Experiments and Modeling for Flexible Biogas Production by Co-Digestion of Food Waste and Sewage Sludge

Abstract

This paper explores the feasibility of flexible biogas production by co-digestion of food waste and sewage sludge based on experiments and mathematical modeling. First, laboratory-scale experiments were carried out in variable operating conditions in terms of organic loading rate and feeding frequency to the digester. It is demonstrated that biogas production can achieve rapid responses to arbitrary feedings through co-digestion, and the stability of the anaerobic digestion process is not affected by the overloading of substrates. Compared with the conventional continuous mode, the required biogas storage capacity in flexible feeding mode can be significantly reduced. The optimum employed feeding organic loading rate (OLR) is identified, and how to adjust the feeding scheme for flexible biogas production is also discussed. Finally, a simplified prediction model for flexible biogas production is proposed and verified by experimental data, which could be conveniently used for demand-oriented control. It is expected that this research could give some theoretical basis for the enhancement of biogas utilization efficiency, thus expanding the applications of bio-energy.

Significance of Pretreatment in Enhancing the Performance of Dry Anaerobic Digestion of Food Waste: An Insight on Full Scale Implementation Strategy with Theoretical Analogy

“…which are achievable theoretically and also it is used to determine the different process parameters. The biogas obtained from dry AD of food waste with pretreatment in two different phased (pretreatment of food waste at 0.5-,1-, 1.5-, 2-, 2.5-kg/cm 2 pressure and pretreatment of food waste at 120 • C and 2-kg/cm 2 pressure for 20, 40, 60, 80 and 100 min) experiments was mathematically modeled by using modified Gompertz equation, which has been established as empirical nonlinear regression model and it is developed by Zwietering [31] in order to determine the kinetics of specific growth rate of methanogenic bacteria in the reactor for the biogas production. The Gompertz equation is basically used in sigmoidal growth curves [32,33] and the equation of modified Gompertz model is described in the Equation (2).…”

The Enhancement of Energy Efficiency in a Wastewater Treatment Plant through Sustainable Biogas Use: Case Study from Poland

“…Thus, the actions aimed at implementing the low-energy or passive WWTPs are being taken [20]. These result in a reduction of the operational costs, improvement of stability and reliability of the wastewater treatment processes, as well as mitigation of the WWTP impact on the aquatic environment [21][22][23].…”

Optimizing the co-digestion supply chain of sewage sludge and food waste by the demand oriented biogas supplying mechanism

“…Co-digestion with sewage sludge is a valid way for the AD of food waste, since sewage sludge is able to provide the alkalinity and micronutrients required for the AD reaction ( Nghiem et al, 2017 ). Some researchers have already shown that if the co-digestion of food waste and sludge is implemented, abrupt increments of the feeding OLR can be adopted without negative impacts on the AD reaction process performance ( Liu et al, 2020 ). On the other hand, the key for implementation of the DO is a valid biogas production process control system ( Mauky et al, 2016 ).…”

“…The main mathematical equations for predicting biogas production under the flexible operating mode (seen in Equations (4) and ( 5 )) are based on the modified first-order kinetics model. For detailed explanations of this equation, refer to Liu et al (2020) …”

“…X n = OLR 0 ∙e^(- mt )% where ‘ m ’ denotes the organic degradation rate, and the calculation method for V maxi and X n can be found in Liu et al (2020) ;…”