乙酸和乳酸对玉米秸秆青贮料有氧稳定性和甲烷产率的影响
Effects of acetic and lactic acid in corn stover silage on aerobic stability and methane yield rate

根据热电偶原理采用无纸记录仪测定温度,研究不同质量浓度乙酸和乳酸对玉米秸秆青贮料有氧稳定性及干物质的影响,并通过批次厌氧发酵工艺,分析不同质量比的乙酸和乳酸对提高青贮料甲烷产率的作用。结果表明:乙酸能有效提高青贮料的有氧稳定性,且随乙酸浓度的增加,青贮料有氧稳定性提高。相应地,乙酸添加量为10%和8%的处理干物质损失分别为1%和3%,而乙酸量添加为2%和没有添加乙酸的处理干物质损失分别为20%和25%,且干物质损失率(x)与甲烷产量减少率(y)呈线性正相关:y=0.705x＋1.224(R2=0.986 2)。在仅以乙酸和乳酸为原料的厌氧发酵体系中,高浓度乙酸的甲烷产率显著高于高浓度乳酸(P<0.05);而在烘干青贮料发酵体系中,乙酸添加量为17%和13%的处理甲烷产率与相同添加量乳酸的处理相比,差异性不显著(P>0.05)。综合评价,乙酸对青贮料的主要贡献在于增加其出料期的有氧稳定性,减少干物质损失,进而提高物料甲烷产率。
Effects of acetic (A) and lactic acid (L) on the aerobic stability of silage were determined by adding mixture of A and L with various mass ratios of A/L to prepared corn stover silage.In addition,the roles of acetic and lactic improving methane yield rate (MYR) of silage in the presence of exposure to ambient air were analyzed using three feedstocks including the silage before and after the aerobic stability test,mixtures of A/L and stove-dried silage with different ratios of A/L.For this purpose,the aerobic stability tests and anaerobic digestion tests were respectively performed using paperless recorder with thermocouple theory and several bath reactors.The results showed that addition of acetic acid significantly extended the aerobic stability of silage and the stability increased along with the increased acetic acid concentration.Accordingly,dry matter(DM)loss of the treatments adding 10% and 8% acetic acid was 1% and 3% respectively,whereas adding 2% and without acetic acid loss 20% and 25% DM respectively.The linear relationship between DM loss of silage(x) and its methane yield decrease(y) was expressed as:y=0.705x＋1.224(R2=0.986 2).MYR of higher acetic acid concentration was significantly higher(P<0.05) than that of higher lactic acid concentration in anaerobic digestion system with acetic and lactic acid as only feedstock.However,adding 17% and 13% acetic acid had less effect on MYR compared to those treatment by adding the same ratios of lactic acid in the stovedried silage.A comprehensive assessment showed increasing acetic acid concentration in silage was beneficial for its aerobic stability,DM loss and MYR.These results suggested that heterofermentative ensiling with higher acetic acid concentration was an effective method of storing fresh feedstock during the feed-out period in the presence of exposure to ambient air for biogas production.