Peer-reviewed publications
For the most up-to-date list, please refer to my Google Scholar page.
2025
This study evaluated the economic and environmental performance of converting food waste into bio-based asphalt binders and coproducts via hydrothermal liquefaction (HTL). Two deployment configurations were considered, including centralized HTL (c-HTL) and decentralized HTL (d-HTL) with upgrading processes to produce biobinders and biofuel additives. Five HTL aqueous phase (AP) management strategies were considered incorporating electrochemical (EC, EC H2, EC Future), disposal to centralized facilities (No EC), and fungal treatment. Techno-economic analysis (TEA) and life cycle assessment (LCA) showed that with an optimal feedstock, a highly cost-competitive biobinder could be produced with net negative emissions in the No EC scenario. On the other hand, current EC-based systems had high MSPs and GWPs due to the large capital and electricity requirements. Sensitivity analysis identified internal rate of return, electricity price, and electrode cost as key cost drivers, which was used in subsequent analyses, where the EC Future scenario demonstrated the potential to close economic and environmental performance gaps with expected technological and infrastructure improvements. Additional analyses on biocrude yield confirmed its significant impacts on system performance, and plant size analysis revealed that based on size, >140 U.S. cities could support cost-competitive biobinder and biofuel production with high-yield food waste alone.
Ahmad, A.; Kawale, H. D.; Summers, S.; Bogarin Cantero, B. C.; Allen, C. M.; Hajj, R.; Davidson, P. C.; Zhang, Y.; Li, Y. Accepted, Chemical Engineering Journal, 2025.
Microalgae-based tertiary wastewater treatment has the potential to meet stringent effluent phosphorus limits, with the added benefit of producing a marketable feedstock. However, the lack of validated mechanistic models and their implementation in process simulators have limited the adoption of this technology. In this study, an updated lumped pathway metabolic model was developed to predict effluent phosphorus concentration and biomass yield in response to dynamic influent and varying environmental conditions. The model was implemented in QSDsan and calibrated and validated using batch experimental data and 45 days of continuous online monitoring data from a full-scale microalgae-based tertiary wastewater treatment plant. Overall, the QSDsan-based microalgae process simulator was able to predict effluent phosphorus within 0.02–0.04 mg-P/L, while also capturing the general trends of state variables according to nutrient availability.
Kim, G.-Y.; Molitor, H.; Zhang, X.; Li, Y.; Shoener, B.; Schramm, S.; Morgenroth, E.; Snowling, S.; Hartnett, E.; Bradley, I.; Pinto, A.; Guest, J. Accepted, npj Clean Water, 2025.
33. An Agile Benchmarking Framework for Wastewater Resource Recovery Technologies
Water resource recovery facilities (WRRFs) face growing pressures to balance compliance, sustainability, and cost while adapting to evolving treatment needs. To support research, development, and deployment (RD&D) of innovative technological solutions, we developed an open-access benchmarking framework comprised of 18 plant-wide simulation models. Implemented in QSDsan, the framework is validated against GPS-XTM simulations while capturing distinct system behaviors, treatment performance, energy demand, and operational costs across diverse designs. It offers a rigorous and transparent foundation for comparative technology evaluations, guiding RD&D decision-making and advancing sustainable water management.
Zhang, X.; Rai, S.; Wang, Z.; Li, Y.; Guest, J. Accepted, npj Clean Water, 2025.
32. Sustainable Triacetic Acid Lactone Production from Sugarcane by Fermentation and Crystallization
Triacetic acid lactone (TAL) has the potential to serve as a bioderived platform chemical for commercial products including sorbic acid and recyclable polydiketoenamine plastics. In this study, we leveraged BioSTEAM to design, simulate, and evaluate (via techno-economic analysis, TEA, and life cycle assessment, LCA) TAL production from sugarcane. We experimentally characterized TAL solubility, calibrated solubility models, and designed a process to separate TAL from fermentation broths by crystallization. Our analyses suggested that the biorefinery could produce TAL as the intermediate for financially viable, low-CI production of sorbic acid and polydiketoenamines. This research highlights the ability of agile TEA-LCA to screen promising designs, navigate sustainability trade-offs, prioritize research needs, and chart quantitative roadmaps to advance bioproducts and biofuels.
