In-depth study of bio-oil and biochar production from macroalgae Sargassum sp. via slow pyrolysis

Repurposing waste-iron electrocoagulated algal biomass as effective heterogenous (bio)electro-fenton catalyst for phthalate removal from wastewater

The presence of refractory micropollutants in natural waters poses significant environmental and health risks. Preferably, advanced oxidation techniques like electro-Fenton (EF) and bio-electro-Fenton (BEF) are used to mitigate micropollutants; nevertheless, their field-scale implementation is limited by prohibitive catalyst cost. As an alternative, waste-iron electrocoagulated algal biomass (A-BC/Fe) was explored as a heterogeneous Fenton catalyst to eliminate dimethyl phthalate (DMP) from wastewater. The Fenton-conducive morphological, chemical, and electrochemical properties of the A-BC/Fe catalyst were revealed by detailed characterisation. In EF treatment, 10 mg/L of DMP was completely degraded within 15 min at pH of 7.0, 50 mM Na2SO4, and cathode potential of - 1.4 V vs. Ag/AgCl. Moreover, the EF system achieved 87.80 ± 2.10% and 96.14 ± 1.10% of DMP removal from secondary and tertiary treated municipal sewage, respectively. The A-BC/Fe catalyst-driven EF process disintegrated DMP into benign non-toxic by-products and showed stable performance over eight batch cycles with only a 1.71% decline in DMP removal efficiency. Further, the A-BC/Fe-catalysed BEF system eliminated 94.81 ± 1.90% of DMP in 4 h while achieving a maximum power density of 124.03 ± 5.64 mW/m2. This investigation underscores the potential of repurposing electrocoagulated algal biomass as a sustainable heterogenous catalyst for micropollutant remediation.

Effect of pyrolysis temperature on physicochemical characteristics and toxic elements for grub manure-derived biochar

While traditional solutions for disposing of animal manure are limited by their time-consuming nature and inefficiency, the pyrolysis of animal manure into biochar is considered a promising disposal option, offering high-value benefits. However, there are few research studies on the physicochemical properties and potential utilization pathway of grub manure-derived biochar (GB) prepared at different temperatures. In this study, grub manure (GM) was pyrolyzed at 450, 600 and 750 °C, and the effect of pyrolysis temperature on the characteristics and applications of GB was illustrated. The results showed that increasing pyrolysis temperature promoted the formation of an aromatic structure, enhanced the stability, and improved the surface pore structure of GB. The relationship between pyrolysis temperature and C/N-containing functional groups in GB was quantitatively analyzed. In the process of pyrolysis of GM to GB, carbonates first decomposed, and then, C[double bond, length as m-dash]O broke into C-O and finally condensed to form an aromatic ring structure at elevated pyrolysis temperature. Although GM was rich in organic matter and total N/P/K, the potentially toxic elements (PTEs) (Ni, Cu, Cd, Pb, Zn and As) in GM presented potential risk. The hazard of PTEs in GB was significantly decreased after GM was pyrolyzed. Overall, pyrolysis provided an opportunity for the sustainable management of GM, and GB is a multi-purpose and high-value product that could be applied in soil improvement, environmental remediation, and climate change mitigation for achieving sustainable development.

Bacterial cellulose microfilament biochar-architectured chitosan/polyethyleneimine beads for enhanced tetracycline and metronidazole adsorption

This study investigates the potential applications of incorporating 2D bacterial cellulose microfibers (BCM) biochar into chitosan/polyethyleneimine beads as a semi-natural sorbent for the efficient removal of tetracycline (TET) and metronidazole (MET) antibiotics. Batch adsorption experiments and characterization techniques evaluate removal performance and synthesized adsorbent properties. The adsorbent eliminated 99.13 % and 90 % of TET and MET at a 10 mg.L-1 concentration with optimal pH values of 8 and 6, respectively, for 90 min. Under optimum conditions and a 400 mg.L-1 concentration, MET and TET have possessed the maximum adsorption capacities of 691.325 and 960.778 mg.g-1, respectively. According to the isothermal analysis, the adsorption of TET fundamentally follows the Temkin (R2 = 0.997), Redlich-Peterson (R2 = 0.996), and Langmuir (R2 = 0.996) models. In contrast, the MET adsorption can be described by the Langmuir (R2 = 0.997), and Toth (R2 = 0.991) models. The pseudo-second-order (R2 = 0.998, 0.992) and Avrami (R2 = 0.999, 0.999) kinetic models were well-fitted with the kinetic results for MET and TET respectively. Diffusion models recommend that pore, liquid-film, and intraparticle diffusion govern the rate of the adsorption process. The developed semi-natural sorbent demonstrated exceptional adsorption capacity over eleven cycles due to its porous bead structure, making it a potential candidate for wastewater remediation.

