The compact chemical reactor includes one or more unit reactors, a front reactant plenum, and a back reactant plenum. Each unit reactor is made of a front and back process layer, a front and back cavity, and a front and back perimeter barrier. The resulting assemblage is configured so the front cavity is in communication with the front side of the compact chemical reactor and the back cavity is in communication with the back side of the compact chemical reactor. The process layers facilitate an exchange of reactants between the reactant plenums.