A process for forming durable, mechanically strong compacts from feed mixtures comprising solid particles in contact with a liquid (e.g., carboniferous particles in contact with water) which does not require use of a binder is disclosed. The process comprises applying a compressive stress to the feed mixture either by compacting the feed in a mold or by extruding the feed through the die of a suitable extrusion apparatus while controlling certain process parameters, including the moisture content and the zeta potential of the particulate feed. The process can be used to form large, cylindrically-shaped compacts from coal particles (i.e., "coal logs") so that the coal can be transported in a hydraulic coal log pipeline or by conventional means.