A semi-closed cycle power system for net carbon negative operation, the power system comprising: an engine subsystem including an engine producing exhaust; a semi-closed-cycle oxygen plant subsystem connected to the engine subsystem; an intake subsystem connected to the SCC oxygen plant subsystem; a carbon capture gas cleanup system connected to the SCC oxygen plant subsystem; a pyrolysis subsystem producing exhaust and connected to the engine subsystem; a waste-heat-to-power subsystem connected to the pyrolysis subsystem to receive the exhaust from the pyrolysis subsystem; an exhaust water separator subsystem connected to the waste-heat-to-power subsystem; an inlet hopper receiving a renewable feedstock; characterised in that the semi-closed cycle power system further comprises a pyrolysis reaction chamber, the pyrolysis reaction chamber comprising: a pipe; a heating jacket surrounding the pipe; a separator vessel, wherein the separator vessel provides a liquid/tar product, a gaseous product, and a char product; a screw concentric with the pipe for moving material through the pipe to the separator vessel; and a burner connected to the heating jacket, and wherein the separator vessel is connected to the burner and wherein the burner is designed to use the liquid/tar product provided from the separator vessel and the exhaust from the engine. an engine subsystem including an engine producing exhaust; a semi-closed-cycle oxygen plant subsystem connected to the engine subsystem; an intake subsystem connected to the SCC oxygen plant subsystem; a carbon capture gas cleanup system connected to the SCC oxygen plant subsystem; a pyrolysis subsystem producing exhaust and connected to the engine subsystem; a waste-heat-to-power subsystem connected to the pyrolysis subsystem to receive the exhaust from the pyrolysis subsystem; an exhaust water separator subsystem connected to the waste-heat-to-power subsystem; an inlet hopper receiving a renewable feedstock; a pyrolysis subsystem producing exhaust and connected to the engine subsystem; a waste-heat-to-power subsystem connected to the pyrolysis subsystem to receive the exhaust from the pyrolysis subsystem; an exhaust water separator subsystem connected to the waste-heat-to-power subsystem; an inlet hopper receiving a renewable feedstock; characterised in that the semi-closed cycle power system further comprises a pyrolysis reaction chamber, the pyrolysis reaction chamber comprising: a pipe; a heating jacket surrounding the pipe; a separator vessel, wherein the separator vessel provides a liquid/tar product, a gaseous product, and a char product; a screw concentric with the pipe for moving material through the pipe to the separator vessel; and a burner connected to the heating jacket, and wherein the separator vessel is connected to the burner and wherein the burner is designed to use the liquid/tar product provided from the separator vessel and the exhaust from the engine. a pipe; a heating jacket surrounding the pipe; a separator vessel, wherein the separator vessel provides a liquid/tar product, a gaseous product, and a char product; a screw concentric with the pipe for moving material through the pipe to the separator vessel; and a burner connected to the heating jacket, and wherein the separator vessel is connected to the burner and wherein the burner is designed to use the liquid/tar product provided from the separator vessel and the exhaust from the engine.