Real-Time Sensor Data Profile-Based Deep Learning Method Applied to Open Raceway Pond Microalgal Productivity Prediction
Not Available
54 ENVIRONMENTAL SCIENCES↗
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Site-specific factors override local climatic conditions in determining microalgae productivity in open raceway ponds
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60 APPLIED LIFE SCIENCES↗
Application of passive vortex generators to enhance vertical mixing in an open raceway pond
A novel use of vortex generators in a raceway pond is described here, with the flow field quantitatively simulated using computational fluid dynamics using the large eddy simulation turbulence model. Persistence lengths of the swirling motion generated by the vortex generators indicate that significant vertical mixing can be achieved by placing vortex generators in the straight section opposite the paddle wheel, downstream of the first hairpin bend. Relatively simple vortex generators are capable of creating stronger swirling motions that persist for a longer distance than those created by the paddle wheel. For optimal performance, vortex generators are positioned side by side but in opposite directions, and their diameters should be equal to or slightly less than the desired liquid depth. The optimal length of a 0.18 m diameter vortex generator in a 0.2 m deep pond was determined to be 0.3 m. As a result, it has been demonstrated that a longer persistence length is achieved by inducing a swirling motion with its rotational axis parallel to the primary flow direction.
09 BIOMASS FUELS↗
Integration of CO 2 capture and microalgae cultivation: demonstration assessment of outdoor Scenedesmus acutus cultivation using gaseous ammonia as a nitrogen source
Towards the goal of integrating CO 2 capture using aqueous ammonia with its utilization for algae cultivation, Scenedesmus acutus (UTEX B72) was grown in 1100 L open raceway ponds using CO 2 and NH 3 supplied from gas cylinders. CO 2 /NH 3 mole ratios of 7 and 10 were employed, the gas mixture acting as a surrogate for the output from a CO 2 scrubbing system using aqueous ammonia. Compared to Scenedesmus acutus grown in open ponds using gaseous CO 2 and NaNO 3 as the N-source, the ponds supplied with gaseous CO 2 and NH 3 displayed higher productivity at both CO 2 /NH 3 ratios, with the higher ratio providing the best growth. Depending on the culturing conditions and CO 2 /NH 3 ratio, CO 2 utilization ranged up to 15.8% and NH 3 utilization to 23.0%. These rather low values reflect the fact the high CO 2 /NH 3 feed rate used, resulting in a substantial release of NH 3 from the ORPs (~45%). Finally, these findings demonstrate the suitability of gaseous NH 3 as a N-source for microalgae cultivation, while highlighting the need for a control strategy that closely balances the CO 2 /NH 3 supply with the algae growth rate. The produced algae biomass possessed a high protein and low ash content, rendering it particularly suitable for use as a bioplastic feedstock.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Microalgae Hydrothermal Liquefaction and Biocrude Upgrading: 2022 State of Technology
A preliminary techno-economic analysis (TEA) was developed for the fiscal year (FY) 2022 state of technology (SOT) assessment to evaluate the benefits and risks of using demonstrated, high-productivity algae strains for fuels generation, including sustainable aviation fuel (SAF). In 2022, the marine algal strain, Picochlorum celeri, which demonstrated the highest outdoor biomass productivities reported to date in the DOE-funded open-pond raceway testbed at the Arizona Center for Algae Technology and Innovation (AzCATI), was tested for continuous hydrothermal liquefaction (HTL) processing at PNNL. HTL testing results demonstrated a biocrude yield of 0.33 g/g algae on an ash-free dry weight (AFDW) basis from P. celeri. The hydrotreatment testing of the HTL biocrude from P. celeri was also conducted to investigate the production of jet fuel from marine algal biomass. To the best of our knowledge, this is the first report of jet fuel production from autotrophically grown marine algal biomass. The current hydrotreating testing demonstrated approximately 22.7 wt% of the hydrotreated oil within the typical boiling-point range of jet fuel (150–250 °C). Initial testing of the jet fuel cut (JFC) showed that the physical properties under investigation were within typical ranges for petroleum-based jet fuels. The experimental work of this study closes the gap between outdoor algae cultivation and algae conversion to critical transportation fuels using the same algae strain for both cultivation and conversion testing. The continuous HTL and the upgrading testing described herein demonstrate the potential of producing sustainable aviation fuel (SAF) from algae cultivated in open-pond systems using the primary inputs of sunlight and carbon dioxide.
