Background: Aquaculture relies significantly on effective aeration systems to ensure optimal conditions for aquatic organisms. This 96-day study investigates the dynamic relationship between Oxygen Transfer Rates (OTR) and seasonal variations, with a specific focus on the impact of seasonal dynamics and the placement of paddle wheel aerators. The study recognizes the pivotal role of Total Dissolved Solids (TDS) and Total Suspended Solids (TSS) as key water quality parameters influencing aeration efficiency. Methodology: A series of water circulation experiments were conducted at regular intervals to assess mixing rates, revealing a nuanced trajectory ranging from 27.05 to 14.22 m³/kWh. The study scrutinized the influence of TDS and TSS on these rates. Additionally, water velocity variations, ranging from 0.45 to 1.67 m/s, were examined, highlighting density-dependent changes, particularly evident post four weeks of operation. Oxygen stratification analysis provided insights into deviations in Dissolved Oxygen (DO) concentrations, with particular attention to climatic aberrations. Rigorous statistical analyses, including chi-squared, Pearson correlation, Gaussian distribution checks, and student's t-tests, validated the methodological robustness and data reliability. Significant findings: Employing a Seasonal Auto Regressive Integrated Moving Average (SARIMA) model, the study achieved a remarkable 97 % accuracy in forecasting DO levels for the subsequent 96 days. Real-time validation, complemented by a Chi-square goodness of fit test, reaffirmed the model's reliability, establishing congruence between observed and forecasted values. This research underscores the critical roles of strategic aerator placement and seasonal considerations in optimizing pond aeration efficiency, providing substantive insights for the sustainable management of aquaculture ecosystems. © 2024 Taiwan Institute of Chemical Engineers

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/policies/article-withdrawal). This article has been retracted at the request of Elsevier's Research Integrity & Publishing Ethics team and an independent ethics advisor. A journal-wide investigation identified violations of the journal's policies on authorship and conflict of interest related to the submission and review of this paper. Review of this submission was handled by the then Editor-in-Chief (Ashok Pandey) despite an extensive record of collaboration, including co-publication, with four of the paper co-authors (Binod Parameswaran, Raveendran Sindhu, Mukesh Kumar Awasthi, Mohammad J. Taherzadeh). In addition, authorship changes were made during the revision of this paper; the authors Deepanraj Balakrishnan and M. Mofijur were added to the revised paper without validation or authorisation. There was a significant increase of citations of papers authored by the Editor-in-Chief between the original submission and the revised version. In summary, 3 papers by Pandey were cited in the original version of the paper. This increased to 10 papers in the revised version. Acceptance of the article was partly based upon the positive advice of a reviewer who was closely linked to one of the authors (Awasthi). This compromised the editorial process and breached the journal's policies. This investigation was carried out by Elsevier's Research Integrity & Publishing Ethics team, independent of the journal editorial board. The findings and recommendations have been confirmed by an independent ethics advisor. The authors disagree with the retraction and dispute the grounds for it. © 2025 Elsevier Ltd

Wastes are unceasingly generated in the world, and most of them can be recycled, reused, or recovered to promote a circular economy. Among waste treatment approaches, the anaerobic digestion (AD) process has been considered as an ideal process due to its ecological benefits (reduction of unpleasant odor, pathogens accumulation, or greenhouse gas emission), social and economic advantages, and energy saving. In addition to biogas production, this process can be used to produce various bioproducts, such as biopolymers, bioplastics, biomass, biofertilizers, and biolipids. Interestingly, the AD process residue or digestate is a nutrient-rich by-product that can be used as a biofertilizer for agronomical purposes to balance N-P cycle in the soils. Despite of numerous benefits of AD, less than 1 % of waste is treated by this process. This process has the potential to be integrated with other waste treatment approaches to increase waste treatment efficiency. Therefore, it is essential to focus on each advantage and clarify ambiguity in order to satisfy more countries for employing AD for waste treatment. In this review, various benefits of AD are evaluated; and its potential impacts on particularly agriculture are examined in detail. Additionally, potential biomass and wastes that can be used for anaerobic digestion worldwide are deliberated. Besides, a critical perspective has been developed on the economic, environmental, and social evaluation of the benefits of AD and, as a final point, focused on an integrated circular cascading approach. © 2024 Elsevier Ltd

Microalgae-based wastewater treatment has resulted in a paradigm shift toward nutrient removal and simultaneous resource recovery. However, traditionally used microalgal biomass quantification methods are time-consuming and costly, limiting their large-scale use. The aim of this study is to develop a simple and cost-effective image-based method for microalgae quantification, replacing cumbersome traditional techniques. In this study, preprocessed microalgae images and associated optical density data were utilized as inputs. Three feature extraction methods were compared alongside eight machine learning (ML) models, including linear regression (LR), random forest (RF), AdaBoost, gradient boosting (GB), and various neural networks. Among these algorithms, LR with principal component analysis achieved an R2 value of 0.97 with the lowest error of 0.039. Combining image analysis and ML removes the need for expensive equipment in microalgae quantification. Sensitivity analysis was performed by varying the train-test splitting ratio. Training time was included in the evaluation, and accounting for energy consumption in the study leads to the achievement of high model performance and energy-efficient ML model utilization. © 2024 American Chemical Society.

