Living microalgae-textile and cyanobacteria-loofah biocomposites for intensified carbon capture, utilisation and storage

PhD ThesisMicroalgae and cyanobacteria have been intensively studied as biological routes for carbon capture. Conventionally, they are cultivated in suspension within open ponds or enclosed photobioreactors (PBR); however, these systems suffer from many drawbacks including large land and water consumption, slow mass transfer rates, and high risk of contamination. This thesis presents a biocomposite culture system to overcome these disadvantages by immobilising cells onto solid supports (textiles and loofah sponge) using non-toxic hydrogel and latex-based binders. The performance of Chlorella vulgaris (a eukaryote microalga) textile-based hydrogel top coated biocomposites were tested in semi-batch CO2 absorption tests, resulting in enhanced CO2 capture. The highest CO2 absorption rate was 1.82 ± 0.10 g CO2 g-1 biomass d-1 from coated cotton biocomposites, followed by 1.55 ± 0.27 g CO2 g-1 biomass d-1 from uncoated cotton biocomposites. There was some degradation of the cotton, which could limit operational lifetime of the biocomposites. Loofah-based Synechococcus elongatus (prokaryote cyanobacterium) latex-based biocomposites had CO2 absorption rates of 0.68 ± 0.18 and 0.93 ± 0.30 g CO2 g-1 biomass d-1 for S. elongatus strain PCC 7942 (PCC) and CCAP 1479/1A (CCAP) respectively; however, cell outgrowth occurred midway through the trials. The formulations of synthetic latex binders were adjusted using different styrene/butyl acrylate blends and a coalescence agent (i.e. TexanolTM), increasing CO2 uptake rates by 14-20 and 3-8 fold for CCAP and PCC relative to their suspension controls. The CCAP biocomposites lasted in excess of 12 weeks whereas the PCC biocomposites experienced cell leaching after four weeks. A simplified techno-economic analysis was conducted, revealing that water and energy consumption were significantly reduced compared to raceway ponds, flat plate PBRs and biofilm-based PBRs

Engineered living photosynthetic biocomposites for intensified biological carbon capture

Carbon capture and storage is required to meet Paris Agreement targets. Photosynthesis is nature’s carbon capture technology. Drawing inspiration from lichen, we engineered 3D photosynthetic cyanobacterial biocomposites (i.e., lichen mimics) using acrylic latex polymers applied to loofah sponge. Biocomposites had CO2 uptake rates of 1.57 ± 0.08 g CO2 g−1biomass d−1. Uptake rates were based on the dry biomass at the start of the trial and incorporate the CO2 used to grow new biomass as well as that contained in storage compounds such as carbohydrates. These uptake rates represent 14–20-fold improvements over suspension controls, potentially scaling to capture 570 tCO2 t−1biomass yr−1, with an equivalent land consumption of 5.5–8.17 × 106 ha, delivering annualized CO2 removal of 8–12 GtCO2, compared with 0.4–1.2 × 109 ha for forestry-based bioenergy with carbon capture and storage. The biocomposites remained functional for 12 weeks without additional nutrient or water supplementation, whereupon experiments were terminated. Engineered and optimized cyanobacteria biocomposites have potential for sustainable scalable deployment as part of humanity’s multifaceted technological stand against climate change, offering enhanced CO2 removal with low water, nutrient, and land use penalties

Immobilising Microalgae and Cyanobacteria as Biocomposites: New Opportunities to Intensify Algae Biotechnology and Bioprocessing

There is a groundswell of interest in applying phototrophic microorganisms, specifically microalgae and cyanobacteria, for biotechnology and ecosystem service applications. However, there are inherent challenges associated with conventional routes to their deployment (using ponds, raceways and photobioreactors) which are synonymous with suspension cultivation techniques. Cultivation as biofilms partly ameliorates these issues; however, based on the principles of process intensification, by taking a step beyond biofilms and exploiting nature inspired artificial cell immobilisation, new opportunities become available, particularly for applications requiring extensive deployment periods (e.g., carbon capture and wastewater bioremediation). We explore the rationale for, and approaches to immobilised cultivation, in particular the application of latex-based polymer immobilisation as living biocomposites. We discuss how biocomposites can be optimised at the design stage based on mass transfer limitations. Finally, we predict that biocomposites will have a defining role in realising the deployment of metabolically engineered organisms for real world applications that may tip the balance of risk towards their environmental deployment

Triboelectric Nanogenerators Based on Immobilized Living Microalgae for Biomechanical Energy Harvesting

