A novel porous nickel-foam filled CO2 absorptive photobioreactor system to promote CO2 conversion by microalgal biomass

Scale-up of microalgal systems for decarbonization and bioproducts: Challenges and opportunities

The threat of global climate change presents a significant challenge for humanity. Microalgae-based carbon capture and utilization (CCU) technology has emerged as a promising solution to this global issue. This review aims to comprehensively evaluate the current advancements in scale-up of microalgae cultivation and its applications, specifically focusing on decarbonization from flue gases, organic wastewater remediation, and biogas upgrading. The study identifies critical challenges that need to be addressed during the scale-up process and evaluates the economic viability of microalgal CCU within the carbon market. Additionally, it analyzes the commercial status of microalgae-derived products and highlights those with high market demand. This review serves as a crucial resource for researchers, industry professionals, and policymakers to develop and implement innovative approaches to enhance the efficiency of microalgae-based CO2 utilization while addressing the challenges associated with the scale-up of microalgae technologies.

Realization process of microalgal biorefinery: The optional approach toward carbon net-zero emission

Increasing carbon dioxide (CO2) emission has already become a dire threat to the human race and Earth's ecology. Microalgae are recommended to be engineered as CO2 fixers in biorefinery, which play crucial roles in responding climate change and accelerating the transition to a sustainable future. This review sorted through each segment of microalgal biorefinery to explore the potential for its practical implementation and commercialization, offering valuable insights into research trends and identifies challenges that needed to be addressed in the development process. Firstly, the known mechanisms of microalgal photosynthetic CO2 fixation and the approaches for strain improvement were summarized. The significance of process regulation for strengthening fixation efficiency and augmenting competitiveness was emphasized, with a specific focus on CO2 and light optimization strategies. Thereafter, the massive potential of microalgal refineries for various bioresource production was discussed in detail, and the integration with contaminant reclamation was mentioned for economic and ecological benefits. Subsequently, economic and environmental impacts of microalgal biorefinery were evaluated via life cycle assessment (LCA) and techno-economic analysis (TEA) to lit up commercial feasibility. Finally, the current obstacles and future perspectives were discussed objectively to offer an impartial reference for future researchers and investors.

Turning C1-gases to isobutanol towards great environmental and economic sustainability via innovative biological routes: two birds with one stone

BACKGROUND

The dramatic increase in greenhouse gas (GHG) emissions, which causes serious global environmental issues and severe climate changes, has become a global problem of concern in recent decades. Currently, native and/or non-native C1-utilizing microbes have been modified to be able to effectively convert C1-gases (biogas, natural gas, and CO₂) into isobutanol via biological routes. Even though the current experimental results are satisfactory in lab-scale research, the techno-economic feasibility of C1 gas-derived isobutanol production at the industrial scale still needs to be analyzed and evaluated, which will be essential for the future industrialization of C1-gas bioconversion. Therefore, techno-economic analyses were conducted in this study with comparisons of capital cost (CAPEX), operating cost (OPEX), and minimum isobutanol selling price (MISP) derived from biogas (scenario #1), natural gas (scenario #2), and CO₂ (scenario #3) with systematic economic assessment.

RESULTS

By calculating capital investments and necessary expenses, the highest CAPEX ($317 MM) and OPEX ($67 MM) were projected in scenario #1 and scenario #2, respectively. Because of the lower CAPEX and OPEX from scenario #3, the results revealed that bioconversion of CO₂ into isobutanol temporally exhibited the best economic performance with an MISP of $1.38/kg isobutanol. Furthermore, a single sensitivity analysis with nine different parameters was carried out for the production of CO₂-derived isobutanol. The annual plant capacity, gas utilization rate, and substrate cost are the three most important economic-driving forces on the MISP of CO₂-derived isobutanol. Finally, a multiple-point sensitivity analysis considering all five parameters simultaneously was performed using ideal targets, which presented the lowest MISP of $0.99/kg in a long-term case study.

CONCLUSIONS

This study provides a comprehensive assessment of the bioconversion of C1-gases into isobutanol in terms of the bioprocess design, mass/energy calculation, capital investment, operating expense, sensitivity analysis, and minimum selling price. Compared with isobutanol derived from biogas and natural gas, the CO₂-based isobutanol showed better economic feasibility. A market competitive isobutanol derived from CO₂ is predicable with lower CO₂ cost, better isobutanol titer, and higher annual capacity. This study will help researchers and decision-makers explore innovative and effective approaches to neutralizing GHGs and focus on key economic-driving forces to improve techno-economic performance.

