Systems to convert a carbonaceous feedstock into a plurality of gaseous products are described. The systems include, among other units, four separate gasification reactors for the gasification of a carbonaceous feedstock in the presence of an alkali metal catalyst into the plurality of gaseous products including at least methane. Each of the gasification reactors may be supplied with the feedstock from a single or separate catalyst loading and/or feedstock preparation unit operations. Similarly, the hot gas streams from each gasification reactor may be purified via their combination at a heat exchanger, acid gas removal, or methane removal unit operations. Product purification may comprise trace contaminant removal units, ammonia removal and recovery units, and sour shift units.