Bhagwat, S. S.; Dell’Anna, M. N.; Li, Y.; Cao, M.; Brace, E. C.; Bhagwat, S. S.; Huber, G. W.; Zhao, H.; Guest, J. S. ACS Sustainable Chem. Eng. 2025, 13 (42), 17794–17805.
31. Recovery of Nutrients from the Aqueous Phase of Hydrothermal Liquefaction—A Review
Hydrothermal liquefaction (HTL) is a thermochemical conversion process that converts wet biomass into biocrude oil, a gas phase, a solid phase, and an aqueous phase (HTL-AP). An obstacle to the development and scaling of HTL is the volume of HTL-AP produced during the process, which has high concentrations of nitrogen and carbon and cannot be disposed of in the environment without treatment. The HTL-AP is enriched with organic compounds, particularly light polar organics and nitrogenous compounds, which are inhibitory to microbial treatment in wastewater treatment plants. This review synthesizes published findings on different types of treatment of the HTL-AP for the recovery of valuable nutrients and the removal of toxic compounds. The literature highlights the importance of increasing nitrogen bioavailability in HTL-AP through two-step treatments and by selecting HTL-AP derived from protein-rich feedstocks, which offer higher initial nitrogen content. Further work is needed to optimize chemical and biological treatments for nutrient recovery from HTL-AP, particularly regarding treatment scale and duration. Additionally, economic analyses across different treatment types are currently lacking, but are essential to evaluate their feasibility and practicality.
Bogarin Cantero, B. C.; Li, Y.; Kalita, P.; Zhang, Y.; Davidson, P. Recovery of nutrients from the aqueous phase of hydrothermal liquefaction – A Review. Water 2025, 17 (14), 2099.
Lack of access to sanitation is a challenge that persists globally, with low sewerage connection rates in many low- and lower-middle-income countries. Engineered nonsewered sanitation (NSS) technologies can meet treatment requirements without sewers, but their relative sustainability varies across potential deployment sites. Here, we characterize the costs and carbon intensity (CI) of three emerging NSS technologies, two community reinvented toilets (CRTs) and one Omni Processor (OP), across 77 countries, identify sustainability performance typologies, and map typology prevalence in countries across the globe. Locality-specific factors such as wages, diet, and material costs drive regional variability in NSS costs by up to 15-fold and CI up to 2-fold within technologies. Across all three NSS technologies and all scenarios evaluated, low-cost, low-CI typologies are predominantly in countries with lower human development indices (HDI 2–4), demonstrating alignment between the sanitation need and the NSS opportunity space. By elucidating key sustainability drivers and defining typologies, this work can support early-stage decision-making for NSS technology research, development, and deployment.
Lohman, H. A. C.; Li, Y.; Zhang, X.; Morgan, V. L.; Watabe, S.; Rowles, L. S.; Cusick, R. D.; Guest, J. S. Environ. Sci. Technol. 2025, 59 (29), 15101–15114.
Low carbon fuel policies such as the U.S. Renewable Fuel Standard (RFS), Canada Clean Fuel Regulations (CFR), and California Low Carbon Fuel Standard (LCFS) as well as the 45Z tax credit are intended to reduce greenhouse gas (GHG) emissions from transportation. Rigid carbon intensity (CI) accounting procedures in current policies may limit CI responsiveness across candidate sites and processing facilities. This work examines a hypothetical biomass-to-sustainable aviation fuel (SAF) pathway using miscanthus and alcohol-to-jet biorefineries. Results demonstrate that GHG accounting using the CFR/LCFS can reasonably account for distinct levels of net electricity production by a biorefinery, but only the CFR yields similar CI sensitivity to spatially explicit factors in scenario-specific analysis, and most GHG accounting frameworks do not capture CI variation across candidate sites in the United States. Ultimately, this work demonstrates the importance of life cycle assessment (LCA) methodological specifications in low carbon fuel policies and tax credits.
Stewart, D.; Guo, W.; Li, Y.; Fan, X.; Coppess, J.; Khanna, M.; Guest, J. ACS Sustainable Resour. Manage. 2025, 2 (7), 1185–1194.
