This study assesses the environmental impact of pine chip-based biorefinery processes, focusing on bioethanol, xylonic acid, and lignin production. A cradle-to-gate Life Cycle Assessment (LCA) is employed, comparing a novel biphasic pretreatment method (p-toluenesulfonic acid (TsOH)/pentanol, Sc-1) with conventional sulfuric acid pretreatment (H2SO4, Sc-2). The analysis spans biomass handling, pretreatment, enzymatic hydrolysis, yeast fermentation, and distillation. Sc-1 yielded an environmental impact of 1.45E+01 kPt, predominantly affecting human health (96.55%), followed by ecosystems (3.07%) and resources (0.38%). Bioethanol, xylonic acid, and lignin contributed 32.61%, 29.28%, and 38.11% to the total environmental burdens, respectively. Sc-2 resulted in an environmental burden of 1.64E+01 kPt, with a primary impact on human health (96.56%) and smaller roles for ecosystems (3.07%) and resources (0.38%). Bioethanol, xylonic acid, and lignin contributed differently at 22.59%, 12.5%, and 64.91%, respectively. Electricity generation was predominant in both scenarios, accounting for 99.05% of the environmental impact, primarily driven by its extensive usage in biomass handling and pretreatment processes. Sc-1 demonstrated a 13.05% lower environmental impact than Sc-2 due to decreased electricity consumption and increased bioethanol and xylonic acid outputs. This study highlights the pivotal role of pretreatment methods in wood-based biorefineries and underscores the urgency of sustainable alternatives like TsOH/pentanol. Additionally, adopting greener electricity generation, advanced technologies, and process optimization are crucial for reducing the environmental footprint of waste-based biorefineries while preserving valuable bioproduct production.
The development of algae is seen as a potential and ecologically sound approach to address the increasing demands in multiple sectors. However, successful implementation of processes is highly dependent on effective growing and harvesting methods. The present study provides a complete examination of contemporary techniques employed in the production and harvesting of algae, with a particular emphasis on their sustainability. The review begins by examining several culture strategies, encompassing open ponds, closed photobioreactors, and raceway ponds. The analysis of each method is conducted in a systematic manner, with a particular focus on highlighting their advantages, limitations, and potential for expansion. This approach ensures that the conversation is in line with the objectives of sustainability. Moreover, this study explores essential elements of algae harvesting, including the processes of cell separation, dewatering, and biomass extraction. Traditional methods such as centrifugation, filtration, and sedimentation are examined in conjunction with novel, environmentally concerned strategies including flocculation, electro-coagulation, and membrane filtration. It evaluates the impacts on the environment that are caused by the cultivation process, including the usage of water and land, the use of energy, the production of carbon dioxide, and the runoff of nutrients. Furthermore, this study presents a thorough examination of the current body of research pertaining to Life Cycle Analysis (LCA) studies, presenting a perspective that emphasizes sustainability in the context of algae harvesting systems. In conclusion, the analysis ends up with an examination ahead at potential areas for future study in the cultivation and harvesting of algae. This review is an essential guide for scientists, policymakers, and industry experts associated with the advancement and implementation of algae-based technologies.
In this study, Sulphated/AlMCM-41 (S/AlMCM-41) catalysts were synthesized and used to produce biodiesel from CFMO. Different percentages of S/AlMCM-41 catalysts were prepared and characterized by X-ray diffraction, BET studies, TPD, and SEM-EDS analysis. Sulphur incorporation to the MCM framework though reduced the surface area, and pore volume of the catalyst, sufficient acidity were produced in the catalyst surface. The existence of functional groups and the composition of the biodiesel obtained was analysed by FTIR and GC-MS. S/AlMCM-41 (80%) catalyst presented a high catalytic activity with maximum biodiesel conversion % when compared to other variants. The bio-ester produced from CFMO with S/AlMCM-41 (80%) catalyst possessed the higher calorific value of 50 MJ/kg and flashpoint of 153 °C and other properties analogous to the standard biodiesel. The engine performance was examined for biodiesel blends with neat diesel, where biodiesel blends performed better than neat diesel. The exhaust gas emission studies also highlighted that the obtained biodiesel showed emission characteristics similar to the standard biodiesel, whereas marginally higher emission for CO and CO2 of about 2.2 and 7.9% was reported.
