Biomass

There is an increasing industrial demand for sustainable resources for lipid-based biofuels and platform chemical production. A promising, CO₂-efficient resource is autotrophically cultivated microalgae, either for direct single-cell oil (SCO) production or as a biomass substrate for fermentative SCO production via organisms like yeasts. Regarding the latter, chemical biomass hydrolysis typically results in high sugar yield and high salt concentrations due to the required neutralization prior to fermentation. In contrast, enzymatic hydrolysis is often lacking in mass efficiency. In this study, the enzymatic hydrolysis of both nutrient-replete and lipid-rich autotrophic Microchloropsis salina biomass was optimized, testing different pre-treatments and enzyme activities. Hereby, the protease treatment to weaken the cell wall integrity and the dosing of the Cellic CTec3 was identified to have the highest effect on hydrolysis efficiency. Sugar yields of 63% (nutrient-replete) and almost 100% (lipid-rich) could be achieved. The process was successfully scaled-up in mini bioreactors at a 250 mL scale. The resulting hydrolysate of the lipid-rich biomass was tested as a substrate of the oleaginous yeast Cutaneotrichosporon oleaginosus in a consumption-based acetic acid fed-batch setup. It outperformed both the model substrate and the glucose control, demonstrating the high potential of the hydrolysate as feedstock for yeast oil production. The presented sequential and circular SCO-producing value chain highlights the potential for mass- and space–time-efficient biofuel production, combining the autotrophic cultivation of oleaginous algae with decoupled yeast oil fermentation for the first time. Full article

Spent coffee grounds (SCGs), a globally abundant by-product of the coffee industry, represent a significant source of lignocellulosic biomass with considerable valorization potential. Rich in organic compounds, lipids, and antioxidants, SCGs are increasingly recognized as a sustainable feedstock for energy, materials, and environmental applications within a circular bioeconomy framework. This review critically examines recent advances in SCG valorization via thermochemical, biochemical, and material-based pathways. The review focuses on the conversion of SCGs into biofuels (biodiesel, bioethanol, biogas, and bio-oil), activated carbon for water and air purification, biodegradable polymers, and soil-enhancing amendments. Comparative analyses of process conditions, product yields, and techno-economic feasibility are provided through summarized tables. Although laboratory-scale studies demonstrate promising outcomes, challenges persist in terms of process scalability, environmental impacts, feedstock variability, and lack of regulatory standardization. Furthermore, comprehensive life cycle assessments and policy integration remain underdeveloped. By merging all findings, this review identifies key knowledge gaps and outlines strategic directions for future research, including the development of integrated valorization platforms, hybrid conversion systems, and industrial-scale implementation. The findings support the role of SCG valorization in advancing sustainable resource management and contribute directly to the achievement of multiple Sustainable Development Goals. Full article

Biomass pyrolysis is a thermochemical process that breaks down organic matter in the absence of oxygen, offering a sustainable route for converting biomass into bio-oil, biochar, and syngas. This review provides a comprehensive overview of pyrolysis, focusing on its fundamental principles, modes, and its applications across different industries. It covers major pyrolysis types and explores the reactors used in these processes and how key parameters, such as temperature, heating rate, and residence time, impact the distribution and quality of pyrolysis products. Special attention is given to bio-oil upgrading methods, including catalytic and non-catalytic processes, and how they affect fuel quality. The study also presents techno-economic assessments of various pathways, identifying cost-effective configurations like pyrolysis combined with hydrotreatment and heat integration. Despite encouraging advancements, scaling up bio-oil technologies continues to face significant challenges, primarily due to cost competitiveness and variability in feedstock supply. This review emphasizes the critical need for continued innovation in reactor design, catalyst efficiency, and integrated process optimization, alongside supportive policy frameworks and strategic investments to accelerate commercial deployment. Finally, this review aims to help researchers, engineers, and policymakers work together to advance pyrolysis technology as a practical solution for producing low-carbon fuels and chemicals. Full article