Hydrogen, a carbon-free fuel, has the potential to aid global nations in achieving eight of the 17 Sustainable Development Goals (SDG). The shortcomings associated with H2 transportation and storage can be mitigated by using NH3 as hydrogen carrier because of its better safety, physical, and environmental properties. However, to achieve the global climate target, green ammonia production must be incremented by four times (688 MT) from the current level. Hence, understanding of advanced green NH3 production and storage technologies, along with the factors that influence them becomes necessary. It also aids in identifying the factors hindering green H2 and NH3 production, which can be resolved by promoting research. At the same time, drafting policies that encourage green H2 and NH3 production can abet in overcoming the bottleneck faced by the industry. Presently, green ammonia production can be made feasible only when the renewable electricity cost is less than $20/MWh and carbon price of $150/t of CO2 emissions is levied. Approximately 80 % of the energy consumed during NH3 is spent on H2 generation; therefore, it is necessary to enact policies that promote green H2 production globally. Producing green H2 can aid in mitigating ∼90 % of the greenhouse gases emitted during NH3 manufacturing thereby facilitating to reduce the carbon footprint of H2 carrier and decarbonize NH3 industry. © 2025 Elsevier B.V.

The use of micro-algae for wastewater treatment is a promising technique that contributes to CO2 capture and nutrient recovery. However, the lack of effective forecasting models limits the scalability of this technique. This study aims to develop a time-series-based forecasting model to predict the growth curve of microalgal biomass under environmental conditions similar to those found in wastewater. Data collected on microalgal growth was used to train six time-series models: Long Short-Term Memory (LSTM), Extreme Gradient Boosting (XGBoost), Auto-Regressive Integrated Moving Average (ARIMA), Random vector functional link (RVFL), Physics-informed neural networks (PINN) and Prophet. The model performance metrics were compared, and the best model was identified. The results demonstrated that the RVFL was the most accurate model, with minimal prediction errors ( < 0.01). Residual analysis confirmed a normal distribution of errors without outliers, supporting the model's reliability. These findings suggest that the proposed RVFL model can effectively forecast microalgal growth, potentially reducing the need for costly and labour-intensive laboratory trials and advancing microalgae-based wastewater treatment. © 2025 The Institution of Chemical Engineers

Microalgae cultivation is gaining interest as a sustainable alternative to the conventional wastewater (WW) treatment and nutrient recovery. Current study presents a comprehensive life cycle assessment (LCA) of microalgae cultivation in distinct wastewaters. Two different microalgae species in three different wastewaters were compared for sustainability performance in six scenarios. LCA was conducted using SimaPro (v9.3.0.3) and ReCiPe 2016 Midpoint method. The findings of the study reveal that global warming potential ranged between −678 and − 1357 g CO2eq./m3. Chlorella sp. cultivated in dairy WW shown higher environmental performance across the scenarios with GWP of −1357 g CO2eq./m3. The average global warming potential (GWP) of single-pot microalgae-based wastewater treatment got reduced by 240 %. The key inference of this study is that cultivation of the microalgae as single-pot treatment system not only helps in environmental sustainability but also holds significant promise for combating climate change as negative emission technology (NET). © 2025 Elsevier Ltd

Flue gases are the gases which are produced from industries related to chemical manufacturing, petrol refineries, power plants and ore processing plants. Along with other pollutants, sulfur present in the flue gas is detrimental to the environment. Therefore, environmentalists are concerned about its removal and recovery of resources from flue gases due to its activation ability in the atmosphere to transform into toxic substances. This review is aimed at a critical assessment of the techniques developed for resource recovery from flue gases. The manuscript discusses various bioreactors used in resource recovery such as hollow fibre membrane reactor, rotating biological contractor, sequential batch reactor, fluidized bed reactor, entrapped cell bioreactor and hybrid reactors. In conclusion, this manuscript provides a comprehensive analysis of the potential of thermotolerant and thermophilic microbes in sulfur removal. Additionally, it evaluates the efficacy of a multi-enzyme engineered bioreactor in this process. Furthermore, the study introduces a groundbreaking sustainable model for elemental sulfur recovery, offering promising prospects for environmentally-friendly and economically viable sulfur removal techniques in various industrial applications. © 2024 Elsevier B.V.

Biogas production through anaerobic digestion (AD) is one of the complex non-linear biological processes, wherein understanding its dynamics plays a crucial role towards process control and optimization. In this work, a machine learning based biogas predictive model was developed for high solid systems using algorithms, including SVM, ET, DT, GPR, and KNN and two different datasets (Dataset-1:10, Dataset-2:5 inputs). Support Vector Machine had the highest accuracy (R2) of all the algorithms at 91 % (Dataset-1) and 87 % (Dataset-2), respectively. The statistical analysis showed that there was no significant difference (p = 0.377) across the datasets, wherein with less inputs, accurate results could be predicted. In case of biogas yield, the critical factors which affect the model predictions include loading rate and retention time. The developed high solid machine learning model shows the possibility of integrating Artificial Intelligence to optimize and control AD process, thus contributing to a generic model for enhancing the overall performance of the biogas plant. © 2024 Elsevier Ltd

Microalgae paves the way towards a negative emission technology; however, single-pot systems combining nutrient removal and wastewater treatment are scarce in the literature. In this study, three different types of wastewater (university, municipality, and dairy industries) were studied using microalgae towards treatment and nutrient removal using Scenedesmus sp. and Chlorella sp. The experiments were carried out in 20 L reactors, for 9 days, where in achieving a maximum of algal growth rate of 770 and 725 mg/L for Scenedesmus sp. and Chlorella sp., respectively. Of the three wastewaters, dairy wastewater had the highest influent COD (3488 mg/L), which was reduced by 92% after 9 days. The pigment content was highest after 6 days (0.22 ± 0.03%), and there was no significant improvement after 9 days, suggesting a trade-off between nutrient removal, photosynthetic performance, and COD reduction. Microalgae act as a sustainable solution and negative emission technology to solve the crisis of wastewater treatment, nutrient removal and production of high-value products. Graphical abstract: (Figure presented.) © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.

