Rethinking the role of steam explosion on biomass composition, structure, and saccharification with new-designed pilot-operated pneumatic decompression mode

Due to the neglect of reactor features which can substantially influence results, there are divergences on whether the decompression step of steam explosion pretreatment affects biomass saccharification and subsequent bioethanol production. An original innovative reactor is presented, which adopts new-designed pilot-operated pneumatic (POP) mode to maximize the effect of decompression, to settle divergences. Based on the reactor, three series of experiments set at 0.5, 1.0, and 1.5 MPa pressure with 0- and 10-min residence times were conducted with wheat straw as feedstock, compositional/structural adaptation, and enzymatic digestibility as targets. Results show that decompression alone improved the porosity of feedstock and led to a maximum increase of 17% in specific surface area (SSA). However, no decompression effects could be confirmed on chemical depolymerization and cellulose crystalline destruction, which were mainly attributed to the hydrothermal autohydrolysis and highly correlated with the severity factor (logR 0 ). According to the enzymatic hydrolysis test, decompression promoted the reducing sugar yield of wheat straw by 6–11% due to the modification of porosity, but autohydrolysis still played the definitive role and an appropriate severity (logR 0 = 3.36) is necessary to sufficiently exploit the function of decompression. This paper provides more integral information for further optimization of the method.