In contrast with complete combustion of a low heating value gas, catalytically combusting a dilute gas stream of low heating value with an insufficient, that is a substoichiometric, amount of air cannot result in a complete elimination of the combustible components. The utilization of substoichiometric combustion of a low heating value gas may be desirable in certain circumstances, such as, for example, when the composition of the gas and therefore its heat content varies with time. The use of a constant substoichiometric amount of air for combustion results in a constant temperature in both the combustion zone and in the exiting combusted gas notwithstanding the variation in the heat content of the low heating value gas. The constant temperature in the combustion zone avoids catalyst damaging cycles of thermally induced expansion and contraction, which can be a significant problem, particularly when large catalyst structures are required to handle very large volumes of low heating value gas. Furthermore, this combusted gas of constant temperature can be used to drive a gas turbine, without expansion-contraction damage to the turbine blades, which protection is necessary, in particular, with gas turbines which are designed for constant temperature operation. However, the production of substantial quantities of carbon monoxide is a significant problem in the substoichiometric combustion of low heating value, hydrocarbon-containing gas streams.