Valorization of Rejected Macroalgae Kappaphycopsis cottonii for Bio-Oil and Bio-Char Production via Slow Pyrolysis

Kappaphycopsis cottonii, a prominent macroalgae species cultivated in an Indonesian marine culture, yields significant biomass, a portion of which is often rejected by industry. This study explores the potential valorization of rejected K. cottonii biomass through slow pyrolysis for bio-oil and biochar production, presenting an alternative and sustainable utilization pathway. The study utilizes a batch reactor setup for the thermal decomposition of K. cottonii, conducted at temperatures between 400 and 600 °C and varying time intervals between 10 and 50 min. The study elucidates the temperature-dependent behavior of K. cottonii during slow pyrolysis, emphasizing its impact on product distributions. The results suggest that there is a rise in bio-oil production when the pyrolysis temperature is raised from 400 to 500 °C. This uptick is believed to be due to improved dehydration and greater thermal breakdown of the algal biomass. Conversely, at 600 °C, bio-oil yield diminishes, indicating secondary cracking of liquid products and the generation of noncondensable gases. Chemical analysis of bio-oils reveals substantial quantities of furan derivatives, aliphatic hydrocarbons, and carboxylic acids. Biochar exhibits calorific values within the range of 17.52-19.46 MJ kg-1, and slow pyrolysis enhances its specific surface area, accompanied by the observation of carbon nanostructures. The study not only investigates product yields but also deduces plausible reaction routes for the generation of certain substances throughout the process of slow pyrolysis. Overall, the slow pyrolysis of rejected K. cottonii presents an opportunity to obtain valuable chemicals and biochar. These products hold promise for applications such as biofuels and diverse uses in wastewater treatment, catalysis, and adsorption, contributing to both environmental mitigation and the circular economy.

Sustainable valorization of macroalgae residual biomass, optimization of pyrolysis parameters and life cycle assessment

The major challenges for the current climate change issue are an increase in global energy demand, a limited supply of fossil fuels, and increasing carbon footprints from fossil fuels, which have necessitated the exploration of sustainable alternatives to fossil fuels. Biorefineries offer a promising path to sustainable fuel production, converting biomass into biofuels using diverse technologies. Aquatic biomass, such as macroalgae in this context, represents an abundant and renewable biomass resource that can be cultivated from water bodies without competing with traditional agricultural land. Despite this, the potential of macroalgae for biofuel production remains largely untapped, with very limited studies addressing their viability and efficiency. This study investigates the efficient conversion of unexplored macroalgae biomass through a biorefinery process that involves lipid extraction to produce biodiesel, along with the production of biochar and bio-oil from the pyrolysis of residual biomass. To improve the effectiveness and overall performance of the pyrolysis system, Response Surface Methodology (RSM) was utilized through a Box-Behnken design to systematically investigate how alterations in temperature, reaction time, and catalyst concentration influence the production of bio-oil and biochar to maximize their yields. The results showed the highest bio-oil yield achieved to be 36 %, while the highest biochar yield reached 45 %. The integration of Life Cycle Assessment (LCA) in the study helps to assess carbon emission and environmental burdens and identify potential areas for optimization, such as resource efficiency, waste management, and energy utilization. The LCA results contribute to the identification of potential environmental hotspots and guide the development of strategies to optimize the overall sustainability of the biofuel production process. The LCA results indicate that the solvent (chloroform) used in transesterification contributes significantly to greenhouse gas emissions and climate change impacts. Therefore, it is crucial to explore alternative, safe solvents that can mitigate the environmental impacts of transesterification.

Waste-to-energy: Co-pyrolysis of potato peel and macroalgae for biofuels and biochemicals

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.

