A method and system of providing compressed low NOx exhaust gas for industrial purposes including for use in augmenting crude oil production including the steps of extracting exhaust gas from an engine consuming a controllable mixture of hydrocarbon fuel and air, compressing and cooling the exhaust gas to condense water therefrom, measuring the pH of the condensed water, employing the measured pH to adjust the ratio of the hydrocarbon fuel and air supplied to the engine to achieve a substantially neutral pH measurement and thereby obtain compressed exhaust gas having a low NOx content.