The study investigates the potential of utilizing banana trunk-derived porous activated biochar enriched with SO3H- as a catalyst for eco-friendly biodiesel production from the microalga Chlorella vulgaris. An extensive analysis, employing advanced techniques such as XRD, FTIR, TGA, XPS, NH3-TPD, BET, SEM-EDX, and TEM, was conducted to elucidate the physicochemical properties of BT-SO3H catalysts. The synthesized catalyst demonstrated its efficiency in converting the total lipids of Chlorella vulgaris into biodiesel, with varying concentrations of 3%, 5%, and 7%. Notably, using a 5% BT-SO3H concentration resulted in remarkably higher biodiesel production about 58.29%. Additionally, the fatty acid profile of C. vulgaris biodiesel indicated that C16:0 was the predominant fatty acid at 24.31%, followed by C18:1 (19.68%), C18:3 (11.45%), and C16:1 (7.56%). Furthermore, the biodiesel produced via 5% BT-SO3H was estimated to have higher levels of saturated fatty acids (SFAs) at 34.28%, monounsaturated fatty acids (MUFAs) at 30.70%, and polyunsaturated fatty acids (PUFAs) at 24.24%. These findings highlight the promising potential of BT-SO3H catalysts for efficient and environmentally friendly biodiesel production from microalgal species.
Cultivation of microalgae in wastewater stream has been extensively reported, especially for simultaneous production of biolipid and wastewater treatment process. This study aimed to derive the research trend and focus on biolipid production from microalgae cultivated in wastewater by using bibliometric approach. The search strategy used in Scopus database resulted in 1339 research articles from 1990 to November 2023. Majority of publications (46%) were affiliated to China and India, showing their predominance in this field. Keywords related to the center of attention included biodiesel, biofuel, biomass and nutrient removal. Meanwhile, keyword with recent publication year, indicating the emerging research trends, revolved around the cultivation techniques and application of the system. Co-culture involving more than one microalgae species, bacteria and yeast showed promising results, while addition of nanoparticles was also found to be beneficial. Increasing exploration on the application of microalgae for treatment of saline wastewater was also reported and the carbon fixation mechanism by microalgae has been widely investigated to promote less environmental impact. Future research on these topics were suggested based on the findings of the bibliometric analyses.
Microalgal lipids are promising and sustainable sources for the production of third-generation biofuels, foods, and medicines. A high lipid yield during the extraction process in microalgae could be influenced by the suitable pretreatment and lipid extraction methods. The extraction method itself could be attributed to the economic and environmental impacts on the industry. This review summarizes the pretreatment methods including mechanical and non-mechanical techniques for cell lysis strategy before lipid extraction in microalgae biomass. The multiple strategies to achieve high lipid yields via cell disruption techniques are discussed. These strategies include mechanical (shear forces, pulse electric forces, waves, and temperature shock) and non-mechanical (chemicals, osmotic pressure, and biological) methods. At present, two techniques of the pretreatment method can be combined to increase lipid extraction from microalgae. Therefore, the extraction strategy for a large-scale application could be further strengthened to optimize lipid recovery by microalgae.
Waste-to-energy conversion presents a pivotal strategy for mitigating the energy crisis and curbing environmental pollution. Pyrolysis is a widely embraced thermochemical approach for transforming waste into valuable energy resources. This study delves into the co-pyrolysis of terrestrial biomass (potato peel) and marine biomass (Sargassum angastifolium) to optimize the quantity and quality of the resultant bio-oil and biochar. Initially, thermogravimetric analysis was conducted at varying heating rates (5, 20, and 50 °C/min) to elucidate the thermal degradation behavior of individual samples. Subsequently, comprehensive analyses employing FTIR, XRD, XRF, BET, FE-SEM, and GC-MS were employed to assess the composition and morphology of pyrolysis products. Results demonstrated an augmented bio-oil yield in mixed samples, with the highest yield of 27.1 wt% attained in a composition comprising 75% potato peel and 25% Sargassum angastifolium. As confirmed by GC-MS analysis, mixed samples exhibited reduced acidity, particularly evident in the bio-oil produced from a 75% Sargassum angastifolium blend, which exhibited approximately half the original acidity. FTIR analysis revealed key functional groups on the biochar surface, including O-H, CO, and C-O moieties. XRD and XRF analyses indicated the presence of alkali and alkaline earth metals in the biochar, while BET analysis showed a surface area ranging from 0.64 to 1.60 m2/g. The favorable characteristics of the products highlight the efficacy and cost-effectiveness of co-pyrolyzing terrestrial and marine biomass for the generation of biofuels and value-added commodities.