Attributional life cycle assessment study examines the environmental impact of raw materials, machinery, and unit operations. In the present work, an attributional life cycle assessment (LCA) was employed to assess the environmental and greenhouse gas impacts of a shrimp feed production system. A commercial shrimp feed mill in Tamil Nadu, India, provided inventory data for one-ton shrimp feed (functional unit) for a Cradle-to-Gate evaluation using environmental impact methodologies, specifically Impact 2002+ in SimaPro® (V9.3.0.3) software. The results showed that human health (0.003357 DALY), ecosystem quality (2720.518 PDF × m2 × yr), climate change (2031.696 kg CO2 eq), and resources (71019.42 MJ primary) were the most significantly impacted. The human health category was found to be the most prominent after normalization and weighting (0.47 pt), and strategies were suggested accordingly. The GWP20 and GWP100 measures for long-term climate change were calculated to be 8.7 and 7.33 kg CO2 eq, respectively. Cast iron used in machinery production (GWP 20–15.40%, GWP100–134.5%) and electricity use (GWP 20–6.13%, GWP 100–6.9%) accounted for sizable portions of the burden. Feed production is estimated to contribute 0.2% of global CO2 emissions within the proposed global context. These findings are significant regarding economically and environmentally sustainable shrimp feed production worldwide. © 2023 Elsevier Inc.

Background: Aquaculture relies significantly on effective aeration systems to ensure optimal conditions for aquatic organisms. This 96-day study investigates the dynamic relationship between Oxygen Transfer Rates (OTR) and seasonal variations, with a specific focus on the impact of seasonal dynamics and the placement of paddle wheel aerators. The study recognizes the pivotal role of Total Dissolved Solids (TDS) and Total Suspended Solids (TSS) as key water quality parameters influencing aeration efficiency. Methodology: A series of water circulation experiments were conducted at regular intervals to assess mixing rates, revealing a nuanced trajectory ranging from 27.05 to 14.22 m³/kWh. The study scrutinized the influence of TDS and TSS on these rates. Additionally, water velocity variations, ranging from 0.45 to 1.67 m/s, were examined, highlighting density-dependent changes, particularly evident post four weeks of operation. Oxygen stratification analysis provided insights into deviations in Dissolved Oxygen (DO) concentrations, with particular attention to climatic aberrations. Rigorous statistical analyses, including chi-squared, Pearson correlation, Gaussian distribution checks, and student's t-tests, validated the methodological robustness and data reliability. Significant findings: Employing a Seasonal Auto Regressive Integrated Moving Average (SARIMA) model, the study achieved a remarkable 97 % accuracy in forecasting DO levels for the subsequent 96 days. Real-time validation, complemented by a Chi-square goodness of fit test, reaffirmed the model's reliability, establishing congruence between observed and forecasted values. This research underscores the critical roles of strategic aerator placement and seasonal considerations in optimizing pond aeration efficiency, providing substantive insights for the sustainable management of aquaculture ecosystems. © 2024 Taiwan Institute of Chemical Engineers

Natural gas is extracted from the subsoil which is not a renewable source, however, the dominance of this product in the international market is significantly higher in future. It reflects the global view of renewable sources (biogas) and hinders the sustainable development of bioenergy. It describes the major issues and trends in the development of biogas industry, paying special attention to current biomass upgrading technologies, methane activation for fuel production and model compounds investigation. The conducted research gives reason to believe that the valorization of organic waste generated worldwide during the production of biomethane that can potentially satisfy. No more than one fifth of global demands for natural gas due to technical difficulties and economic constraints associated with the purification of biogas. The existing production potential of biogas production is focused on obtaining biomethane and high growth rates of demand for biohydrogen. A pressing need arises the possibilities for further development of biogas industry lie in optimizing the biomethanation processes, which allows to reduce the costs of biogas modernization system and decreasing the negative effect on climate changes by replacing petrochemical derived fuels with biofuels in various sectors of economy. © 2024 Elsevier B.V.

Lignocellulosic biomass is the richest regenerative resource in nature. Especially in the context of continuous consumption of fossil energy and environmental pollution, it is urgent to use lignocellulosic biomass to prepare clean energy such as biofuels. But lignocellulose has a strong natural barrier against degradation, which needs to be pre-treated by physical, chemical and microbial means and then converted into biofuels and other high value-added products at lower cost and higher efficiency. This chapter mainly describes the pretreatment techniques of lignocellulose in recent years, including traditional physical methods, chemical methods and biological methods. And the mechanism of each pretreatment method is briefly introduced, and its advantages and disadvantages are analysed and summarized. At the same time, the economic feasibility and influencing factors of these technologies are discussed and analysed. Finally, the development and application of lignocellulosic pretreatment technology are prospected and suggested, aiming at providing some reference for the more efficient development and utilization of cellulose. © 2025 Elsevier Ltd. All rights reserved.

