Dimethyl ether (DME) is a well-known propellant and coolant, an alternative clean fuel for diesel engines which simultaneously is capable of achieving high performance and low emission of CO, NO and particulates in its combustion. It can be produced from a variety of feed-stocks such as natural gas, coal or biomass: and also can be processed into valuable co-products such as hydrogen as a sustainable future energy. This review, which also can be counted as an extensive, pioneer review paper on this topic, presents recent developments in synthesis methods of dimethyl ether as an alternative energy while focuses on conventional processes and innovative technologies in reactor design and employed catalysts. In this context, synthesis methods are classified according to their use of raw material type as direct and indirect methods as well as other routes, since different methods need their own operating condition. Also, the available data for the selectivity to DME and its yield as a function of H-2/CO and CO2 content of the feed is discussed. (C) 2014 Elsevier B.V. All rights reserved.