Enhanced split-phase resource utilization of kitchen waste by thermal pre-treatment

• Split-phase processing using thermal hydrolysis promotes resource management of kitchen waste.
• Thermal hydrolysis enhanced anaerobic digestion process of kitchen waste.
• Efficiency of feed and biodiesel’ characteristics depend on the hydrolysis degree.
• Changes in product quality and modification mechanisms caused by thermal hydrolysis are discussed.

Our society currently faces the twin challenges of resource reclamation from rapidly escalating KW (kitchen waste) and increasingly expensive depletion costs and restrictive disposal legislation due to environmental impacts and fast depleting global resources necessitate action. This work studied the influence of thermal hydrolysis on the utilization of KW based on the principle of split phase processing, including solid phase for pig feed, liquid phase for anaerobic digestion and floating oil for biodiesel. It shows that the solid phase of KW after thermal treatment could satisfy the nutrition content requirements as raw materials for pig feed. The efficiency of the subsequent anaerobic digestion of liquid phase increased for KW pretreated at 120 °C and higher methane production and soluble chemical oxygen demand reduction were achieved after a pretreatment time of 40 min. Composition analysis of floating oil during thermal hydrolysis indicates that unsaturated fatty acid accounts for more than 61% and the main ingredients are monounsaturated fatty acid (more than 36%). All parameters important for biodiesel quality except the acid value could satisfy the biodiesel requirements according to the European standard. From overall analysis, the thermal pre-treatment was profitable with output value of $ 57.52 ton−1 KW.