Inoculum’s influence on anaerobic co-digestion of food waste and grass
DOI:
https://doi.org/10.6008/CBPC2179-6858.2020.001.0014Keywords:
inoculum, anaerobic co-digestion, biogas, food waste, grassAbstract
The inoculum is an important parameter in the performance of anaerobic digestion, since it provides the microbial community necessary for the beginning of the process of conversion and stabilization of organic matter, contributing to the balance of other parameters essential to the functioning of digestion, such as pH. Given the advantages of using a high solids system and the gap in the literature on the ratio substrate / inoculum for such systems, this research aimed to verify the influence of the amount of inoculum on anaerobic co-digestion of food waste and grass with high solids content. For this, the accumulated biogas production, reduction of volatile solids and pH of the digested mass were quantified. The influence of inoculum content was verified by varying from 100 to 200 ml, maintaining the same proportions of grass and food waste. The digestion test was conducted based on German VDI 4630 and DIN 38 414 (S8) standards, and the results analyzed by hypothesis testing for two samples. Volatile solids were reduced by 14% more for the 200 ml triplicate, as well as about 3.6 and 2.6 times higher biogas production and pH compared to 100 ml. With 5% significance it was concluded that the increase in the amount of inoculum contributes to the average increase of biogas generation. It’s possible to infer, therefore, that the volume of 100 ml was not efficient to provide sufficient microorganisms to overcome the production of volatile organic acids, which occurs in greater quantity after the first day of incubation. Thus, it appears that the amount of inoculum plays a relevant role in biogas generation, which goes beyond pH control.
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