Advancing Pilot-Scale Integrated Systems for Algal Carbon Capture and Biofuel Production

Biological CO2 capture and utilization with algae has the potential to mitigate major environmental problems associated with greenhouse gas emissions and excess wastewater nutrient discharges, and at the same time, generate a valuable biomass product that can be used for biofuels and/or animal feed. However, there are important practical limitations in currently available systems and technology that have limited pilot demonstration and applications for this technology. This project addressed critical challenges to practical demonstrations of biological CO2 capture systems and subsequent thermochemical conversion of biomass to biofuels. First, the capability to harvest and store actual power plant flue gas samples in pressurized cylinders was developed, and these samples were then used to study acclimation in algae cultivation systems dosed with flue gas. Second, this project demonstrated the use of anaerobic digestion to recover residual energy from the aqueous byproduct of hydrothermal liquefaction (HTLaq), which is generated during the conversion of algae or other organic feedstocks to biofuels. Algae cultivation experiments showed that a mixed culture of algae is capable of using CO2 from power plant flue gas without a negative impact on the algal growth rate. In fact, the algal biomass productivity was up to 67% higher with flue gas injection than that from control cultures. The CO2 removal efficiency was between 18 to 25%, and there is room for further improvement. A heavy metal analysis of algal biomass cultivated with flue gas inputs showed that algae can overaccumulate certain heavy metals (Zn, Pb, and Cu) that could limit its use for some animal feed products. Further study is needed to identify the factors controlling heavy metal uptake and develop mitigation strategies. In the second part of this study, we demonstrated anaerobic treatment of HTLaq combined with sewage sludge from municipal wastewater treatment at both the lab and full-scale operations. The lab-scale experiments showed that compared to a control digester with sewage sludge only, 18% more biogas was produced when HTLaq was dosed at 12% of the total organic loading to the digester. This dosing level is substantially higher than reported in other literature. The higher dosing level was accomplished via gradual acclimation of the anaerobic cultures to increasing amounts of HTLaq. Full-scale testing was conducted in the anaerobic digesters at a local wastewater treatment plant, which was dosed with up to 0.4% of the organic loading from HTLaq. This experiment was limited by the amount of HTLaq available, but showed successful anaerobic digestion without any evidence of inhibition or negative impacts on biogas production. Future work should investigate higher loading rates of HTLaq at both the lab and full-scale operations to further enhance bioenergy production. A techno-economic analysis performed showed that bioenergy production at a typical wastewater plant could be increased by up to 70% by integrating HTL conversion of sewage sludge upstream of anaerobic digestion. The total annualized cost for this combination was also lower than anaerobic digestion alone for a greenfield land application.Illinois Sustainable Technology Center Sponsored Research Program ; HWR18-252Ope

Characterizing the Effects of Thermochemical Bioenergy Production Processes on Emerging Contaminants and Wastewater Reuse Potential

