(7fz) Renewable Transportation Biofuel and Value-Added Chemical Production from Wet Biowaste

My research enthusiasm was influenced by my past and present research which encompasses biofuel conversion technologies, biowaste treatment, and systematical analysis of the nutrient and bioenergy recovery processes. Combining both laboratory and computational methods to link local processes to up-scaled system in our dynamic environment can help address the following questions:

(1) How to energetically harness available energy and nutrients from wet organic wastes?

Catalytic hydrothermal gasification (CHG) is an emerging technology for wet organic waste conversions with much faster reaction times (minutes), high conversion efficiencies (>90%), and a cost trajectory that is projected to be competitive with fossil fuels when the feedstock has a low or negative cost. However, there are no full-scale applications of this technology because commercial-scale equipment has not been developed, and the literature highlights several potential concerns (e.g.,

Anaerobic digestion (AD) is traditionally a dominant conversion technology used for wet organic wastes. In order to achieve a higher organic loading rate and energy recovery, a two-stage AD process is proposed in my research program and the results will be compared to those from a conventional AD. By optimizing the conditions of sludge loading rate, operating temperatures, and the types/dosage of adsorbents, the yields of hydrogen and methane as well as the energy recovery of the proposed two-stage AD system can be improved. Conventional AD process produces mainly methane, while two-stage AD can produce more hydrogen because it can better control the reaction environment and pathways by dividing the fermentation process into hydrolysis, acidogenesis, and methanogensis separately.

CHG and AD can both substantially recover the carbon nutrients in wet organic wastes, but not nitrogen and phosphate. On the other hand, aquatic biomass such as macrophytes and algae has been proven to have removal efficiencies of greater than 80% and 95% for nitrogen and phosphorous, respectively. In addition, crops that can grow in the hydroponic system also have the potential to further assimilate the residual nutrients in the CHG and AD effluents. Therefore, an algal treatment and/or a hydroponic farming system are proposed in my research program to simultaneously uptake the nutrients and remediate the wastewaters coming from AD and CHG. In this case, research efforts on algal biotechnology and hydroponic cropping development for concentrated wastewater treatment can be advanced to satisfy growing need in the FEW nexus, while the potential of these concentrated effluents as nutrient sources for aquatic biomass grown can be realized.

(2) How to selectively fine tune the biomass conversion processes to obtain valuable products?

No full-scale applications of the hydrothermal treatment technology have been realized so far, because the data available highlights several practical concerns that need to be resolved before large investments in the technology are justified.

(i) Catalysts development for effective CHG

Previous studies have extensively focused on using noble or transitional metal catalysts such as Pt and Ni for CHG. To make CHG a more affordable technology for the public, other economic catalysts such as activated carbons, zeolites, calcium carbonates and iron, will be explored and their catalysts performance will be evaluated. Further, synthesizing two catalysts with different functions would be explored for CHG reactions. Different synthesis methods (e.g.,

(ii) activity under CHG

Fouling of catalyst is another issue under hydrothermal processes and will be studied in my research program. One previous study using CHG to treat waste newspaper present that unless the catalysts can be reused and regenerated, CHG can produce more net-energy and show a more efficient energy consumption ratio than AD of waste newspaper. Thereby, a detailed physicochemical characterization of catalysts before/after CHG reactions would be valuable to provide information regarding catalyst deactivation mechanisms. In my research program, the catalysts will be characterized before and after the reactions to understand the deactivation mechanisms through SEM, TEM, TGA/DSC, XRD, and XRF analyses. Different regeneration methods for catalysts will be explored and the morphology of the regenerated catalysts will be investigated. Meanwhile, the lifespan of the catalysts will be understood. Ultimately, methodologies to minimize the catalysts deactivation will be established.

(iii) network for bioactive chemicals under CHG

Literature has demonstrated that CHG and HTL can effectively degrade bioactive chemicals, such as fatty acids, environment hormones and phenols, entrained in wet organic wastes. However, the reaction kinetics and network of these bioactive chemicals remained unknown. Understanding the reaction kinetics and network for bioactive chemicals would help design the up-scaled CHG reactor and make CHG a more versatile tool for treating different types of bioactive chemicals. In order to achieve this goal, I propose to conduct CHG with model bioactive compounds and isotopes. The products obtained at different reaction conditions will be analyzed by GC/MS, NMR, and FTIR assays to understand the reaction pathways of biowastes under CHG. Sensitivity analysis will also be conducted to explore significant factors governing CHG reactions.

(iv) Supercritical fluids (SCFs) applications to extract value-added products

The majority of recent research involving thermochemical conversion of biomass has been focused on fuels rather than on value-added products. However, analysis has shown that integrating co-products with biofuels offers a substantially higher return on investment while simultaneously meeting energy and economic goals. Supercritical fluids (SCFs) is a promising solvent for extracting value-added products from biomass, due to their relative lack of intrinsic hazard and robust tolerance of water content. For example, supercritical carbon dioxide (scCO₂) has been used to extract triacylglycerides (TAGs) from microalgae leading to a comparable yield as conventional extractions with organic solvents, but with the additional advantage of increased selectivity. Furthermore, solvation ability of SCFs can be tuned based on their density or by adding SCFs entrainers, such as ethanol, which have been shown to enhance solubility and increase yield of TAGs and value-added chemicals, such as astaxanthin (AX), from microalgae. As a consequence, I want to explore the possibility of using SCFs to develop viable and cost-effective process trains to selectively extract valuable products such as nutraceuticals from biomass, particularly from wet organic wastes.

