Pre-treatments in advanced anaerobic digestion (AAD) enhance methane production by overcoming the rate-limiting step of macromolecule hydrolysis, though their mechanisms remain unclear. This study examines biological hydrolysis (BH) deployed at full-scale by Anglian Water. Full-scale sludge characterisation revealed that BH improves protein and fibre hydrolysis but also increases carbohydrate content due to biological growth, creating a hydrolysis blind spot in the digester. Dosing with α-amylase, which targets this blind spot, increased biomethane yield by over 30% in lab batch tests. In pilot-scale continuous stirred-tank reactors (CSTRs), α-amylase addition boosted biogas production by 13% and reduced residual biogas potential by 25%, with notable changes in the digester matrix compared to the undosed control. The higher residual biogas potential in the control suggests that carbohydrate hydrolysis occurs after leaving the digester in CSTR mode, suggesting that a reaction gradient through plug flow could maximise biogas uplift when transitioning from batch to continuous mode. This research demonstrates a scalable method to improve biogas yield and process efficiency through a mechanistic understanding of sludge digestion, enabling better control over feedstock and output