The primary objective of this research was to improve our understanding of the water quality effects of thermochemical bioenergy production processes that can be applied to wet organic-laden wastes, such as animal manures, municipal wastewater, and food processing wastes. In particular, we analyzed the impacts of a novel integrated process combining algal wastewater treatment with hydrothermal liquefaction (HTL) on the fate of emerging bioactive contaminants (e.g., pharmaceuticals, estrogenic compounds, antibiotic-resistance genes, etc.) and the potential for wastewater reuse. We hypothesized and then confirmed that the elevated temperature and pressure of an HTL process can effectively convert the bioactive organic compounds into bioenergy products or otherwise break them down to inactive forms. High performance liquid chromatography (HPLC) with a photodiode array (PDA) detector was used to quantify emerging contaminants (florfenicol, ceftiofur, and estrone) before and after HTL treatment showed the removal of tested bioactive compounds to below detection limits when HTL was operated at 250°C for 60 min or at 300°C for ≥ 15 min. Complete breakdown or inactivation of antibiotic-resistance genes in wastewaters by the HTL process was also obtained at all tested HTL conditions (250-300°C, 15-60 min reaction time). The presence of HTL feedstocks such as swine manure or Spirulina algae reduced the removal of bioactive compounds and plasmid DNA when HTL was operated at 250°C for a short retention time (15 min). However, this effect was minimal when HTL was operated at 250°C for 60 min or at 300°C for ≥ 15 min. Detailed analysis of the aqueous product of HTL, also called HTL wastewater (HTL-WW), showed the occurrence of hundreds of nitrogenous organic compounds (NOCs). Reference materials for nine of the most significant NOC peaks were obtained and used to positively identify and quantify their concentrations. The chronic cytotoxicity effects of these NOCs were evaluated using a Chinese hamster ovary (CHO) cell assay, and found that the rank order for chronic cytotoxicity of these NOCs was 3-dimethylaminophenol > 2,2,6,6-tetramethyl-4-piperidinone > 2,6-dimethyl-3-pyridinol > 2-picoline > pyridine > 1-methyl-2-pyrrolidinone > σ-valerolactam > 2-pyrrolidinone > ε-caprolactam. However, none of the individual NOC compounds exhibited cytotoxicity at concentrations found in HTL-WW. In contrast, the complete mixture of organics extracted from HTL-WW showed significant cytotoxicity, with our results indicating that only 7.5% of HTL-WW would induce a 50% reduction in CHO cell density. Further testing showed three out of eight tested NOCs could cause 50% inhibition of algal growth at their detected concentration in HTL-WW. In addition, we found that treatment of HTL-WW with a batch-fed algal bioreactor could effectively remove more than 99% of NOCs after seven days of operation and 40% of the CHO chronic toxicity. We also found that over 90% of the CHO toxicity could be eliminated by filtering with granular activated carbon (GAC) after algal bioreactor treatment. These post-treatments of HTL-WW synergistically integrate with HTL bioenergy production because both the GAC and the algal biomass from the bioreactor can potentially be fed back into HTL to generate additional biocrude oil, which facilitates beneficial reuse of the nutrient content of HTL-WW. All in all, this novel treatment approach offers significant advantages for reducing the potential toxicity risks associated with byproducts of HTL bioenergy production and for improving wastewater effluent quality for subsequent water reuse applications.Illinois Sustainable Technology Center Sponsored Research Program ; Grant No. HWR12226Ope

Improving bioenergy recovery from municipal wastewater with a novel cloth-filter anaerobic membrane bioreactor

Anaerobic membrane bioreactors (AnMBR) have been used for treating high-strength industrial wastewater at full-scale and the potential to use them for mainstream municipal wastewater treatment presents an important opportunity to turn energy-intensive plants into net-energy producers. However, several limitations of the AnMBR technology have prevented their adoption in the municipal wastewater industry, namely, high membrane cleaning energy demand and low membrane flux. This study demonstrated a novel AnMBR configuration that uses a commercially available cloth filter technology to address the key limitations of cleaning energy and membrane flux. The cloth filter anaerobic membrane bioreactor (CFAnMBR) is comprised of an anaerobic fixed-film bioreactor coupled with a cloth filter membrane with nominal pore size of 5 µm. The pilot CFAnMBR was operated for 150 days through the winter at a municipal wastewater plant in central Illinois (minimum/average influent temperature 5/13°C). The CFAnMBR increased membrane flux by more than 2 orders of magnitude (3,649 ± 1,246 L per meter squared per hour) and reduced cleaning energy demand by 78%—92% (0.0085 kWh/m3) relative to previously reported AnMBR configurations. With the CFAnMBR, average chemical oxygen demand and total suspended solids removal were 66% and 91%, respectively, and were shown to be increased up to 88% and 96% by in-line coagulant dosing with ferric chloride. Average headspace methane yield was 154 mL CH4/g CODremoved by the end of the study period with influent temperatures of 11°C± 4°C. The CFAnMBR resolves major limitations of AnMBR technology by employing a commercially-available technology already used for other municipal wastewater treatment applications

Fate and Transport of Manure Estrogenic Compounds During Integrated Treatment for Water Quality and Bioenergy Production

An integrated manure treatment system, including a mixed algal-bacterial bioreactor (MABB) and hydrothermal conversion of biosolids to biofuels, was found to remove 76-97% of the total estrogenic hormones from the liquid portion of animal manure. The resulting biosolids mixture could be hydrothermally converted into either biocrude oil with a yield of up to 40% yield, or syngas with a yield of up to 54%. Adding biologically activated carbon in the MABB enhanced the removal of estrogenic hormones (+7.2%), cytotoxicity (+58%), and heavy metals (+10%). Thus, the novel manure treatment system proposed in this study highlights a new paradigm that can simultaneously reduce the release of emerging contaminants from animal manure to the environment and provide value-added bioenergy co-products to help offset the cost of providing environmental benefits.Ope

