Abstract: An anaerobic digester for digesting a slurry of organic waste comprising: a tank having an outer side wall and a lower inner wall, a first radiant heating floor between the outer wall and a first side of the inner wall forming a first chamber and a second radiant heating floor between the outer wall and a second and opposite side of the inner wall forming a second chamber, an inlet pipe for delivering the slurry to a lower portion of the first chamber and a outlet pipe for removing digested slurry from a lower portion of the second chamber, the slurry maintained at a depth that is greater than a height of the inner wall; and a gas collection chamber sealed to the tank along the length of the upper surface of the outer wall.