Sustainable development strategies, including biomass waste valorization and life cycle-based carbon management approaches, are being adopted worldwide to mitigate climate change and reduce pollution. Numerous materials or products are under development to meet the demands related to a lowered carbon footprint, higher safety, access to renewable energy, and so on. One such material is biochar, which has been employed in a plethora of applications, areas ranging from soil amendment, polymer composites, energy storage and conversion, building materials, to environmental remediation. However, no two biochars are created equal. This disparity in inherent material properties in biochar means that they should be subjected to effective engineering to tailor their properties to a specific targeted application. This means that a biochar that is suitable for concrete applications may not be appropriate for polymer composite applications. Even biochar properties that were designed for a specific application may not have the desired or expected impact. This can lead to several negative effects of biochar. Hence, this article has collated and reviewed the instances where biochar has had unintended consequences in different applications. Using the knowledge presented herein, researchers can be aware of the potential disadvantages of biochar applications and take necessary steps to abate the negative effects. 

As interest in sustainable, high-performance flame-retardant technologies continues to grow, ECOFRAM 2026 brings together experts from academia and industry in an engaging international forum. The contents of the conference mark an important step forward in the shared pursuit of safer, more sustainable flame retardant solutions.

ECOFRAM 2026 focuses on cutting-edge research and emerging trends in areas such as:

• Bio-based flame-retardant additives and materials

• Polymers and composites containing biowaste-derived flame retardants

• Biodegradable flame-retardant polymers and composites

• Recyclable flame-retardant polymers and composites

• Sustainability in flame-retardant polymers and composites

• Eco-friendly flame-retardant coatings, textiles, and wood-based products

• Bio-based fire-safe materials for construction applications

• Toxicological and environmental impacts of flame retardants

• Regulations governing flame retardants

The conference seeks to spark interdisciplinary dialogue bridging science, engineering, and environmental responsibility, addressing not only how the fire safety of materials can be improved, but also how this can be achieved in a sustainable and environmentally responsible manner.

Wood is an attractive renewable construction material, but its inherent flammability, hygroscopicity, and poor resistance to leaching limit its broader application in fire-safe structures. This study investigates a catalytic heat treatment (CHT) approach combining ammonium dihydrogen phosphate, citric acid, oxalic acid, and glyoxal to improve durable fire retardancy and moisture resistance in poplar wood. Several formulations were screened based on weight percentage gain (WPG), equilibrium moisture content (EMC), and leach resistance (EN 84), leading to the selection of an optimized formulation (S3) for detailed characterization. Chemical fixation was confirmed by FTIR spectroscopy, revealing esterification, acetal crosslinking, and phosphorus–oxygen bonding, which remained partially intact after leaching. SEM–EDX analysis confirmed the incorporation of phosphorus within the treated wood and its partial retention after leaching. Optical microscopy demonstrated lumen filling and pronounced cell-wall bulking, consistent with reduced hygroscopicity and increased hardness. Flexural testing indicated a decrease in bending strength (26% and 36%) while elastic stiffness remained largely unchanged before leaching. Thermogravimetric analysis showed enhanced char formation and altered degradation pathways, while cone calorimetry revealed pronounced reductions in heat release rate (≈60%), smoke production (≈75%), and total heat release (≈40%), alongside increased residue yield. The limiting oxygen index increased from 24% for raw wood to 42% for treated wood. Microscopic observations of combustion residues revealed a more cohesive char structure in the treated samples. Fire dynamics simulator (FDS) modelling further demonstrated reduced compartment temperatures for treated wood. Neural network models were developed to predict carbon monoxide and smoke production rates, achieving high predictive accuracy for CO production (R² ≈ 0.96). Overall, the catalytic heat-treatment system promotes chemical fixation of phosphorus-containing species and improves fire performance while retaining a relatively simple processing route, offering a favourable balance between fire performance, durability, and processing simplicity.

This study investigates the effect of thermo-mechanical densification on the fire behaviour of wood using cone calorimetry. Scots pine wood was thermo-mechanically densified from an initial thickness of 20 mm to target thicknesses of 14 and 10 mm and compared with non-densified specimens of the same thickness as well as non-densified 20 mm samples. For non-densified specimens, the time to ignition (TTI) remained nearly constant (18–20 s) across the investigated thicknesses, indicating thermally thick behaviour. In contrast, delayed ignition was observed for the specimens densified to 10 mm (the higher densification ratio), with TTI increasing to 28 s. While the first peak heat release rate (pHRR) remained comparable across samples, densification increased the time to the second peak heat release rate by up to 85% and its magnitude by approximately 9% relative to non-densified specimens of the same thickness (10 mm). Densification was found to alter the combustion behaviour of wood by modifying the thermal inertia of the material and the characteristics of the resulting char layer, thereby affecting the transport and release of pyrolysis gases and producing distinct effects at different stages of combustion rather than an overall enhancement of fire performance.

Increasing concerns and regulatory restrictions associated with conventional flame retardants have driven research into halogen-free and bio-based alternatives that combine fire safety with reduced environmental impact. Lignin, a macromolecule prevalent in biomass, has emerged as a promising candidate for flame-retardant applications owing to its intrinsic charring ability, high carbon content, and chemical versatility. This review provides a comprehensive and critical overview of lignin-derived flame retardants, addressing fire behavior assessment, structure–property relationships, flame-retardant mechanisms, and practical applications in polymers, coatings, textiles, and construction materials. The influence of plant origin and extraction method on thermal decomposition, char formation, and combustion behavior is discussed in detail, with particular emphasis on condensed-phase mechanisms governing fire performance. Strategies employing unmodified lignin, chemically modified lignin (phosphorus-, nitrogen-, and silicon-containing systems), lignin-containing intumescent formulations, and lignin-derived nanocomposites are systematically reviewed. Their effects on flammability metrics, heat release characteristics, smoke suppression, and mechanical performance are critically assessed. While lignin-based systems demonstrate significant potential to reduce heat release and enhance char stability, challenges remain related to dispersion, compatibility, processing stability, and the sustainability of modification routes.

