Abstract: A system for concentrating gas, using the concentrated gas to pump liquid, and recycling the gas and liquid is disclosed. The system comprises a body of liquid, a down pipe in fluid communication with the body of liquid, a gas injection apparatus for introducing gas into the liquid that passes through the down pipe, a separator for separating compressed gas from the liquid, and a gas-liquid recycle loop. The down pipe and the gas injection apparatus are structured and arranged to compress the gas. The gas-liquid recycle loop comprises a compressed gas storage vessel containing the separated gas, a reservoir containing liquid separated from the compressed gas, and a gas-liquid pump. The gas-liquid pump has a gas inlet in communication with the gas storage vessel, and a fluid inlet in communication with the reservoir. The gas-liquid pump is structured and arranged for pumping the liquid back to the body of liquid and delivering the gas to the gas injection apparatus.