Generation of a tremendous amount of domestic sewage sludge pushes
society to look for an alternate and viable option rather than its direct disposal. The
organic-rich constituents of sludge make it an asset rather than waste. Sludge to energy
conversion is a feasible option to combat the demand for renewable energy. Resource
recovery from waste leads to socio-economic development by reducing fossil
dependency with clean and green energy. This chapter mainly focuses on the potential
of ultrasound-based techniques for the pretreatment of DSS to enhance bio-crude
production. Thermochemical and biochemical treatment are two routes of sludge
valorization with their advantages and limitations. Pyrolysis, gasification, combustion,
and hydrothermal processing come under thermochemical treatment whereas,
anaerobic digestion, aerobic digestion, and fermentation form the basis of biochemical
treatment. Thermochemical routes demand energy, whereas biochemical routes are a
time-consuming process. Pretreatment of sludge is a viable option to overcome these
limitations. Ultrasound pretreatment increases COD solubilization, volatile suspended
solids reduction, biogas production during AD, increases the yield and HHV of biocrude during thermochemical treatment, and favors lipid extraction for biodiesel
production, and also promotes bioethanol production. Moreover, integrated ultrasound
pretreatment positively affects the overall process by reducing the overall cost and
increasing bio-crude production.
Keywords: Biochemical conversion, Bio-crude, Biorefinery, Cavitation, Domestic sewage sludge, Thermochemical conversion, Ultrasound pretreatment.
