Gas is produced by passing steam into a mixture of carbonaceous solid fuel and CaO, in which process the steam is introduced into the reactor at 777°-982° and under a pressure that is at least 3.40-1.89 x 10ˉ2 (t-1,430) +4.48 x 10ˉ4 (t-1,430)2 atm., where t is the temperature in ° F. The amount of CaO is sufficient to convert substantially all the CO2 produced to carbonate. The process also includes the use of mixtures consisting of 120-300 parts, by weight, CaO per 100 parts C in the fuel. After completion of the steam-C reaction, air is circulated at atmospheric pressure through the solid residue to regenerate the CaO. Under the above conditions the overall reaction will be at least thermoneutral and preferably exothermic. To produce a gas rich in CH4 with a heating value in excess of 400 B. t. u. per ft.3, the minimum pressure in atmospheres can be expressed by 5.0+4.2 x 10ˉ2 (t-1,430) + 2.7 x 10ˉ4 (t-1,430)2. The yield of CH4 can be increased by carrying out the steam-C reaction at 910°-966° and then passing the products in contact with carbonaceous solids at 777°-871°. The steam-C-CaO reaction may be accelerated by impregnating the CaO with a small amount of a catalyst, such as an oxide of Fe, Ni, Co, or Mn.