A fuzzy logic based model to predict the effects of ZnO nanoparticles on methane generation in landfills.

Nano-ZnO enters landfills mostly through disposal of cosmetics, sunscreens and catalysts. However, its effects on waste degradation are still unclear. In this paper, a fuzzy-based model is proposed to predict biogas and methane production from a bioreactor landfill in the presence of ZnO nano-particles. Eight deterministic inputs (pH, RedOx potential, chemical oxygen demand, volatile fatty acids, alkalinity, Zn concentration, Zn background and recirculation flow rate) were identified as antecedent variables. Two outputs, or consequents, were chosen: methane production rate and methane concentration in biogas. Antecedents and consequents were linked by 30 IF-THEN rules, which stated the effects of the input parameters in a linguistic form. The fuzzy model was tested on the data of a lab-scale study simulating a bioreactor landfill with 0.15 g of added nano-ZnO/kg of waste. The fuzzy model showed good performance in the prediction of methane generation, also compared to the commonly used Gompertz equation. The results confirm the potential use of fuzzy macro-approach for complex processes taking place in landfill environments with unusual operating conditions.