Process Modeling and Optimization of Anaerobic Co-Digestion of Peanut Hulls and Swine Manure Using Response Surface Methodology

Abstract

Anaerobic co-digestion of peanut hulls and swine manure was investigated. The interaction effects of the total solid percentage (TS%), carbon–nitrogen ratio (C/N ratio), and inoculum volume percentage (I%) on the total biogas production and methane content were evaluated using quadratic regression models and response surface methodology (RSM). The results show, with the assistance of the developed quadratic model, that the influence of the three factors on the biogas production and methane content followed the order TS% > I% > C/N ratio. With the assistance of RSM, when the TS%, C/N ratio, and I% were 5.83%, 29.31:1, and 30.00%, respectively, the maximum biogas production (1280.65 mL/g VS) was achieved; when the TS%, C/N ratio, and I% were 5.85%, 34.06:1, and 30.00%, respectively, the highest methane content was obtained (686.06 mL CH4/g VS). The C/N ratio insignificantly affects the biogas production and methane content in this experiment. In the low concentration of anaerobic digestion (AD), the inoculum concentration is positively correlated with the biogas production and methane content. However, in the high-concentration AD, the inoculum concentration is negatively correlated with the biogas production and methane content. To ensure the efficiency of the biogas production and increase the volume utilization of the anaerobic digester, in the case of low I% in anaerobic co-digestion of peanut hulls and swine manure, batch feeding can be adopted by gradually increasing the TS%.

Simulation and Optimization of Anaerobic Co-Digestion of Food Waste with Palm Oil Mill Effluent for Biogas Production

“…Closeness of R 2 and adjusted R 2 indicates the adequacy of the model. The predicted R 2 indicated how well the regression model predict the response for new observation [38]. The adjusted and predicted R 2 are also align with each other as their difference is less than 0.2 [35].…”

Process optimization of the anaerobic co-digestion of Alternanthera philoxeroides and corn straw enhanced by biochar and Fe3O4

“…The biogas was determined by a gas chromatograph (GC2014C, Japan ). The injector temperature was set to 110 ℃ and the column box temperature was 90℃ with argon as the carrier gas, the ow rate was 25 mL/min (Deng et al 2019). The C/N ratio was measured by an Elemental analyzer (Vario MACRO cube, Germany).…”

“…This is attributed to the fact that a smaller TS% determines a larger IS ratio (ratio of inoculum to substrate) when the amount of inoculum was constant. During the start-up period, excessive organic loading rates lead to severe acid inhibition and even the cessation of AD (Deng et al 2019). The biogas production of Run 18 was delayed until the 11th day, while Run 9 was terminated on the 3rd day.…”

“…1b), suggesting that the CMY increased with the increase of the TS% within a certain range of TS%. However, a sharp decrease in CMY has occurred at excessively high TS%, which might be attributed to the higher organic loading, resulting in severe disruption of methanogenic pathways (Deng et al 2019). The variation trend of methane content in each treatment was similar, ie., rose rapidly in the initial stage and remained in a stable state with the progress of anaerobic digestion (Fig.…”

“…Cai et al(2021) explored the effects of total ammonia nitrogen, pH and temperature on anaerobic digestion of chicken manure with the help of RSM, which provided a theoretical basis to develop the way of relieving ammonia inhibition. Deng et al(2019) used quadratic regression model and RSM to evaluate the interactive effects of TS%, C/N ratio and inoculum volume percentage (I%) on total biogas production and methane content.…”