Thermal hydrolysis integration in the anaerobic digestion process of different solid wastes: Energy and economic feasibility study

• Thermal hydrolysis pretreatment to anaerobic digestion is energetically evaluated.
• Six different solid wastes have been studied.
• Energy integration leads to important savings (5 €/tonne raw waste).
• Thermal hydrolysis enhances up to 40% the incomes of the digestion plant.
• In a MSW full-scale plant, thermal hydrolysis provides almost 0.5 M€/year benefits.

An economic assessment of thermal hydrolysis as a pretreatment to anaerobic digestion has been achieved to evaluate its implementation in full-scale plants. Six different solid wastes have been studied, among them municipal solid waste (MSW). Thermal hydrolysis has been tested with batch lab-scale tests, from which an energy and economic assessment of three scenarios is performed: with and without energy integration (recovering heat to produce steam in a cogeneration plant), finally including the digestate management costs. Thermal hydrolysis has lead to an increase of the methane productions (up to 50%) and kinetics parameters (even double). The study has determined that a proper energy integration design could lead to important economic savings (5 €/t) and thermal hydrolysis can enhance up to 40% the incomes of the digestion plant, even doubling them when digestate management costs are considered. In a full-scale MSW treatment plant (30,000 t/year), thermal hydrolysis would provide almost 0.5 M€/year net benefits.