TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The nitrate salt of the nitrate salt solution is selected from sodium nitrate, potassium nitrate, calcium nitrate or magnesium nitrate (preferably calcium nitrate). The nitrate solution contains the dissolved nitrate salt (10-60 wt.%). The nitrate is not cupric nitrate. The amount of inorganic nitrate added for increasing methane production is 1-4% of COD. Preferred Method: The process involves introducing sludge or wastewater into an anaerobic biological sludge or wastewater treatment system; measuring the COD level of the sludge or wastewater material at a monitoring point of the sludge or wastewater treatment system; calculation of the nitrate dosage to be added; and adding nitrate in an amount corresponding to 1-4% of feed COD based on the calculations in calculating step. The nitrate is added at the beginning of each batch of sludge treatment. The sludge treatment process is working continuously, where the addition of nitrate is dosed periodically. For increasing methane production, the nitrogen solution is added periodically or continuously during the anaerobic sludge treatment process in the reactor. The nitrogen solution is added to the first reactor(s) or stage(s) of a dual or multi stage anaerobic digestion process. EXAMPLE - Twelve batch reactors consisting of syringes were used as lab scale batch reactors. Each syringe was connected to a needle blocked by a small rubbery stopper to stop leakage of both gas and liquid. The syringes were kept in an incubator at a temperature of 35 plus minus 1.0 degrees C. Inoculums (39 ml) consisting of an initial inoculum taken from a municipal wastewater sludge continuous flow anaerobic digestion treatment plant and nutrient solution containing starch, peptone, yeast extract, KH2PO4 and K2HPO4, and tap water were feed into each batch reactor. Calcium nitrate solution was added in the beginning of the test. Two parallel groups were set. Ten of the reactors were added calcium nitrate solutions corresponding to different percentage of O2 as follows: 0%, 2%, 4%, 8% and 16% (as percentages of feed COD load). Two reactors were kept without feeding and the other 10 were fed a 1 ml starch solution having 54468 mg/l COD. Biogas generation was measured for all the reactors at various times. The composition of gas collected was analyzed using Hewlett Packard. It was demonstrated that reactors fed with 1688 mg/l concentration of nitrate (equal to 2% oxygen of feed COD) showed the highest biogas generation compared with the other laboratory scale reactors. The results further showed that the biogas formation increased with increasing amounts of nitrate up to a level corresponding to 2% oxygen. The results further showed that the biogas formation was higher compared with the reactor not having any added nitrate, i.e. corresponding to strictly anaerobic conditions, until the amount of oxygenation equivalent nitrate exceeded about 4%. At nitrate solutions added equal to 1%, 2% and 4% oxygenation, respectively, both SCOD and TCOD were lower compared with the reactor having no nitrate solution added or having even higher amounts of nitrate solution added (i.e. equal to 8% and 16% oxygenation). The results thus showed that by adding nitrate solution to an anaerobic sludge treatment reactor, where the amount of nitrate was 1-4% oxygenation, higher methane production and lower COD were obtained. The most optimal conditions were obtained where the nitrogen solution added was 2% oxygenation.