Browsing by Author "Labatut, Rodrigo A."

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    A PRACTICAL APPROACH FOR ESTIMATING INFLUENT-EFFLUENT MASS FLOW DIFFERENCES IN DAIRY MANURE-BASED ANAEROBIC CO-DIGESTION SYSTEMS
    (2022) Labatut, Rodrigo A.; Morris, James W.; Gooch, Curt A.
    During co-digestion of dairy manure and off-farm organic waste in farm anaerobic co-digestion (AcoD) systems, the process's conversion of biodegradable organics to biogas reduces the volumetric mass (or mass-volume) of the effluent discharged compared to the mass-volume fed. In this study, we present three methods for estimating the mass-flow difference between influent and effluent due to conversion to biogas based on widely accepted, rigorously applied, biological and engineering principles. Monthly operating data from three full-scale AcoD systems, operated under different conditions for a full year were used to compare results using the three calculation methods. Results revealed that the predictions of influent mass flow loss obtained using a simplified input-based method primarily based on influent volumetric flow rates and biodegradability data were in good agreement with those obtained using more accurate, real-time data, namely methane concentration and biogas production. For AcoD systems adding off-site wastes at around 30% or less of the total influent volatile solids (VS), the estimated reduction in effluent flow was in the range of 3% or less. In one case, for VS additions up to approximately 60% of the AcoD system's influent load, the reduction was 12%. Accepted fundamental water vapor relationships were also applied to biogas generation. Biogas water vapor loses were estimated to comprise approximately 0.2% of the total biogas mass-volume typically produced. Since in most anaerobic digestion systems, biogas condensate water is returned to the influent, this insignificant amount may be ignored.
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    Design of a High-Rate Wastewater Treatment Process for Energy and Water Recovery at Biorefineries
    (2023) Li, Yalin; Kontos, George A.; Cabrera, Daniela V.; Avila, Nickolas M.; Parkinson, Thomas W.; Viswanathan, Mothi Bharath; Singh, Vijay; Altpeter, Fredy; Labatut, Rodrigo A.; Guest, Jeremy S.
    Industrial wastewaters rich in organic carbon have potential for value generation, but conventional, low-rate, anaerobic-aerobic wastewater treatment (WWT) processes often incur significant capital expenses and energy consumption. In this study, we leveraged experimental data for biorefinery-derived wastewaters to characterize the implications of transitioning from a conventional, low-rate process to a high-rate, multistage anaerobic process. We designed and simulated these WWT processes across seven first-and second-generation (1G/2G) biorefineries and evaluated the implications for biorefinery sustainability through techno-economic analysis (TEA) and life cycle assessment (LCA). Compared to the conventional design, the new process can substantially reduce capital costs and electricity usage. These improvements were particularly evident for 2G biorefineries, translating to 5%-13% lower minimum product selling prices (MPSPs) and 7%-135% lower 100-year global warming potentials (GWPs; the 135% reduction is due to the transition of one biorefinery from net emission [0.87 kg of CO2e center dot gal-1] to net sequestration [-0.31 kg of CO2e center dot gal-1]). Biorefineries could further reduce the MPSP through the renewable identification number (RIN) credits by upgrading and selling the biogas as renewable natural gas, but at the expense of increasing GWP. When normalized, the COD management cost ranged from $-56 to $465 per tonne of COD, indicating that wastewater could be a net source of revenue for some biorefineries.
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    Enhancing energy recovery of wastewater treatment plants through hydrothermal liquefaction
    (2023) Cabrera, Daniela V.; Barria, David A.; Camu, Esteban; Celis, Crispin; Tester, Jefferson W.; Labatut, Rodrigo A.
    Sewage sludge (SS) management constitutes both a challenge and an opportunity for the sustainability of wastewater treatment plants (WWTPs). Standalone anaerobic digestion (AD) stabilizes the biodegradable organics contained in SS but recovers only a fraction of the chemical energy stored therein and produces large amounts of un-stabilized sludge. Hydrothermal liquefaction (HTL) coupled with AD can enhance the treatment and energy recovery of SS. Standalone AD was compared against (1) an HTL-AD configuration, with SS as HTL input, and the generated aqueous product (AP) as AD input; and (2), an AD-HTL-AD configuration, with SS as AD input, the digestate as HTL input, and the generated AP as AD input. Both configurations decreased the SS' COD from 27.5 to 0.6 g L-1, while the overall energy recovered was increased up to 2.2-fold relative to conventional SS treatment using only AD. Under the HTL-AD configuration, biocrude yields were higher (i.e., 26.4 vs. 15.8) and the AP generated was more biodegradable (0.78 vs. 0.65), than those obtained under the AD-HTL-AD configuration. Monte Carlo uncertainty analyses confirmed that overall energy recoveries would follow the order AD-HTL-AD > HTL-AD > AD; with energy recoveries (95% confidence) between, 63.5-94.7%, 54.6-91.2%, and 33.2-71.1%, respectively. This study shows that, by implementing HTL as a standalone SS treatment, WWTPs can recover more energy than using AD alone. Furthermore, WWTPs with existing AD would recover additional energy through HTL of the generated digestate, significantly reducing the environmental impacts and costs of conventional solids management.
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    Granular sludge is a preferable inoculum for the biochemical methane potential assay for two complex substrates
    (2020) Posmanik, Roy; Kim, Andrew H.; Labatut, Rodrigo A.; Usack, Joseph G.; Angenent, Largus T.
    The biochemical methane potential (BMP) assay is a standard method for characterizing biomethane potential and anaerobic biodegradability organic waste streams. Therefore, the BMP protocol must be standardized to reliably compare these parameters for various substrates. Here, the effect of inoculum selection on biomethane potential was investigated through BMP tests using two different substrates and inocula obtained from four different anaerobic digesters. It was found that inocula in the form of granular sludge yielded overall higher biomethane potential and generally had faster kinetics than suspended biomass. Furthermore, acclimation of inocula to substrate appeared to have little effect on degradation rates, and co-inoculation (with both suspended and granular biomass) did not perform better than single inoculation (e.g., with suspended sludge alone). These results emphasize the role of granular sludge as an preferable inoculum for BMP assay.
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    Grease trap waste valorization through hydrothermal liquefaction and anaerobic digestion: a circular approach to dairy wastewater treatment
    (2024) Cabrera, Daniela V.; Adema-Yusta, Ingrid; Santibanez, Maria J.; Celis, Crispin; Tester, Jefferson W.; Labatut, Rodrigo A.
    Grease traps are commonly used in the dairy industry to separate fats from their generated wastewater. Due to its properties, grease trap waste (GTW) is predominantly incinerated or landfilled despite its high energy content. In this study, hydrothermal liquefaction (HTL) was used to convert dairy industry GTW into biocrude while the generated HTL-wastewater (AP) was subjected to anaerobic digestion (AD) to recover biomethane. To maximize organic carbon to biocrude conversion, and to minimize the use of freshwater, a fraction of the AP was recirculated in subsequent HTL reactions. AP recirculation increased biocrude yields (73 vs. 78 wt%) but decreased both the higher heating value (HHV) (38 vs. 37 MJ kg-1) and the fraction (72 vs. 64%) of lighter hydrocarbons. Continuous AD using an EGSB reactor proved to be an effective method to further reduce the COD of the AP from 6.5 g L-1 to 0.7 g L-1 and enhance the overall energy recovery of the GTW from 81% (HTL only) to 83.1% (HTL-AD). Integrating HTL with AD and recycling a fraction of the AP in the HTL process allows for efficient wastewater treatment and a recovery of up to 84.8% of the energy contained in the GTW.