Backyard composting is widely used to process vegetable, fruit and garden wastes (biowastes) in gardens. Unfortunately, little is known about the hygienisation efficiency during this small-scale composting process. In a 6-month experiment, the eradication of tobacco mosaic virus (TMV), Plasmodiophora brassicae, Heterodera schachtii and of tomato seeds was followed during corn-posting in four 200–1 vessels. In conformity with the German BioAbfV norms which were used as guideline for this research, the pathogens were incorporated as TMV-infected tobacco leaves, as a mixture of clubroot-infected cauliflower roots and infested soil, as cysts or as seeds packed in nylon fibre nets. Two vessels were totally filled; two others were half-filled. At the end of the 6-month composting period, only TMV was completely eliminated, while H. schachtii and the tomato seeds were almost completely eliminated. On the other hand, P. brassicae survived the composting process. Destruction of the tomato seeds, of TMV and of H. schachtii could partly be explained on the basis of heat treatment. Other factors may have contributed to the sanitising effect observed during this rather low-temperature composting process.