Food waste is primarily generated in marketplaces, agricultural fields, hotels, food manufacturers units, and halls. Food waste have a major impact on food security, quality and safety, economic development, and cause environment pollution. The improper disposal of food waste without proper treatments leads to generation of new diseases, unpleasant odour, air, water, and soil pollution. Nevertheless, food waste is a good substrate which can be disintegrated by digestion process because it exhibits more water contents and biodegradability. The conversion of food waste into biomethane is an appreciable solution in food waste management steps. This manuscript reviews the physico-chemical properties of food waste, various pretreatment methods of food waste to enhance the efficiency of anaerobic digestion (AD) process used to produce biomethane and discussed the impact of operational factors on biomethane production. Subsequently, the need for a biomethane upgradation using physical, chemical, and biological purification approaches was reviewed. In order to improve the efficiency of the anaerobic digestion (AD) process to a large-scale industrial level, the challenges and possible future developments needed to enhance biomethane generation from food waste were also reviewed significantly. © 2024 Elsevier Ltd

Heavy industries play a crucial role in the economic growth of India through their contribution towards meeting demand, including exports and GDP. Every functional unit of the production process related to hard-to-abate industries has to depend upon power sources for manufacturing the final product. The major power source for heavy industries namely power plants, iron and steel, cement, paper, and fertilizer are coal. During the process of energy conversion from coal through combustion, they produce a large amount of greenhouse gases. As production capacity is increased to meet the growing demand, it is essential to mitigate carbon emissions. There are many routes adopted by various sectors to decarbonize the production process. These include the use of alternative fuels, using the best available techniques, carbon capture utilization, and storage. Most of these techniques have shown positive impacts after implementation. In this study, the production process of each sector is analyzed to find the hotspots, the mitigation strategies followed by each industry, and mainly the use of green hydrogen as a power source. It elaborates on the routes of production of green hydrogen, the major challenges in the implementation part, the policy making of green hydrogen in India, its relationship to heavy industries, and how green hydrogen plays a role in net-zero emission goals. © 2024 American Chemical Society.

Biohythane (a mixture of hydrogen and methane) may play a significant role in a future decarbonised energy system. The production of biohythane can be achieved by sequential dark hydrogen fermentation and anaerobic digestion. However, the technology readiness level of biohythane can be limited by many process constraints negatively affecting its commercial feasibility. Here, a pilot experiment on fermentative hythane production from cassava stillage residue (CSR) incorporating dilute acid pretreatment and enzymolysis was undertaken. The production of hydrogen and methane was 72.0 ± 10.7 and 295.4 ± 28.5 mL/g volatile solid, respectively. Different scenarios for techno-economic analysis were developed in terms of the dried/wet form of CSR and total solids content during fermentation. Results suggested that hythane from CSR was not economically feasible with a high production cost (1.39–2.33 €/m3). There was a trade-off relationship between the increase in methane yield through pretreatment and the associated cost. © 2023 Hydrogen Energy Publications LLC

Microalgae-based nutrient recovery has the potential to efficiently recover nutrients while simultaneously treating wastewater. However, the absence of an optimization model for this technology hinders its full potential. This study has developed a model to optimize the biomass yield in micro algae-based wastewater treatment. Seven machine learning models, including Decision Trees (DT), Random Forest (RF), K-Nearest Neighbours (KNN), Gradient Boosting Regressor (GBR), Multi-Layer Perceptron Regression (MLPR), Support Vector Regression (SVR), and Artificial Neural Networks (ANN), were compared. Among other algorithms, ANN performed superiorly, achieving an R2 value of 0.98 with the lowest error. The optimal biomass yield of 948 mg/L was obtained when the COD, phosphate, nitrate, nitrite, pH, and retention times were maintained at 350 mg/L, 50 mg/L, 60 mg/L, 140 mg/L, 7.1, 9 days respectively. When compared to experimental yield, the prediction shows 31.7 % higher biomass yield. The pH and retention time were the critical factors for prediction of algal biomass. 20 % of variation in the train test split ratio caused 21 % increase in the error value and 75:25 ratio was found to be optimal for better performance of the model. This study serves as a valuable reference point for integration of artificial intelligence (AI) with algae-based wastewater treatment. © 2024 Elsevier Ltd

The major share of energy consumption during steel manufacturing is spent on iron making. The unavailability of the required quantity of recyclable steel in India has made the industries depend on sponge iron (SI) for steel manufacturing. However, 78.5% of the SI manufactured in India uses coal as an energy source. Thus, increasing the carbon footprint of steel manufactured in India by 18% compared to the global level. Hence, in this study, the potential of palm kernel shell charcoal (PKSC) to decarbonize the rotary kiln-based SI production process was analysed by framing three scenarios and comparing them with the business-as-usual (BAU). Meanwhile, the life cycle assessment of the SI production through different scenarios was done to identify the sustainability of the process. A cradle-to-gate approach was adopted, and it was found that during BAU, the net greenhouse gas (GHG) emissions were 2525 CO2eq./t SI. However, usage of PKSC (scenario 3) in the SI production process aided in achieving negative net GHG emissions of −41 kg CO2eq./t SI. Meanwhile, the net GHG emission was 1092 kg CO2eq./t SI and 1197 kg CO2eq./t when the coal used in the feed and injection end was replaced with PKSC in scenario 1 and scenario 2, respectively. Thus, the usage of the PKSC instead of coal can abet in decarbonizing the sponge iron industry thereby aiding in reducing the GHG emitted during the production of 1 t of steel in India to 2.4 t by 2030–31. © 2024 Elsevier Ltd

