| Summary: |
PhotoBioValue aims to develop a novel technology for microalgal production and valorisation, increasing the flexibility for bioproducts synthesis under the biorefinery concept. Specific objectives are: (a) to develop and test a new and disruptive photobioreactor (PBR) design to optimise the biomass production - channel PBR; (b) to evaluate the effect of environmental stresses (light intensity and exposure, temperature and salinity) on the biochemical composition of microalgae; (c) to explore the potential of tubular PBRs with compound parabolic collectors (CPCs) to promote these stress conditions to microalgae; (d) to study a two-step cultivation system for both biomass production and valorisation; and (e) to perform a techno-economic analysis and evaluate the process sustainability.
Microalgae may play an essential role in the future of society concerning environmental protection, energy and food supply, and commodities production [1-3]. As photosynthetic microorganisms, they capture CO2 using solar energy, converting it into chemical energy with higher efficiency when compared with terrestrial plants. Microalgal biomass has several applications, and its composition depends on the cultivated species and production conditions. Like many other biological processes, the reactor is the crucial process unit, and the economic viability of microalgae production strongly depends on the system used. From the identified technical problems in outdoor production of microalgae, light supply is commonly the main limitation in open and closed PBRs [4-6]. Under outdoor environment, microalgal growth can be inhibited by the absence (photolimitation) or very high light intensity exposure (photoinhibition). Moreover, only a few PBR designs promote a uniform spatial distribution of light to the cells. The excess of solar radiation also promotes heat accumulation in the culture, raising its temperature. Without an effective temperature control system, this parameter can reach  |
Summary
PhotoBioValue aims to develop a novel technology for microalgal production and valorisation, increasing the flexibility for bioproducts synthesis under the biorefinery concept. Specific objectives are: (a) to develop and test a new and disruptive photobioreactor (PBR) design to optimise the biomass production - channel PBR; (b) to evaluate the effect of environmental stresses (light intensity and exposure, temperature and salinity) on the biochemical composition of microalgae; (c) to explore the potential of tubular PBRs with compound parabolic collectors (CPCs) to promote these stress conditions to microalgae; (d) to study a two-step cultivation system for both biomass production and valorisation; and (e) to perform a techno-economic analysis and evaluate the process sustainability.
Microalgae may play an essential role in the future of society concerning environmental protection, energy and food supply, and commodities production [1-3]. As photosynthetic microorganisms, they capture CO2 using solar energy, converting it into chemical energy with higher efficiency when compared with terrestrial plants. Microalgal biomass has several applications, and its composition depends on the cultivated species and production conditions. Like many other biological processes, the reactor is the crucial process unit, and the economic viability of microalgae production strongly depends on the system used. From the identified technical problems in outdoor production of microalgae, light supply is commonly the main limitation in open and closed PBRs [4-6]. Under outdoor environment, microalgal growth can be inhibited by the absence (photolimitation) or very high light intensity exposure (photoinhibition). Moreover, only a few PBR designs promote a uniform spatial distribution of light to the cells. The excess of solar radiation also promotes heat accumulation in the culture, raising its temperature. Without an effective temperature control system, this parameter can reach values that can damage the culture [5]. Regarding biomass valorisation, the understanding of microalgal response to environmental stresses (light intensity and exposure period, temperature and salinity) is vital to define process strategies to produce targeted bioproducts, taking advantage of the cell metabolism modification. Managing environmental stress can be an approach with a high potential for application in the context of microalgal biorefineries [7, 8].
An innovative channel PBR will be developed and tested for microalgal cultures to efficiently supply light to cells, considering its intensity and wavelength (increasing the energy conversion efficiency). The walls/baffles of this PBR will contain light-emitting diodes (LEDs), optimising the light supply. LEDs present low heat generation, avoiding the need for a temperature control system. Also, static spargers placed at the bottom of the channel will promote CO2 feed, pH control and culture mixing. All the energy required will be provided by photovoltaic (PV) solar panels that occupy the same area of the PBR. Considering the current efficiency of PV systems (>20%) and LEDs (60% for blue and 40% for red), this disruptive PBR design will achieve an energy conversion efficiency close to the theoretical value for solar to biomass (8-10%, while the current outdoor systems only reached 3% of conversion efficiency) [9, 10]. Also, this compact and scalable design presents a ratio of illuminated area to land area twelve times higher than flat panel PBRs (7.7 and 0.64), reducing land-use change [11], and enabling the achievement of higher areal biomass productivities (>60 g/m2/d is expected). With an optimised biomass production unit, the next step is its valorisation. The study of microalgal behaviour under environmental stresses will define the process parameters to modify cell metabolism to produce target compounds (carotenoids, lipids and proteins). The valorisation unit comprises a tubular PBR with CPCs that increases the light intensity reaching the culture and its temperature. This two-step cultivation is complemented with two oscillatory flow reactors (OFRs). These units have already shown high mass transfer between gaseous and liquid phases, being a promising technology to remove CO2 from the gaseous streams (increasing the efficiency of CO2 use by microalgae).
PhotoBioValue guarantees progress in the knowledge and innovation of PBR design for both biomass production and valorisation, allowing technological breakthroughs in the microalgal industry. Implementing the studied technologies at an industrial scale will improve the competitiveness of the companies associated with this project: AQUALGAE and Allmicroalgae. Also, it will contribute to the development of a commercial and sustainable production chain for microalgae-based commodity products, applying the biorefinery concept. This research project is aligned with the United Nations Sustainable Development Goals (SDG13 and SDG15). |