2024
Oilcane—an oil-accumulating crop engineered from sugarcane—and microbial oil have the potential to improve renewable oil production and help meet the expected demand for bioderived oleochemicals and fuels. To assess the potential synergies of processing both plant and microbial oils, the economic and environmental implications of integrating microbial oil production at oilcane and sugarcane biorefineries were characterized.
Cortés-Peña, Y. R.; Woodruff, W.; Banerjee, S.; Li, Y.; Singh, V.; Rao, C. V.; Guest, J. S. GCB Bioenergy 2024, 16 (11), e13183.
Point-of-use (POU) water disinfection technologies can be adopted to provide access to safe drinking water by treating water at the household level; however, navigating various POU disinfection technologies can be difficult. This research assessed the sustainability of four different POU technologies (chlorination using sodium hypochlorite, a silver-nanoparticle-enabled ceramic water filter, ultraviolet mercury lamps, and ultraviolet light-emitting diodes). Leveraging open-source Python packages (QSDsan and EXPOsan), the cost and environmental impacts of these POU technologies were assessed using techno-economic analysis and life cycle assessment. All technologies were further evaluated across ranges of adoption times, and contextual analysis was performed to evaluate the implications of technology deployment across the world.
Elijah, B. C.; Ahmad, A.; Li, Y.; Plazas-Tuttle, J.; Rowles, L. S. ACS Environ. Au 2024, 4 (5), 248–259.
Mixed community microalgal wastewater treatment technologies have the potential to advance the limits of technology for biological nutrient recovery while producing a renewable carbon feedstock, but a deeper understanding of their performance is required for system optimization and control. In this study, we characterized the performance of a 568 m3·day–1 Clearas EcoRecover system for tertiary phosphorus removal (and recovery as biomass) at an operating water resource recovery facility (WRRF).
Molitor, H. R.; Kim, G.-Y.; Hartnett, E.; Gincley, B.; Alam, M. M.; Feng, J.; Avila, N. M.; Fisher, A.; Hodaei, M.; Li, Y.; McGraw, K.; Cusick, R. D.; Bradley, I. M.; Pinto, A. J.; Guest, J. S. Environ. Sci. Technol. 2024, 58 (20), 8803–8814.
25. Characterizing the Opportunity Space for Sustainable Hydrothermal Valorization of Wet Organic Wastes
Resource recovery from wet organic wastes can support circular economies by creating financial incentives to produce renewable energy and return nutrients to agriculture. In this study, we characterize the potential for hydrothermal liquefaction (HTL)-based resource recovery systems to advance the economic and environmental sustainability of wastewater sludge, FOG (fats, oils, and grease), food waste, green waste, and animal manure management through the production of liquid biofuels (naphtha, diesel), fertilizers (struvite, ammonium sulfate), and power (heat, electricity). Overall, our work demonstrates the potential of HTL-based resource recovery systems to reduce the costs and carbon intensity of resource-rich organic wastes.
Feng, J.; Li, Y.; Strathmann, T. J.; Guest, J. S. Environ. Sci. Technol. 2024, 58 (5), 2528–2541.
2023
Catalytic hydrothermal processing is a promising technology for the production of biofuels used in transportation to alleviate the energy crisis. An important challenge for these processes is the need for an external supply of hydrogen gas to accelerate the deoxygenation of fatty acids or lipids. This study reports on the use of various alcohol and carboxylic acid amendments as sources for in situ hydrogen production to accelerate Ru/C-catalyzed hydrothermal deoxygenation of stearic acid. Addition of these amendments significantly increases yields of liquid hydrocarbon products, including the major product heptadecane, from stearic acid conversion at subcritical conditions (330 °C, 14–16 MPa during the reaction). This research provided guidance for simplifying the catalytic hydrothermal process of biofuel production, making the production of the desired biofuel in one pot possible without the need for an external H2 supply.
Wang, J.; Yao, X.; Li, Y.; Zhang, J.; Zhao, C.; Strathmann, T. J. ACS Omega 2023, 8 (22), 19969–19975.
