Advanced treatment of toluene emissions with a cutting-edge algal bacterial photo-bioreactor: Performance assessment in a circular economy perspective

Post-Treatment of CO₂ Emissions With Microalgae: Magnetic Field-Induced Improvements in an AirLift Photoreactor

Atmospheric pollution from volatile organic compounds (VOCs) and rising global temperatures due to greenhouse gases (GHGs) emissions, such as carbon dioxide (CO2) pose significant threats to air quality and public health. Coupled biological systems can mitigate VOC emissions, generating CO2, which is then assimilated by microalgae. Static magnetic field (SMF) stimulation has been shown to enhance microalgal growth and CO2 fixation. This study evaluated the impact of SMF on CO2 fixation in an airlift photoreactor (ARL) following VOCs treatment in a semi-continuous stirred tank reactor (S-CSTR) processing toluene vapors. The ARL was exposed to SMF at 45 mT for 6, 4, and 2 h d-1. Results demonstrated a 96% increase in CO2 capture after 4 h of exposure, while removing 45% of the remanent toluene. The highest biomass increase (12%) occurred after 6 h of exposure, whereas total chlorophyll content peaked at 18.4 mg L-1 under 4 h of SMF, compared with 6.8 mg L-1 in the control. Therefore, 4 h exposure at 45 mT was identified as the optimal condition, balancing VOCs reduction, CO2 mitigation, and high pigment production. Microalgal cultures under SMF present a promising and versatile approach for air pollution control and carbon valorization, offering potential economic benefits through biomass applications and supporting circular economy initiatives.

Enhancing process monitoring and control in novel carbon capture and utilization biotechnology through artificial intelligence modeling: An advanced approach toward sustainable and carbon-neutral wastewater treatment

Integrating carbon capture and utilization (CCU) technologies into wastewater treatment plants (WWTPs) is essential for mitigating greenhouse gas (GHG) emissions and enhancing environmental sustainability, but further advancements in process monitoring and control are critical to optimizing treatment performance. This study investigates the application of artificial intelligence (AI) modeling to enhance process monitoring and control in a novel integrated CCU biotechnology with a moving bed biofilm reactor (MBBR) sequenced with an algal photobioreactor (aPBR). This system reduces GHG and odour emissions simultaneously. Several machine learning (ML) models, including artificial neural networks (ANNs), support vector machines (SVM), random forest (RF), and least-squares boosting (LSBoost), were tested. The LSBoost was the most suitable for modeling the MBBR + aPBR system, exhibiting the highest accuracy in predicting CO2 (R2 = 0.97) and H2S (R2 = 0.95) emissions from the MBBR. LSBoost also achieved the highest accuracy for predicting CO2 (R2 = 0.85) and H2S (R2 = 0.97) outlet concentrations from the aPBR. These findings underscore the importance of aligning AI algorithms to the characteristics of the treatment technology. The proposed AI models outperformed conventional statistical methods, demonstrating their ability to capture the complex, nonlinear dynamics typical of processes in environmental technologies. This study highlights the potential of AI-driven monitoring and control systems to significantly improve the efficiency of CCU biotechnologies in WWTPs for climate change mitigation and sustainable wastewater management.

Integration of Moving Bed Biofilm Reactor (MBBR) and algal PhotoBioReactors (aPBR) for achieving carbon neutrality in wastewater treatment

Carbon neutrality is a primary goal for wastewater treatment plants (WWTPs), as they are responsible for significant greenhouse gas (GHG) emissions as well as unpleasant odour emissions. The paper shows a new modular biotechnology that enables simultaneous treatment of gaseous emissions and biofixation of CO2. A comparative assessment of system performances in removing target pollutants (toluene, p-xylene and hydrogen sulphide) was implemented. Results showed that the highest removal efficiency (RE) was recorded for the toluene, equaling 99.9 ± 0.1 %, for an inlet load (IL) of 9.91 ± 3.44 g m-3 d-1. During the experimental tests regarding hydrogen sulphide removal, the system recorded the highest CO2 assimilation, equal to -3.03 ± 0.93 g m-3 d-1. However, this assimilation rate did not correspond to the maximum volumetric biomass productivity (MVBP), equal to 1.3 g L-1 d-1, recorded with toluene treatment, with a maximum lipid productivity (MLP) of 450 mg L-1 d-1. The results demonstrated the complete adaptability of the investigated system, which can help to fill the gaps in the current technological landscape, providing an innovative biotechnology that can be directly implemented and environmentally sustainable.

Carbon capture and utilisation (CCU) solutions: Assessing environmental, economic, and social impacts using a new integrated methodology

Carbon Capture and Utilisation (CCU) technologies play a significant role in climate change mitigation, as these platforms aim to capture and convert CO2 that would be otherwise emitted into the atmosphere. Effective and economically sustainable technologies are crucial to support the transition to renewable and low-carbon energy sources by 2030 and beyond. Currently, studies exploring the financial viability of CCU technologies besides the joint analyses of life-cycle costs and environmental and social impacts are still limited. In this context, the study developed and validated an innovative and integrated methodology, called Life Cycle Cost and Sustainability Assessment (LCC-SA) which allows the joint assessment of (i) project life-cycle costs, (ii) socio-cultural and environmental externalities. This tool was validated with an application to an algal photobioreactors (PBRs) and allowed to assess the economic and environmental sustainability besides identifying the main critical issues to be addressed during the transition from pilot-scale plant to industrial application. The methodology's implementation estimated benefits in two main areas: (i) environmental, including CO2 removal and avoidance through biodiesel production instead of fossil-derived diesel; (ii) socio-cultural, encompassing new patents, knowledge spillovers, human capital formation, and knowledge outputs. The analysis returned as main result that the present value of the social externalities amounts to around EUR 550,000 and the present value of the costs to approximately EUR 60,000. The Economic Net Present Value (ENPV) is EUR 487,394, which shows the significance of the extra-financial effects generated by the research project. At full-scale application, environmental benefits include capturing 187 to 1867 tons of CO2 per year and avoiding 1.7 to 16.7 tons of CO2 annually through biodiesel production instead of fossil-derived diesel.