Cassava, a staple food crop, is widely used for starch production, but its inconsistent supply, price volatility, and substantial waste generation pose challenges to the cassava industrial market's growth. This study aims to identify a sustainable biorefinery pathway by optimizing conventional cassava starch plants (business-as-usual, BAU) for economic and environmental benefits. Four scenarios were evaluated: animal feed from peel waste (Scenario 1), fungal protein from thippi waste (Scenario 2), fish feed from digested wastewater (Scenario 3), and conversion of all waste streams into animal feed, fish feed, and fungal protein (Scenario 4). Scenario 4 emerged as the best pathway using the multi-criteria decision-making (MCDM) approach, with a performance score of 0.282. Despite the highest energy consumption (18.91 MWh), Scenario 4 was favored for producing four value-added products alongside starch, yielding the highest profit at USD 8.85 million. In contrast, profits for BAU, Scenario 1, Scenario 2, and Scenario 3 were 1.91, 2.30, 5.01, and USD 8.79 million, respectively. Waste valorization in Scenarios 1, 2, 3, and 4 resulted in CO2 avoidance of 36.5., 42.6., 21.7, and 57.45 t CO2eq., respectively. However, producing value-added products increased energy consumption by 13, 73, 7, and 74% compared to BAU (4.58 MWh). The global warming potential analysis showed negative values for scenarios 2 and 4, at -436 and -434 kg CO2eq./t root, respectively. This study highlights the potential of a biorefinery approach for sustainable cassava starch production, providing insights for future research and policy development. © 2024 Alpha Creation Enterprise CC BY 4.0.

Bioenergy with carbon capture and storage (BECCS) is gaining attention as an energy source and the most effective path to achieve negative CO2 emissions by photosynthesis and capturing CO2. However, BECCS has certain challenges and limitation which needs to be addressed to make the technology feasible. Concerns about food security, land, water use, and the possibility of large-scale implementation are critical in commercialization. As an emerging field, BECCS will need dynamic research and development over the next few decades, as well as strong policy backing, to clinch that it can be implemented on time for fulfilling the Paris agreement targets. The goal of this critical review is to find the impending obstacles that BECCS is facing, as well as the approaches to overcome them, while also emphasizing the advances in the field over the last decade. Detailed technology assessment is provided for a better understanding. © 2023 Elsevier Ltd

Hydrogen is considered as the fuel of the future not only because of its high energy density but also due to its zero-carbon emission potential during combustion. However, to achieve sustainable growth, the hydrogen generation process must be techno-economically feasible and have minimum carbon footprint. The techno-economic analysis (TEA) of various hydrogen generation process aids in identifying the effective bio-hydrogen generation process at minimal cost thereby aiding in faster dissemination of the system by attracting investors. Among the various techniques available for bio-hydrogen production, gasification was found to be most economical ($1.2/kg H2) followed by anaerobic digestion process ($1.25/kg H2). Meanwhile, after carrying out the life cycle analysis (LCA) of the different bio-hydrogen generation process, it was found that generation of bio-hydrogen by gasification of eucalyptus wood produced least carbon foot of −1.6 kg CO2eq./kg H2. Thus, the TEA and LCA of different biohydrogen production process also helps to identify the bottlenecks haunting the penetration of hydrogen in energy market which can be overcome by framing effective policies by the governing agencies. © 2023 Elsevier Ltd

Sustainable Biorefining of Woody Biomass to Biofuels and Biochemicals explores various technologies and pathways for the valorization of woody biomass to produce sustainable biofuels and bioproducts. Focusing on commercialization, the book discusses woody biomass availability, including harvesting, transportation and storage, biomass structure, advanced biorefinery technologies, and the economic and environmental sustainability of woody biomass-based biorefineries. Various technologies are described and assessed from a commercial perspective and practical solutions to the latest challenges are provided. The last section of the book is dedicated to the commercialization aspects of biorefineries, providing details about the techno-economic viability and environmental impact of various biorefinery approaches.This book provides readers with a unique and comprehensive reference that will help students and researchers alike identify and overcome the challenges involved in woody-biomass biorefining for biofuels and biochemicals. It will also be of interest to researchers and professionals involved more broadly in bioenergy and renewable energy, and interdisciplinary teams working across biotechnology, chemistry and chemical engineering, environmental science, and plant sciences. © 2023 Elsevier Inc. All rights reserved.

Due to resource scarcity, current industrial systems are switching from waste treatment, such as wastewater treatment and biomass, to resource recovery (RR). Biofuels, manure, pesticides, organic acids, and other bioproducts with a great market value can be produced from wastewater and activated sludge (AS). This will not only help in the transition from a linear economy to a circular economy, but also contribute to sustainable development. However, the cost of recovering resources from wastewater and AS to produce value-added products is quite high as compared to conventional treatment methods. In addition, most antioxidant technologies remain at the laboratory scale that have not yet reached the level at industrial scale. In order to promote the innovation of resource recovery technology, the various methods of treating wastewater and AS to produce biofuels, nutrients and energy are reviewed, including biochemistry, thermochemistry and chemical stabilization. The limitations of wastewater and AS treatment methods are prospected from biochemical characteristics, economic and environmental factors. The biofuels derived from third generation feedstocks, such as wastewater are more sustainable. Microalgal biomass are being used to produce biodiesel, bioethanol, biohydrogen, biogas, biooils, bioplastics, biofertilizers, biochar and biopesticides. New technologies and policies can promote a circular economy based on biological materials. © 2023 Elsevier Ltd

Carbon capture storage and utilization (CCSU) has the potential to become a key tool to mitigate climate change, thus, aiding in achieving the objectives of the 2015 Paris Agreement. Even though the relevant remediation technology has achieved technical maturity to a certain extent, implementation of CCSU on a larger scale is currently limited because of non-technical parameters that include cost, legalization, lack of storage reservoir, and market mechanism to penalize CO2 emitter. Among these, cost emerges as the primary barrier to the dissemination of CCSU. Hence, necessary policy frameworks and incentives must be provided by governing agencies to enable faster dissemination of carbon capture and utilization (CCU) and carbon capture and storage (CCS) globally. Meanwhile, strict implementation of a carbon tax across nations and market demand for products generated using captured CO2 can aid in the fast adoption of CCU and CCS. This review assessed the economic feasibility and sustainability of CCS and CCU technologies to identify the barriers to commercializing these technologies. © 2023 Elsevier B.V.