Enhanced microwave assisted pyrolysis of waste rice straw through lipid extraction with supercritical carbon dioxide

A combination of supercritical carbon dioxide (scCO2) extraction and microwave-assisted pyrolysis (MAP) have been investigated for the valorisation of waste rice straw. ScCO2 extraction of rice straw led to a 0.7% dry weight yield of lipophilic molecules, at elevated temperatures of 65 °C and pressures of 400 bar. Lipid compositions (fatty acids, fatty alcohol, fatty aldehydes, steroid ketones, phytosterols, n-alkanes and wax esters) of the waxes obtained by scCO2 were comparable to those obtained Soxhlet extraction using the potentially toxic solvent n-hexane. ScCO2 extraction positively influenced the pyrolysis heating rate, with a rate of 420 K min-1 for particles of 500-2000 μm, compared to 240 K min-1 for the same particle size of untreated straw. Particle size significantly affected cellulose decomposition and the distribution of pyrolysis products (gaseous, liquid and char), highlighting the importance of selecting an adequate physical pre-treatment. TG and DTG of the original rice straw and resulting biochar produced indicated that cellulose was completely decomposed during the MAP. While a rapid pressure change occurred at ∼120 °C (size > 2000 μm) and ∼130 °C (size 500-2000 μm) during MAP and was associated with the production of incondensable gas during cellulose decomposition, this takes place at significantly lower temperatures than those observed with conventional pyrolysis, 320 °C. Wax removal by scCO2 influences the dielectric properties of the straw, enhancing microwave absorption with rapid heating rates and elevated final pyrolysis temperatures, illustrating the benefits of combining these sustainable technologies within a holistic rice straw biorefinery.

Comprehensive review on lignocellulosic biomass derived biochar production, characterization, utilization and applications

Biochar is an ample source of organic carbon prepared by the thermal breakdown of biomass. Lignocellulosic biomass is a promising precursor for biochar production, and has several applications in various industries. In addition, biochar can be applied for environmental revitalization by reducing the negative impacts through intrinsic mechanisms. In addition to its environmentally friendly nature, biochar has several recyclable and inexpensive benefits. Nourishing and detoxification of the environment can be undertaken using biochar by different investigators on account of its excellent contaminant removal capacity. Studies have shown that biochar can be improved by activation to remove toxic pollutants. In general, biochar is produced by closed-loop systems; however, decentralized methods have been proven to be more efficient for increasing resource efficiency in view of circular bio-economy and lignocellulosic waste management. In the last decade, several studies have been conducted to reveal the unexplored potential and to understand the knowledge gaps in different biochar-based applications. However, there is still a crucial need for research to acquire sufficient data regarding biochar modification and management, the utilization of lignocellulosic biomass, and achieving a sustainable paradigm. The present review has been articulated to provide a summary of information on different aspects of biochar, such as production, characterization, modification for improvisation, issues, and remediation have been addressed.

Biochar supported nano core-shell (TiO2/CoFe2O4) for wastewater treatment

The porous structure of biochar, its large surface area, and its anti-oxidant properties are extensively used for pollutant removal strategies. The literature to date has reported that the biochar assisted metal-oxide core-shells have a dominating degradation ability under solar irradiation. Therefore, this study is significantly focused on cinnamon biochar as an active anti-oxidant agent incorporated in titania-cobalt ferrite nanocore-shell (Biochar/TiO2/CoFe2O4) structures for the first time in wastewater treatment against chlorophenol pollutants. Pure materials, core-shells, and biochar aided composites were synthesized by chemical methods, and their characteristics were analyzed using various instrumentation techniques. The diffraction outcomes of Biochar/TiO2/CoFe2O4 showed the mixed phases containing biochar, TiO2, and CoFe2O4. The morphological characteristics revealed that the biochar creates porosity and a peripheral layer covering the core-shell. Meanwhile, absorption studies of TiO2/CoFe2O4 core-shell and Biochar/TiO2/CoFe2O4 samples achieved 65% and 92% degradation efficiencies when exposed to visible light against chlorophenol pollutants, respectively. All these results confirm the presence of distinct functional groups as well as the combined synergistic effects that activated the charge separation, resulting in the successful destruction of water pollutants. In addition, the highly efficient Biochar/TiO2/CoFe2O4 sample was recycled, and the efficiency was maintained stable for five repeated degradation processes. Thus, Biochar/TiO2/CoFe2O4 will be utilized to expand the possibilities for biofuel generation and energy storage devices.

