Abstract: A biochemical process for the aerobic thermophyllic fermentation of cotton gin waste is disclosed which converts a presently useless pest ridden agricultural waste product into a useful medium for the culture of horticultural and agronomic plants as well as micoorganisms useful to man. By the aeration, water content and physical shape and size of the waste product, piles are so conditioned that by means of the resulting biodegradation processes plant pathogenic microorganisms, insects, viruses, spider mites and related pests are destroyed. Additionally, pesticidal residues, chemical plant growth regulators and certain harvest aid materials normally added to the growing cotton crop for production purposes are reduced to materials harmless to plant life. The resulting humus like material provides improved plant growth, nearly five times that of a good river loam soil, and contains a microbial population that prevents the spread of soil borne plant pathogenic microorganisms reintroduced into the medium.