The energy sector accounts for three-quarters of the greenhouse gas emission happening around the world. So, it is necessary to move toward a sustainable fuel with minimal carbon emissions to mitigate the rise in global temperature. Bioenergy is considered an effective resource to satisfy the rising global energy demand with minimal carbon emissions. The presence of proven and well-mature technology to convert biomass into various forms of fuels and chemical products provides an upper hand to bioresources over other energy sources. However, the rise in the cost of feedstocks, transportation cost of low-density bioresources, and lack of reliable biomass supply chain network has made them least preferred when compared to solar and wind energy technologies. Hence, it is important to access the scope for commercialization of biomass-based products, which will aid in framing policies to create a sustainable market for them. © 2024 Elsevier Inc. All rights reserved.

The global nations are under pressure to develop a renewable and environmentally friendly fuel/technology from sustainable feedstock, such as woody biomass, to reduce greenhouse gas emissions and meet the energy demand. But several factors must be addressed to achieve the daunting task, which includes technological advancement, financial viability, environmental sustainability, and finally government backing in the form of sensible regulations and increased public awareness. To reduce the world's reliance on fossil fuels and ensure a sustainable future, biofuel policies are crucial. The production of biofuel from woody biomass makes the system not only to reduce the cost of the feedstock but also to decrement the dependency on first-generation feedstocks, which dominates the present biofuel market. Hence, this chapter deals with the need for governing bodies to draft an effective policy for the successful adoption of woody biomass-based biorefinery technologies to mitigate global emissions and to fulfill the growing energy demand thereby enabling a sustainable economy. © 2023 Elsevier Inc. All rights reserved.

Bioenergy resources, when harvested sustainably, have the potential not only to satisfy the growing energy demand but can also aid in achieving a negative carbon footprint. The Intergovernmental Panel on Climate Change (IPCC) has also identified bioenergy resources as an effective tool to achieve zero emissions by 2050 because biomass can be valorized into various products, namely, producer gas, syngas, bioethanol, biomethanol, biochar, bio-oil, etc. by adopting different conversion pathways, thus, aiding in the reduction in consumption of fossil fuel, thereby decreasing the anthropogenic greenhouse gas (GHGs) emission into the atmosphere. However, it is necessary to analyze the economic viability of these biorefinery systems for the faster penetration of these products into the global market and to identify the bottleneck haunting its faster dissemination. In this regard, this chapter analyses the technical and economic factors which affect the biorefinery of woody biomass by employing thermo-chemical and bio-chemical conversion processes. © 2023 Elsevier Inc. All rights reserved.

Woody lignocellulosic biomass is identified as a promising feedstock for liquid biofuel production since it is available throughout the year at a low cost in addition to carbon negative emission capability and no scrutiny as a food source. However, using woody biomass incurs expensive and energy-intensive pretreatment and processing steps in fuel production. This chapter covers woody biomass processing through biochemical routes for liquid transportation fuels (bioethanol and biobutanol) and aviation fuel production. It includes sources of various hardwood and softwood species alongside their compositions. Available pretreatment and hydrolysis techniques and different biochemical conversion approaches are discussed. Lastly, this chapter critically analyzes different studies to identify their processing approaches and operating conditions used for liquid biofuel yield enhancement. It is seen that biochemical conversion fermentation is primarily used for bioethanol and biobutanol production, whereas various thermochemical conversion processes are dominated in bio-jet fuel production from woody biomass. This critical discussion can be helpful for future liquid biofuel production planning, scale-up, and energy policy preparation. © 2023 Elsevier Inc. All rights reserved.

Pretreatment is a critical step in processing lignocellulosic biomass into biofuel and bioproducts and is considered the energy and cost center of the biomass conversion process. Although a large number of pretreatment technologies have been developed, not all the techniques are viable on a commercial scale at this stage. Moreover, the technology choice and process conditions depend highly on the type of biomass and the overall biorefinery scheme. This chapter provides an overview of different pretreatment methods, including their mechanism, important process parameters, current status, and challenges. The opportunities associated with new technologies and approaches are presented. Emphasis is placed on low-severity thermal pretreatment technologies. The chapter also provides a brief discussion of the challenges to achieving the economic viability of the technologies on a commercial scale. © 2023 Elsevier Inc. All rights reserved.

