TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: In pretreating biomass, the steps of (a)-(c) are repeated for n cycles, n being an integer between 1 and 50. The method further comprises converting the at least one component retained by the filter into ethanol. The temperature of the liquid in step (a) is between 120 degrees C and 240 degrees C. The temperature of the liquid in step (a) of a repeating cycle is at least 1 degrees C higher than the temperature of the liquid in step (a) of the cycle immediately prior to the repeating cycle; or the temperature of the liquid in step (a) of a repeating cycle is between 5 degrees C and 10 degrees C higher than the temperature of the liquid in step (a) of the cycle immediately prior to the repeating cycle. The filter has an average pore size of less than 2 nm. It comprises ceramic material. At least one component is a carbohydrate having a molecule weight of less than 1000 daltons. Preferred System: In the system, the material is a biomass. At least one component of the biomass is dissolved in the effluent. The system further comprises a fast operation valve for discharging solid biomass from the vessel. The filtering means comprises a nanoporous membrane having a pore size of 2 nm or smaller. It comprises a nanoporous membrane, the nanoporous membrane being capable of functioning at a temperature higher than 120 degrees C. The filtering means comprises a ceramic membrane. The system also comprises a first heating means for increasing the temperature inside the vessel, the first heating means being located inside the vessel; a second heating means for increasing the temperature of the filtrate, the second heating means being located outside the vessel; a heating means for increasing the temperature of the biomass inside the vessel, the heating means being a steam injector configured to inject steam into the vessel; and a heat exchanging means, where the heat exchanging means is configured to recover heat from liquid exiting the vessel and to provide the recovered heat to the liquid entering the vessel. EXAMPLE - No suitable example given.