Seekao Narongsak, Sangsri Sawinee, Rakmak Nirattisai, Dechapanya Wipawee, Siripatana Chairat
School of Engineering and Technology, Walailak University, 80161, Nakhon Si Thammarat, Thailand.
Biomass and Oil-Palm Excellence Center, Walailak University, 80161, Nakhon Si Thammarat, Thailand.
Heliyon. 2021 Feb 10;7(2):e06204. doi: 10.1016/j.heliyon.2021.e06204. eCollection 2021 Feb.
In Thailand, the palm oil industry produces a huge amount of palm oil mill effluent (POME), mostly used for electricity generation through biogas production. Co-digestion with other waste can further improve biogas yield and solve waste management problems. Most previous studies relied on biochemical methane potential (BMP) assay or batch co-digestion to obtain the optimal mixing ratio, ignoring the kinetic part or treat it for sole discussion of the results. This work directly uses mechanistic models based on Monod kinetics to describe the experimental results obtained from the co-digestion of POME (40 ml, BMP = 281.2 mlCH/gCODadded)) with chicken manure (CM) (0-50 g) and crude glycerol (Gly) (0-10 ml). The best mixing ratio between CM and POME was 5 gCM: 40 mlPOME (BMP = 276.9 mlCH/gCODadded). The best ratio for Gly and POME was 2 mlGly: 40 mlPOME (BMP = 211.9 mlCH/gCODadded). Adding Gly only 2 mlGly/40 mlPOME doubled the amount of biogas. Hence, crude glycerol is a good substrate for on-demand biogas output. The co-digestion increases the methane output but with a decreased yield. A multi-substrate Monod model was developed based on the levels of digestion difficulty. A partial-least squared fitting was used to estimate its main parameters. All parameters included in the model passed the significant tests at a 95% confidence level. The model can describe the experimental results very well, predict observable state variables of batch co-digestion, and allow a simple extension for continuous co-digestion dynamics. A limited continuous experiment was conducted to confirm the applicability of the model parameters of POME digestion obtained from BMP tests to predict a continuous AD. The results show good potential but must be carefully interpreted. It is generally possible and practical to directly obtain design and operational parameters from BMP assays based on only accumulated biogas curves and initial and final COD/VS.
在泰国，棕榈油产业产生了大量的棕榈油厂废水（POME），这些废水大多通过沼气生产用于发电。与其他废物进行共消化可以进一步提高沼气产量并解决废物管理问题。此前的大多数研究都依赖于生化甲烷潜力（BMP）测定或批次共消化来获得最佳混合比例，而忽略了动力学部分或将其单独用于结果讨论。本研究直接使用基于莫诺德动力学的机理模型来描述从POME（40毫升，BMP = 281.2毫升CH/克添加COD）与鸡粪（CM）（0 - 50克）和粗甘油（Gly）（0 - 10毫升）共消化实验中获得的结果。CM与POME之间的最佳混合比例为5克CM:40毫升POME（BMP = 276.9毫升CH/克添加COD）。Gly与POME的最佳比例为2毫升Gly:40毫升POME（BMP = 211.9毫升CH/克添加COD）。仅添加2毫升Gly/40毫升POME就能使沼气量翻倍。因此，粗甘油是按需产出沼气的良好底物。共消化增加了甲烷产量，但产率有所降低。基于消化难度水平建立了多底物莫诺德模型。使用偏最小二乘拟合来估计其主要参数。模型中包含的所有参数在95%置信水平下均通过了显著性检验。该模型能够很好地描述实验结果，预测批次共消化的可观测状态变量，并允许对连续共消化动力学进行简单扩展。进行了有限的连续实验以确认从BMP测试获得的POME消化模型参数对预测连续厌氧消化的适用性。结果显示出良好的潜力，但必须谨慎解读。通常仅根据累积沼气曲线以及初始和最终的COD/VS，直接从BMP测定中获得设计和操作参数是可行且实际的。