Lignocellulosic wastes have emerged as a potential feedstock in the last decades. There are multiple reasons for its abundance, easy availability, economic, and abundant sources. It can be used to produce several value-added products. Among them, fuel is considered one of the important requirements. Production of fuel from lignocellulosic biomass is a tricky business. The major reason for its failure is the low product yield. Therefore, high yield and low-cost are the two key parameters which need significant optimization. To achieve the target several newer technologies such as pyrolysis, hydrothermal liquefaction and gasification have emerged. These techniques are much more efficient than that of conventional acid or alkali. At the same time quality of the product is also improved. The focus of this review is to analyze the efficiency of chemical conversion of lignocellulosic residues into valuable fuels keeping in mind the cost-reduction strategies. © 2023 Elsevier Ltd

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In this study, a mild two-stage hydrothermal pretreatment was employed to optimally valorize industrial hemp (Cannabis sativa sp.) fibrous waste into sugars for Poly(3-hydroxybuyrate) (PHB) production using recombinant Escherichia coli LSBJ. Biomass was pretreated using hot water at 160, 180, and 200 °C for 5 and 10 min (15% solids), followed by disk refining. The sugar yields during enzymatic hydrolysis were found to improve with increasing temperature and the yields for hot water-disk refining pretreatment (HWDM) were higher compared to only hot water pretreatment at all conditions. The maximum glucose (56 g/L) and cellulose conversion (92%) were achieved for HWDM at 200 °C for 10 min. The hydrolysate obtained was fermented at a sugar concentration of 20 g/L. The PHB inclusion and concentration of 48% and 1.8 g/L, respectively, were similar to those from pure sugars. A pH-controlled fermentation resulted in a near bi-fold increase in PHB yield (3.46 g/L). © 2023 Elsevier Ltd

Biowaste is a major source of organic material that can be converted into energy through various processes such as anaerobic digestion, composting, and pyrolysis. However, emerging pollutants, such as pharmaceuticals, pesticides, herbicides, and personal and household products, are a growing concern in wastewater treatment that can be effectively removed by biowaste-to-energy processes. While these contaminants pose significant challenges, the development and implementation of effective monitoring programs and risk assessment tools help to mitigate their impact on human health and the environment. Likewise, monitoring programs, challenges, legislations, and risk assessment tools are essential for understanding and managing the risks associated with emerging pollutants. Biowaste recycling is an important aspect of a biocircular economy perspective as it involves the conversion of organic waste into valuable resources that can be reused sustainably. The review discusses the modern approaches that offer several advantages, including reducing the waste disposal and generating renewable energy while addressing emerging wastewater treatment pollutants. To achieve the goal of a circular economy, modern biotechnological approaches including anaerobic digestion, composting, bioleaching, bioremediation, and microbial fuel cells offer a sustainable and effective way to convert waste into valuable products. These bioproducts alongside energy generation using waste-to-energy technologies can provide economic benefits through revenue generation, reduced waste disposal costs, and improved resource efficiency. To achieve a biocircular economy for biowaste valorization, several stakeholders, including waste collectors, waste management companies, policymakers, and consumers need to be involved. The sustainable conversion of biowaste to energy is an essential and instrumental technology in environmental sustainability. Graphical Abstract: [Figure not available: see fulltext.]. © 2023, The Author(s), under exclusive licence to Springer Nature Switzerland AG.

Woody biomass, the most abundant and high energy density bioenergy resource, is used inefficiently to satisfy the domestic heating and cooking demands of the people. Despite being a carbon-neutral source when harvested sustainably, the inefficient use of biomass to satisfy the cooking demand of marginalized people led to poor indoor air quality and causing respiratory health problems. Hence, it is necessary to identify a technology that enables the conversion of woody biomass into fuel that does not affect indoor air quality. In this regard, the conversion of woody biomass into biogas by anaerobic digestion emerges as the viable option. However, the recalcitrance nature of woody biomass necessitates a pretreatment before being fed to an anaerobic digestor, increasing the capital and operating cost of the biogas system. But usage of this technology to convert woody biomass to gaseous fuel can aid in sustainable development. The waste digested from the anaerobic digestor can be used as manure for agricultural crops in rural areas. Meanwhile, fly ash generated during the combustion of the woody biomass is also inhibited thereby resulting in an improvement in air quality. In this regard, this chapter presents the recent developments and factors affecting biogas production from woody biomass. © 2023 Elsevier Inc. All rights reserved.

Nutrient recovery systems can help to mitigate the negative effects of N and P in WW (wastewater), which when not recovered causes eutrophication in aquatic ecosystems. Using SimaPro (V9.3), the lifecycle assessment (LCA) of four nutrient recovery systems and sewage treatment plant (STP) were compared in this study. The findings showed that a fuel cell with a single-pot WW treatment system can function as a negative emission system with a global warming potential (GWP) of −234 gCO2 Eq./m3 of WW. Nutrient recovery reduces carbon footprint by 56–98% when compared to traditional fertilizers like diammonium phosphate (DAP) and urea. One of the main conclusions of this research was that single-pot systems perform better for the environment than add-on systems, which suggests that microalgae could perform better for the environment in a single-pot system. Recovering nutrients from WW not only improves self-reliance in the economy by decrementing the fertilizer import but also saves the environment. © 2023 Elsevier Ltd

