The present study aims at studying the supercritical water gasification (SCWG) of the leftover Brazilian ginseng roots after phytochemicals extraction for synthetic natural gas (SNG) production, envisioning the development of a promising Brazilian ginseng roots valorization route using sub/supercritical fluids in different steps. A multi-objective energetic-economic-environmental optimization of the proposed SCWG process was assessed through the use computational simulation tools. The results showed that for a given leftover biomass input of 20MW a specific cost of 62-66 USD/MWh of SNG is obtained, which is higher than the average price in Brazilian market. On the other hand, the production process of SNG from this residue showed to be a promising option, being energetically self-sufficient and environmentally friendly. In order to become more economically attractive this alternative process we proposed the construction of the SCWG and the sub/supercritical extraction units in the same location, sharing part of the same high-pressure equipments