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This study explores strategies to maximize salinity gradient power (SGP) generation using reverse electrodialysis (RED), focusing on key operating parameters under Swedish environmental conditions. Herein, using a full-factorial experimental design, seawater salinity, flow velocities, and water temperature is varied across three levels to assess their impact on SGP output. machine learning methods predict power density (PD), including 1) ensemble learning with decision tree (DT), 2) gaussian process regression (GPR), and 3) artificial neural network (ANN). Fivefold cross-validation confirms the ANN's high accuracy (root mean squared error (RMSE): 1.173%, R2: 99.35%), closely followed by GPR (RMSE: 1.95%, R2: 99.17%). A feature and trend pattern analysis among the input factors reveals sea salinity as the primary influence on PD, with temperature as the secondary contributor. Complementing this, a life cycle assessment examines the environmental impact of RED systems, identifying the Seawater River RED and brine-wastewater treatment plant RED systems as having environmental effects, particularly on ozone layer depletion and freshwater toxicity. Carbon fiber-based (CF) electrodes, especially lignin CF, demonstrate a lower impact, yet concerns remain over key sustainability challenges. These findings highlight SGP's potential as a viable renewable source, highlighting areas for future material selection and system efficiency improvements.

Lignin is a potential sustainable alternative to polyacrylonitrile (PAN) precursor for the production of carbon fibers. The high purity lignin extracted from residual forest biomass via organosolv process undergoes stabilization and carbonization treatment to produce carbon fibers. Recent developments suggest the potential of producing organosolv lignin carbon fibers (OLCF) with competing mechanical properties similar to PAN carbon fibers. This is likely to enable the use of OLCF in structurally demanding applications such as wind turbine blades. In this work, a life cycle assessment (LCA) is performed with a threefold objective. First, the environmental footprint of OLCF is quantified and results are compared with PAN-CF produced in Sweden and elsewhere in Europe i.e., electricity demands met by European average electrical grid (RER). Second, the environmental performance of OLCF reinforced wind turbine blades (referred as BIOMAT) to be installed in 0.8 MW capacity is evaluated against incumbent variants: glass fiber turbine blade (GFTB), PAN-CF based turbine blades manufactured in Sweden (CFTB-SE), and other parts of Europe (CFTB-RER). Finally, the total environmental externality costs (EEC) of these blades and corresponding lifetime electricity generation when they are installed in 0.8 MW capacity wind turbine blade are calculated. Our results indicate that the environmental impacts of OLCF are lower by 71–94% than PAN-CF-RER in nine, and lower by 43–90% than PAN-CF-SE in six out of ten impact categories quantified respectively. BIOMAT blades also have better overall environmental performance than existing blade variants and particularly lucrative because of their negative total climate change impact. The total EEC of BIOMAT blades is 74%, 83% and 88% lower than GFTB, CFTB-SE and CFTB-RER respectively. Correspondingly, the total EEC of lifetime electricity generated by wind turbine equipped with BIOMAT blades is 11%, 17% and 23% lower than the respective blade variants.

Arctic melting is an effect of climate change; the use of fossil fuels in marine shipping emits large amounts of air emissions that impact climate change, and Arctic aquatic and human life. Swedish pulp and paper mills generate large amounts of waste and side streams that could be utilized. The production of forest-based biofuel may be a promising solution to achieve sustainable Arctic marine shipping. This review highlights the socio-economic impacts associated with the production of forest-based biofuel in Sweden, the related opportunities, challenges, knowledge gaps, and further need of research. From the economic perspective, it was found that the production and use of forest-based biofuel have short and long-term economic sustainability benefits: (a) short-term benefits, the use of the waste and side streams of the pulp and paper industry is a low-cost available feedstock, unlike first-generation biofuel from crops like corn forest-based biofuels neither require additional land use, water resources nor compete with food. (b) Long-term benefits: (i) the Swedish shipping sector depends on imported fossil fuels, these new biofuels can replace partly those imported fossil fuels that will reduce shipping costs, and generate economic benefits for local consumers. (ii) Usage of forest-based biofuels as blends with conventional fuels in existing engines will reduce greenhouse gas emissions from the Arctic shipping to the set limits in the region. (iii) One of the important socio-economic impacts of forest-based biofuel production and use is the new job creation and employment opportunities that will impact the local communities and livelihoods of indigenous people in the area. From a societal perspective, stakeholder involvement is essential to address the sustainability challenges of biofuel production: EU policymakers need to encourage the production and use of biofuels by developing policies that promote biofuel use. Further studies are needed to develop more efficient and low-cost biofuel production routes, more investments in related research and development are required as well. Local indigenous communities must be involved in the decision-making process through surveys, local dialogues, and research studies. The production of forest-based biofuels has great potential and many social-economic impacts alongside the environmental benefits.

