秸秆双发酵联产乙醇沼气的生物质耦合降解和有机碳联合利用机制

Bio-ethanol and biogas are two important biomass and bioenergy utilizatin of the crop residue. There are many advantages in the poly-generation system of bio-ethanol and biogas, but how to take the differences in the biomass degradation, carbohydrate utilization and metabolic pathways to form an efficient biorefinery systems in the dual fermentation system, which need further exploration in the theory. The aim of this project was to enhance the biomass utilization in the two dual fermentation process. For the two proposed types of poly-generation system, this study analysis the joint utilization and metabolic of the hydrolysis of organic carbon such as hexose,pentose and derivations in the dual fermentation system, then compared the biomass conversion and utilization differences at the different stages of two types dual fermentation system, thereby revealing the synergistic lignocellulose degradation by the ethanol fermentation and anaerobic fermentation of straw, clarifying the mechanism of reducing the binding and a polymerization degree of cellulose crystallinity by taking the primary and secondary fermentation together, and illustrating the theory of promoting lignocellulose component separation to increase the biomass availability. Then this study plan to discuss the control of the flow of carbon regulation based on the hydrolysis condition, and the control of the ethanol fermentation pathway in anaerobic digestion based on the ethanol addition, so to achieve the process optimization and the stable operation in the dual fermentation. The research could provide a useful reference for the further understanding of the degradation of biomass ethanol and biogas generation process, and be helpful to further reorganization of the mechanism of organic carbon utilization and system regulation.

生物乙醇和生物沼气是当前生物质能源化利用的两个重要方向，秸秆联产乙醇沼气在生物质利用方面具有较多优势，但如何利用秸秆双发酵系统在生物质降解、糖类利用和代谢途径等方面差异，形成高效的生物精炼系统，对此有待更深入研究。本项目以实现生物质全效利用为目标，针对秸秆联产生物乙醇和生物沼气的两种模式，探寻乙醇发酵和乙醇发酵对生物质的耦合降解机理，分析双发酵系统的六碳糖、五碳糖、以及水解衍生物等有机碳源的联合利用和代谢规律，阐明利用初级发酵和次级发酵结合降低纤维素结晶度和聚合度、促进组分分离、可发酵糖联合转化、毒副抑制物代谢从而提高生物质可利用率的机理。进而，研究基于水解手段调控的双发酵系统有机碳流向调节，以及基于乙醇添加的厌氧乙醇型发酵途径调控，实现双发酵系统的工艺优化和生物质高效转化。项目研究可为深入认识秸秆双发酵联产乙醇和沼气的生物质降解和有机碳利用机理及系统调控提供有益参考。

生物甲烷和生物乙醇是当前生物质能源化利用的两个重要方向，以生物质全效利用为目标，本项目提出了沼气和乙醇双发酵偶联的二级系统，分别研究了甲烷-乙醇工艺路线和乙醇-甲烷工艺路线的生物质次第降解和利用机理。首先探寻了预处理对秸秆水解液六碳糖、五碳糖组分比例的影响，利用优化预处理条件以调节水解液六碳糖、五碳糖组分比例，最优葡萄糖木糖比例为40:60时，水解液产甲烷效率更高，相应的酸水解条件为HCl 1%， TS 7.5%，60°C水解48 h。其次，对比了秸秆产甲烷、“乙醇甲烷”联产、“乙醇甲烷”连续发酵、“甲烷乙醇”等4种工艺，乙醇甲烷联产和连续发酵的能量输出比直接厌氧发酵分别提高了17.12%和49.36%，“甲烷乙醇”能量输出较低原因在于厌氧消化纤维的乙醇产率较低，需优化其预处理方法。. 然后，甲烷-乙醇工艺路线中，为加强沼渣中有机碳的联合和连续利用，对比酸碱处理，最终确定0.75~1.00 g/g的臭氧用量和6h的氨水浸泡为厌氧消化纤维的最宜臭氧氨水联合预处理条件，可提高沼气产量38.3%。稀酸稀碱低温预处理最大单位厌氧消化纤维的乙醇产量为87g/kg，而臭氧氨水预处理可进一步提至123g/kg。高浓度高温发酵的厌氧纤维具有较优的能量转化率，55℃、17%和24天的厌氧沼渣达到了最高的净能量平衡，为6416kJ/kg，反映出甲烷乙醇联产过程中高效的生物质联合和连续利用。. 最后，在乙醇-甲烷工艺路线中，主要通过糟液与秸秆混合发酵实现协同降解，糟液作为一种外源有机碳对秸秆厌氧发酵起到添加剂和促进剂的作用，且嗜氢产甲烷途径增强，甲烷体积分数从低于60%增至70%以上，揭示了一种新型的原位沼气提纯技术。最大VFAs比对照高2.8～4.7倍，产气延迟增加，从混合型发酵变为典型丁酸型发酵。糟液在不同碳源条件下，有着不同的代谢促进途径，是一种高效的共发酵体系，糟液在刺激促进秸秆产气提升和解除抑制风险的同时，自身也得到高效降解利用，是一种高效的二级联合发酵系统。