Fundamentals in applications of algae biomass: A review

Algae play an extremely important ecological role. They form the basis of trophic webs, produce oxygen that allows the respiration of many of the organisms in aquatic environments, absorb CO₂, and serve as refuge areas and habitats for thousands of species. Many species can also absorb organic pollutants from seawater. Algae have been used for many centuries by humans as a source of food, fertilizer, fodder, and for the extraction of compounds with antifungal, antiviral, anticancer, and antibacterial properties. More recently, some species have been used for the production of biofuels. It has been shown that mixing small proportions of algae with the feed of cattle can reduce methane emissions from their digestive activity by more than 95%. One of the most widespread but least known applications of algae is the extraction of their phycocolloids for utilization in food, pharmaceutical, wine, and textile industries, among others. These compounds have gelling, stabilizing, and thickening properties and are therefore frequently included in creams, ice creams, cheeses, jellies, flavored milks, sauces, shampoos, medications, toothpaste, and many other products. The phycocolloids agar and carrageenan are extracted from red algae, whereas alginate is extracted from brown algae, being used in dental impressions, emulsifying lotions, and paints, among others, and in the preparation of wine and beer. Algae are of particular interest in the research and development of new biosorbent materials, not only because of their high adsorption capacity, but also because they are present in the seas and oceans in abundant and easily accessible quantities. Marine algae are a promising biosorbent for the removal of heavy metals and various pollutants and, due to their intrinsic characteristics, have received increasing attention in recent decades. Their application as biosorbents for the sorption of heavy metals and radionuclides could be interpreted as the use of waste to remove waste. Algae have attracted particular interest in the field of biotechnology for economic reasons, given that large amounts are naturally produced and left lying on beaches as waste material. The composition of algae biomass makes it a promising candidate for an extensive list of applications that continues to lengthen. The development of appropriate technologies and policies can transform the presence of algae in coastal ecosystems from an unpleasant and potentially harmful phenomenon into a source of major benefits. This review discusses the capacity of algae biomass to remove pollutants and also delves into its applicability in the production of dyes, oils, and biofuels and for animal feed and fertilizer industries, among others. Further research is warranted on strategies to convert a biomass that is currently considered waste into a means of addressing environmental problems.

Conversion and rate behavior of brown macroalgae in pyrolysis: Detailed effects of operating parameters

Non-catalytic pyrolysis of brown macroalgae (Padina sp.) was studied in a batch reactor at temperature ranges of 400-600 °C and 10-90 min reaction times on the product distribution and conversion rate behavior. The highest pyro-oil and pyro-gas yields were obtained at 600 °C, which reached 67 wt% and 27 wt%, respectively, when the reaction times were prolonged (30-90 min). In addition, the high reaction temperature resulted in more generations of heavy tar and a considerable enhancement in aromatization degree. N-aromatic groups and phenol were observed from pyro-oil at 500 °C and 600 °C, respectively. Tar yield increased with reaction temperature, reflecting an order of reaction greater than one for tar production. The rate constant of tar formation was found to be 0.0013/s at 400 °C; 0.0023/s at 500 °C; and 0.0033/s at 600 °C, respectively, with the reaction order being higher than one (1.25). These findings highlighted that the proposed model could be used to accurately predict the pyrolysis process's behavior.

Eco-Friendly Alternative Disposal through the Pyrolysis Process of Meat and Bone Meal

The capitalization of agri-food waste is essential for the sustainability of a circular economy. This work focuses on a solution to eliminate such waste, meat and bone meal (MBM), which is produced in large quantities by the food industry and is prohibited for use as animal feed under the European directives. Therefore, with the focus of converting waste to energy, the catalytic pyrolysis of MBM in the presence of mesoporous silica nanocatalysts (SBA-3 and SBA-16 materials and metallic derivates) was investigated in a home-made reactor for the production of renewable energy. The mesoporous silica materials were synthesized using relatively simple methods and then characterized in order to determine their morpho-structural characteristics. The MBM pyrolysis behavior under different experimental conditions was examined in detail, both in the presence and absence of the new catalysts. The resulting MBM-based pyrolysis products, MBM_PYOILs and MBM_PYGASs, were also assessed as potential alternative fuels, highlighting comparable energy values to conventional fuels. The outcomes of this investigation offer a potential pathway to the clean production of gas and oil, thus promoting the high-grade utilization of MBM waste.