The coffee cherry processing produces various waste products, such as coffee husks, which are a valuable source of pectin and phenolic acids that can be used as high-value biomolecules in human and animal food, cosmetics, and pharmaceutical production chains. This study aims to optimize the eco-friendly extraction of polysaccharides, as pectin, and phenolic compounds from coffee peel using response surface methodology (RSM). This model was used to evaluate the extraction variables (temperature, time, pH, ionic strength, ultrasonic frequency, particle size, and solid/liquid ratio in water) to identify the critical factors. All responses were fitted to the RSM model, which revealed high estimation capabilities. Ionic strength and temperature were found to be critical process variables for pectin extraction, while the main factors responsible for phenolic extraction were ultrasonic frequency, pH, and solid/liquid ratio. Therefore, the operating conditions to optimize the extraction of both pectin and phenolic compounds were 80 °C, ultrasonic frequency 60 kHz, solid/liquid ratio 1:20, using pH 2 or 12 in the case of pectin or polyphenols, respectively. Direct Analysis in Real Time Mass Spectrometry (DART-MS) and Fourier-Transform Infrared Spectroscopy–Attenuated Total Reflectance (FTIR-ATR) analyses were performed to evaluate the chemical profile of the extracts and pectin. The recycling of coffee husk waste into bioproducts in view of the circular economy contributes to minimizing the impact on the environment and to generating additional income for coffee growers. Full article

Porous carbon from renewable resources like biomass is a key material utilized in many applications ranging from environmental remediation to energy storage. There are limited reports in the literature on the effects of biomass pretreatment, production process parameters, and downstream processing on the final product properties. This is the first study aimed at closing the latter research gap. Six different types of underutilized biomass were examined: eastern red cedar wood, pecan shells, hazelnut shells, algal biomass, miscanthus, and sludge produced at municipal wastewater treatment facilities. Although pretreatment of biomass with KOH or ZnCl₂ enhanced formation of micro- and mesopores, carbon yield was lower (15.3–32.5%) than that obtained via non-catalytic pyrolysis (28.3–48%). An optimization study performed using response surface methodology and cedar wood has shown the significant effects (p < 0.05) of temperature and catalyst/biomass ratio on total BET pore volume and surface area. Additionally, catalyst/biomass ratio had a significant effect on the crystal structure and pore size distribution in the carbon produced by pyrolysis. Hence, optimization of process temperature, hold time, and activation ratio is capable of yielding porous carbon from cedar wood pyrolysis with desirable properties. Full article

Corn residues are an abundant and low-cost lignocellulosic feedstock that provides a renewable carbon platform for the production of biofuels, bioplastics, and high-value aromatic volatile compounds (AVCs). Isoamyl alcohol, an important AVC, has applications in the food, cosmetics, and biofuel industries. This study evaluated the bioconversion of corn cob acid hydrolysates by Meyerozyma guilliermondii into isoamyl alcohol and ethanol. Corn cob was selected as feedstock due to its high hemicellulose content. A Box–Behnken (BBD) design was used to optimize phosphoric acid hydrolysis. The optimal treatment (2.49% v/v H₃PO₄, 130 °C, 120 min, 1 mm particle size) generated 19.79 g L⁻¹ xylose with 2.74 g L⁻¹ acetic acid. Then, agitation speed and nitrogen concentration were optimized via a central composite design (CCD) in synthetic and hydrolysate-based media fermentations. Isoamyl alcohol specific yield after 48 h of fermentation was higher in hydrolysate medium (12.08 ± 0.67 mg·g⁻¹) than in synthetic medium (8.274 ± 0.83 mg·g⁻¹). Free amino nitrogen (FAN) and intracellular protein analyses revealed higher nitrogen consumption in synthetic media fermentation and greater biomass production in acid hydrolysate media. In addition to isoamyl alcohol (33 mg·L⁻¹), and ethanol (10.18 g·L⁻¹), 1-butanol (61.2 mg·L⁻¹), 1-propanol (13.25 mg·L⁻¹), and acetaldehyde (14.88 mg·L⁻¹) were produced. These results demonstrate the potential of M. guilliermondii to convert corn cob into value-added products. Full article

