Kinetic modeling and interrelationship aspects of biogas production from waste activated sludge solubilized by enzymatic and thermal pre-treatment

[Display omitted] •Kinetic aspects of enzymatic and thermal solubilization of WAS were evaluated.•First-order and transfer function gave the kinetic parameters of biogas production.•Thermal and enzymatic solubilization increased the biogas production, reaching 71%.•Monte Carlo simulation provide 95% confidence intervals of parameters.•Two-way ANOVA showed the interrelations between thermal and enzymatic solubilization. Monte Carlo Simulation (MCS) and kinetic models were applied using data from the biogas production test of waste activated sludge (WAS) pre-treated samples. Indeed, eleven different pre-treatments were applied, combining enzymatic and thermals technologies of sludge solubilization. The main study was proposed to understand the kinetic dynamics of the anaerobic digestion (AD) process and its biogas production potential as a renewable energy source, optimized by distinct solubilization techniques that can be applied to enhance biogas production. As a result, most of the evaluated scenarios significantly improved the biogas production, when compared to the control scenario. Among those, the scenario with thermal solubilization and enzymatic solubilization associated in series, obtained the greatest biogas production potential, reaching 291 ± 3 NmL.gVSS-1, corresponding to a production increase of about 71%. The maximum rate of biogas production obtained was 33.5 ± 0.7 NmL.gVSS-1.day−1. The average lag phase duration (λ) was 0.56 days, and the hydrolysis coefficient (kh) varied between the minimum value of 0.08 ± 0.002 and the maximum of 0.15 ± 0.003 days−1. The two-way ANOVA indicated that there is an interrelationship between the solubilization techniques applied. The confidence interval obtained through MCS allowed us to conclude that the adjustments of the models and the obtention of its parameters to all the scenarios, with exception of the control one, do not have significant differences between them. Therefore, more than a single application of kinetic models to biogas production test results, the statistical approaches supported to elucidate and measure the influence of solubilization techniques in the bioconversion of WAS to biogas as renewable energy source.