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Separation technologies for current and future biorefineries—status and potential of membrane-based separation



Biorefinery is one of the most important industries in the modern world, as it provides a variety of products, particularly renewable bioenergy, which is highly vital to human existence (?). Among the separation technologies applied in biorefinery, membrane-based separation has received great attention in past decades as it is in line with the worldwide move toward higher energy efficiency and lower environmental impact. Analysis of the academic and industrial activities being undertaken reveals that porous membranes like nanofiltration, ultrafiltration, and microfiltration are generally associated with pretreatment and hydrolysis procedures where separation is relied on for recovering value-added materials with wide range of molecular weight and facilitating follow-up bioconversion. An emerging field that highly appreciates porous membranes is biodiesel purification. Molecular level separations including gas product separation existing in thermal and anaerobic conversions and liquid alcoholic products recovery in microbial/enzymatic process offer more opportunity to membrane-based gas separation and pervaporation using dense membranes. Membrane distillation and supported liquid membrane, commonly classed as new generation of membrane technology, show the potential in bioethanol recovery and hydrolysis step, respectively. Nonetheless, their competitiveness is to be confirmed. The function of membrane separation is being pushed further. Bearing in mind the importance of membranes with higher quality in terms of separation efficiency and material stability, we must also be prepared for the challenges deriving from some engineering aspects such as membrane fouling, module design, and process optimization.