Olive mill wastewater (OMW) is a phenol-rich effluent with high organic load, posing significant environmental disposal challenges in the Mediterranean countries. This study evaluated the bioremediation and valorization potential of OMW by eleven edible and/or medicinal fungal strains (Agrocybe cylindracea, Lentinula edodes, Pleurotus sapidus, Pleurotus sajor-caju, Flammulina velutipes, Ganoderma adspersum, Tuber aestivum and Tuber mesentericum). Firstly, screening for mycelial growth on agar media with commercial glucose and OMW (concentrations from 0 to 50%, v/v) revealed a strain-specific tolerance to phenolic toxicity. Although all tested strains could grow on OMW-based media, G. adspersum, T. mesentericum and T. aestivum presented the highest mycelial growth rates (Kr), exceeding 10 mm/day at elevated OMW levels (50%, v/v). Based on screening outcomes, seven strains were selected for further evaluation under static liquid fermentations in media with 15 and 35% (v/v) OMW. Growth kinetics, substrate consumption, phenolic removal, decolorization capacity, intracellular polysaccharide (IPS) and total lipid content were assessed. Tuber spp. and G. adspersum exhibited the highest tolerance to phenolic compounds, producing biomass exceeding 15 g/L at 35%, v/v OMW. Maximum IPS production reached up to 46.23% (w/w), while lipid content exceeded 15% (w/w) of dry biomass in F. velutipes and T. mesentericum, indicating an oleaginous microorganism-like behavior. Phenolic removal surpassed 80% in most cases, demonstrating efficient enzymatic degradation. Decolorization efficiency varied between strains, but remained above 70% for L. edodes, G. adspersum and F. velutipes. These findings highlight the potential of edible and/or medicinal fungi to simultaneously detoxify OMW and produce biomass and high-value metabolites, supporting a sustainable, low-cost agro-industrial waste management aligning with circular bioeconomy principles. Full article

The brewing industry generates vast amounts of by-products of biotic and abiotic nature that require proper handling to reduce their environmental footprint annually. Simultaneously, and in alignment with the current circular economy dynamics, there is a growing trend towards the valorization of such by-products, through upcycling and/or repurposing. Biotic by-products are a low-cost source of valuable compounds, such as proteins, carbohydrates, lipids and phenolic compounds, which, with adequate recovery methods, can be used in various industries, e.g., agro-food and pharma, among others, where their bioactive and physical-chemical properties can be harnessed effectively. Abiotic by-products are increasingly valorized through pathways that prioritize material recovery and functional reuse. This work aims to address the most relevant by-products from brewing by providing a broad perspective that abridges their sources alongside the manufacturing chain, the composition of the different by-products, and current and foreseen handling and valorization strategies. Full article

Every year, a substantial amount of food is discarded globally. A significant portion of this waste is composed of fruit by-products or fruits that do not meet consumer standards. Apples rank as the third most extensively produced fruit crop globally, generating substantial waste. This study examined apples that did not meet food industry standards and were destined for disposal. The objective was to recover bioactive compounds from their juice using Cloud Point Extraction (CPE). Like other extraction methods, CPE isolates target compounds from the sample, enhancing recovery yield. A primary advantage of CPE is that it operates without requiring specialized equipment or hazardous reagents. Additional benefits include efficacy, simplicity, safety, and speed. Furthermore, a food-grade surfactant, lecithin, was used to encapsulate bioactive compounds, ensuring non-toxicity for both humans and the environment. After three CPE steps, we recovered 95.95% of the total polyphenols from second-grade apple juice (initial TPC: 540.36 mg GAE/L). The findings highlight CPE’s effectiveness for polyphenol extraction and for producing antioxidant-rich extracts. These extracts may be utilized as nutritional supplements, feed additives, and for nutraceutical or medicinal applications. Full article

Sunflower seed hulls and meal are among the most abundant by-products of the food industry. They are an example of waste and, at the same time, a plentiful biomass that cannot be utilized directly in human and animal diets due to their hard digestibility and low nutritional value. Besides their main compounds—carbohydrates, lipids, and proteins—they possess valuable constituents such as vitamins, minerals, and especially phenolics that contribute to their antioxidant capacity. Numerous benefits can be retrieved from such by-products. Since sunflower meal and seed hulls are cheap renewable sources of beneficial substances, their potential in relation to the improvement in our daily life needs to be studied. This is the reason why, in recent years, there has been such a serious interest in their utilization and valorization towards the concept of a circular bio-based economy and process sustainability. This review aims to trace the potential applications and implementation of sunflower meal and hulls in the different fields of industry and environmental protection strategies. Full article

Development of biodegradable packaging materials and valorization of agri-food waste are necessary to produce more sustainable materials while reducing the environmental impact. Starch-based biocomposite films reinforced with beer bagasse fractions with different purification degrees were developed and characterized in structural, mechanical, thermal and optical properties. To this aim, 5% and 10% (w/w) of either beer bagasse (BB) or its lignocellulosic-rich fibers (LF), obtained by subcritical water extraction at temperatures between 110 and 170 °C, were incorporated into starch matrices. Elastic modulus and tensile strength values increased by up to eight-fold and 2.5-fold, respectively, compared to the control film. The incorporation of BB or LF significantly enhanced the mechanical resistance of the films. In general, the increment in the filler:polymer ratio significantly increased the EM values (p < 0.05), while decreasing the stretchability of the films around 80–85%, regardless of the type of filler. This effect suggests a good interfacial adhesion between the fillers and the polymeric matrix, as observed by FESEM. The biocomposite films exhibited a dark reddish appearance, reduced transparency, light blocking barrier capacity and remarkable antioxidant activity due to the presence of phenolic compounds in the fibers. The water vapor and oxygen barrier properties were better preserved when using the more purified LF obtained at 170 °C. Overall, starch films reinforced with beer bagasse fractions showed strong potential for the development of biodegradable food packaging materials. Full article

