475052 Renewable Transportation Biofuel Production from Wet Biowaste

Sunday, November 13, 2016
Continental 4 & 5 (Hilton San Francisco Union Square)
Wan-Ting Chen, Agricultural & Biological Engineering, University of Illinois, Urbana, IL

Research Interests:
  • Summary

Increasing wet organic waste production has become an unavoidable issue in the US. Although often considered as environmental pollutants, these wet organic feedstocks contain large amounts of unharnessed energy and nutrients. My research aims to recover the energy and nutrients from the wet organic waste with appropriate waste remediation systems. Hydrothermal treatments, including catalytic hydrothermal gasification (CHG) and hydrothermal liquefaction (HTL), is a new energy efficient thermochemical process that can generate high-energy content biogas/biocrude and simultaneously reduce total organic carbon in wastewater. In contrast, anaerobic digestion (AD) is a widely utilized biochemical process that similarly produces renewable biogas. Application of different catalysts and adsorbents in each scenario can increase energy yields and nutrient recovery. Running both systems in parallel on identical wet organic wastes can compare energy returns and pollutant reduction through techno-economic analysis. In addition, effluent waters from each process containing high concentrations of nitrogen and phosphorous, amongst other dilute nutrients, can be further recycled as a desirable substrate for production of crops (e.g. algal biomass or crops grown in hydroponic systems). Secondary algal treatment of wastewaters from CHG/HTL and AD will clean water for environmental discharge meeting EPA standards and also generate renewable resources for further application. Simultaneously, using isotopes with representative model compounds in CHG/HTL process can further elucidate the reaction kinetics, network, and mechanism in this biomass conversion system. Successful completion of these objectives will provide clearer understanding of how advanced thermochemical and biochemical waste remediation technologies can alleviate the food-water-energy nexus.

  • Rationale:

Wet biowastes have been an increasing interest to researchers for the potentials to produce bioenergy, reuse nutrients and improve the environment. Each year, the United States produces 79 million dry tons of wet biowastes including food-processing waste and livestock manure (DOE, 2011; FAO, 2016; USDA, 2010). These wet biowaste exceeds the ‘Impactful tonnage’ (>50million ton per year) as a bioenergy feedstock according to DOE, and containing nutrients (N&P) that can substitute about 1.5 million tons of reactive nitrogen as fertilizers. Carbon, nitrogen and phosphorous, along with other minerals contained in wet biowastes are often discharged to environment as pollutants because they cannot be efficiently recovered and utilized. Based on data provided by USDA (USDA, 2011), it is estimated that as much as 45% of nitrogen and 70% of phosphorous could be recycled from such agricultural waste streams. One of the main reasons this energy and nutrients are not effectively harvested is the large water content (20-98%), which greatly reduces the number of bioenergy conversion technologies that can have a net positive energy balance. On the other hand, energy content approximately over 10 quads, equal to all current US renewable energy production, could be recovered for beneficial reuse with appropriate technologies or systems. Moreover, the growth of the global population has placed an ever-increasing stress on food, energy, and water (UN, 2015). Advancing knowledge/technologies that foster more efficient, safe, and secure use of resource within the food-energy-water nexus remains a significant challenge (NSF, 2016).

  •  Research Topics

My research enthusiasm was influenced by my past and present research which encompasses thermochemical conversion processes, biofuel production, biowaste treatment, biomass pretreatment, value-added chemical extraction, techno-economic analysis of the nutrient and bioenergy recovery processes, and reaction network under supercritical fluid. 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 waste and what are the most relevant factors affecting the biomass conversion process? (2) How to control and fine tune the biomass conversion processes more precisely to obtain more valuable products? (3) How do we combine new technologies with multiple scale (e.g. from laboratory to pilot to demonstration scale) of investigation to demonstrate an affordable system, minimize greenhouse gas emission, maximize the recovered energy, and identified research gaps to strengthen a robust food-energy-water nexus? To answer these questions, my research closely couples innovative thermochemical, biological, environmental, and computational approaches to provide an integrated perspective to establish a solid energy-water-food nexus.

