A mobile, modular multi-chamber composting system for the composting of organic material includes a composting unit having a pair of adjacent composting chambers enclosed by sidewalls, a roof, and closure panels, with the chambers delimited by a separation panel, and the first chamber having a uni-directional tilting floor and the second chamber having a bi-directional tilting floor so that organic material can be placed in the first chamber and transferred to the second chamber to facilitate decomposition of the material. Hydraulic mechanisms are interconnected to each floor to facilitate the tilting of the floor and the transference of the material, and the second chamber can transfer the material back to the first chamber or expel the material from the unit or transfer the material to another adjoined composting unit. The composting units are stackable one atop another, and the composting units are towable by a lawn tractor, a vehicle, or can be configured as an industrial-sized system towable by a tractor-trailer.