This study optimizes the production of activated carbons from hydrothermally carbonized (HTC) biomass using potassium hydroxide (KOH) and phosphoric acid (H₃PO₄) as activating agents. A 2³ factorial experimental design evaluated the effects of agent-to-precursor ratio, dry impregnation time, and activation duration on mass yield and iodine adsorption capacity. KOH-activated carbons achieved superior iodine numbers (up to 1289 mg/g) but lower mass yields (18–35%), reflecting enhanced porosity at the cost of material loss. Conversely, H₃PO₄ activation yielded higher mass retention (up to 54.86%) with moderate iodine numbers (up to 1117.3 mg/g), balancing porosity and yield. HTC pretreatment at 190 °C reduced the ash content, thereby enhancing the stability of hydrochar. These findings highlight the trade-offs between adsorption performance and process efficiency, with KOH suited for high-porosity applications (e.g., water purification) and H₃PO₄ for industrial scalability. The study advances biomass waste valorization, aligning with circular economy principles and offering sustainable solutions for environmental and industrial applications, such as water purification and energy storage. Full article

The feasibility of utilizing biochar as a static floating material for agricultural applications was researched to prevent evaporation from open water static storage systems or as a floating barrier in slurry pits, for instance. Five types of biochar were created from chips, bark, and pellets of pine and residues from two acacia species using a pyrolysis time between 60 and 120 min and mean temperatures between 380 and 690 °C in a simple double-chamber reactor. Biomass and biochar were characterized for their main properties: bulk density, moisture content, volatile matter, ash content, fixed carbon, and pH. Biochar was also evaluated through a basic floatability test over 27 days (648 h) in distilled water. The highest fixed carbon content was observed in pine bark biochar (69.5%), followed by the pine pellets (67.4%) and pine chips (63.4%). Despite their high carbon content, the pellets exhibited a low floatability level, whereas pine bark biochar showed superior static floatage times, together with chip and ground chip biochar. These results suggest that biochar produced from bark and wood chips may be suitable for application as floatability material in water or slurry management systems. These results warrant further research into the static floating of biochar. Full article

This research aimed to evaluate the biological resistance to xylophagous organisms and the dimensional stability related to water absorption in plastic wood panels manufactured by compression molding and produced with pine wood and recycled thermoplastics. The wood–plastic composites (WPCs) were prepared from 50% pine sawdust and 50% recycled plastics (polyethylene terephthalate-PET, high-density polyethylene-HDPE, and polypropylene-PP). The thickness swelling test was carried out by immersing of the WPC samples in water at room temperature (25–30 °C) and evaluating the total change in WPC thickness after 1500 h (≈9 weeks or two months). In addition, the coefficient of initial swelling was evaluated to verify the variability of the swelling. For the biological resistance evaluation of the WPCs, tests were carried out with soil or arboreal termites (Nasutitermes corniger) and drywood termites (Cryptotermes brevis). The WPC loss of mass and termite mortality were evaluated. The use of PP promoted the best response to thickness swelling. The simple mathematical model adopted offers real predictions to evaluate the thickness of the swelling of the compounds in a given time. For some variables there were no statistical differences. It was shown that treatment 3 (T3) presented visual damage values between 0.4 for drywood termites and 9.4 for soil termites, in addition to 26% termite mortality, represented by the lowest survival time of 12 days. The developed treatments have resistance to termite attacks; these properties can be an important starting point for its use on a larger scale by the panel industries. Full article

