Microwave and thermal pretreatment as methods for increasing the biogas potential of secondary sludge from municipal wastewater treatment plants

► Microwave irradiation and thermal heating as methods for sludge pre-treatment. ► Microwave irradiation turned out to be superior over thermal pre-treatment. ► 900 W irradiation showed to be less energy demanding compared to 700 W. ► Pre-treatment at 70 °C allowed to achieve the highest energy profit. ► Microwave pre-treatment ensured high degree of sludge sanitation.