a cost - effective solution for the disposal of heavy residue bottoms recovered from a slurry hydrocracking process that include solid heterogeneous catalyst particles is provided by their introduction into a membrane wall gasification reactor in the form of a flowable slurry to produce a synthesis gas and , optionally , subjecting the synthesis gas to a water - gas shift reaction to produce a more hydrogen - rich product stream . process steam and electricity are produced by recovering the sensible heat values from the hot synthesis gas .