Home furnaces burn a lot of natural gas and put the water in the sewer and the CO2 in the air. I wonder how much tweaking the sewer system would need to start a

Home furnaces burn a lot of natural gas and put the water in the sewer and the CO2 in the air. I wonder how much tweaking the sewer system would need to start acting as a CO2 return system also. If it were a closed loop system you could at least be carbon neutral, and stockpiling methane for the winter is easier than stockpiling electricity.