Mature fine tailings (MFT) are extracted from a tailings pool (such as those in oil sands) and supplied to an MFT processing facility for processing. The MFT may be extracted using one or more barges that support submersible pumps for pumping up the MFT or include a trapping mechanism (e.g. net, grate, fence) for capturing larger masses of MFT at or near a surface of the pool and either transporting them to shore for further processing or further processing them on the barge and then pumping the homogenized MFT to the shore based terminal for final processing. The processing facility breaks, heats, compresses and separates the captured MFT into a methane-rich gas mixture that may be used to: (1) both generate electricity or liquid fuel (e.g. diesel, ethanol, methanol etc.) and (2) possibly power portions of the MFT processing facility. The processing facility also produces an inorganic solids stream suitable for disposal to landfill.