One of the most pressing problems of our industrialized society is the uncertainty of maintaining an adequated supply of energy. As fossil fuels continue to decline in availability, the search for alternative sources of energy intensifies. One alternative is the production of methane gas by the fermentation of various types, of biomass. Research has been conducted for the cultivation of the fresh-water macrophyte, the water hyacinth (Eichhornia crassipes), as a potential biomass source able to be converted into methane and as a nutritive feed. The results were the anaerobic filter digester had a maximum production of 130 liters methane/Kg volatile solids added with a hidraulic retention time of 10 days and the biogas contains 64% methane. The contact process had a maximum production of 162 I CH/Kg v.s. added with a hidraulic retention time of 15 days and the biogas contains 65% methane. The mixed flow reactor had a maximum production of 146 L CH/Kg v.s. added with hidraulic retention time of 25 days and the biogas contains 65% methane. The maximum depuration obtained for these digesters were 49% with a hidraulic retention time of 10 days for the anaerobic filter digester. The contact proce s and mixed flow eactors had 65% for 15 and 25 days of hidraulic retention time, repectively. Finally, the acids volatile concentration for these digesters were for the anaerobic filter digester 71 mg acetic/l with a retention time of 10 days. For the contact process 65 mg acetic/l with retention time of 15 days and for the mixed flow reactor 58 mg acetic/l with retention time of 25 days. © 1992, Taylor & Francis Group, LLC. All rights reserved.