A system and method for vertically-oriented, modular, automated, emissions-controlled composting. In a preferred embodiment, the system and method involve construction of a vertically-oriented set of composting modules comprising a receiving and offloading level, one or more composting bay levels, a feedstock staging level, a biofilter level, a vertical conveyor for uploading feedstock to the feedstock staging level, a freight and personnel elevator, and a leachate tank. This composting system and method reduces the land area required for composting, increases the capture of emissions from composting, and reduces the labor-intensive and heavy-equipment-intensive nature of current methods.