진학프로석·박사 채용 접수 플랫폼

Scientific Context

Microalgae are emerging as one of the most promising renewable resources for producing biofuels, bioproducts, and CO2-mitigating biomass because of their rapid growth, high lipid content, and ability to valorize residual nutrients (Chisti, 2007; Wijffels & Barbosa, 2010). However, the challenge lies in reconciling high productivity with environmental sustainability and economic feasibility, especially when up-scaling from controlled laboratory photobioreactors (PBRs) to outdoor, low-energy systems.

While closed PBRS ensure rigorous control of environmental variables and high areal productivity, recent comparative studies indicate that open raceway ponds (ORPs) can offer superior energy efficiency, cost-effectiveness, and scalability for large-volume biomass generation under certain usage scenarios (Narala et al., 2016; Usman et al., 2024). Their low infrastructure and operational energy demands make them particularly attractive for decentralized or seasonal production, where access to solar light and local resource recycling outweigh precision control (Skifa et al., 2024). Life-cycle assessments confirm that energy use in closed PBRs-particularly from pumping, lighting, and cooling-represents the main environmental hotspot (Gurreri et al., 2024), whereas outdoor raceways relying on sunlight can achieve carbon footprints one to two orders of magnitude lower for comparable dry biomass outputs.

Low-tech yet integrated cultivation chains enhance this advantage further when coupled with harvesting and water-reuse processes such as simple sand filtration. Slow or bio-sand filters can efficiently remove suspended solids and organic residues, allowing partial nutrient recovery and safe reuse of culture media at minimal energy cost (Esen, 1991; Liu et al., 2019). Reusing cultivation water significantly reduces freshwater and nutrient inputs without necessarily compromising algal growth, positioning filtration-based recycling as a key enabler of sustainable large-scale microalgae systems (Lu et al., 2020). The harvesting constitutes another bottleneck for large scale developments. Significant challenges originate from the small cell size and low biomass concentration (0.5-5.0 g/L) of microalgae suspension in cultivation medium (T. Mathimani 2018). Traditional methods such as centrifugation, flocculation-flotation or filtration suffer from large energy demands, long processing time or use of chemicals. New sustainable methods need to be implemented.

Such circular system designs, combining low-energy open ponds and low-impact water treatment, present a viable alternative to intensive PBRs in specific scenarios-for example, seasonal outdoor operations, co-location with wastewater or flue gas sources, or regions prioritizing low capital and energy inputs over year-round consistency. Exploring this trade-off between process intensity and circular efficiency is central to the research objectives of this postdoctoral project.

Scientific Challenges and Objectives

The main scientific bottlenecks to address include:

• Achieving optimal balance between growth rate and lipid accumulation under nutrient stress.
• Scaling up laboratory findings from controlled photobioreactors to outdoor semiindustrial raceways while ensuring productivity stability.
• Modeling hydrodynamics and energy-efficient mixing regimes in large-scale open ponds.
• Developing and testing water, gas, and nutrient recycling strategies integrated with downstream processing.
• Quantifying the impact of culture parameters on HTL biocrude yield and quality.

Main Tasks and Responsibilities

The postdoctoral researcher will:

• Conduct experimental optimization of culture parameters (light, nutrient composition) in bench-top photobioreactors and outdoor raceway ponds.
• Evaluate the use of new sources of nutrients including NaHCO3 as an alternative inorganic carbon source to replace CO2 gas streams.
• Apply nitrogen stress and other stressing strategies to maximize lipid production without compromising overall productivity.
• Develop hydrodynamic models to improve mixing efficiency and energy use in open ponds.
• Perform biochemical analyses (lipid, protein, carbohydrate quantification) and monitor growth kinetics.
• Assess the influence of seasonal variations (light, temperature) on productivity and robustness of cultures.
• Coordinate with consortium partners to correlate cultivation conditions with upstreams processes
• Evaluate mass and energy balances, nutrient cycles, and LCA-relevant data for sustainability assessments.
• Design and test optimization strategies for biomass harvesting and process water reuse, including filtration and nutrient recovery.
• Assist the project PI and participate to the project management (meeting and reporting)

Chisti, Y. (2007). Biodiesel from microalgae. Biotechnology Advances, 25(3), 294–306. DOI: 10.1016/j.biotechadv.2007.02.001

Wijffels, R.H., & Barbosa, M.J. (2010). An outlook on microalgal biofuels. Science, 329(5993), 796- 799. DOI: 10.1126/science.1189003

Narala, R.R. et al. (2016). Comparison of microalgae cultivation in photobioreactor, open raceway pond, and hybrid systems. Frontiers in Energy Research, 4, 29. DOI: 10.3389/fenrg.2016.00029

Gurreri, L. et al. (2024). Life Cycle Assessment Based on Primary Data of an Industrial-Scale Microalgae Plant. Chemical Engineering Transactions, 109, 499-506.

Lu, Z. et al. (2020). Water reuse for sustainable microalgae cultivation. Bioresource Technology, 315, 123914. DOI: 10.1016/j.biortech.2020.123914

Esen, I.I. (1991). Algae removal by sand filtration and reuse of filter material. Water Research, 25(7), 885-890. DOI: 10.1016/0043-1354(91)90298-J

Liu, L. et al. (2019). Applying bio-slow sand filtration for sustainable water treatment. Polish Journal of Environmental Studies, 28(4), 2673-2683. DOI: 10.15244/pjoes/89544

Usman, H.M. et al. (2024). A Comparative Analysis Assessing Growth Dynamics of Raceway and Photobioreactor Systems. Bioresource Technology Reports, 28, 101367. DOI: 10.1016/j.biteb.2024.101367

Skifa, I. et al. (2024). Microalgae cultivation in raceway ponds: advances, challenges, and future trends. Algal Research, 78, 103157. DOI: 10.1016/j.algal.2024.103157

Mathimani, Mallick, (2018) A comprehensive review on harvesting of microalgae for biodiesel - Key challenges and future directions, Renewable and Sustainable Energy Reviews, 91,1103. doi.0.1016/j.rser.2018.04.083.