Flowthrough pretreatment with compressed-hot water can significantly increase the removal of xylan and lignin and enhance xylose sugar yields and cellulose digestibility, especially at high flow rates. However, continuous flowthrough operations that realize these benefits suffer from a large amount of water consumption that leads to high energy requirements for pretreatment and downstream processing. Because high flow rates are particularly effective early in hemicellulose hydrolysis and less effective later, flow with compressed-hot water was applied at selected intervals, and performance was compared with that of batch and flowthrough operations for corn stover pretreated with compressed-hot water at 200 degrees C. Partial flow reduced water consumption by 60% compared with continuous flowthrough operation but still achieved higher xylose sugar yields (84-89%) compared to batch pretreatment (46.6%). In addition, corn stover cellulose pretreated by partial flow had higher enzymatic digestibility (88-90%) than batch operations (similar to 85%) at otherwise identical conditions, apparently due to much higher lignin removal for the former (40-45% vs 10-12%). Partial flow also reduced degradation, with recovery of xylose and glucose in the solids and hydrolyzate increased to 90-92% vs only about 76% for batch operation. The partial flow approach could be further improved by optimizing the operating strategy and reaction conditions, suggesting that this novel pretreatment could lead to advanced biomass pretreatment technology. (c) 2005 Elsevier Ltd. All rights reserved.