Due to resources depletion, fossil fuels are not capable of compensating the growing energy needs. However, still most of the power plants driven by fossil based fuels such as coal, natural gas or oil. The underlying motivation of this study is to reveal what types of biomass can be a better choice to replace fossil fuels by comparing both environmental impacts and systems performance. In order to achieve this target, a solar-assisted combined cycle is modeled thermodynamically for seven different fuels. Also, a comparative life cycle assessment (LCA) is carried out by using CML 2001 method for evaluation of the environmental impacts of the considered fuels to produce electricity through a combined cycle. Although natural gas fired solar-assisted combined cycle emits the least amount of CO2 to the atmosphere, global warming potential (GWP) and ozone layer depletion potential (ODP) of natural gas are determined as the highest among the considered fuels. According to the results, sawdust and wet wood would be the rewarding alternatives of natural gas with relatively lower amounts of CO2 emissions (11.37 kg/s for the sawdust and 11.78 kg/s for the wet wood) as well as having the lowest environmental impacts.