Triboelectric nanogenerators (TENGs) are gaining attention for energy supply because of higher demands in decentralized energy production. TENGs are known for being self-energy harvesters, converting wasted mechanical energy to useful electrical energy under an ambient environment. Advantages of TENGs include a clean energy supply, a wide range of materials selection, and an energy scavenging capability in the ambient environment. However, TENGs still suffer from their low electrical outputs compared to existing electrical supplies such as fuel cells and batteries. In bio-photovoltaic (BPV), there has been an interest in the use of microalgae, which are photosynthetic microorganisms capable of carbon capture and generating bioelectricity both day and night through electron transport chains via photosynthesis and cell respiration. To increase the current output of BPV, many have tried to immobilize living microalgal cells onto electrodes for higher mass transfers leading to higher photosynthetic rates. In this study, we have used immobilized living microalgae (Chlorella sp.) onto aluminium sheets to fabricate the TENG systems and investigate biomechanical energy harvesting. This proof of concept shows that this integration of microalgae with TENG can enhance the voltage and current output achieved by the dual operation modes of TENG. One issue raised during the tests was maintaining microalgae alive for several days, which has given opportunities for further studies in nutrient and light supplies to this innovative sustainable hybrid technology. The results confirm that the microalgae can be an excellent triboelectric layer in TENG for biomechanical energy harvesting. Graphical Abstract: [Figure not available: see fulltext.]. © 2023, The Author(s) under exclusive licence to The Korean Institute of Metals and Materials.FALS

Piezoelectric energy harvesting systems for biomedical applications

In the present era, self-powered technology and smart materials have paved the way for the design of numerous implantable energy harvesting and biomedical applications. Piezoelectric is a class of materials that could generate an electrical output on the application of strain or stress. Piezoelectric energy harvesters (PEHs) are capable of harvesting various types of ubiquitous mechanical energy into electricity, unlike several other technologies such as triboelectric and electromagnetic. The piezoelectric effect is an important component for the PEH to deliver the maximum electrical output, considering its superior properties such as high electromechanical coefficient, wide environment, and thermal stability. The wide variety of piezoelectric biomaterials and numerous device designs could directly boost performance and make them compatible with various operational environments. Motions from human movements and vital organs could be an effective medium for transforming mechanical vibrations into electrical energy through PEH. This review sheds light upon the use of PEH in biomedical and implantable energy harvesting devices. A detailed summary of various piezoelectric biomaterials, device designs, and possible applications such as health monitoring, cell stimulation, stimulation of the brain, and tissue engineering. The future challenges and the roadmap for sustainable development of PEH are also outlined. Overcoming the existing problems in PEHs can lead to their acting as an alternative power source for biomedical applications and future healthcare sensors. Further, this review highlights the recent developments in piezoelectric biomaterials and their potential in various biomedical applications. © 2022 Elsevier LtdFALS

A focused review on three-dimensional bioprinting technology for artificial organ fabrication

Three-dimensional (3D) bioprinting technology has attracted a great deal of interest because it can be easily adapted to many industries and research sectors, such as biomedical, manufacturing, education, and engineering. Specifically, 3D bioprinting has provided significant advances in the medical industry, since such technology has led to significant breakthroughs in the synthesis of biomaterials, cells, and accompanying elements to produce composite living tissues. 3D bioprinting technology could lead to the immense capability of replacing damaged or injured tissues or organs with newly dispensed cell biomaterials and functional tissues. Several types of bioprinting technology and different bio-inks can be used to replicate cells and generate supporting units as complex 3D living tissues. Bioprinting techniques have undergone great advancements in the field of regenerative medicine to provide 3D printed models for numerous artificial organs and transplantable tissues. This review paper aims to provide an overview of 3D-bioprinting technologies by elucidating the current advancements, recent progress, opportunities, and applications in this field. It highlights the most recent advancements in 3D-bioprinting technology, particularly in the area of artificial organ development and cancer research. Additionally, the paper speculates on the future progress in 3D-bioprinting as a versatile foundation for several biomedical applications

Synergistic Integration of Nanogenerators and Solar Cells: Advanced Hybrid Structures and Applications

The rapid growth of global energy consumption and the increasing demand for sustainable and renewable energy sources have urged vast research into harnessing energy from various sources. Among them, the most promising approaches are nanogenerators (NGs) and solar cells (SCs), which independently offer innovative solutions for energy harvesting. This review paper presents a comprehensive analysis of the integration of NGs and SCs, exploring advanced hybrid structures and their diverse applications. First, an overview of the principles and working mechanisms of NGs and SCs is provided for seamless hybrid integrations. Then, various design strategies are discussed, such as piezoelectric and triboelectric NGs with different types of SCs. Finally, a wide range of applications are explored that benefit from the synergistic integration of NGs and SCs, including self-powered electronics, wearable devices, environmental monitoring, and wireless sensor networks. The potential for these hybrid systems is highlighted to address real-world energy needs and contribute to developing sustainable and self-sufficient technologies. In conclusion, this review provides valuable insights into the state-of-the-art developments in NGs and SCs integration, shedding light on advanced hybrid structures and their diverse applications.</p