Shifting the perspective on sludge from mere waste to a valuable resource has spurred researchers to delve into the extraction of valuable resources. Additionally, harnessing energy from wastewater sludge emerges as a sustainable solution to meet both current and future energy needs. Essentially, considering wastewater sludge for energy and material recovery provides a practical and environmentally friendly alternative that aligns with legislative requirements and circular economy principles. This chapter extensively explores the types and compositions of sludge produced by wastewater treatment plants (WWTP), along with the challenges associated with traditional sludge management and disposal methods. It further examines the potential for recovering various value-added products from sludge. The subsequent discussion covers a range of emerging biotechnological approaches for the recovery of these products. The chapter also discusses the integration of sustainable sludge management strategies into existing WWTPs, highlighting the associated benefits over conventional methods and emphasizing the contribution to a circular economy.