BRIGE: Cellulose saccharification observed in real-time in a high-temperature microreactor - research and outreach

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Technical Description: Despite years of effort, breaking down lignocellulosic feedstocks into small molecule building blocks remains prohibitively expensive. A major challenge is that the primary component of lignocellulosic biomass, cellulose, is highly crystalline and recalcitrant to most enzymatic and biological decomposition techniques. As a result, expensive and energy intensive pre-treatment steps are required to convert biomass into a form that is amenable to enzymatic breakdown into constituent sugars -- a process termed saccharification. Making pre-treatment more efficient can greatly reduce the capital costs of biofuel production. Progress in this direction has been impeded by the fact that pre-treatment conditions are harsh -- acidic with temperatures typically greater than 100 °C. Pre-treatment reactors are therefore not typically optically accessible, and the vast majority of pre-treatment studies have only been able to evaluate end effects achieved after the pre-treatment process has been completed. For this reason, engineering data on how to design, scale-up, and operate pre-treatment reactors is lacking information on how the solid biomass phase responds over time during pre-treatment reactions. In this work, we will use a high-temperature microreactor for a real-time study of cellulose de-crystallization, an important step in the overall pre-treatment process. The microreactor will be constructed with an optically transparent pyrex window that will permit microscopic and spectroscopic monitoring of cellulose particles as they undergo decrystallization reactions. Specifically, we plan to use on-line Raman microscopy to follow decrystallization and sugar forming reactions that occur when cellulose is heated in the presence of acids. These data will be used to develop detailed engineering models that can be used to design and optimize large-scale pre-treatment reactors.Broader Significance and Importance:Results from this study will help decrease the costs of converting lignocellulosic biomass into fuels, chemicals, and materials. Cellulose is the world's most abundant carbon source. Hence, utilizing cellulose as a feedstock for production of fuels, chemicals, and materials will reduce reliance on petroleum, a non-renewable resource. Utilizing biomass cellulose is currently cost prohibitive, largely due to the expensive pre-treatment processes that are required to render cellulose into a form that can be converted into simple carbohydrates. Pre-treatment reactors are currently designed empirically and the data and engineering models developed in this project will contribute fundamental knowledge to reactor design and operation, thereby reducing their costs.Broadening Participation of Underpresented Groups in Engineering:Outreach is an integrated component of the proposed effort. The primary data product of the microreactor studies will be sets of vibrational frequencies that are characteristic of the degrading cellulose. With collaborators in the Humanities Department at WPI, we will convert the vibrational data into audible sounds, a process termed "sonification". Following this, we will develop an algorithm to re-modulate the vibrational "sounds" into a musical form. Given the anticipated structure of the vibrational data sets, we anticipate that it will naturally be converted most easily into repetitive, beat-driven, forms of music, such as hip-hop or techno. The outreach component will recruit graduate and undergraduate students to participate in the microreactor research, develop the hip-hop outreach tool, and to serve as mentors and role models as part of the K-12 outreach. Local faculty from underrepresented groups will be invited to give talks to the outreach students, providing an additional mentorship and role-model forum.This research has been funded through the Broadening Participation Research Initiation Grants in Engineering solicitation, which is part of the Broadening Participation in Engineering Program of the Engineering Education and Centers Division.