Impact of supplementary nutrients on codigestion of agricultural waste: study of temperatures
Different wastes treated together can be the supplement of nutritional deficiencies for the microorganisms involved in anaerobic codigestion (AcoD). In this study, the presence of macromolecules and trace elements on AcoD of agricultural waste was assessed. An extra nutrients solution that plays a key role in the microbiological metabolism was used at three different conditions: mesophilic (35 degrees C), intermediate (42 degrees C) and thermophilic (55 degrees C). The main results showed that at 35 degrees C in the presence of nutrients, biogas production reached 1.5-fold the production of biogas without them. Additionally, productivity was 1.9 times higher than that for the process without nutrients. Also, 42 degrees C without nutrients posed an interesting approach due to the uncommon use of this intermediate temperature, which has been demonstrated to be worth considering (55% of VS removal and 7.4 L-biogas). The AcoD at 55 degrees C showed that biogas production also surpassed 10.2 L with nutrients and that mL-CH4/g-VS were 1.2-fold of that obtained for the process without extra solution. Results for each temperature indicate that the nutrients solution contributes to AcoD. Furthermore, 35 degrees C, the most widespread temperature range at industrial scale, was the temperature at which the impact of nutrients was more remarkable. A deeper knowledge of AD nutritional limitations according to temperatures can optimize the industrial process in order to get better biogas yields and biomass removal. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.