Abstract: Methods for forming glass compositions from cullet include providing the cullet to a submerged combustion melter and melting the cullet with the aid of heat generated upon the combustion of a hydrocarbon from landfill gas and, in some cases, a polymeric material, in the presence of an oxidant. The melted cullet is then directed to a fiberization unit to generate a glass composition, such as vitreous fiber. The glass composition can be used to form various structural components, such as glass fiber insulation. Methods and systems provided herein can be used to form low global warming potential products.