Gas can be carbon negative. If you make methane from syngas by gasifying or pyrolyzing biomass, you're still left with either ash, or carbon black, depending on

Gas can be carbon negative. If you make methane from syngas by gasifying or pyrolyzing biomass, you're still left with either ash, or carbon black, depending on the process used. This is solid carbon that was pulled out of the atmosphere by a plant, that can be sequestered away.