  1. How to energetically harness available energy and nutrients from wet organic waste?

Catalytic hydrothermal gasification (CHG) is an emerging new technology alternative for wet biowaste conversions with much faster reaction times (minutes), high conversion efficiencies (>90%), and a cost trajectory that is projected to be competitive with current 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 data available from the current literature highlights several potential practical concerns (e.g. catalysts fouling issues) that need to be addressed before large investments in the technology are justified. Anaerobic digestion (AD) is traditionally a dominant conversion technology used for wet 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 system. By optimizing the conditions of sludge loading rate, operating temperatures (30-55ºC), the dosage of adsorbents, and the types of adsorbents, the yields of hydrogen and methane (hythane) and 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 (e.g., pH) and pathways by dividing the fermentation process into hydrolysis, acidogensis, and methanogensis separately (Massanet-Nicolau et al., 2013; Schievano et al., 2014). According to recent studies, CHG and AD can both substantially recover the carbon nutrients in swine manure, but not nitrogen and phosphate (Breinl & Zhang, 2015; Shin & Schideman, 2015; Tommaso et al., 2014). 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 (Möller & Müller, 2012; Polomski et al., 2009; Woertz et al., 2009). In addition, crops (e.g. lettuce and tomatoes) that can grow in the hydroponic system also have the potential to further assimilate the residual nutrients in the CHG and AD effluents. Therefore, a hydroponic farming system is proposed in my research program to simultaneously uptakes the nutrients and remediates the wastewaters coming from AD and CHG. In this case, research efforts on hydroponic cropping development and algal biotechnology for concentrated agricultural wastewater treatment can be advanced to satisfy growing need in the food-water-energy nexus, while the potential of these concentrated agricultural effluents as nutrient sources for aquatic biomass grown in hydroponic systems can be realized. In short, my research program aims to investigate the efficacy of using AD and CHG to harness the chemical energy stored in wet biowastes (e.g. animal manure and citrus processing waste containing value-added chemicals such as flavonoids). The ultimate goal of my research program is to demonstrate the feasibility of a novel concept for integrated bioenergy and biomass production, and wastewater reuse via parallel treatment of CHG and a two-stage AD of wet organic wastes.

2. How to control and fine tune the biomass conversion processes more precisely to obtain more valuable products? No full-scale applications of the hydrothermal treatment technology have been realized so far, because the data available from the current literature highlights several potential practical concerns that need to be addressed before large investments in the technology are justified.

(i) Catalysts development for effective CHG. Previous literature (Elliott, 2008; Stucki et al., 2009) has extensively focused on using noble or transitional metal catalysts such as Pt, Ru, and Ni for catalytic hydrothermal gasification. To make CHG a more affordable technology for the public, other economic catalysts such as activated carbons, zeolites, calcium carbonates derived from waste shells, and iron recovered from slag will be explored and their catalysts performance (e.g. yield of hydrogen) will be evaluated.

(ii) Catalyst activity under CHG. Fouling of catalyst is another issue under hydrothermal processes and will be investigated in my research program. The previous study (Ong, 2013) using CHG to catalyze waste newspaper shows that unless the catalysts can be regenerated and recycled, CHG can produce more net-energy and present a more efficient energy consumption ratio (ECR, defined as energy input divided by energy output) than anaerobic digestions of waste newspaper. Thereby, in my research program, the catalysts will be characterized before and after the reactions to understand the deactivation mechanisms (e.g. catalysts fouling or catalysts poison) 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 studied. Meanwhile, the life of the catalysts will be understood. Ultimately, methodologies to minimize the catalysts deactivation will be established through my research program.

(iii) Reaction Kinetics and Network for bioactive chemicals under CHG. Previous studies have demonstrated that CHG can effectively degrade bioactive chemicals, such as environment hormones (e.g. estrogens) and antibiotics (e.g. florfenicol), entrained in swine manure (Shin & Schideman, 2015). However, the reaction kinetics and reaction network of these bioactive chemicals remained unknown. Understanding the reaction kinetics and network for bioactive chemicals may help design the up-scaled CHG reactor in a more practical way and make CHG a more versatile tool for treating different types of bioactive chemicals (e.g. virus and pathogens). In order to achieve this goal, CHG of model bioactive compounds with heavy water (i.e., deuterium oxide) will be conducted at 150-400 °C for 0-2 hr. The CHG products obtained at different reaction time will be analyzed under GC/MS, NMR (1D and 2D), and FTIR essay to further elucidate the reaction pathways of wet biowaste. Sensitivity analysis will also be conducted to explore significant factors governing CHG processes.

3. How do we combine new technologies with multiple scale (e.g. from lab to pilot scale) of investigation to demonstrate an affordable system, minimize greenhouse gas emission, and maximize the recovered energy to strengthen the current food-energy-water nexus?

System analysis of the proposed parallel CHG and AD systems can help understand and identify research gaps to establish a roust food-energy-water nexus. For example, the necessity of reusing residual nutrients in the aqueous products (PHWW) obtained from hydrothermal liquefaction (HTL) processes has been identified through a multi-component mass balance. Conducting the mass balance, energy balance, and economic analyses of the integrated system using the STELLA® and SuperPro software can further elucidate and identify the revenue streams, quantification of cost functions, capital allocations, upstream suppliers, and downstream customers. Simultaneously, life cycle analysis (LCA) through quantitative and computational modeling will be utilized to optimize this system and significantly advance the understanding of the proposed food-energy-water nexus.

  • Indication and Expected Outcomes:

Successful results of this research program will lead to bridging gaps between biowaste management and energy/nutrient recovery. Modification of two-stage AD processes including fermentation concentration and operating temperatures will help optimize treatment efficiency and yield greater energy content in the form of methane and hydrogen, which is underdeveloped. More recently investigated thermochemical technologies like HTL and CHG show great promise to efficiently convert wet organic feedstocks into high-energy content products such as biocrude oil and biogas, and the combination of different catalysts and reaction parameters can improve overall energy recovery and at the same time lowering energy inputs. Comparison of improvement in two-stage AD and CHG systems will demonstrate the ability to remediate different types of wet biowaste. Once carbonaceous contents are recovered as biogas, the remaining nitrogen and phosphorous will be assimilated by aquatic biomass for more renewable feedstock and/or food production. The reuse of nutrient can amplify the biomass thus the bioenergy production. An overall techno-economic assessment will elucidate the sustainability of the proposed parallel CHG and AD systems.

