要课题。跨季节贮存的过程和方法不同会使贮存后的原料理化特性存在差异，并对厌氧产甲烷效能产生不同影响。本项目以玉米秸秆、甜高粱、菊芋渣、酒糟、中药渣等纤维质原料为研究对象，充分考虑原料贮存和产甲烷过程的物质联系基础与能量转换路径，从有机营养成分、有机元素组成、贮存发酵品质构成要素、木质纤维组分及其物理结构等理化特性角度出发，探寻不同贮存过程及理化特性与产甲烷效能之间的联系机制，通过厌氧消化动力学分析和厌氧微生物菌群多样性解析，阐释贮存过程及理化特性对其产甲烷效能的影响作用，揭示贮存和产甲烷过程中物质与能量的传递与转换机理。同时，探索贮存发酵过程“蕴藏”的生物预处理作用规律并进行强化，提高木质纤维原料的水解速率和产甲烷效能。纤维素酶、木聚糖酶、瘤胃液和沼液4种添加剂均能使青贮体系pH值显著下降至4.3以下，乳酸占总有机酸比例始终高于0.6，乳酸与乙酸比值始终高于2.0，说明均达到优良青贮发酵品质；其中纤维素酶、木聚糖酶更有利于青贮pH值下降、减少氨氮和乙酸含量、增加乳酸含量。青贮90 d时，4个添加剂组的干物质、可溶性碳水化合物、中性洗涤纤维、酸性洗涤木质素和半纤维素的含量均显著低于原料，纤维素含量和生物降解潜力均显著高于原料；其中BT组在强化青贮过程中的木质纤维组分降解效果最好。结构表征发现加入沼液和瘤胃液均能促使甜高粱茎秆的木质纤维抗降解屏障结构得到有效瓦解，茎秆微观表面出现明显孔洞和裂缝，纤维素相对结晶度指数显著降低。上述结构和组分的联动变化使青贮甜高粱的酶解得率显著高于原料，且BT组和RT组的酶解得率明显高于CT组和XT组，尤其添加沼液进行长时间（90 d）强化青贮后的酶解得率最高，生物强化作用效果最有效。本项目研究成果不仅能解决纤维质原料沼气化利用过程中的保质贮存和高效产甲烷等实际问题，还为贮存、产甲烷过程的紧密衔接奠定理论基础。