Gasification of biomass is usually understood to mean pyrolysis of dry material, usually wood. This process has been known and used for many years, but does not produce natural gas. Its product is called syngas, which is a mixture of carbon monoxide and hydrogen, and cannot be used with the same infrastructure as natural gas.
The Genifuel gasifier, known as Catalytic Hydrothermal Gasification (CHG) is the second stage in Hydrothermal Processing. It converts organic matter remaining in the effluent water after formation of oil in the Hydrothermal Liquefaction stage. The CHG stage is licensed from Battelle using patents developed at the Pacific Northwest National Laboratory by research scientist Doug Elliott and colleagues in the Chemical and Biological Process Group). It produces methane gas and clean, sterile water which contains residual elements making it valuable as a liquid fertilizer. The process operates at much lower temperatures than other gasification methods, approximately 350oC and 21 MPa (662oF and 3000 psi), making the construction and operation of the equipment easier and less expensive than pyrolysis.
For a more detailed description of the gasification process, see Elliott's original paper on catalytic gasification of wet biomass. (Paper made available by permission of The Institution of Chemical Engineers.)
Another technology often used to produce methane from wet biomass is anaerobic digestion. A comparison of Genifuel CHG and anaerobic digestion is here.