Characterization of biocomposite using coconut oil impregnated biochar as latent heat storage insulation

Use of biochar co-mediated chitosan mesopores to encapsulate alkane and improve thermal properties

Phase-change materials (PCMs) plays a significant role in energy conservation and thermal management systems. However, excessive seepage and insufficient thermal conductivity of pristine PCMs are restricting its real-world applications. Herein, "anisotropic-like" biochar with favorable pore characteristics is designed by combining it with chitosan for dodecane encapsulation. The use of biochar could overcome high manufacturing costs and associated environmental issues of PCM supporting materials. Biochar co-mediated chitosan enrich the mesopore proportion (96.5%) and provide interactive synergistic architecture. The prepared composite PCM exhibited outstanding latent heat retention of 95.9% after repeated cycling, high loading ratio, enhanced thermal conductivity (0.373 W/(m·K)), leakage-free, and repeatable utilization properties above the melting point of pristine dodecane. A figure of merit of 33.94 × 10⁶ W² S/(m^4oC) was achieved, far surpassing that measure among reported biochar-based composite PCMs. This study provides insights into next-generation sustainable energy storage development for a key global sustainability goal.

Preparation and thermal conductivity enhancement of a paraffin wax-based composite phase change material doped with garlic stem biochar microparticles

The addition of thermally conductive nanomaterials is an effective strategy for increasing the thermal conductivity of phase change materials (PCMs). However, nanomaterials are expensive and may significantly reduce the latent heat capacity of PCMs. In this study, low-cost and eco-friendly biochar microparticles were prepared from garlic stems, a common food waste in Singapore. The thermal properties of paraffin wax (PW) doped with 1, 3, and 5 wt% garlic stem biochar (GSB) microparticles were investigated. The GSB microparticles prepared at 700 °C had three-dimensional porous and two-dimensional flake-like structures, which contributed to the formation of additional heat transfer pathways in the PW. The addition of 5 wt% GSB microparticles enhanced the thermal conductivity of PW by 27.3% and 7.2% in the solid and liquid phases, respectively. The T-history test revealed that the melting and solidification rates of PW improved by 90 and 115 s, respectively. The improved heat transfer performance was mainly ascribed to the high degree of graphitization and the interconnected porous carbon structure of the GSB microparticles. The phase change temperatures of PW were slightly changed upon the addition of GSB microparticles, and the latent heat capacity was only reduced by 6.1%. These results suggest that the GSB microparticles can be used as a potential alternative to other nanoadditives such as metal- and metal oxide-based nanoadditives.

Thermal Properties of Novel Phase-Change Materials Based on Tamanu and Coconut Oil Encapsulated in Electrospun Fiber Matrices

The accumulation of thermal energy in construction elements during daytime, and its release during a colder night period is an efficient and green way to maintain a comfortable temperature range in buildings and vehicles. One approach to achieving this goal is to store thermal energy as latent heat of the phase transition using the so-called phase-change materials (PCMs). Vegetable oils came recently into focus as cheap, widely available, and environmentally friendly PCMs. In this study, we report the thermal properties of PCMs based on tamanu and coconut oils in three configurations: pure, emulsion, and encapsulated forms. We demonstrate the encapsulation of pure coconut- and tamanu-oil emulsions, and their mixtures and mixtures with commercial PCM paraffins in fiber matrices produced by a coaxial electrospinning technique. Polycaprolactone (PCL) was used as a shell, the PCM emulsion was formed by the studied oils, and sodium dodecyl sulfate (SDS) and polyvinyl alcohol (PVA) were used as emulsifiers. The addition of commercially available paraffin RT18 into a 70/30 mixture of coconut and tamanu oil, successfully encapsulated in the core of a PCL shell, demonstrated latent heats of melting and solidification of 63.8 and 57.6 kJ/kg, respectively.

Emerging application of biochar as a renewable and superior filler in polymer composites

Biochar is conventionally and widely used for soil amendment or as an adsorbent for water treatment. Nevertheless, the need for transition to renewable materials has resulted in an expansion of biochar for use as a filler for polymer composites. The aim is to enhance the physical, chemical, mechanical and rheological properties of the polymer composite. The reinforcement of biochar into a polymer matrix however is still new, and limited reports are focusing on the effects of biochar towards polymer composite properties. Hence, this review highlights the unique properties of biochar and its effect on the crystallization, thermal, flammability, electrical conductivity, and mechanical properties of polymer composites. This review does not solely summarize recent studies on biochar-polymer-based composites, but also offers insights into a new direction of biochar as a renewable and superior polymer filler in the future.

