A first system includes a feedstock load port and a feedstock discharge port. The first system also includes a tank configured to retain biomass feedstock for aerobic biodegradation. The first system further includes a mechanical ventilator in fluid communication with the tank. The mechanical ventilator is configured to supply air to facilitate the aerobic biodegradation of the biomass feedstock. The first system also includes an exhaust port configured to receive gas generated during the aerobic biodegradation. A second system includes a feedstock load port and a feedstock discharge port. The second system also includes a pressure vessel configured to retain biomass feedstock for anaerobic biodegradation. The second system further includes a gas release device to facilitate migration of gas within the pressure vessel. The second system also includes a water cycler configured to cycle water within the pressure vessel. The second system further includes an exhaust port.

A system includes a vessel configured to couple with a gas source for drawing gas into the vessel. The vessel is also configured to receive liquid. The system includes an overflow port in fluid communication with the environment external to the vessel. The overflow port is configured to separate gas within the vessel from the external environment. The system also includes an overflow conduit having an end within the overflow port so that when gas pressure within the vessel increases, liquid is received by the overflow conduit. Another system includes a tank defining an air space for receiving gas generated during the biodegradation of biomass feedstock. The second system also includes an exhaust port, a first evaporator, a first condenser, an expansion valve, and a compressor. The second system also includes a heat exchanger, a second evaporator, and a second condenser.

A system includes a vessel configured to couple with a gas source for drawing gas into the vessel. The vessel is also configured to receive liquid. The system includes an overflow port in fluid communication with the environment external to the vessel. The overflow port is configured to separate gas within the vessel from the external environment. The system also includes an overflow conduit having an end within the overflow port so that when gas pressure within the vessel increases, liquid is received by the overflow conduit. Another system includes a tank defining an air space for receiving gas generated during the biodegradation of biomass feedstock. The second system also includes an exhaust port, a first evaporator, a first condenser, an expansion valve, and a compressor. The second system also includes a heat exchanger, a second evaporator, and a second condenser.