Dealing with the current defaults of environmental toxicity, heating, waste management, and economic crises, exploration of novel non-edible, toxic, and waste feedstock for renewable biodiesel synthesis is the need of the hour. The present study is concerned with Buxus papillosa with seeds oil concentration (45% w/w), a promising biodiesel feedstock encountering environmental defaults and waste management; in addition, this research performed simulation based-response surface methodology (RSM) for Buxus papillosa bio-diesel. Synthesis and application of novel Phyto-nanocatalyst bimetallic oxide with Buxus papillosa fruit capsule aqueous extract was advantageous during transesterification. Characterization of sodium/potassium oxide Phyto-nanocatalyst confirmed 23.5 nm nano-size and enhanced catalytic activity. Other characterizing tools are FTIR, DRS, XRD, Zeta potential, SEM, and EDX. Methyl ester formation was authenticated by FTIR, GC-MS, and NMR. A maximum 97% yield was obtained at optimized conditions i.e., methanol ratio to oil (8:1), catalyst amount (0.37 wt%), reaction duration (180 min), and temperature of 80 °C. The reusability of novel sodium/potassium oxide was checked for six reactions. Buxus papillosa fuel properties were within the international restrictions of fuel. The sulphur content of 0.00090% signified the environmental remedial nature of Buxus papillosa methyl esters and it is a highly recommendable species for biodiesel production at large scale due to a t huge number of seeds production and vast distribution.
The augmentation of biogas production can be achieved by incorporating metallic nanoparticles as additives within anaerobic digestion. The objective of this current study is to examine the synthesis of Fe-Ni-Zn and Fe-Co-Zn trimetallic nanoparticles using the co-precipitation technique and assess its impact on anaerobic digestion using palm oil mill effluent (POME) as carbon source. The structural morphology and size of the synthesised trimetallic nanoparticles were analysed using a range of characterization techniques, such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDX) . The average size of Fe-Ni-Zn and Fe-Co-Zn were 19-25.5 nm and 19.1-30.5 nm respectively. Further, investigation focused on examining the diverse concentrations of trimetallic nanoparticles, ranging from 0 to 50 mgL-1. The biogas production increased by 55.55% and 60.11% with Fe-Ni-Zn and Fe-Co-Zn trimetallic nanoparticles at 40 mgL-1 and 20 mgL-1, respectively. Moreover, the lowest biogas of 11.11% and 38.11% were found with 10 mgL-1 of Fe-Ni-Zn and Fe-Co-Zn trimetallic nanoparticles. The findings of this study indicated that the trimetallic nanoparticles exhibited interactions with anaerobes, thereby enhancing the degradation process of palm oil mill effluent (POME) and biogas production. The study underscores the potential efficacy of trimetallic nanoparticles as a viable supplement for the promotion of sustainable biogas generation.
Microalgae showcase an extraordinary capacity for synthesizing high-value phytochemicals (HVPCs), offering substantial potential for diverse applications across various industries. Emerging research suggests that subjecting microalgae to abiotic stress during cultivation and the harvesting stages can further enhance the accumulation of valuable metabolites within their cells, including carotenoids, antioxidants, and vitamins. This study delves into the pivotal impacts of manipulating abiotic stress on microalgae yields, with a particular focus on biomass and selected HVPCs that have received limited attention in the existing literature. Moreover, approaches to utilising abiotic stress to increase HVPCs production while minimising adverse effects on biomass productivity were discussed. The present study also encompasses a techno-economic assessment (TEA) aimed at pinpointing significant bottlenecks in the conversion of microalgae biomass into high-value products and evaluating the desirability of various conversion pathways. The TEA methodology serves as a valuable tool for both researchers and practitioners in the quest to identify sustainable strategies for transforming microalgae biomass into high-value products and goods. Overall, this comprehensive review sheds light on the pivotal role of abiotic stress in microalgae cultivation, promising insights that could lead to more efficient and sustainable approaches for HVPCs production.
