Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway.
Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway; Department of Environmental Engineering, Bitlis Eren University, 13000 Bitlis, Turkey.
J Environ Manage. 2014 Apr 1;136:9-15. doi: 10.1016/j.jenvman.2014.01.028. Epub 2014 Feb 15.
The effects of recirculating the liquid fraction of the digestate during mesophilic anaerobic co-digestion of steam-exploded Salix and cow manure were investigated in laboratory-scale continuously stirred tank reactors. An average organic loading rate of 2.6 g VS L(-1) d(-1) and a hydraulic retention time (HRT) of 30 days were employed. Co-digestion of Salix and manure gave better methane yields than digestion of manure alone. Also, a 16% increase in the methane yield was achieved when digestate was recirculated and used instead of water to dilute the feedstock (1:1 dilution ratio). The reactor in which the larger fraction of digestate was recirculated (1:3 dilution ratio) gave the highest methane yields. Ammonia and volatile fatty acids did not reach inhibitory levels, and some potentially inhibitory compounds released during steam explosion (i.e., furfural and 5-hydroxy methyl furfural) were only detected at trace levels throughout the entire study period. However, accumulation of solids, which was more pronounced in the recycling reactors, led to decreased methane yields in those systems after three HRTs. Refraining from the use of fresh water to dilute biomass with a high-solids content and obtaining a final digestate with increased dry matter content might offer important economic benefits in full-scale processes. To ensure long-term stability in such an approach, it would be necessary to optimize separation of the fraction of digestate to be recirculated and also perform proper monitoring to avoid accumulation of solids.
在中温厌氧共消化蒸汽爆破柳枝和牛粪过程中循环利用消化液的效果在实验室规模连续搅拌槽式反应器中进行了研究。采用平均有机负荷率为 2.6 g VS L(-1) d(-1)和水力停留时间（HRT）为 30 天。柳枝和粪便的共消化比单独消化粪便产生了更高的甲烷产量。此外，当用消化液代替水稀释原料（1:1 稀释比）时，甲烷产量增加了 16%。当消化液的较大部分被循环利用（1:3 稀释比）时，反应器的甲烷产量最高。氨和挥发性脂肪酸未达到抑制水平，并且在蒸汽爆炸过程中释放的一些潜在的抑制性化合物（即糠醛和 5-羟甲基糠醛）在整个研究期间仅以痕量水平检测到。然而，在循环利用的反应器中，固体的积累更加明显，导致这些系统在三个 HRT 后甲烷产量下降。避免使用新鲜水稀释高固体含量的生物质，并获得干物质含量增加的最终消化液，可能在大规模工艺中带来重要的经济效益。为了确保这种方法的长期稳定性，有必要优化要循环利用的消化液部分的分离，并进行适当的监测，以避免固体的积累。
