Position your drum onto the heat source (we used a gas burner), pouring around 40 litres of water into the drum. Place a suitable platform at the bottom of the drum, one that will keep the bags above the water yet allow steam to rise. Insert a material bin liner and fill with the prepared bags of straw. Close off the bags with the liner and cover the drum with a lid. Heat the drum, steaming the bags for approximately 60 minutes. It should take around 30 minutes for the steam to make its way to the top bags (the temperature should near 95ºC ~200ºF). Leave to cool, removing the bags and transferring them to the growing area.