裹包青贮提高玉米秸秆厌氧消化效率的实验研究

Round bale silage on anaerobic fermentation efficiency of corn straw

秸秆是重要的沼气工程原料,秸秆预处理对其后续厌氧消化效率影响巨大。采用田间裹包青贮方法,设计3因素正交实验,考察了秸秆含水率、压缩比和添加剂对玉米秸秆发酵时间和厌氧消化产沼气的影响。结果表明：秸秆经过裹包青贮,发酵总时间（total fermentation time,TFT）减少1～2 d,累积产气量达到总产气量的90%所用时间（TFT90%）减少了40%～50%,消化效率明显提高;秸秆含水率对产气效果有明显影响,随着含水率增加,单位总固体（total solid,TS）累计产气量（cumulative biogas yields per TS,CBYT）和沼气日产率（biogas yields rate average day,BYR）由高到低排序为：35%～40%,40%～45%,30%～35%;秸秆压缩比对产气效果有明显影响,随着压缩比的增加,其对CBY和BYR的效应由高到低排序为：185、143与138 kg/m3;添加剂类型对产气效果亦有明显影响,在不同添加剂处理下,其对CBYT和BYR的效应由高到低排序为：尿素处理〉甲酸处理〉无添加剂处理;正交实验极差分析表明,对CBYT和BYR的影响排序为：含水率﹥压缩比﹥添加剂,其田间裹包青贮进行厌氧发酵的优化组合为：青贮秸秆含水率为35%～40%,压缩比为185 kg/m3,添加剂为营养型,青贮20 d,CBYT和BYR达到最大,分别为646.57 m L/g和173.25 m L/（d·g）。

Corn straw is an important raw material for biogas engineering. Different pretreatments of corn straw could have a great impact on the biogas fermentation performance. In this study,one orthogonal experiment for three-level factors was designed to study the effects of moisture content,compression rate,and three silaging additives（ urea and formic acid） on both fermentation time and biogas production efficiency,such as total fermentation time（ TFT）,total fermentation time of 90%（ TFT90%）,cumulative biogas yields per total solid（ CBYT）,and biogas yield rate average per day（ BYR）. The results are as follows： TFT diminished from 1 to 2 d and TFT90%also decreased from 40% to 45% compared with TFT. Therefore,round bale silage of corn straw could markedly improve the biogas production efficiency. The moisture content of corn straw had a significant effect on biogas production efficiency; as the moisture content of corn straw increased,the effects of the moisture gradient on both CBYT and BYR were ranked as follows： 35% to 40%,40% to 45%,30% to 35%. The compression rate of corn straw had a marked effect on the production efficiency of biogas; as the compression ratio of corn straw increased,the effects of the compression ratio gradient on both CBYT and BYR were ranked as follows： 185 kg / m3〉 143 kg / m3 〉138 kg / m3. Silage additives clearly influenced the biogas production efficiency; the effects of additives on both CBYT and BYR were ranked as follows： urea 〉formic acid 〉no additives. The orthogonal experiment range analysis showed that the primary and secondary order of promoting effects of water content,compression ratio,and additives on CBYT and BYR were arranged as follows： water content 〉compression ratio 〉additive. The optimized combination was A2B3C3; that is,the range of water content was from 35% to 40%,the straw compression ratio was 185 kg / m3,and through a round bale silaging pretreatment of corn straw for biogas production,the top-priority mix of moisture content and compression ratio was from 35% to 40% and 185 kg / m3 with the addition of a nutrient additive for anaerobic digestion. Both CBYT and BYR reached the maximum peak value and the respective values of both CBYT and BYR were 646. 57 m L / g and 173. 25 m L /（ d·g） after straw silaging for 20 d.