2 co 3 which is added in amount approximately 10 of the bone dry weight bdw of the chips added to the vessel 16 the regular soda ash is added from a liquor supply 20 that injects the soda ash with the cooking liquor into the vessel of the cooking system 16 or into the chip feed system 14 upstream of the vessel the chips and cooking liquor are heated in the vessel 16 such as with steam 18 injected to the vessel to a temperature in a range of 330 degrees deg fahrenheit f to 380 deg f or in a range 360 deg f to 370 f the chips are retained in the vessel for a period such as two 2 to fifteen 15 minutes or 4 to 10 minutes the chips are mechanically fiberized in a chip fiberizing vessel 17 such as defiberator or refiner vessel to a shines content of for example 10 to 50 or 30 to 45 the fiberized chips are discharged from the fiberizing vessel 17 and directed to one or more stages 22 of delignification such as a continuous or batch chemical reactor s 24 the delignification stages may remove or oxidize the lignin in the fiberized chips using oxidizing agents 26 such as one or more of oxygen hydrogen peroxide and ozone the fiberized chips.