TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The microbial consortium comprises anaerobic bacteria selected from Thermoanaerobacterium species, Thermotoga species or Thermococcus species.Preferred Method: The incubation in step (2) is carried out at 70 - 90 (preferably 90) degreesC. The proliferation temperature of the microbial consortium in step (4) is 70 - 90 degreesC.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Medium: The nutrient medium I comprises (quantity g/l): mineral nutrients (MgSO4.7H2O (0.5 - 1.5), K2HPO4 (0.4 - 0.6), KH2PO4 (0.1 - 0.6)), nitrogenous substrates (NH4Cl (0.5 - 1.5), yeast extract (1 - 4), Tryptone (0.5 - 1)), reducing agents (cysteine HCl (1 - 5) and Na2S.9H2O (2 - 5)), Carbon source (molasses (50 - 100) and corn steep liquor (50 - 100)), buffering agent NaHCO3 (1 - 2.5), vitamin stock solution (10 - 20 ml) and trace mineral stock solution (15 - 20 ml). The nutrient medium II comprises (quantity g/l): mineral nutrients (MgSO4.7H2O (0.05 - 0.15), K2HPO4 (0.2 - 0.4), KH2PO4 (0.2 - 0.4)), nitrogenous substrates NH4Cl (0.5 - 1.5), reducing agents (cysteine HCl (0.1 - 0.5) and Na2S.9H2O (0.1 - 0.5)), Carbon source (molasses (15 - 30) and corn steep liquor (50 - 100)), buffering agent NaHCO3 (1 - 2.5), vitamin stock solution (5 - 10 ml) and trace mineral stock solution (5 - 10 ml). The trace mineral stock solution of nutrient media I and II has pH of 6.5 - 7.5 and comprises (quantity g/l): nitrilotriacetic acid (sodium salt) (0.82 - 2), MgSO4 (2.5 - 3.2), MnSO4.2H2O (0.2 - 0.8), NaCl (0.7 - 1.2), FeSO4.7H2O (0.05 - 0.12), CoCl2/CoSO4 (0.07 - 0.14), ZnSO4 (0.08 - 0.12), CuSO4.5H2O (0.008 - 0.015), Alk (SO4)2 (0.007 - 0.015), H3BO3 (0.009 - 0.012) and Na2MoO4.2H2O (0.008 - 0.13). The vitamin solution of nutrient media I and II having pH of 6.5 - 7.5 comprises (quantity mg/l): biotin (1.2 - 2.2), folic acid (1.7 - 2.4), pyridoxine HCl (7 - 12), thiamine HCl (7 - 12), riboflavin (6 - 7), nicotinic acid (4 - 6), DL-calcium pentothenate (3 - 6.2), para-aminobenzoic acid (4.1 - 5.6), vitamin B-12 (0.08 - 13) and lipoic acid (2.8 - 5.4). The nutrient medium I is prepared by dissolving mineral nutrients, nitrogenous substances, reducing agents, buffering agents, carbon source and trace mineral in water; adjusting the pH to 7 - 7.5; autoclaving the solution at 120 - 125degreesC, and at a pressure of 15 - 20 psi for 20 - 25 minutes; maintaining the temperature of the solution up to 90degreesC; adding vitamin solution and adjusting pH to 6.5 - 7.5 using alkali to obtain nutrient medium I. The nutrient medium II is prepared by dissolving mineral nutrients, nitrogenous substances, reducing agents, buffering agents, carbon source and trace mineral in formation water; adjusting pH to 7 - 7.5; autoclaving the solution at 120 - 125 degreesC and at a pressure of 15 - 20 psi for 20 - 25 minutes; maintaining the temperature up to 90 degreesC; adding vitamin solution and adjusting pH to 6.5 - 7.5 using alkali solution to obtain nutrient medium II. The alkali is sodium hydroxide or potassium hydroxide.