Beer production produces significant amounts of brewers’ spent grain (BSG), a lignocellulosic by-product with important environmental and economic impacts. Despite its high moisture content and rapid microbial breakdown, BSG has a stable, nutrient-rich composition, especially high in protein, fiber, and polyphenolic compounds. While its perishability limits direct use in food systems, BSG is often repurposed as livestock feed. Recent advances in bioprocessing and extraction technologies have expanded their use across different sectors. This review explores the composition of crude BSG and evaluates innovative valorization methods, including recovering bioactive compounds with pharmaceutical and nutraceutical value, and converting them into biofuels such as biogas, biodiesel, and bioethanol. Special focus is given to methods involving enzymatic hydrolysis, fermentation, and chemical extraction to isolate proteins, peptides, amino acids, sugars, and polyphenols. By analyzing emerging applications and industrial scalability challenges, this review highlights BSG’s growing role within circular economy models and its potential to promote sustainable innovations in both the brewing industry and the wider bioeconomy. Full article

This review examines sustainable cascading biorefinery strategies for the green alga Ulva, which is globally prevalent in eutrophic marine waters and often forms extensive “green tides.” These blooms cause substantial environmental and economic damage to coastal communities. The primary target products within an Ulva biorefinery typically encompass salts, lipids, proteins, cellulose, and ulvan. Each of these components possesses unique properties and diverse applications, contributing to the economic robustness of the biorefinery. Salts can be repurposed for agricultural or even human consumption. Lipids offer high-value applications in nutraceuticals and animal feed. Proteins present significant potential as plant-based nutritional supplements. Cellulose can be transformed into various advanced materials. Finally, ulvan, a polyanionic oligosaccharide unique to Ulva, holds promise due to its distinct properties, particularly in the biomedical field. Furthermore, state-of-the-art chemical modifications of ulvan are presented with the aim of tailoring its properties and broadening its potential applications. Future research should prioritize optimizing these integrated extraction and fractionation processes. Furthermore, a multi-product biorefining approach, integrated with robust Life Cycle Assessment studies, is vital for transforming this environmental challenge into a significant opportunity for sustainable resource valorization and economic growth. Full article

This study explored the production and activation of biochar from rice straw residue for dye adsorption applications. Rice straw, a widely available but underutilized biomass, was processed to isolate lignin and generate biochar through pyrolysis at 450 °C and 550 °C. Activation using chemical agents (e.g., KOH and NaOH) was performed to enhance surface area and porosity. Among the tested conditions, KOH activation at a char-to-agent ratio of 1:3 produced activated carbon at 800 °C with the highest BET surface area (835.2 m²/g), and high fixed carbon (44.4%) after HCl washing. Thermogravimetric analysis was used to investigate pyrolysis kinetics, with activation energies determined using the Kissinger, Flynn–Wall–Ozawa, and Kissinger–Akahira–Sunose models. The brown solid showed a higher activation energy (264 kJ/mol) compared to isolated lignin (194 kJ/mol), indicating that more energy is required for decomposition. The AC was evaluated for the adsorption of methylene blue (MB) and methyl orange (MO) from aqueous solutions. Both dyes followed the Langmuir isotherm model, indicating that monolayer adsorption occurred. The maximum adsorption capacities reached 222 mg/g for MB and 244 mg/g for MO at 303 K, with higher values at elevated temperatures. Adsorption followed a pseudo-second-order kinetic model and was governed by a physisorption mechanism, as supported by thermodynamic analysis (ΔH < 20 kJ/mol and E_a < 40 kJ/mol). These findings demonstrate that KOH-activated biochar from rice straw residue is a high-performance, low-cost adsorbent for dye removal, contributing to sustainable biomass utilization and wastewater treatment. Full article

This study investigates biochar-enriched organic fertilizers made from bagasse, ash, spent wash, and cane tops, assessing their impact on corn growth over 45 days. A randomized complete block design with three replicates was used, testing six formulations with biochar levels at 0%, 10%, and 20%, along with soil-only and commercial fertilizer controls. Treatments T5 (bagasse + ash + spent wash + cane tops), T11 (T5 + 10% biochar), and T17 (T5 + 20% biochar) showed the best results for plant height, leaf development, and biomass production, with T17 performing the best for growth, biomass, and girth. The biochar in T17 had a pH of 9.37 ± 0.16, 18.00 ± 1.25% ash content, and a surface area of 144.58 m²/g. Nutrient analysis of the compost showed 2.85% potassium, 1.12% phosphorus, 1.85% nitrogen, 4.1% calcium, 0.23% magnesium, and 130 mg/kg zinc. The elemental composition was 68.50% carbon, 4.50% hydrogen, 6.00% nitrogen, and 25.30% oxygen, with 85.00% total organic carbon (TOC). This study concludes that T17 is the most effective formulation, offering both environmental and financial benefits, with composting potentially generating $11.16 million in profit, compared to the $19.32 million spent annually on waste management in Sri Lanka’s sugar industry. Full article