Algae-based biofuel developed over the past decade has become a viable substitute for petroleum-based energy sources. Due to their high lipid accumulation rates and low carbon dioxide emissions, microalgal species are considered highly valuable feedstock for biofuel generation. This review article presented the importance of biofuel and the flaws that need to be overcome to ensure algae-based biofuels are effective for future-ready bioenergy sources. Besides, several issues related to the optimization and engineering strategies to be implemented for microalgae-based biofuel derivatives and their production were evaluated. In addition, the fundamental studies on the microalgae technology, experimental cultivation, and engineering processes involved in the development are all measures that are commendably used in the pre-treatment processes. The review article also provides a comprehensive overview of the latest findings about various algae species cultivation and biomass production. It concludes with the most recent data on environmental consequences, their relevance to global efforts to create microalgae-based biomass as effective biofuels, and the most significant threats and future possibilities.
This critical review for anaerobic degradation of complex organic compounds like butyrate using reactors has been enormously applied for biogas production. Biogas production rate has a great impact on: reactor granulation methanogenesis, nutrient content, shear velocity, organic loading and loss of nutrients taking place in the reactor continuously. Various technologies have been applied to closed anaerobic reactors to improve biogas production and treatment efficiency. Recent reviews showed that the application of closed anaerobic reactors can accelerate the degradation of organics like volatile fatty acid-butyrate and affect microbial biofilm formation by increasing the number of methanogens and increase methane production 16.5 L-1 CH4 L-1 POME-1. The closed anaerobic reactors with stable microbial biofilm and established organic load were responsible for the improvement of the reactor and methane production. The technology mentioned in this review can be used to monitor biogas concentration, which directly correlates to organic concentrations. This review attempts to evaluate interactions among the: degradation of organics, closed anaerobic reactors system, and microbial granules. This article provides a useful picture for the improvement of the degradation of organic butyrate for COD removal, biogas and methane production in an anaerobic closed reactor.
The prevalence of organic solid waste worldwide has turned into a problem that requires comprehensive treatment on all fronts. The amount of agricultural waste generated by agro-based industries has more than triplet. It not only pollutes the environment but also wastes a lot of beneficial biomass resources. These wastes may be utilized as a different option/source for the manufacturing of many goods, including biogas, biofertilizers, biofuel, mushrooms and tempeh as the primary ingredients in numerous industries. Utilizing agro-industrial wastes as good raw materials may provide cost reduction and lower environmental pollution levels. Agro-industrial wastes are converted into biofuels, enzymes, vitamin supplements, antioxidants, livestock feed, antibiotics, biofertilizers and other compounds via solid-state fermentation (SSF). By definition, SSF is a method used when there is little to no free water available. As a result, it permits the use of solid materials as biotransformation substrates. Through SSF methods, a variety of microorganisms are employed to produce these worthwhile things. SSFs are therefore reviewed and discussed along with their impact on the production of value-added items. This review will provide thorough essential details information on recycling and the use of agricultural waste.