Achieving safely managed sanitation and resource recovery in areas that are rural, geographically challenged, or experiencing rapidly increasing population density may not be feasible with centralized facilities due to space requirements, site-specific concerns, and high costs of sewer installation. Nonsewered sanitation (NSS) systems have the potential to provide safely managed sanitation and achieve strict wastewater treatment standards. One such NSS treatment technology is the NEWgenerator, which includes an anaerobic membrane bioreactor (AnMBR), nutrient recovery via ion exchange, and electrochlorination. The system has been shown to achieve robust treatment of real waste for over 100 users, but the technology’s relative life cycle sustainability remains unclear. This study characterizes the financial viability and life cycle environmental impacts of NEWgenerator and prioritizes opportunities to advance system sustainability through targeted improvements and deployment.
Watabe, S.; Lohman, H. A. C.; Li, Y.; Morgan, V. L.; Rowles, L. S.; Stephen, T.; Shyu, H.-Y.; Bair, R. A.; Castro, C. J.; Cusick, R. D.; Yeh, D. H.; Guest, J. S. ACS Environ. Au 2023, 3 (4), 209–222.
In resource-limited settings, conventional sanitation systems often fail to meet their goals – with system failures stemming from a mismatch among community needs, constraints, and deployed technologies. This work introduces a multi-criteria decision analysis framework and the open-source tool DMsan for the sustainability analyses of sanitation and resource recovery technologies.
Lohman, H. A. C.; Morgan, V. L.; Li, Y.; Zhang, X.; Rowles, L. S.; Cook, S. M.; Guest, J. S. ACS Environ. Au 2023, 3 (3), 179–192.
21. Design of a High-Rate Wastewater Treatment Process for Energy and Water Recovery at Biorefineries
This work introduces a high-rate, multistage anaerobic wastewater treatment process that has the potential to substantially improve the economic and environmental sustainability of biorefineries.
Li, Y.; Kontos, G. A.; Cabrera, D. V.; Avila, N. M.; Parkinson, T. W.; Viswanathan, M. B.; Singh, V.; Altpeter, F.; Labatut, R. A.; Guest, J. S. ACS Sustainable Chem. Eng. 2023, 11 (9), 3861–3872.
This study evaluates the influence of U.S. state-level tax incentives and economic parameters on cellulosic and conventional biofuel production costs.
Stewart, D. W.; Cortés-Peña, Y. R.; Li, Y.; Stillwell, A. S.; Khanna, M.; Guest, J. S. Environ. Sci. Technol. 2023, 57 (6), 2262–2271.
An engineered Saccharomyces cerevisiae capable of producing 2,3-butanediol (2,3-BDO) from glucose without accumulating ethanol and glycerol was constructed in this work. Techno-economic analysis (TEA) and life cycle assessment (LCA) of the production of methyl ethyl ketone (MEK) through catalytic dehydration of 2,3-BDO was performed and demonstrated the feasibility of cost-competitive and sustainable bio-based MEK production via yeast fermentation. Further, the fermentation broth containing 2,3-BDO was also tested in Arabidopsis thaliana for its potential to be used as a biostimulant, proving the broth could induce drought tolerance without a complicated purification process.
Lee, J. W.; Bhagwat, S. S.; Kuanyshev, N.; Cho, Y. B.; Sun, L.; Lee, Y.-G.; Cortés-Peña, Y. R.; Li, Y.; Rao, C. V.; Guest, J. S.; Jin, Y.-S. Chem. Eng. J. 2023, 451, 138886.
2022
Research, development, and deployment (RD&D) of innovative technologies are often impeded by the lack of transparent, systematic, and agile approaches to prioritize investment across the expansive landscape of technologies and design/operational decisions. This tutorial review synthesizes research on sustainability analyses to present Quantitative Sustainable Design (QSD) – a structured methodology to expedite the RD&D of water, sanitation, and resource recovery technologies.
Li, Y.; T. Trimmer, J.; Hand, S.; Zhang, X.; G. Chambers, K.; C. Lohman, H. A.; Shi, R.; M. Byrne, D.; M. Cook, S.; S. Guest, J. Environ. Sci.: Water Res. Technol. 2022, 8 (11), 2439-2465.
