The cultivation of vegetable crops occupies a large proportion in the current cultivation of crops. At the same time, vegetables production bases, processing plants, transit transport stations, and urban farmers' markets will produce a large amount of vegetable waste due to the regional and concentration of vegetable production. Vegetable waste has a high moisture content and organic matter content, and it is extremely perishable and is not suitable for mainstream treatment technologies such as landfill and incineration. However, this feature is suitable for anaerobic digestion, thereby obtaining clean energy for biogas, and it can also use the digestion residue as an organic fertilizer. The problem to be faced in the anaerobic digestion process is that the characteristics of perishable and highly soluble carbohydrate content of vegetable wastes often lead to acidification, inhibit methanogens, and eventually cause anaerobic system instability and stop gas production. Continuous and stable operation of biogas projects.
Based on this, the Chengdu Institute of Biology, Chinese Academy of Sciences, conducted an early warning study on the anaerobic digestion instability of vegetable wastes through an impact load test. Firstly, a total of 13 first-order parameters for continuous monitoring of the liquid phase and gas phase of the vegetable anaerobic digestion process were monitored. Then, based on the first-level parameters, five secondary parameters are created by coupling. Finally, a total of 18 operational parameters were analyzed for sensitivity to load shocks. The ratio of methane to carbon dioxide (CH4/CO2), ratio of total volatile fatty acids to bicarbonate alkalinity (VFA/BA), propionic acid, and butadiene were selected. Five parameters with strong early warning capabilities, such as acid and isovaleric acid, were used as warning indicators for instability, and the warning thresholds for mild instability and severe instability were determined for these five parameters. On the surface of the research results, the instability is mainly due to the insufficient alkalinity of bicarbonate due to the characteristics of raw materials with higher soluble carbohydrates and lower ammonia nitrogen, which in turn results in inadequate buffering capacity of the anaerobic digestion system. The research team believes that the organic loading rate of the stable operation of vegetable waste and the gas production capacity of the pool can be increased by returning the biogas slurry, adding an external alkalinity substance or a biogas accelerator.
Related research results were published in Bioresource Technology. The study was funded by the National Natural Science Foundation of China and the Chinese Academy of Sciences Green Promotion Association.
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