There are several environmental and human health impacts if human hair waste is not adequately disposed of. In this study, pyrolysis of discarded human hair was carried out. This research focused on the pyrolysis of discarded human hair under controlled environmental conditions. The effects of the mass of discarded human hair and temperature on bio-oil yield were studied. The proximate and ultimate analyses and calorific values of disposed of human hair, bio-oil, and biochar were determined. Further, chemical compounds of bio-oil were analyzed using a gas chromatograph and a mass spectrometer. Finally, the kinetic modeling and behavior of the pyrolysis process were characterized through FT-IR spectroscopy and thermal analysis. Based on the optimized mass of disposed of human hair, 250 g had a better bio-oil yield of 97% in the temperature range of 210-300 °C. The different parameters of bio-oil were: pH (2.87), specific gravity (1.17), moisture content (19%), heating value (19.34 MJ/kg), and viscosity (50 CP). C (56.4%), H (6.1%), N (0.16%), S (0.01%), O (38.4%), and Ash (0.1%) were discovered to be the elemental chemical composition of bio-oil (on a dry basis). During breakdown, the release of different compounds like hydrocarbons, aldehydes, ketones, acids, and alcohols takes place. According to the GC-MS results, several amino acids were discovered in the bio-oil, 12 abundant in the discarded human hair. The FTIR and thermal analysis found different concluding temperatures and wave numbers for functional groups. Two main stages are partially separated at about 305 °C, with maximum degradation rates at about 293 oC and 400-4140 °C, respectively. The mass loss was 30% at 293 0C and 82% at temperatures above 293 0C. When the temperature reached 4100C, the entire bio-oil from discarded human hair was distilled or thermally decomposed.
This study aimed at investigating the biohydrogen and biomethane potential of co-digestion from palm oil mill effluent (POME) and concentrated latex wastewater (CLW) in a two-stage anaerobic digestion (AD) process under thermophilic (55 ± 3 °C) and at an ambient temperature (30 ± 3 °C) conditions, respectively. The batch experiments of POME:CLW mixing ratios of 100:0, 70:30, 50:50, 30:70, and 0:100 was investigated with the initial loadings at 10 g-VS/L. The highest hydrogen yield of 115.57 mLH2/g-VS was obtained from the POME: CLW mixing ratio of 100:0 with 29.0 of C/N ratio. While, the highest subsequent methane production yield of 558.01 mLCH4/g-VS was achieved from hydrogen effluent from POME:CLW mixing ratio of 70:30 0 with 21.8 of C/N ratio. This mixing ratio revealed the highest synergisms of about 9.21% and received maximum total energy of 19.70 kJ/g-VS. Additionally, continuous hydrogen and methane production were subsequently performed in a series of continuous stirred tank reactor (CSTR) and up-flow anaerobic sludge blanket reactor (UASB) to treat the co-substate. The results indicated that the highest hydrogen yield of POME:CLW mixing ratio at 70:30 of 95.45 mL-H2/g-VS was generated at 7-day HRT, while methane production was obtained from HRT 15 days with a yield of 204.52 mL-CH4/g-VS. Thus, the study indicated that biogas production yield of CLW could be enhanced by co-digesting with POME. In addition, the two-stage AD model under anaerobic digestion model no. 1 (ADM-1) framework was established, 9.10% and 2.43% of error fitting of hydrogen and methane gas between model simulation data and experimental data were found. Hence, this research work presents a novel approach for optimization and feasibility for co-digestion of POME with CLW to generate mixed gaseous biofuel potentially.
Life cycle assessment was used to evaluate the environmental impacts of phytoplanktonic biofuels as possible sustainable alternatives to fossil fuels. Three scenarios were examined for converting planktonic biomass into higher-value commodities and energy streams using the alga Scenedesmus sp. and the cyanobacterium Arthrospira sp. as the species of interest. The first scenario (Sc-1) involved the production of biodiesel and glycerol from the planktonic biomass. In the second scenario (Sc-2), biodiesel and glycerol were generated from the planktonic biomass, and biogas was produced from the residual biomass. The process also involved using a catalyst derived from snail shells for biodiesel production. The third scenario (Sc-3) was similar to Sc-2 but converted CO2 from the biogas upgrading to methanol, which was then used in synthesizing biodiesel. The results indicated that Sc-2 and Sc-3 had a reduced potential (up to 60 % less) for damaging human health compared to Sc-1. Sc-2 and Sc-3 had up to 61 % less environmental impact than Sc-1. Sc-2 and Sc-3 reduced the total cumulative exergy demand by up to 44 % compared to Sc-1. In conclusion, producing chemicals and utilities within the biorefinery could significantly improve environmental sustainability, reduce waste, and diversify revenue streams.