In this study, the metal–organic framework (MOF) was applied as a precursor template to synthesize Co3O4 nanoparticles with a carbon matrix shell (M-Co3O4). The effects of catalyst dosage, methanol dosage, water dosage, temperature, and reaction time on catalytic efficiency were examined with stearic acid as the model reactant. Under the designed condition, M-Co3O4 exhibited high catalytic performance and the catalyst showed higher conversion of stearic acid (98.7%) and selectivity toward C8–C18 alkanes (92.2%) in comparison with Pt/C (95.8% conversion and 93.2% selectivity toward C8–C18). The catalysts were also characterized by a series of characterization techniques including electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption isotherms (Brunauer–Emmett–Teller (BET) method), and thermogravimetric analysis (TGA). Finally, we proposed that decarbonization (deCO) could be the presumably mechanistic pathway for the production of C8–C18 alkanes from the decomposition of stearic acid.
Zeng, D.; Li, Y.; Xia, T.; Cui, F.; Zhang, J. ACS Omega 2022, 7 (37), 33482–33490.
16. Financial Viability and Environmental Sustainability of Fecal Sludge Treatment with Omni Processors
In this study, QSDsan was used to characterize the financial viability and environmental implications of fecal sludge treatment via pyrolysis-based omni processor technology (biogenic refinery) treating mixed and source-separated human excreta and to elucidate the key drivers of system sustainability.
Rowles, L. S.; Morgan, V. L.; Li, Y.; Zhang, X.; Watabe, S.; Stephen, T.; Lohman, H. A. C.; DeSouza, D.; Hallowell, J.; Cusick, R. D.; Guest, J. S. ACS Environ. Au 2022, 2 (5), 455–466.
Robust and agile tools are needed to support the research, development, and deployment (RD&D) of sanitation and resource recovery technologies. This work introduces QSDsan – an open-source Python tool that integrates system design, simulation, and sustainability characterization (techno-economic analysis and life cycle assessment) to quickly identify critical barriers, prioritize research opportunities, and navigate multi-dimensional sustainability tradeoffs for technology RD&D.
Li, Y.; Zhang, X.; Morgan, V. L.; Lohman, H. A. C.; Rowles, L. S.; Mittal, S.; Kogler, A.; Cusick, R. D.; Tarpeh, W. A.; Guest, J. S. Environ. Sci.: Water Res. Technol. 2022, 8 (10), 2289–2303.
2021
14. Sustainable Production of Acrylic Acid via 3-Hydroxypropionic Acid from Lignocellulosic Biomass
Sustainable design of lignocellulosic 3-hydroxypropionic acid biorefineries producing acrylic acid, with agile techno-economic analysis and life cycle assessment under uncertainty.
Bhagwat, S. S.; Li, Y.; Cortés-Peña, Y. R.; Brace, E. C.; Martin, T. A.; Zhao, H.; Guest, J. S. ACS Sustainable Chem. Eng. 2021, 9 (49), 16659–16669.
Deoxygenation of fatty acids to diesel-like hydrocarbons over Metal–Organic Framework (MOF)-derived metal oxides.
Zeng, D.; Li, Y.; Ma, H.; Cui, F.; Zhang, J. ACS Sustainable Chem. Eng. 2021, 9 (46), 15612–15622.
12. Vapor-Phase Catalytic Conversion of Aqueous 3-Hydroxybutyric Acid and Crotonic Acid to Propylene
Vapor-phase dehydration and decarboxylation of polyhydroxybutyrate-derived monomer acids (3-hydroxybutyric acid and crotonic acid) to propylene over solid acid catalysts using a packed-bed continuous-flow reactor for dilute waste carbon valorization.
Leow, S.; Koehler, A. J.; Cronmiller, L. E.; Huo, X.; Lahti, G. D.; Li, Y.; Hafenstine, G. R.; Vardon, D. R.; Strathmann, T. J. Catal. Sci. Technol. 2021, 11 (20), 6866–6876.
Solids residence time can be leveraged as a selective pressure to tailor mixed phototrophic communities for wastewater nutrient removal and biofuel production.
Bradley, I. M.; Li, Y.; Guest, J. S. Environ. Sci. Technol. 2021, 55 (18), 12574–12584.
