Impact of temperature, inoculum flow pattern, inoculum type, and their ratio on dry anaerobic digestion for biogas production

Mathematical Model-Based Optimization of Trace Metal Dosage in Anaerobic Batch Bioreactors

Anaerobic digestion (AD) is a promising and yet a complex waste-to-energy technology. To optimize such a process, precise modeling is essential. Developing complex, mechanistically inspired AD models can result in an overwhelming number of parameters that require calibration. This study presents a novel approach that considers the role of trace metals (Ca, K, Mg, Na, Co, Cr, Cu, Fe, Ni, Pb, and Zn) in the modeling, numerical simulation, and optimization of the AD process in a batch bioreactor. In this context, BioModel is enhanced by incorporating the influence of metal activities on chemical, biochemical, and physicochemical processes. Trace metal-related parameters are also included in the calibration of all model parameters. The model's reliability is rigorously validated by comparing simulation results with experimental data. The study reveals that perturbations of 5% in model parameter values significantly increase the discrepancy between simulated and experimental results up to threefold. Additionally, the study highlights how precise optimization of metal additives can enhance both the quantity and quality of biogas production. The optimal concentrations of trace metals increased biogas and CH4 production by 5.4% and 13.5%, respectively, while H2, H2S, and NH3 decreased by 28.2%, 43.6%, and 42.5%, respectively.

Evaluation of the efficiency of dry anaerobic digester in the production of biogas and fertilizer using activated sludge and plant waste

The process of dry anaerobic digestion (DAD) is an effective economic and environmentally friendly method due to its features such as reducing the volume of waste, destroying pathogens, consuming less energy, and producing biogas rich in energy and fertilizer. This study was conducted on a pilot scale with a reactor volume of 24 L in 30 days for three ratios of C/N: 30, 25, and 20 separately using a mixture of activated sludge and plant waste. During the process, the temperature, pH, and ratio of C/N were measured at certain times, and the percentage of gases produced by the Gas chromatography (GC) device was also measured. The results were compared with the National standard of Iran (Compost, Physical, and Chemical Specifications) at the end of the process. The results showed that the average volume of biogas produced in ratios of C/N: 30, 25, 20 is 1.7, 2.5, and 1.5 L. d-1, respectively. The results showed that in the C/N ratio of 20, and 25, the amount of, C/N ratio and NO3 are in the range the standard of class 1, and the amount of Phosphorus pentoxide (P2O5) is in the range the standard of class 2. The results showed that the average microbial parameters in ratios of C/N: 30, 25, and 20 are lower than the national standard of Iran. The dry digester is an efficient method in waste treatment, methane gas production, and quality fertilizer close to the national standard of Iran.