Scientists from the Institute of Chemical Engineering, Vienna University of Technology (Austria) and the Department of Chemical Engineering, Lund University (Sweden) report a comparative study of a single-step, "dual temperature profile", dilute acid hydrolysis (DAH) of spruce (a type of softwood) and the conventional two step process. The conventional two-step DAH method usually involves an acid hydrolysis step under conditions of low severity (to hydrolyze the hemicelluloses fraction), followed by one of "higher severity" (to degrade the cellulose). The main drawback of the two-step process is said to be the "energy-intensive" washing process that is done between the two steps. The researchers explored the use of a single step process, performing the DAH at two temperatures in a single reactor. This effectively would remove the "energy-intensive" washing step. Results showed that the highest measured glucose yield was obtained after "DAH cycles of 3 minutes at 209°C and 6 minutes at 211°C with 1% H2SO4. However, the dual-temperature DAH method "did not yield decisively better results than the single-temperature, one-step DAH". The full results are published in the open-access journal, Biotechnology for Biofuels (URL above).