INTRODUCTION Trichoderma is a cosmopolitan fungus with a worldwide distribution, common in soil, litter and humus. It has cellulose decomposing ability of municipal garbage (Samuels, 1996), and effective as biocontrol agents against soil born plant pathogens (Kelley, 1976; Jeffers and Wilcox, 1990). It is reported that T. harzianum is capable of degrading organochlorine pesticides such as DDT, dieldrin, endosulfan, pentachloronitrobenzene, pentachlorophenol and hence has potential applications for bioremediation (Kelley, 1976). Solid wastes, which contribute to air, water and land pollution, can be classified into domestic, industrial and agricultural (Drobny et al ., 1971; Bond and Straub, 1973; Sell, 1981). Everyday huge amount of solid wastes are generated in all the developed and developing countries. Although developing countries spend 20 to 40% of Municipal reserves for waste management, but a significant amount of solid waste in urban centers remain untreated (Thomas-Hope, 1998; Bartone, 2000 and Schubeler, 2000). Only a few Asian cities like Tokyo, Singapore and Hong Kong have adequate solid waste disposal facilities. Bangladesh also generates huge amount (0.5 kg/capita/ day) of solid waste which creating environmental hazards and have adverse effect on health (Zurbrügg, 2002). To overcome the ever-increasing serious problem, conversion of solid waste into organic compost seems to be a fruitful solution (Walker and Willson, 1973 and Wootton et al ., 1981). Therefore, the present study was undertaken to screen the potential strains of Trichoderma for their efficiency as effective bioconversion agents on solid waste. MARETIALS AND METHODS For effective decomposition of organic solid waste, five local Trichoderma isolates, i.e. T. virens (IMI- 392430), T. pseudokoningii (IMI-1392431), T. harzianum (IMI-392432), T. harzianum (IMI- 392433) and T. harzianum (IMI-392434) were collected from stock culture of Biotechnology and Plant Environ. Dev. 1(1):61-66, 2007 (June) ©Department of Botany, University of Rajshahi, e-mail: plant.environ.dev@gmail.com ISSN 1994-1501 Mode of action of Trichoderma spp. on organic solid waste for bioconversion M.A. Bari, M.F. Begum, K.K. Sarker, M.A. Rahman, A.H. Kabir and M.F. Alam* Department of Botany University of Rajshahi, Rajshahi-6205, Bangladesh. *e mail: falambt@yahoo.com Abstract Five strains of Trichoderma were used to select the most effective strain for bioconversion of Municipal solid waste. Culture pellet was found more effective than spore suspension. The highest weight loss was 31.80 %, when culture pellet (6 pieces) was used and it was 12% higher than control. Autoclaved solid waste was good for degradation than non-autoclaved. Among the studied strains, T. harzianum (IMI-392432) was found most effective. Using combination of Trichoderma showed 10% better result than single strain used. Keywords: Bioconversion, Organic solid waste, Trichoderma , Culture pellet, Spore suspension.