Enhancement of anaerobic co‐digestion of waste‐activated sludge and agriculture waste by hybrid process of thermo‐alkaline hydrolysis and hydrodynamic cavitation

Improving sludge solubilization and biogas generation through thermal, alkaline, and hydrodynamic pre-treatment methods is considered one of the most important research points in the anaerobic digester field. Results revealed that the hybrid method is better than other methods as it achieved 0.64 (CODs/energy consumed) ratio and the gas production rate ranged between (23.34 L/kg COD.d) at RT 30 days. While thermo-alkaline mixed with AW (1: 1 by mass) is very effective in the digesters by reusing agricultural waste into useful biogas, reached at RT 30-day high gas rates (11.55 L/kg COD.d) and cumulative gas volume about (0.43 L/g of COD added), even though CO₂ emissions initially limited the production. Compared to traditional digesters, pretreatment methods significantly decreased CO₂ emissions early on. Additionally, heating agricultural waste with sludge above 100°C facilitated a reduction in sludge volume, as cellulose components in agricultural residues, particularly from sugarcane, absorb water from the sludge-this factor is crucial for minimizing the capital costs of drying beds. Overall, alkaline pretreatment improved biodegradability overall and shortened digester retention times. PRACTITIONER POINTS: Hybrid method the best method 0.64 CODs/energy consumed ratio is achieved, 98% CODs' removal percent, Thermo-alkaline with AW is very effective, gas rates 0.46 Lit/day, cumulative volume 30 Lit at 30-day Thermo-alkaline with AW is an essential cheap solution for solid waste management, reducing air pollution impacts from firming the AW Pretreatment helps lowering the (CO₂ gases) released in the first 10 days compared to conventional AD units without pretreatment, Heating AW with the sludge higher than 100°C leads to adsorb the water content in the mixture.