The present invention provides a plasma generating system that includes: a plurality of plasma reactors. Each plurality of plasma reactors includes: a waveguide for transmitting a microwave energy therethrough; a plasma chamber coupled to the waveguide and configured to generate a plasma therein using the microwave energy; a gas inlet for introducing a gas into the plasma chamber; an exhaust gas pipe for carrying an exhaust gas from the plasma chamber, wherein the plasma converts the gas into the exhaust gas; and a pressure control device installed in the exhaust gas pipe and configured to control a pressure of the exhaust gas in the exhaust gas pipe. The plasma generating system also includes a manifold coupled to the exhaust gas pipes of the plurality of plasma reactors and configured to receive the exhaust gas from the exhaust gas pipes.