(3) How do we combine new technologies with multiple scale of investigation to demonstrate an affordable system, minimize greenhouse gas emission, FEW nexus?

System analysis of the proposed biomass conversion systems can help understand and identify research gaps to establish a robust FEW nexus. For example, the necessity of reusing residual nutrients in the aqueous products (PHWW) obtained from hydrothermal treatment (HT) processes has been identified through a multi-component mass balance. Conducting the mass/energy balance and process design of the integrated system using the Aspen Plus^®, STELLA^®, SimaPro, and CHEMCAD software can elucidate and identify the techno-economic feasibility and life cycle loadings. A multi-objective optimization will also be carried out to create Pareto curves that aim to maximize the bioenergy production and minimize the environmental impact of the proposed FEW nexus.

In short, my research program aims to harness the chemical energy stored in wet organic biowastes. The ultimate goal of my research program is to demonstrate the feasibility of a novel concept for integrated bioenergy/value-added chemical production, biowaste treatment, as well as nutrient/water reuse via treatments of CHG, SCFs, and a two-stage AD of wet organic wastes.

Teaching Interests:

My teaching philosophy was molded by my education as an engineer. For me, education is significantly more than imparting knowledge found in textbooks. As an engineering student involved in a multidisciplinary research group, I had the opportunity to gain a great deal of know-hows by participating in different research activities. This experience also motivated and reinforced my teaching philosophy. I truly believe that by involving students with hands-on projects and real-world solid examples, learning new knowledge can be more effective while creative thinking and innovative solutions will be strongly encouraged. As Benjamin Franklin has said, "Tell me and I forget. Teach me and I remember. Involve me and I learn."

Teaching Philosophy

I am deeply committed to effective teaching and mentorship. I have been very fortunate to have had many positive and influential mentors during my education. This experience incentivizes and eagerly drives me to be a supportive and helpful mentor to my students. My objective when teaching and mentoring is to create a learning environment that simultaneously develops critical thinking skills and fosters an open mind to all possibilities by emphasizing the rich conceptual issues that defines sustainable energy science and engineering and how this discipline impacts our lives. By expanding not only the students’ scientific understanding of engineering problems but most especially how they apply it to the real world, we can critically review more available sustainable engineering practices and/or stewardship. Advantages and limitations of the established methods would be identified during this critical thinking process, and valid alternative state-of-the-art methods can then be developed. Ultimately, I hope my students can think “outside the box” and develop their confidence in proposing solution to existing and new problems.

Teaching experience

As I have served as a teaching assistant (TA) in the class of . As a mentor, I usually ask students some questions and give some solid examples to initiate their interest. Literature review and experimental design are generally required in class projects. Through lab projects, students can gain knowledge on bioenvironmental engineering design, particularly about biomass conversion and sustainable energy engineering, while I always benefit from the mentoring and discussion. Teaching and mentoring are not only a give-and-take process but also an interactive and mutual beneficial discussion with the mentored undergraduates at the same time.

Mentoring experience

By participating a multidisciplinary research programs in University of Illinois, joining the algae club in my home department, and involving with SWE (Society of Women Engineers) on campus, I was very fortunate to have ample opportunities to mentor or work with students from elementary school, high school, to different levels of undergraduate students. As providing technical training and helping them develop research topics, I always benefit from the mutual beneficial discussion. Students often inspire me from a different point of view and pay more attention to details than I do. This mutually beneficial discussion has been a cornerstone of my research career. For example, when I worked with my first undergraduate, sparked by her previous experience on centrifugation, we began to develop a more sustainable pretreatment technique, combining centrifugation and ultrasonic processes, for improved bioenergy conversion efficiency from algal biomass. Another instance is that I have further advanced my knowledge on gas-chromatography mass-spectrometry (GC-MS) by instructing several undergraduate and graduate students on using this equipment for analyzing biocrude oil and volatile aqueous products—mentoring itself is an intensive learning experience.

Teaching methods

When I served as a TA four years ago, I found it was drastically different between knowing the knowledge and transferring to others. For instance, demonstrating a practice example is likely more helpful to the novice than throwing a challenging problem at him/her, which may spoil a student’s interests and confidence. During my work with undergraduate students from different departments and culture background in University of Illinois, I realized that working on projects can significantly motivate students to learn a specific topic and inspire students’ potential as well as establish their confidence. Therefore, I will combine lecture and lab projects in my classes. For fundamental classes (e.g. transport phenomenon and heat and mass transfer), I plan to apply in-class discussion to one of the weekly lectures with a worksheet. I will also separate students into different groups and assign different groups of students to design the worksheet every week. This type of student-centered learning method can further help students think about why the lecturer/textbook asks questions like that way and why those questions matter. For advanced classes, I will combine lectures, lab projects, field trips, term-paper writing, and practice proposal writing together. When I took classes and served as a TA in University of Illinois, I found out lab projects usually can make students effectively learn hands-on skills and apply what they learnt in classes to real-world problems while field trips can greatly initiate students’ interest on a specific topic. In addition, term paper and practice proposal writing can help students synthesize their thoughts on specific topics and present their ideas in a professional way. Furthermore, I will conduct an early feedback, which will happen in the one third or half of the semester, in my classes so that I will have time to fine tune my teaching style or adjust course content during the semester. Overall, by using versatile teaching methods and techniques, I hope to give students a great incentive to learn different levels of courses and understand how they may change and impact the world.