Lignocellulose-containing materials are treated with lime (calcium hydroxide) and water at a relatively high temperature and for a certain period of time under certain conditions. The process variables were: lime loading which ranged from about 2 to about g Ca(OH)2 /100 g dry material; water loading which ranged from about 6 to about 19 g water/g dry material; treatment temperature which varied from about 50 C. to about 150 C.; and treatment time which varied from about 1 to about 36 hours. The effects of treatment time and temperature were interdependent.A process for lime recovery is developed. The soluble Ca(OH)2 was washed out of the pretreated material with water and converted to insoluble CaCO3, by reacting with CO2, and was thus separated. The CaCO3 can be heated to produce CaO and CO2. The CaO is hydrated to Ca(OH)2 which can be reused as the lignocellulose treatment agent. Carbon dioxide is reused for lime recovery.