Improving the Economic Viability of Biological Utilization of Coal Power Plant CO2 by Improved Algae Productivity and Integration with Wastewater

The Illinois Sustainable Technology Center (ISTC) at the University of Illinois, in partnership with Helios-NRG, will further develop a novel algae-based technology for efficient cost-effective capture and utilization of carbon dioxide (CO2) from coal-fired power plant flue gas to generate algal biomass products for which there is a large market (liquid transportation fuels and livestock animal feeds). The team will first produce selected algae strains in a cultivation environment infused with simulated flue gas and concentrated wastewater nutrient liquids at bench-scale and then transition to pilot-scale using a proprietary multi-stage bioreactor to achieve an average biomass productivity of 35 grams per square meter per day, and carbon capture above 70 percent. Nutrient input costs will be reduced by integrating algae cultivation with wastewater treatment operations, providing an extra revenue stream for wastewater nutrient removal, and potentially providing a low-cost method of transporting flue gas through the sewer system. Two novel membrane separation processes will be tested that can significantly reduce the cost and energy needed for dewatering algal biomass and concentrating the aqueous byproduct of hydrothermal conversion of algal biomass to biofuels. A techno-economic analysis and a life-cycle analysis will also be performed. This novel algae-based technology provides significant improvements in the cost and environmental impact of utilizing CO2 from coal-fired power plants by providing an economically viable method to grow algae biomass suitable for large-volume, value-added commodity markets. Related projects Improving the Cost-Effectiveness of Algal CO2 Utilization by Synergistic Integration with Power Plant and Wastewater Treatment Operations [DE-FE0032098]U.S. Department of Energy ; DE-FE0030822Openhttps://netl.doe.gov/project-information?p=FE003082

Development of a Multi-Component Competitive Adsorption Model for GAC Systems and Application to Improve Hybrid Sorption -Membrane Processes

109 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006.Granular activated carbon (GAC) adsorption is an important water treatment technique, but accurate, long-term prediction of trace compound adsorption has been elusive because of difficulties accounting for the competitive effects of heterogeneous natural organic matter (NOM). NOM exerts several significant competitive effects in GAC columns that can vary temporally and spatially. This study develops a 3-component GAC model, COMPSORB-GAC, that quantitatively describes trace compound adsorption in the presence of NOM with greater accuracy and elegance than previously possible. The model separately tracks adsorption of the trace compound and two fictive NOM fractions- a strongly competing and a pore blocking fraction. To accurately describe GAC column adsorption, three competitive effects were needed: direct competition for sites, intraparticle pore blockage, and external surface pore blockage. COMPSORB-GAC is the first model to incorporate these three competitive effects as explicit functions of NOM surface concentration. COMPSORB-GAC uses a moving-grid, finite-difference formulation of the governing equations that makes it possible for the first time to reflect spatial variations in adsorption parameters and to directly simulate counter-current, moving-bed reactors. A parameterization procedure consisting of independent, short-term tests with fresh and batch preloaded adsorbent was demonstrated and used to validate the modeling approach experimentally. Possible simplifications of the parameterization procedure are also presented to reduce the experimental and data fitting requirements. COMPSORB-GAC modeling showed that moving-bed GAC adsorbers can reduce carbon usage rates (CURs) for atrazine removal from a local groundwater by 45-55% in comparison to conventional fixed-bed adsorbers. The model was also used to evaluate the novel Upflow Adsorption-Ultrafiltration (UA-UF) process developed during this study to improve the performance and treatment capabilities of hybrid sorption-membrane processes. UA-UF consists of an upflow bed of granular adsorption media situated adjacent to a low-pressure membrane system. The downstream membrane allows the adsorbent to operate in a counter-current mode that increases adsorption efficiency. Concurrently, the upstream adsorbent bed provides pretreatment that improves membrane hydraulic performance. COMPSORB-GAC showed that UA-UF can reduce the CURs of current hybrid processes by more than 90%. Other advantages include small space requirements, less sludge, and the ability to regenerate and reuse the adsorbent.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD