This paper presents a unified techno-economic and environmental mathematical model for market driven operation optimization of different Distributed Multi-Generation (DMG) options in district heating schemes. The identified concepts of DMG are capable of providing significant operational benefits in that they have the flexibility to respond to electricity market signals, which is particularly important in the presence of a less flexible and more intermittency dominated power system. At the same time, the formulation allows assessment of the environmental benefits under different scenarios. The optimization formulation cast as a mixed integer linear program (MILP), is capable to incorporate the use of different multi-energy technologies and explicitly model inter-temporal constraints that allow assessment of the benefits of thermal storage, amongst the others.