Biomethane from anaerobic digestion of agricultural feedstock is a versatile energy vector for decarbonising agriculture, heavy transport and heat. To lower costs and increase the emission-savings potential, photosynthetic biogas upgrading, cogenerating microalgae with biomethane is investigated here. In a first-of-its-kind work, this paper reports the enviro-economic performance and the marginal (CO2) abatement cost (MAC) of a polygeneration plant co-producing energy (biomethane), food (Spirulina powder) and bio-fertiliser (digestate) from agricultural feedstock using photosynthetic biogas upgrading at small, medium, and industrial scales. A negative MAC at industrial scale (3 MW biomethane), highlighted the environmental and economic benefit (net present value > 11.5 million€ and internal rate of return >40%) of the process as a low-carbon technology over conventional biomethane production processes at a biomethane sale price of 3 c€/kWh (comparable to natural gas). The operational expenditure, including the cost of the Spirulina cultivation medium and the plant capacity factor had the highest influence on its profitability. Replacing beef as a complete food with Spirulina powder maximised the emission savings rather than replacing beef protein with Spirulina protein. Economic allocation as opposed to energy allocation ensured that the levelised cost and specific greenhouse gas emissions of biomethane (<5 c€/kWh; < 3.5 gCO2-eq/MJ), Spirulina powder (<68 €/kg; < 4 kgCO2-eq/kg) and digestate (<5.60 €/tonne; < 0.41 kgCO2-eq/kg-nitrogen) are better than market-available alternatives across all scales. Trading emission savings from biomethane in the European Union emission trading system should allow the financial viability of smaller-scale processes by 2030. © 2022

Biomethane is a viable alternative to natural gas and diesel for decarbonising hard-to-abate sectors such as agriculture, industry and heavy transport. Unlike conventional biogas upgrading, photosynthetic biogas upgrading cogenerates biomethane, biofertiliser and microalgal bioproducts with the potential to improve resource utilisation and process performance in a circular economy. In this paper, a photosynthetic biogas upgrading-based polygeneration process is proposed and analysed to co-produce biofuel (biomethane), bio-fertiliser (digestate) and food (Spirulina powder, protein supplement) using agricultural feedstock. Based on a multi-criteria performance assessment, the economic and environmental benefits of the process are demonstrated. Thermodynamic performance of the process revealed that reducing the energy for greenhouse heating to cultivate microalgae would enable a higher energy output than input. Using economic allocation, a carbon footprint of biomethane less than 10 gCO2-eq/MJ (lower than 32.9 gCO2-eq/MJ for sustainable biomethane use in transport in the EU Renewable Energy Directive (Recast) (RED-II)); Spirulina protein of 0.8 kgCO2-eq/100 g protein (compared to 50 kgCO2-eq/100 g protein for beef); and digestate of 0.4 kgCO2-eq/kgN (comparing positively to 1.5–3 kgCO2-eq/kgN for synthetic nitrogenous fertiliser) was achieved. Unlike the current RED-II mandated methodology, the analysis established that the energy, CO2 emissions, land and water footprints of each co-product are best represented using an economic allocation principle. Based on the extended nutrition profile, Spirulina as a complete food outperforms most meat and plant-based protein alternatives in terms of CO2 emissions, land, and water footprints. © 2022

With the huge energy demand inevitably exacerbates the non-renewable resources depletion and ecological-social challenges, renewable energy has become a crucial participant in sustainable strategy. Biorefinery emerged as a sustainable approach and recognized promising transformation platforms for products, to achieve circular bioeconomy which focuses on the biomass efficient and sustainable valorization, promotes resource regeneration and restorative. The emerged biowaste biorefinery has proved as sustainable approach for integrated bioproducts and further applied this technology in industrial, commercial, agricultural and energy sectors. Based on carbon neutral sustainable development, this review comprehensive explained the biowaste as renewable resource generation and resource utilization technologies from the perspective of energy, nutrient and material recovery in the concept of biorefinery. Integrate biorefinery concepts into biowaste management is promise for conversion biowaste into value-added materials and contribute as driving force to cope with resource scarcity, climate changes and huge material demand in circular bioeconomy. In practice, the optimal of biorefinery technologies depends on environmentally friendly, economic and technical feasibility, social and policy acceptance. Additionally, policy interventions are necessary to promote biowaste biorefinery implements for circular bioeconomy and contribute to low-carbon cleaner environment. © 2022 Elsevier Ltd

Increases in population and urbanization leads to generation of a large amount of food waste (FW) and its effective waste management is a major concern. But putrescible nature and high moisture content is a major limiting factor for cost effective FW valorization. Bioconversion of FW for the production of value added products is an eco-friendly and economically viable strategy for addressing these issues. Targeting on production of multiple products will solve these issues to greater extent. This article provides an overview of bioconversion of FW to different value added products. © 2022 Elsevier Ltd

This review provides an update on the state-of-the art technologies for the valorization of solid waste and its mechanism to generate various bio-products. The organic content of these wastes can be easily utilized by the microbes and produce value-added compounds. Microbial fermentation techniques can be utilized for developing waste biorefinery processes. The utilization of lignocellulosic and plastics wastes for the generation of carbon sources for microbial utilization after pre-processing steps will make the process a multi-product biorefinery. The C1 and C2 gases generated from different industries could also be utilized by various microbes, and this will help to control global warming. The review seeks to expand expertise about the potential application through several perspectives, factors influencing remediation, issues, and prospects. © 2022 Elsevier Ltd

Lignocellulosic ethanol has been proposed as a green alternative to fossil fuels for many decades. However, commercialization of lignocellulosic ethanol faces major hurdles including pretreatment, efficient sugar release and fermentation. Several processes were developed to overcome these challenges e.g. simultaneous saccharification and fermentation (SSF). This review highlights the various ethanol production processes with their advantages and shortcomings. Recent technologies such as singlepot biorefineries, combined bioprocessing, and bioenergy systems with carbon capture are promising. However, these technologies have a lower technology readiness level (TRL), implying that additional efforts are necessary before being evaluated for commercial availability. Solving energy needs is not only a technological solution and interlinkage of various factors needs to be assessed beyond technology development. © 2019 Elsevier Ltd