This disclosure may generally relate to a pressured vessel and, more particularly, to systems and methods for pressurizing a pressured vessel by producing a biogas using a recessed roof system. A pressured vessel may comprise a shell, wherein the shell may comprise a plurality of panels. The pressured vessel may further comprise a recessed roof and a deck. A method of collecting biogas from a pressure vessel may comprise disposing a liquid into the pressure vessel, disposing an anaerobic microorganism into the pressure vessel, adjusting a path of the biogas with a protruding baffle, collecting the biogas with the recessed roof, applying pressure to the outside of the recessed roof with the liquid such that the biogas pressure inside the recessed roof is increased, and removing the biogas from inside the recessed roof through a gas collection system.
