A novel waste-to-energy conversion plant based on catalytic pyrolytic conditions: Modeling and optimization using supervised machine learning and desirability-driven methodologies

The persistent nature of plastics significantly contributes to waste generation, making their disposal a critical issue. Pyrolysis, which converts plastic waste into fuel, is a promising solution to the energy crisis. This study evaluates the pyrolysis potential of low-density polyethylene (LDPE) plastic waste, focusing on the influence of process parameters (reactor temperature, residence time, N2 flow rate, and catalyst concentration) and their optimization using seven supervised machine learning models (RF, GB, ET, DT, KNN, AB, and XGB) and a desirability approach. Feature selection techniques (PCC, F-score, and MI) were employed to identify pertinent input features, with MI exhibiting superior performance in accurately identifying and combining the most relevant features for the model's predictive accuracy. The gradient boosting (GB) model demonstrated the highest predictive accuracy with R2 scores of 0.948, 0.9799, and 0.9802 for bio-oil, biochar, and syngas yields, respectively, and the lowest errors (RMSE: 0.6859, 0.1349, and 0.4194; MAE: 0.4505, 0.078, and 0.2673; MAPE: 0.681, 1.1379, and 0.9629). The tree-based pipeline optimization approach shows the optimal conditions of a reactor temperature of 450 °C, a residence time of 2 h, an N2 flow rate of 150 mL/min, and a catalyst concentration of 6 wt %, resulting in a maximum bio-oil yield of 72.20 % and biochar and syngas yields of 6.35 % and 23.48 %, respectively. Detailed characterization via GC-MS analysis indicated that bio-oil, which is composed of various organic compounds, such as phenols, ketones, alcohols, esters, and aromatic hydrocarbons, can be upgraded for use as a hydrocarbon fuel. Biochar and syngas can be used in power generation, heating, industrial boilers, cement kilns, and as soil amendments or chemical feedstocks. These findings support the effective use of LDPE as a plastic waste for bioenergy precursor production.