碳氮比对稻秸厌氧发酵过程的影响

摘要

在实验室条件下,考察了C/N对稻秸厌氧发酵过程的影响,重点研究了不同C/N对稻秸厌氧发酵前后氮素转化的影响,实验设置初始C/N分别为15∶1(T1),25∶1(T2),35∶ 1(T3)和45∶1(T4)4个处理.结果表明,C/N对稻秸厌氧发酵产气的影响较大,C/N太高发酵初期会出现酸化现象,以C/N 25∶1的产气效果最好,TS产气量为 286.82 mL·g-1；不同C/N对甲烷含量的影响不大,各处理平均甲烷含量均在55％左右；厌氧发酵后,稻秸中有机物被大量分解,VS,纤维素和半纤维素含量大幅降低,纤维素结晶区受到较大破坏,木质素相对被浓缩,FTIR和XRD的结果与常规分析的结果一致；厌氧发酵过程中,氮素的损失较大,T1,T2,T3和T4的氮素损失率分别为43.97％,42.94％,33.71％和32.34％；氮素主要流向沼液中,但随着初始C/N从15∶1提高到45∶1,保留在沼渣中氮素的比例从29.77％增加到42.86％；厌氧发酵后厌氧系统中氮素以铵态氮和有机氮为主,随着C/N增加,总氮中铵态氮的比重降低,有机氮的比重增加,硝态氮无论是在沼渣还是沼液中含量均不高.%Effect of C/N on anaerobic digestion of rice straw and nitrogen transformation during the process were studied. Four treatments with the initial C/N ratio of 15= 1 (Tl) , 25:1 (T2) , 35:1 (T3) and 45:1 (T4) were designed. The results indicated that, biogas production of rice straw was influenced significantly by initial C/N ratio; too higher initial C/N ratio was adverse to biogas production; the highest TS biogas yield of 286.82 mL · g-1 was obtained at initial C/N ratio of 25:1. Average methane content of all treatments was about 55%. After anaerobic digestion, much organic matter and crystalline of cellulose in rice straw were decomposed, content of volatile solid, cellulose and hemi-cellulose were decreased largely, and percentage of lignin was increased, which was consistent to the results of physic-chemical analysis. Much nitrogen was lost during anaerobic digestion. The nitrogen loss rate of Tl, T2, T3 and T4 were 43. 97% , 42.94% , 33.71% and 32.34% , respectively. Much nitrogen went into fermentation slurry after anaerobic digestion, but amount of nitrogen remained in fermentation residue increased from 29. 77% to 42. 86% with the initial C/N ratio increased from 15: 1 to 45:1. The major nitrogen forms in anaerobic system was ammonium nitrogen and organic nitrogen, and the rate of ammonium nitrogen to total nitrogen decreased and the rate of organic nitrogen to total nitrogen increased with the increase of initial C/N ratio. Content of nitrate in anaerobic system was low.