Life cycle assessments of microalgal cultivation systems are often conducted to evaluate the sustainability and feasibility factors of the entire production chain. Unlike widely reported conventional microalgal cultivation systems, the present work adopted a microalgal-bacterial cultivation approach which was upscaled into a pilot-scale continuous photobioreactor for microalgal biomass production into biodiesel from wastewater resources. A multiple cradle-to-cradle system ranging from microalgal biomass-to-lipid-to-biodiesel was evaluated to provide insights into the energy demand of each processes making up the microalgae-to-biodiesel value chain system. Energy feasibility studies revealed positive NER values (4.95-8.38) for producing microalgal biomass but deficit values for microalgal-to-biodiesel (0.14-0.23), stemming from the high energy input requirements in the downstream processes for converting biomass into lipid and biodiesel accounting to 88-90% of the cumulative energy demand. Although the energy balance for microalgae-to-biodiesel is in the deficits, it is comparable with other reported biodiesel production case studies (0.12-0.40). Nevertheless, the approach to using microalgal-bacterial cultivation system has improved the overall energy efficiency especially in the upstream processes compared to conventional microalgal cultivation systems. Energy life cycle assessments with other microalgal based biofuel systems also proposed effective measures in increasing the energy feasibility either by utilizing the residual biomass and less energy demanding downstream extraction processes from microalgal biomass. The microalgal-bacterial cultivation system is anticipated to offer both environmental and economic prospects for upscaling by effectively exploiting the low-cost nutrients from wastewaters via bioconversion into valuable microalgal biomass and biodiesel.
Microalgae have been recognized as emerging cell factories due to the high value-added bio-products. However, the balance between algal growth and the accumulation of metabolites is always the main contradiction in algal biomass production. Hence, the security and effectiveness of regulating microalgal growth and metabolism simultaneously have drawn substantial attention. Since the correspondence between microalgal growth and reactive oxygen species (ROS) level has been confirmed, improving its growth under oxidative stress and promoting biomass accumulation under non-oxidative stress by exogenous mitigators is feasible. This paper first introduced ROS generation in microalgae and described the effects of different abiotic stresses on the physiological and biochemical status of microalgae from these aspects associated with growth, cell morphology and structure, and antioxidant system. Secondly, the role of exogenous mitigators with different mechanisms in alleviating abiotic stress was concluded. Finally, the possibility of exogenous antioxidants regulating microalgal growth and improving the accumulation of specific products under non-stress conditions was discussed.
The depletion of fossil fuel sources and increase in energy demands have increased the need for a sustainable alternative energy source. The ability to produce hydrogen from microalgae is generating a lot of attention in both academia and industry. Due to complex production procedures, the commercial production of microalgal biohydrogen is not yet practical. Developing the most optimum microalgal hydrogen production process is also very laborious and expensive as proven from the experimental measurement. Therefore, this research project intended to analyse the random time series dataset collected during microalgal hydrogen productions while using various low thermally pre-treated palm kernel expeller (PKE) waste via machine learning (ML) approach. The analysis of collected dataset allowed the derivation of an enhanced kinetic model based on the Gompertz model amidst the dark fermentative hydrogen production that integrated thermal pre-treatment duration as a function within the model. The optimum microalgal hydrogen production attained with the enhanced kinetic model was 387.1 mL/g microalgae after 6 days with 1 h thermally pre-treated PKE waste at 90 °C. The enhanced model also had better accuracy (R2 = 0.9556) and net energy ratio (NER) value (0.71) than previous studies. Finally, the NER could be further improved to 0.91 when the microalgal culture was reused, heralding the potential application of ML in optimizing the microalgal hydrogen production process.
Sustainable energy transition has brought the attention towards microalgae utilization as potential feedstock due to its tremendous capabilities over its predecessors for generating more energy with reduced carbon footprint. However, the commercialization of microalgae feedstock remains debatable due to the various factors and considerations taken into scaling-up the conventional microalgal upstream processes. This review provides a state-of-the-art assessment over the recent developments of available and existing microalgal upstream cultivation systems catered for maximum biomass production. The key growth parameters and main cultivation modes necessary for optimized microalgal growth conditions along with the fundamental aspects were also reviewed and evaluated comprehensively. In addition, the advancements and strategies towards potential scale-up of the microalgal cultivation technologies were highlighted to provide insights for further development into the upstream processes aimed at sustainable circular bioeconomy.