Microalgae to biodiesel: A novel green conversion method for high-quality lipids recovery and in-situ transesterification to fatty acid methyl esters

Greenhouse gases (GHGs) emissions due to increasing energy demand have raised the need to identify effective solutions to produce clean and renewable energy. Biotechnologies are an effective platform to attain green transition objectives, especially when synergically integrated to promote health and environmental protection. In this context, microalgae-based biotechnologies are considered among the most effective tools for treating gaseous effluents and simultaneously capturing carbon sources for further biomass valorisation. The production of biodiesel is regarded as a promising avenue for harnessing value from residual algal biomass. Nonetheless, the existing techniques for extracting lipids still face certain limitations, primarily centred around the cost-effectiveness of the process.This study is dedicated to developing and optimising an innovative and cost-efficient technique for extracting lipids from algal biomass produced during gaseous emissions treatment based on algal-bacterial biotechnology. This integrated treatment technology combines a bio-scrubber for degrading gaseous contaminants and a photobioreactor for capturing the produced CO2 within valuable algal biomass. The cultivated biomass is then processed with the process newly designed to extract lipids simultaneously transesterificated in fatty acid methyl esters (FAME) via In Situ Transesterification (IST) with a Kumagawa-type extractor. The results of this study demonstrated the potential application of the optimised method to overcome the gap to green transition. Energy production was obtained from residuals produced during the necessary treatment of gaseous emissions. Using hexane-methanol (v/v = 19:1) mixture in the presence KOH in Kumagawa extractor lipids were extracted with extraction yield higher than 12% and converted in fatty acid methyl esters. The process showed the enhanced extraction of lipids converted in bio-sourced fuels with circular economy approach, broadening the applicability of biotechnologies as sustainable tools for energy source diversification.

Carbon neutrality in wastewater treatment plants: An integrated biotechnological-based solution for nutrients recovery, odour abatement and CO2 conversion in alternative energy drivers

Wastewater treatment plants play a crucial role in water security and sanitation, ensuring ecosystems balance and avoiding significant negative effects on humans and environment. However, they determine also negative pressures, including greenhouse gas and odourous emissions, which should be minimized to mitigate climate changes besides avoiding complaints. The research has been focused on the validation of an innovative integrated biological system for the sustainable treatment of complex gaseous emissions from wastewater treatment plants. The proposed system consists of a moving bed biofilm reactor coupled with an algal photobioreactor, with the dual objective of: i) reducing the inlet concentration of the odourous contaminants (in this case, hydrogen sulphide, toluene and p-xylene); ii) capturing and converting the carbon dioxide emissions produced by the degradation process into exploitable algal biomass. The first reactor promoted the degradation of chemical compounds up to 99.57% for an inlet load (IL) of 22.97 g m-3 d-1 while the second allowed the capture of the CO2 resulting from the degradation of gaseous compounds, with biofixation rate up to 81.55%. The absorbed CO2 was converted in valuable feedstocks, with a maximum algal biomass productivity in aPBR of 0.22 g L-1 d-1. Dairy wastewater has been used as alternative nutrient source for both reactors, with a view of reusing wastewater while cultivating biomass, framing the proposed technology in a context of a biorefinery within a circular economy perspective. The biomass produced in the algal photobioreactor was indeed characterized by a high lipid content, with a maximum percentage of lipids per dry weight biomass of 35%. The biomass can therefore be exploited for the production of alternative and clean energy carrier. The proposed biotechnology represents an effective tool for shifiting the conventional plants in carbon neutral platform for implementing principles of ecological transition while achieving high levels of environmental protection.

Effect of gas components on the degradation mechanism of o-dichlorobenzene by non-thermal plasma technology with single dielectric barrier discharge

In this paper, the degradation of o-DCB under different gas-phase parameter conditions was investigated using the SDBD-NTP system. The results showed that the increase in initial and oxygen concentrations had opposite effects on the degradation of o-DCB. Among them, the increase of oxygen concentration promoted the degradation of o-DCB. Relative humidity promoted and then inhibited the degradation of o-DCB. The highest degradation efficiency of o-DCB was achieved at RH = 15%, reaching 91% at 29W. In the study of by-products, it was found that O3 and NOx were the main inorganic by-products, and that different oxygen levels and relative humidity conditions had a large effect on the production of O3 and NOx. In all of them, the concentration of O3 decreased with the increase of input power. NOx increased with increasing oxygen concentration, but the increase in relative humidity inhibited the production of NO and N2O and promoted the conversion of NO2. A study of organic by-products revealed this. In the absence of oxygen, a higher number of benzene products appeared. Whereas, with the addition of oxygen, only in the by-products under conditions where no relative humidity was introduced, benzene ring products were predominantly present in the by-products. However, when RH was added, n-hexane was found to be present in the by-products. This may be because the introduction of OH• favors the destruction of the benzene ring. Finally, the possible reaction pathways and reaction mechanisms of o-DCB under different gas-phase parameters are given. It provides a reference for future related scientific research as well as scientific problems in practical applications.