Teaching Interests:

  • Summary

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 Transportation Phenomenon(ABE 341), I have designed weekly worksheets for students, conducted office hours, worked with students on their lab projects, and graded homework and worksheets. Moreover, I realized that effective communication is a key element to help students understand fundamental theories (e.g. fluid dynamics) and accomplish lab projects successfully. A smooth communication can inspire students’ potential and establish their confidence. For example, I always encouraged students to come to office hours and work on those difficult problems together. Textbook and homework are not something to beat them but tools to help them learn. Working as a team to solve problem sets usually can help them develop critical thinking skills and address problems more efficiently. For instance, one of my students learnt that units may help her check if the answer makes sense in a fluid dynamics problem. Additionally, I have served as a guest TA for several class projects (ABE 100, ABE 225, CEE 398 and TSM 431, please refer to my CV). 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 (please refer to my CV). 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 (e.g. classes provided for senior undergraduate students or graduate students), I will combine lectures, lab projects, field trips (e.g. visit a zero energy residence building, a bio-ethanol plant, or a pilot scale continuous reactor to generate biofuels/biogas), 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. For instance, when I wrote my practice proposal for Green Chemistry (CHEM 460) and Polymer Chemistry(CHEM 480), I read a lot of papers about biorefienries and reviewed different biomass conversion techniques. In the end, I gained deeper insights about renewable energy and value-added chemical production processes, which ultimately contribute to part of my PhD thesis. 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.


Breinl, J., Zhang, Y. 2015. Hydrothermal Gasification of HTL wastewater.

DOE. 2011. US billion-ton update: Biomass supply for a bioenergy and bioproducts industry. Oak Ridge National Laboratory (ORNL).

Elliott, D.C. 2008. Catalytic hydrothermal gasification of biomass. Biofuels, Bioproducts and Biorefining2(3), 254-265.

FAO. 2016. Database of Food and Agriculture Organization of the United Nations

Massanet-Nicolau, J., Dinsdale, R., Guwy, A., Shipley, G. 2013. Use of real time gas production data for more accurate comparison of continuous single-stage and two-stage fermentation. Bioresource technology129, 561-567.

Möller, K., Müller, T. 2012. Effects of anaerobic digestion on digestate nutrient availability and crop growth: A review. Engineering in Life Sciences12(3), 242-257.

NSF. 2016. Innovations at the Nexus of Food, Energy and Water Systems (INFEWS).

Ong, M. 2013. Evaluation of anaerobic membrane bioreactors and hydrothermal catalytic gasification for enhanced conversion of organic wastes to renewable fuels, University of Illinois at Urbana-Champaign.

Polomski, R.F., Taylor, M.D., Bielenberg, D.G., Bridges, W.C., Klaine, S.J., Whitwell, T. 2009. Nitrogen and phosphorus remediation by three floating aquatic macrophytes in greenhouse-based laboratory-scale subsurface constructed wetlands. Water, air, and soil pollution197(1-4), 223-232.

Schievano, A., Tenca, A., Lonati, S., Manzini, E., Adani, F. 2014. Can two-stage instead of one-stage anaerobic digestion really increase energy recovery from biomass? Applied Energy124, 335-342.

Shin, Y.H., Schideman, L. 2015. Characterizing the fate and transport of Chemicals of Emerging Concerns (CECs) from integrated bioenergy and manure management system. 2015 ASABE Annual International Meeting. American Society of Agricultural and Biological Engineers. pp. 1.

Stucki, S., Vogel, F., Ludwig, C., Haiduc, A.G., Brandenberger, M. 2009. Catalytic gasification of algae in supercritical water for biofuel production and carbon capture. Energy & Environmental Science2(5), 535-541.

Tommaso, G., Chen, W.-T., Li, P., Schideman, L., Zhang, Y. 2014. Chemical Characterization and Anaerobic Biodegradability of Hydrothermal Liquefaction Aqueous Products from Mixed-culture Wastewater Algae. Bioresource Technology.

UN. 2015. World Population Prospects: The 2015 Revision, Volume I: Comprehensive Tables. United Nations Publications.

USDA. 2010. Manure and Byproduct Utilization.

USDA. 2011. U.S. consumption of nitrogen, phosphate, and potash, (1960-2011).

Woertz, I., Feffer, A., Lundquist, T., Nelson, Y. 2009. Algae grown on dairy and municipal wastewater for simultaneous nutrient removal and lipid production for biofuel feedstock. Journal of Environmental Engineering.

Zhou, Y., Schideman, L., Yu, G., Zhang, Y. 2013. A synergistic combination of algal wastewater treatment and hydrothermal biofuel production maximized by nutrient and carbon recycling. Energy & Environmental Science6(12), 3765-3779.

Extended Abstract: File Uploaded