Scots pine (Pinus sylvestris L.) sapwood was modified using maleic anhydride (MA) and sodium hypophosphite (SHP) to improve its durability against wood-deteriorating fungi, mechanical strength, and fire retardancy (thermal stability). The modification significantly reduced mass loss caused by wood-decaying fungi (Trametes versicolor, Rhodonia placenta, and soft rot fungi) due to the formation of cross-links between wood, MA, and SHP, which limited the moisture uptake and altered the chemical structure of wood. On the other hand, the modification did not provide improved resistance to fungi growth on the wood surface, which indicated that the modification had little impact on the accessibility of nutrients on the surface. A bending test showed that the modulus of elasticity (MOE) was not affected by the treatment, whilst the modulus of rupture (MOR) decreased to half the value of untreated wood. Thermal resistance was improved, as demonstrated by micro-scale combustion calorimeter testing, where the total heat release was halved, and the residue percentage nearly doubled. These results indicate that phosphonate protects the modified wood via the formation of a protective char layer on the surface and the formation of radical moieties. Based on the results, wood modified with MA and SHP shows potential for possible use in outdoor, non-loadbearing structures.

The focus of this study is to investigate the fire performance of cellulose-based radiative cooling wood. Although offering passive cooling benefits, radiative cooling wood’s inherent flammability is a critical drawback. This research evaluated pristine balsa wood (PW), cooling wood (CW), and cooling wood flame-retarded with borax (FR CW). Fire performance was evaluated via cone calorimetry (20–50 kW m⁻²), thermal analysis (thermogravimetry and differential scanning calorimetry), and Fire Dynamics Simulator (FDS) modelling. The results demonstrate significantly enhanced fire safety for FR CW wherein the Critical Heat Flux increased by up to 80 % and ignition temperature by up to 36 % compared to CW. Borax treatment extended ignition times, promoted charring, and substantially reduced Heat Release Rate. The Fire Growth Index for FR CW at 50 kW m⁻² decreased by ≈ 77–81 %. FDS simulations confirmed significantly lower compartment fire temperatures with FR CW. This research shows that borax, an eco-friendly mineral, effectively mitigates fire risks in radiative cooling wood, improving key safety parameters like Heat Release Rate, Maximum Rate of Heat Emission, carbon monoxide, and smoke production, thus enhancing its viability as a sustainable construction material.

This study introduces a novel hexagonal honeycomb lattice design incorporating integrated diagonal struts, developed to enhance compression strength and energy absorption in 3D-printed polymer structures. Five distinct lattice configurations were fabricated using polylactic acid (PLA) filament and evaluated through uniaxial compression testing. The results showed that Lattice 5, which features a hexagonal unit cell with diagonal struts from top left to bottom right, had the highest compression strength of 45.78 MPa and absorbed 14,406 J of energy. In comparison, Lattice 1, with a regular hexagonal unit cell, had 15 % lower compression strength and 20 % lower energy absorption. Analytical models based on honeycomb geometry and PLA material properties were used to predict how the structures would deform. Finite element analysis (FEA) was also conducted to study the deformation under dynamic loading, with Lattice 5 proving to be the most efficient design. The diagonal struts in Lattice 5 helped to redistribute the load more evenly, reducing stress concentrations and allowing for a more gradual deformation. The FEA results matched the experimental data closely, confirming the accuracy of the predictions. These findings offer useful insights for improving lattice structures for applications that require high performance in terms of both structural strength and energy absorption.

3D printing offers the ability to fabricate lightweight structural profiles with controlled infill and geometry. This study examines the mechanical behaviour of 3D-printed polylactic acid (PLA) structures with a 10% infill density under four load conditions (10, 15, 20, and 25 N). Four designs (M1, M2, M3, and M4), representing commonly used structural profiles found in beam and column applications, were analysed using ANSYS finite element simulations. Each design was evaluated under roller and nodal boundary conditions to study deformation, stress, and strain responses. Three-point flexural tests were also carried out on all four designs, and the measured peak flexural stress and apparent flexural modulus were compared with the simulated stiffness values. Both the simulations and experimental results showed that Design M3 exhibited the highest stiffness and more consistent behaviour compared to the other designs, while Design M4 showed higher deformation and lower bending resistance. Roller supports generally reduced deformation through better load distribution, whereas nodal supports increased local stiffness in selected designs. Although the magnitude of stiffness differed between simulation and experiment, the ranking of the designs remained consistent. Overall, the study confirms that the geometry plays an important role in their load-bearing performance, and the numerical model provides a reliable tool for comparing and selecting suitable designs before fabrication.

Using biochar as a replacement for sand in concrete provides a sustainable solution to the ecological degradation and environmental pollution. This study investigates the use of biochar for internal curing when substituting sand in concrete. Various properties, including slump, mechanical strength, and hydration products, were assessed. The results show that prewetted biochar effectively preserves the slump of fresh concrete. The prewetted biochar provides internal curing by extending the hydration process, resulting in a 56 % increase in the duration between the first and third hydration peaks at the 100 % replacement level. This extended hydration process reduced the amount of unhydrated cement clinkers and enhanced the development of Calcium Silicate Hydrate (C-S-H) and CaCO₃, indicating a more complete degree of hydration of cement. Furthermore, the addition of biochar effectively reduces the total shrinkage of concrete by 65 % at a 100 vol% replacement level at 28 days and guarantees later strength development of concrete.