Biogas production from municipal wastewater sludge

Edition 5 of the Metcalf and Eddy (M&E) "Wastewater Engineering - treatment and resource recovery" state on page 1521 that with regard to biogas production "Typical values vary from 0.75 to 1.12 m3/kg volatile solids destroyed." but does not state state pressure and temperature at which these volumes apply. Can someone please confirm if this is at standard temperature and pressure (0 C, and 1 atm), or what pressure and temperature should be assumed for this biogas production rate? Thank you!