TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The system comprises a gas separator configured to separate the exhaust gas into at least a first gas and a second gas, where the gas supply system is configured to use the first gas as the recycle gas. The first gas comprises carbon dioxide separated from the exhaust gas and used as the recycle gas. The gas separator comprises a pressure swing absorption system. The system comprises the combustion system configured to generate the exhaust gas from a combustion of the producer gas. The system comprises a controller coupled to the gas supply system, where the controller has a first mode configured to provide the recycle gas to the gasifier and a second mode configured to provide the recycle gas to the producer gas purification system. The gasifier comprises: a first opening configured to receive the oxidant; and a second opening configured to receive the recycle gas, where the second opening is separate from the first opening. In the system: the gas supply system is configured to supply the recycle gas to the producer gas purification system at a lower temperature than the producer gas; the producer gas purification system comprises at least one scrubber, and the recycle gas is configured to cool producer gas in the scrubbers; and the recycle gas comprises the exhaust gas, carbon dioxide separated from the exhaust gas and/or nitrogen separated from the exhaust gas. The combustion system is configured to combust the producer gas from the producer gas purification system to generate an exhaust gas. The pressure swing adsorption system is configured to separate the exhaust gas from the combustion system into a first gas and a second gas, where the pressure swing absorption system is configured to supply the first gas at least one of the gasifier, and/or the producer gas purification system. The producer gas purification system comprises at least one scrubber configured to scrub the producer gas from the gasifier, and the pressure swing absorption system is configured to supply the first gas to the at least one scrubber at a lower temperature than the producer gas to facilitate cooling. The producer gas purification system comprises: a first water scrubber configured to receive the producer gas from the gasifier; a second water scrubber configured to receive the producer gas from the gasifier or the first water scrubber, where at least one of the first or second water scrubbers comprises a chilled water scrubber; and a water source configured to supply water to at least one of the first or second scrubbers, where the first gas is configured to facilitate cooling in at least one of the first or second scrubbers. The first gas comprises carbon dioxide. The first mode of the controller is configured to provide the first gas, the second gas, or the exhaust gas to the gasifier, where the second mode is configured to provide the first gas, second gas or the exhaust gas to the producer gas purification system. Preferred Method: In the method: supplying the first gas comprises controlling a flow rate of the first gas based on a temperature of the producer gas in the gasifier; supplying the first gas to the gasifier comprises facilitating a reaction to convert char into carbon monoxide; and supplying the first gas to the producer gas purification system comprises facilitating cooling in at least one scrubber used to scrub the producer gas.