Refused Derived Fuel (RDF) could be considered as an alternative energy source, which not only helps to improve waste management, but also effectively reduce energy consumption and environmental pollution in huge industries. In the present study, the potential of energy valorization of rejected streams of municipal solid waste (MSW) processed in Isfahan mechanical and biological treatment (MBT) plant is investigated through RDF production. Therefore, various physical and chemical analysis of mechanical treatment rejects (MTR) and composting rejects (CR), as two streams being currently landfilled, were carried out. The results show that, RDF produced from both of these two streams could be classified as net calorific value (NCV): 3, Cl: 1 and Hg: 1 according to the European committee for standardization (CEN standard). Considering the amount of produced RDF from these two streams in Isfahan (300 t/d from MTR and 120 t/d from CR) and their NCVs, about 2 million GJ/year would be saved. As a result, in many cities of developing countries with the same condition like Isfahan, MTR and CR can be used as sources of RDF production and alternative fuels in the cement industry. Display omitted •The potential of two Isfahan MBT plant rejects were investigated as a source of RDF production.•The MTR and CR can be used as an alternative fuel in the cement industry.•The obtain results can be generalized to other developing countries.