A process for producing a humic acid (HA)-derived foam, comprising: (a) preparing a HA dispersion having multiple HA molecules and an optional blowing agent dispersed in a liquid medium having a blowing agent-to-HA weight ratio from 0/1.0 to 1.0/1.0; (b) dispensing and depositing the HA dispersion onto a surface of a supporting substrate to form a wet HA layer; (c) partially or completely removing liquid medium from the wet HA layer to form a dried HA layer; and (d) heat treating the dried HA layer at a first heat treatment temperature from 80° C. to 3,200° C. at a desired heating rate sufficient to induce volatile gas molecules from the non-carbon elements or to activate the blowing agent for producing the HA-derived foam.