10. Catalytic Hydrothermal Deoxygenation of Lipids and Fatty Acids to Diesel-like Hydrocarbons: A Review
This reviews summarizes the reactions, catalysts, and influencing factors in the hydrothermal deoxygenation of lipids and fatty acids to diesel-like hydrocarbons.
Yao, X.; Strathmann, T. J.; Li, Y.; Cronmiller, L. E.; Ma, H.; Zhang, J. Green Chem. 2021, 23 (3), 1114–1129.
9. Sustainable Lactic Acid Production from Lignocellulosic Biomass
Sustainable design of lignocellulosic biorefineries for lactic acid production with agile techno-economic analysis and life cycle assessment under uncertainty.
Li, Y.; Bhagwat, S. S.; Cortés-Peña, Y. R.; Ki, D.; Rao, C. V.; Jin, Y.-S.; Guest, J. S. ACS Sustainable Chem. Eng. 2021, 9 (3), 1341–1351.
2020
This study shows that PFAS sorbed to sludge degrade to varying degrees when sludge is subjected to hydrothermal liquefaction for production of liquid fuel.
Yu, J.; Nickerson, A.; Li, Y.; Fang, Y.; Strathmann, T. J. Environ. Sci.: Water Res. Technol. 2020, 6 (5), 1388–1399.
2019
Investigation of reaction mechanism and development of a kinetic network model for hydrothermal conversion of polyhydroxybutyrate (PHB) for wastewater valorization.
Li, Y.; Strathmann, T. J. Green Chem. 2019, 21 (20), 5586–5597.
6. Catalytic Hydrothermal Decarboxylation and Cracking of Fatty Acids and Lipids over Ru/C
Low-cost Ru catalysts can be applied to produce a mixture of alkanes, matching properties of existing petroleum diesel or jet fuel.
Zhang, J.; Huo, X.; Li, Y.; Strathmann, T. J. ACS Sustainable Chem. Eng. 2019, 7 (17), 14400–14410.
Evaluation of the treatment efficacy and economic performance of an algal wastewater treatment and valorization system across different seasons.
Li, Y.; Slouka, S. A.; Henkanatte-Gedera, S. M.; Nirmalakhandan, N.; Strathmann, T. J. Environ. Sci.: Water Res. Technol. 2019, 5 (9), 1545–1557.
4. Demonstration and Evaluation of Hybrid Microalgae Aqueous Conversion Systems for Biofuel Production
Experiments and model predictions show increased algal biofuel yields at lower prices via proposed hybrid conversion systems.
Li, Y.; Leow, S.; Dong, T.; Nagle, N. J.; Knoshaug, E. P.; Laurens, L. M. L.; Pienkos, P. T.; Guest, J. S.; Strathmann, T. J. ACS Sustainable Chem. Eng. 2019, 7 (6), 5835-5844.
2018
3. A Unified Modeling Framework to Advance Biofuel Production from Microalgae
Integrating biological cultivation model with thermochemical/biological unit process models to increase modeling fidelity, provide mechanistic links among unit operations, and quantify minimum selling prices of algal biofuels via techno-economic analysis.
Leow, S.; Shoener, B. D.; Li, Y.; DeBellis, J. L.; Markham, J.; Davis, R.; Laurens, L. M. L.; Pienkos, P. T.; Cook, S. M.; Strathmann, T. J.; Guest, J. S. Environ. Sci. Technol. 2018, 52 (22), 13591-13599.
Design, demonstration, and economic anlaysis of an aqueous-based system for the conversion of wastewater-derived algae and upgrading of crude products.
Li, Y.; Tarpeh, W. A.; Nelson, K. L.; Strathmann, T. J. Environ. Sci. Technol. 2018, 52 (21), 12717-12727.
2017
1. Quantitative Multiphase Model for Hydrothermal Liquefaction of Algal Biomass
A multiphase component additivity (MCA) model to quantitatively predict both yields and characteristics of products from hydrothermal liquefaction of microalgae.
Li, Y.; Leow, S.; C. Fedders, A.; K. Sharma, B.; S. Guest, J.; J. Strathmann, T. Green Chem. 2017, 19 (4), 1163-1174.
Public Media
Li., Y. The Conversation, 2019.