Waste management is a major concern in large cities under heavy demographic pressure. Landfill, the oldest form of solid waste management is gradually being replaced by new technics such as biométhanisation. With the purpose of contributing to the achievement of one of the Sustainable Development Goals, particularly SDG7 (affordable and clean energy), the aim of this study is to assess the fermentable fraction of organic wastes into biogas. This survey was carried out in and around Douala city. Biological material consisted of water hyacinth (WH), household wastes (HW), oil palm wastes (OPW) and a mixture of these three substrates (MS) was collected and introduced with cow dung used as inoculum in a biodigester. Some physico-chemical parameters of substrates were determined. Results have shown that substrates used have a pH around neutral. The C/N ratio has shown an excess of nitrogen in the WH, but a deficit in the OPW and MS. The household wastes have presented an ideal ratio for the biological stability of the anaerobic digestion system (21.153 ± 0.695). At the end of the experimentation, a large degradation of organic matter has been observed with COD decrease rates of 37.55 ± 0.12 % (WH), 45.46 ± 0.60% (HW), 48.27 ± 0.34% (OPW) and 46.71 ± 0.26% (MS). All air chambers were inflated and the combustion has shown a blue flame, proof of very high proportions of methane in the flammable biogas. A sanitation process has led to clean energy production.