The increased water scarcity, depletion of freshwater resources, and rising environmental awareness are stressing for the development of sustainable wastewater treatment processes. Microalgae-based wastewater treatment has resulted in a paradigm shift in our approach toward nutrient removal and simultaneous resource recovery from wastewater. Wastewater treatment and the generation of biofuels and bioproducts from microalgae can be coupled to promote the circular economy synergistically. A microalgal biorefinery transforms microalgal biomass into biofuels, bioactive chemicals, and biomaterials. The large-scale cultivation of microalgae is essential for the commercialization and industrialization of microalgae biorefinery. However, the inherent complexity of microalgal cultivation parameters regarding physiological and illumination parameters renders it challenging to facilitate a smooth and cost-effective operation. Artificial intelligence (AI)/machine learning algorithms (MLA) offer innovative strategies for assessing, predicting, and regulating uncertainties in algal wastewater treatment and biorefinery. The current study presents a critical review of the most promising AI/MLAs that demonstrate a potential to be applied in microalgal technologies. The most commonly used MLAs include artificial neural networks, support vector machine, genetic algorithms, decision tree, and random forest algorithms. Recent developments in AI have made it possible to combine cutting-edge techniques from AI research fields with microalgae for accurate analysis of large datasets. MLAs have been extensively studied for their potential in microalgae detection and classification. However, the ML application in microalgal industries, such as optimizing microalgae cultivation for increased biomass productivity, is still in its infancy. Incorporating smart AI/ML-enabled Internet of Things (IoT) based technologies can help the microalgal industries to operate effectively with minimum resources. Future research directions are also highlighted, and some of the challenges and perspectives of AI/ML are outlined. As the world is entering the digitalized industrial era, this review provides an insightful discussion about intelligent microalgal wastewater treatment and biorefinery for researchers in the field of microalgae.

Dehydrogenation of methanol (CH3OH) into direct current (DC) in fuel cells can be a potential energy conversion technology. However, their development is currently hampered by the high cost of electrocatalysts based on platinum and palladium, slow kinetics, the formation of carbon monoxide intermediates, and the requirement for high temperatures. Here, we report the use of graphene layers (GL) for generating DC electricity from microbially driven methanol dehydrogenation on underlying copper (Cu) surfaces. Genetically tractable Rhodobacter sphaeroides 2.4.1 (Rsp), a nonarchetypical methylotroph, was used for dehydrogenating methanol at the GL-Cu surfaces. We use electrochemical methods, microscopy, and spectroscopy methods to assess the effects of GL on methanol dehydrogenation by Rsp cells. The GL-Cu offers a 5-fold higher power density and 4-fold higher current density compared to bare Cu. The GL lowers charge transfer resistance to methanol dehydrogenation by 4 orders of magnitude by mitigating issues related to pitting corrosion of underlying Cu surfaces. The presented approach for catalyst-free methanol dehydrogenation on copper electrodes can improve the overall sustainability of fuel cell technologies.

Owing to limited markets for recycled products, the United States annually discards~294 million tons of municipal solid waste (MSW) into landfills. These recycling rates for plastics and food wastes are as low as 7% and 3%, respectively. There is a need for stimulating innovative strategies for upcycling MSWs. This chapter discusses viable strategies for upcycling MSWs as precursors for graphene production using well-established nano-manufacturing techniques. We discuss the use of readily available MSW components as raw materials and the waste-to-energy infrastructure as a source of waste heat.

The scarcity of water resources and environmental pollution have highlighted the need for sustainable wastewater treatment. Existing conventional treatment systems are energy-intensive and not always able to meet stringent disposal standards. Recently, algal-bacterial systems have emerged as environmentally friendly sustainable processes for wastewater treatment and resource recovery. The algal-bacterial systems work on the principle of the symbiotic relationship between algae and bacteria. This paper comprehensively discusses the most recent studies on algal-bacterial systems for wastewater treatment, factors affecting the treatment, and aspects of resource recovery from the biomass. The algal-bacterial interaction includes cell-to-cell communication, substrate exchange, and horizontal gene transfer. The quorum sensing (QS) molecules and their effects on algal?bacterial interactions are briefly discussed. The effect of the factors such as pH, temperature, C/N/P ratio, light intensity, and external aeration on the algal-bacterial systems have been discussed. An overview of the modeling aspects of algal-bacterial systems has been provided. The algal-bacterial systems have the potential for removing micropollutants because of the diverse possible interactions between algae-bacteria. The removal mechanisms of micropollutants ? sorption, biodegradation, and photodegradation, have been reviewed. The harvesting methods and resource recovery aspects have been presented. The major challenges associated with algal-bacterial systems for real scale implementation and future perspectives have been discussed. Integrating wastewater treatment with the algal biorefinery concept reduces the overall waste component in a wastewater treatment system by converting the biomass into a useful product, resulting in a sustainable system that contributes to the circular bioeconomy.