09 BIOMASS FUELS↗
Sustainable production of plastic-degrading enzymes in Chlamydomonas pacifica
AbstractThe discovery of a new extremophile alga,Chlamydomonas pacifica, provides an opportunity to expand on heterologous protein expression beyond the traditionalChlamydomonas reinhardtii. C. pacificais a unicellular extremophile capable of surviving at high pH, high temperatures, and high salinity. These various growth conditions allow C. pacifica to outcompete any invading contaminants in open-air environments. Developing this novel species as a platform for recombinant protein production could significantly advance commercial microalgal recombinant protein production. We have previously shown thatC. reinhardtiican secrete a plastic-degrading enzyme: a PETase known as PHL7. This PETase is capable of cleaving ester bonds and has been used commercially for the degradation of PET plastics. However, the expression of such an enzyme has yet to be done in open raceway ponds and on a large scale. Here, we describe the culturing of PHL7 transgenic C. pacifica strain in three 80L raceway ponds and the measurements of recombinant enzymatic expression and activity found in the culture media. Our work provides proof of concept that this new organism can produce functional PHL7 enzymes in addition to producing the valuable components that inherently exist in theC. pacificaalgae biomass.Graphical Abstract
Diaz, Crisandra Jade (ORCID:0000000173429041)↗
Gene Expression in Dunaliella tertiolecta +/- Iron
Dunaliella tertiolecta is an extremophilic, green alga from the Chlorophyte lineage. It is found in coastal marine environments around the world. D. tertiolecta can tolerate extremes of heat, light, pH, and salinity. D. tertiolecta is under development for the production biofuels and other bioproducts because it can produce large quantities of neutral lipids, and it can be grown in open raceway ponds using only the inputs of seawater and sunlight. This isolate of D. tertiolecta (UTEX LB 999) was found in Oslofjord, Norway in 1938. This accession includes an RNA-Seq analysis of D. tertiolecta cultures grown in iron-replete (1.5 µM) or iron-deficient (0 µM) media.
54 ENVIRONMENTAL SCIENCES↗
Improving the Cost-Effectiveness of Algal CO2 Utilization by Synergistic Integration With Power Plant and Wastewater Treatment Operations
Creating an economic demand for carbon utilization products will require lowering the overall cost of the products to compete within the current market. Photosynthetic uptake of carbon dioxide is an emerging pathway for product development in the animal feed market that globally amounts to over 400 Billion USD and is expected to continue growing. This project aims to continue the development of a process that utilizes carbon dioxide while increasing the cost competitiveness of algae as an animal feed product. The overall goal of the project is to demonstrate an engineering-scale open raceway pond algae cultivation system (180 m2) including integration of technologies that utilize coal-fired power plant CO2 and wastewater nutrient inputs. The system is designed to maximize the cost-effectiveness and environmental benefits of algal biomass production for commodity animal feed.
20 FOSSIL-FUELED POWER PLANTS↗
Ammonium Looping with Membrane Absorber and Distributed Stripper for Enhanced Algae Growth
The objective of this project is to conduct a comprehensive investigation to develop and demonstrate a practical, reliable, and cost-effective integrated carbon dioxide (CO 2 ) capture and biofixation process for algae production. This process utilizes a chemical hindered ammonium solution (NH 4 OH) as both a capture reagent and an algae nutrient. The membrane absorber employed in the system ensured minimal ammonia (NH 3 ) emissions in the treated flue gas. Additionally, distributed solar-energy powered strippers located near the bioreactor modules facilitate solvent regeneration and enable just-in-time delivery of CO 2 and NH 3 to the algae, thereby minimizing the pH swing for enhanced productivity. The proposed membrane CO 2 absorber and solar-powered stripper is designed and seamlessly integrated with the existing 0.1 MWth bench-scale CO 2 capture system (CCS) and open raceway ponds (ORPs) at the University of Kentucky Center for Applied Energy (UK CAER) campus. The entire integrated process has undergone construction, operation, testing, and analysis. Furthermore, technology has been evaluated with a techno-economic analysis (TEA), technology gap analysis (TGA), life-cycle analysis (LCA), and a technology maturation plan (TMP). This project was performed within two budget periods, 54 months in duration. There are fourteen Project Tasks, twelve Milestones and four Success Criteria.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Final Report for FE0032098: Improving the cost-effectiveness of algal CO2 utilization by synergistic integration with power plant and wastewater treatment operations
The overall goal of this project was to demonstrate an engineering-scale open raceway pond algae cultivation system (approximately 180 m²), including the integration of technologies that utilized carbon dioxide (CO₂) from a coal-fired power plant and wastewater-derived nutrient inputs for cost-effective and environmentally friendly biomass production. The key advantages associated with the innovative algae cultivation system and its integration with wastewater treatment functions, as described herein, had been demonstrated in previous bench- and pilot-scale work by the project team partners. This project combined those approaches to maximize practical benefits and available synergies, resulting in a significant reduction in the net cost of producing algal biomass products. The primary target algal species for the project was Spirulina, which served as a high-protein content ingredient for food and animal feed. Spirulina was selected because it had already been approved by the FDA, was in use as a food ingredient, and commanded prices of up to $30/kg. It had a typical protein content of 50–75%, comparable to other high-protein concentrates, featured high digestibility without requiring pretreatment, and offered a high conversion ratio in animal feed applications. In addition, Spirulina had a relatively high content of the blue pigment phycocyanin, which could be extracted as a high-value co-product prior to using the remaining biomass for nutritional purposes.
