In this study, a hythane based cogeneration system integrated with multi-effect desalination, reverse osmosis, gasification and digestion subsystems is proposed to provide electricity and freshwater using biomass sources. The system is analyzed for various wastes to compare their performance in terms of environment, energy, and exergy. The parametric studies are conducted for the ambient temperature and the hydrogen fraction in hythane. Biomass-based energy systems are employed to produce electricity, heat, and freshwater while providing an effective solution to disposal of the wastes. In Istanbul, which is the biggest city in Turkey, a total of 6.75 million tons of municipal wastes is collected and treated every year. The overall energy and exergy efficiencies of the integrated system are calculated as 37.04% and 19.78%, respectively. Here, 2.498 kg/s of municipal solid waste and 0.1314 kg/s of olive oil waste are utilized to generate 4.49 MW electricity by a steam turbine and 92.29 kg/s freshwater by multi-effectdesalination and reverse osmosis units.