Influence of Sintering on Thermal, Mechanical and Technological Properties of Glass Foams Produced from Agro-Industrial Residues

This study investigates the technological, thermal, mechanical, and technological properties of glass foams produced with soda-lime glass residues and rice husk ash sintered at 850-950 °C. The results for apparent density (0.28-0.30 g/cm³), porosity (82-87 ± 4%), compressive strength (1.18 ± 0.03-1.25 ± 0.03 MPa), and thermal conductivity (0.283-0.326 W/mK) are within the limits for commercial foams. The volumetric expansion potential and low thermal conductivity of the glass foams produced favor their use as thermal insulating materials in coat walls, thus improving thermal comfort in the construction sector. The results of X-ray fluorescence show that the foam glass is of the soda-lime type (SiO₂, Na₂O, and CaO), the rice husk ash is rich in SiO₂, CaO, Na₂O, Al₂O₃, K₂O and Fe₂O₃, and the calcium carbonate is rich in CaO. The glass foams produced in this study are promising because they present more economical and efficient manufacturing, resulting in lightweight materials with thermal insulating properties that can be used in the construction sector. These glass foams also reduce the consumption of natural and synthetic raw materials, adding value to the waste used in this study by transforming them into co-products, thus favoring the economic circulation of the region.

A Review of Trends in the Energy Use of Biomass: The Case of the Dominican Republic

This review examines the use of residual biomass as a renewable resource for energy generation in the Dominican Republic. The odology includes a thorough examination of scientific publications in recent years about logistics operations. The use of mathematical models can be beneficial for the selection of areas with a high number of residual biomass and processing centers; for the design of feedstock allocation; for the planning and selection of the mode of transport; and for the optimization of the supply chain, logistics, cost estimation, availability of resources, energy efficiency, economic performance, and environmental impact assessment. It is also essential to consider the exhaustive analysis of the most viable technological solutions among the conversion processes, in order to guarantee the minimum emissions of polluting or greenhouse gases. In addition, this document provides a critical review of the most relevant challenges that are currently facing logistics linked to the assessment of biomass in the Dominican Republic, with a straightforward approach to the complementarity and integration of non-manageable renewable energy sources.

Effects of substrates containing different concentrations of sewage sludge on physiological parameters and quality of Alibertia edulis (Rubiaceae) seedlings

Sewage sludge (SS), a solid residue of effluent treatment, is rich in organic matter and nutrients, while also containing heavy metals and other potential contaminants. The feasibility of employing SS as a substrate component for seedling production depends on its composition and dose, as well as on the tolerance limit of individual plant species. To expand the knowledge base on the use of SS in the production of plants native to the Brazilian Cerrado biome, we evaluated the physiological responses and quality of Alibertia edulis seedlings grown under distinct SS concentrations. Chlorophyll a fluorescence (ChlF), stomatal conductance (gs), leaf temperature (Lt), biomass, growth, and seedling quality were investigated. At 25%, SS improved growth, biomass, and seedling quality, while substrates containing 50% or more SS affected gs, Lt, and ChlF. Seedling quality was strongly worsened by SS at 75% and 100%, as shown by lower biomass and impaired growth, including leaf symmetry loss and leaf deformities possibly related to contaminants, particularly heavy metals. Accordingly, we conclude that SS exhibited potential as a fertilizer at concentrations below 50%, but exerted a toxic effect on seedlings at higher concentrations.

Developing staggered woven mesh aerator with three variable-micropore layers in recycling water pipeline to enhance CO2 conversion for improving Arthrospira growth

A staggered woven mesh (SWM) aerator equipped with three variable-micropore layers was developed to enhance the CO₂ conversion into HCO₃^- in a recycling water pipeline for promoting CO₂ utilization efficiency and Arthrospira growth in large-scale raceway ponds. The input CO₂ gas was broken into smaller bubbles (0.78- 2.43 mm) through the first-stage shear with axial rectangles, second-stage shear with radial rectangles (equivalent pore diameter = 150 μm), and third-stage shear with uniform micropores. A high-speed camera (MotionXtra HG-100K CMOS) and an Image J image processing software were employed to capture the bubble pictures. Compared to the traditional steel pipe (TSP) aerator, the bubble generation diameter and time in the SWM aerator reduced by 72.3% and 48.6%, respectively. The optimized structure (ε = 14, pore = 23 μm) of the SWM aerator promoted the carbonization efficiency and HCO₃^- conversion efficiency into biomass by 78.6% and 64.6% than the TSP aerator. Further, the chlorophyll fluorescence and biomass measurements showed an increase in the actual photochemical efficiency (analyzed by Hansatech FMS1 chlorophyll fluorescence instrument) and biomass yield by 1.8 times and 80.1%.

Strengthening mass transfer with the Tesla-valve baffles to increase the biomass yield of Arthrospira platensis in a column photobioreactor

In this study, the Tesla-valve (TV) baffles were used to optimize the flow field in a column photobioreactor (PBR) in order to promote mass transfer of CO₂ gas in the solution. The TV baffles were composed of many tilted plates with central holes and curved arcs facing downwards, installed along inner rising section of the column PBR. Many clockwise and anti-clockwise vortices were generated during the rising flow while passing through proposed TV baffles. An optimum TV baffle structure (30° plate angle, 8 cm arc width) decreased mixing time by 36.4% and increased the mass transfer coefficient by 50%. The TV baffles supported the movement of the A.platensis cells between light and dark regions to enhance their photochemical efficiency ϕPSII by 24.6% and Fv/Fm by 12.7%. Therefore, the biomass yield increased by 28.1% and exhibited an increased helix pitch and trichome length in comparison with traditional column PBR without baffles.