Schideman, Lance [University of Illinois]↗
Autonomous monitoring of algal biomass: Success stories and lessons learned from long-term field deployment
Autonomous, high-frequency monitoring of outdoor algal ponds is needed to quantify biomass productivity and detect culture decline in environments prone to contamination, grazers, and variable operating conditions. We report successes and lessons learned in translating a laboratory spectroradiometric monitoring approach to a multi-year autonomous field deployment at the Arizona Center for Algae Technology and Innovation (AzCATI). The system measures spectrally resolved pond reflectance by ratioing upwelling radiance from each raceway to simultaneous downwelling sky irradiance using fiber-coupled spectrometers. A physics-based reflectance model (ASHARP) is fit to each spectrum pair to estimate optical parameters, including a biomass-proxy coefficient (C a ) which enables near-real-time tracking of biomass accumulation and culture state at 2–5 min intervals. From May 2022 through September 2025 the platform operated continuously while scaling from two to six raceway ponds. Several strains of algae were monitored successfully, including the high productivity Tetraselmis striata and Picochlorum celeri. Transitioning data acquisition from a Windows laptop to a Raspberry Pi improved uptime from 57% (2022) to ~89% (2024–2025) and enabled routine real-time analysis. Further, we converted relative biomass estimates to absolute ash-free dry weight (AFDW) using experimentally-derived calibrations, providing field-relevant biomass predictions with conservative confidence bounds. These results demonstrate the feasibility of long-term, autonomous optical monitoring for well-mixed open-raceway algal cultivation and provide practical guidance for reliable field operation and scaling.
Katinas, Christopher Michael [Sandia National Labo↗
A streamlined approach to characterize microalgae strains for biomass productivity under dynamic climate simulation conditions
Screening microalgae strains under static light and temperature flask conditions cannot directly quantify the biomass productivities of algae growing in the dynamically fluctuating light and temperature conditions of outdoor ponds. In this effort, we describe a testing pipeline that screens for productivity under climate simulated conditions. A validated, miniaturized Laboratory Environmental Algae Pond Simulator (mini-LEAPS) photobioreactor was used to determine optimal medium salinities and biomass productivities of cold-tolerant microalgae collected from Arctic, subarctic, Antarctic, and subalpine habitats. Strains characterized in this effort include: Chlorella antarctica UTEX1959, Chlorella sp. UTEXSNO69, Chloromonas rosae UTEXSNO11, Phaeodactylum tricornutum UTEX646, and Stichococcus minutus CCALA727. Observed productivities of the characterized strains ranged from 1.74 ± 0.25 to 8.18 ± 0.81 g m –2 day –1 (as ash-free dry weight). For each strain, a temperature tolerance profile was generated to identify the most appropriate season (s) for cultivation. The two most promising strains, Chlorella sp. UTEX SNO69 and P. tricornutum UTEX646, were tested alongside the DISCOVR winter benchmark strain Monoraphidium minutum 26B-AM in outdoor open ponds at the PNNL Algae Testbed (PAT) in Arizona. Further, under cold-season outdoor pond conditions, Chlorella sp. UTEXSNO69 achieved average areal biomass productivities of 8.21 ± 0.50 g m –2 day –1 , not significantly different from that of the benchmark strain (8.52 ± 0.43 g m –2 day –1 , p > 0.05). Under spring outdoor pond conditions, P. tricornutum UTEX646 achieved average areal biomass productivities 10.34 ± 0.27 g m –2 day –1 , not significantly different from that of the benchmark (10.07 ± 0.50 g m –2 day –1 ) under the tested conditions (p > 0.05). The streamlined pipeline was thus demonstrated to successfully characterize productive microalgae strains for outdoor deployment by weeding out algae strains that were not productive under the tested dynamic light and temperature conditions.
59 BASIC BIOLOGICAL SCIENCES↗