Municipal wastewater treatment plants (WWTPs) could become valuable contributors to a circular economy by implementing the 3R principles (reduce, reuse, and recycle). While reducing the pollution load of sewage is the primary objective of a WWTP, this process generates several potentially valuable byproducts including treated effluent, biogas, and sludge. The effluent can be reused in various end use applications and biogas can be reused as a fuel (for electricity generation, transportation, and cooking) or a chemical feedstock. The sludge can either be directly recycled as soil conditioner or via thermochemical/biochemical processing routes to recover material (e.g., hydrochar), energy (e.g., heat, and syngas), and resource value (phosphorus). This work presents a five-layered assessment framework for quantitatively evaluating the sustainable value of municipal WWTPs by using life cycle assessment (LCA) and life cycle costing assessment (LCCA) tools. In addition, indicators reflecting potential benefits to stakeholders and society arising from investments into municipal WWTPs such as the private return on investment (PROI) and the environmental externality costs to investment ratio (EECIR). The framework is validated in a hypothetical case study where the sustainable value of a circularly managed municipal WWTP is evaluated in situations involving multiple byproduct utilization pathways. Four future circular options (FCOs) are examined for a 50,000 m3/d capacity WWTP treating sewage up to tertiary standards. The FCOs mainly differ in terms of how biogas is reused (to meet the WWTP's internal energy demands, as cooking fuel, or as fuel for city buses after upgrading) and how sludge is recycled (as soil conditioner or by producing hydrochar pellets for electricity generation). The FCO in which treated effluent is reused in industry, biogas is used as cooking fuel, and sludge is used as a soil conditioner provides the greatest sustainable value (i.e., the lowest private costs and environmental externality costs (EEC) together with high revenues), the highest PROI, and the lowest EECIR. The strengths and limitations of the proposed assessment framework are also discussed.

Polymers reinforced with virgin carbon fibers (VCF) are being used to make spar caps of wind turbine (WT) blades and polymers with glass fibers (GF) to make skins of the blade components. Here, we assess the life cycle environmental performance of the hybrid blades with spar caps based on VCF and the shells and shear webs based on RCF (recycled CF) composites (RCF-hybrid). The production of the WT blades and associated reinforced polymers is assumed to occur in Sweden, with their uses and end-of-life management in the European region. The functional unit is equivalent to three blades in an offshore WT with the market incumbent blades solely based on the GF composite or the hybrid option. The RCF-hybrid blades offer 12-89% better environmental performance in nine out of 10 impact categories and 6-26% better in six out of 10 impact categories. The RCF-hybrid blades exhibit optimum environmental performance when the VCF manufacturing facilities are equipped with pollution abatement systems including regenerative thermal oxidizers to reduce ammonia and hydrogen cyanide emissions; spar caps are made using VCF epoxy composites through pultrusion and resin infusion molding, and the blade scrap is mechanically recycled at the end of life. The energy and carbon payback times for the RCF-hybrid blades were found to be 5-13% lower than those of the market incumbents.

International shipping in the Arctic region is one of the key contributors to changes in the region due to the generated air emissions from marine fuels combustion, usage of forest-based biofuels as an alternative to conventional fossil fuels in marine shipping seem as an attractive alternative. However, a system analysis perspective is needed to ensure its sustainability. Life cycle assessment was used to estimate the environmental impacts of the production and use of two forest-based biofuels. These fuels, biodiesel and bioethanol, were derived from pulp and paper mills for use by marine shipping. They were compared to fossil fuels currently used by the marine shipping industry, those being Marine Gas Oil (MGO) and Heavy Fuel Oil (HFO). Future projection scenarios in 2030 and 2050 for estimating the environmental impacts of a transition from fossil fuels to biofuels in Arctic shipping were studied as well. The results indicate that a holistic view is very important for biofuel use. The production and use of forest-based bioethanol (BE) had a significantly lower impact on climate change (CC) potential, but had a higher impact on Human toxicity non-cancer effects (HTX), Human toxicity cancer effects (CE), Particulate matter (PM), Photochemical ozone formation (POF), Acidification potential (AP), Terrestrial eutrophication (TE), Freshwater Eutrophication (FE), Marine eutrophication (ME) and Freshwater Ecotoxicity (FEC). Replacing HFO with forest-based biodiesel reduced the potential AP by 55%. It also had a lower impact on the categories CC, PM, POF, TE, ME and FEC. Furthermore, a reduction in emissions generated by shipping in the Arctic and a better overall environmental performance can be achieved by using blends of MGO with BE.