Abstract: A steam reformer that produces hydrogen gas from water and a carbon-containing feedstock, such as an alcohol or a hydrocarbon. The steam reformer includes a hydrogen-producing region, in which a mixed gas stream containing hydrogen gas and other gases is produced from water and a carbon-containing feedstock. The steam reformer includes a separation region, in which the mixed gas stream is separated into a hydrogen-rich stream containing at least substantially pure hydrogen gas, and a byproduct stream containing at least a substantial portion of the other gases. In some embodiments, the steam reformer is a vertically oriented fuel processor. In some embodiments, the separation region includes at least one hydrogen-selective membrane. In some embodiments, the steam reformer further includes a polishing region, in which the hydrogen-rich stream produced in the separation region is further purified. In some embodiments, the reformer includes an external metal or sealed ceramic shell.