Effects of biochar pyrolysis temperature on thermal properties of polyethylene glycol/biochar composites as shape-stable biocomposite phase change materials

The characteristics of biochar are of great significance to its application in the field of phase change energy storage. The objective of this research was to explore the effects of pyrolysis temperature on the characteristics of a biochar matrix and further on the heat energy storage properties of the promising green biochar-supported shape-stable biocomposite PCMs (ss-BCPCMs). Corn straw biochars (CSBCs) obtained under different pyrolysis conditions were loaded with polyethylene glycol (PEG) by an ultrasound-assisted vacuum impregnation method. The micro-morphology, specific surface area, pore structure and surface properties of biochar have been characterized and analyzed by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) method and Fourier transform infrared spectroscopy (FTIR). The thermal properties (chemical stability, latent heat storage, thermal conductivity, thermal stability, and thermal insulation) of PEG/CSBC composites have been characterized by FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and laser flash analysis (LFA). The study revealed that both pore structure and surface activity of biochar are key factors affecting the energy storage performance of biochar-based ss-BCPCMs. The obtained PEG/CSBC composite showed a high latent heat storage up to 100.2 J g⁻¹, good shape stability and leakage resistance, suggesting its high thermal storage stability that is beneficial for thermal energy storage applications. In addition, its excellent photothermal conversion efficiency (68.95%) provides application potential in photothermal energy storage.

The micropore and mesopore of biochar and the interaction between PEG and biochar surface effectively prevented the leakage of PEG and affected the crystallization and adsorption properties of PEG and the heat storage of composite PCMs.

Biochar for agronomy, animal farming, anaerobic digestion, composting, water treatment, soil remediation, construction, energy storage, and carbon sequestration: a review

In the context of climate change and the circular economy, biochar has recently found many applications in various sectors as a versatile and recycled material. Here, we review application of biochar-based for carbon sink, covering agronomy, animal farming, anaerobic digestion, composting, environmental remediation, construction, and energy storage. The ultimate storage reservoirs for biochar are soils, civil infrastructure, and landfills. Biochar-based fertilisers, which combine traditional fertilisers with biochar as a nutrient carrier, are promising in agronomy. The use of biochar as a feed additive for animals shows benefits in terms of animal growth, gut microbiota, reduced enteric methane production, egg yield, and endo-toxicant mitigation. Biochar enhances anaerobic digestion operations, primarily for biogas generation and upgrading, performance and sustainability, and the mitigation of inhibitory impurities. In composts, biochar controls the release of greenhouse gases and enhances microbial activity. Co-composted biochar improves soil properties and enhances crop productivity. Pristine and engineered biochar can also be employed for water and soil remediation to remove pollutants. In construction, biochar can be added to cement or asphalt, thus conferring structural and functional advantages. Incorporating biochar in biocomposites improves insulation, electromagnetic radiation protection and moisture control. Finally, synthesising biochar-based materials for energy storage applications requires additional functionalisation.

Review on the Integration of Phase Change Materials in Building Envelopes for Passive Latent Heat Storage

Latent heat thermal energy storage systems incorporate phase change materials (PCMs) as storage materials. The high energy density of PCMs, their ability to store at nearly constant temperature, and the diversity of available materials make latent heat storage systems particularly competitive technologies for reducing energy consumption in buildings. This work reviews recent experimental and numerical studies on the integration of PCMs in building envelopes for passive energy storage. The results of the different studies show that the use of PCMs can reduce the peak temperature and smooth the thermal load. The integration of PCMs can be done on the entire building envelope (walls, roofs, windows). Despite many advances, some aspects remain to be studied, notably the long-term stability of buildings incorporating PCMs, the issues of moisture and mass transfer, and the consideration of the actual use of the building. Based on this review, we have identified possible contributions to improve the efficiency of passive systems incorporating PCMs. Thus, fatty acids and their eutectic mixtures, combined with natural insulators, such as vegetable fibers, were chosen to make shape-stabilized PCMs composites. These composites can be integrated in buildings as a passive thermal energy storage material.

Climate-Based Analysis for the Potential Use of Coconut Oil as Phase Change Material in Buildings

One of the most efficient measures to reduce energy consumption in buildings is using passive thermal comfort strategies. This paper shows the potential of coconut oil as a bio-based phase change material (PCM) incorporated into construction components to improve the thermal performance of buildings for several climates, due to its environmental advantages, wide availability, and economic feasibility. The thermophysical properties of coconut oil were determined through differential scanning calorimetry. Numerical simulations were conducted in ESP-r, comparing an office space with a gypsum ceiling to one with coconut oil as PCM for 12 climate types in the Köppen–Geiger classification. The results show that coconut oil is a suitable PCM for construction applications under tropical and subtropical climates. This PCM can provide year-round benefits for these climates, even though a higher melting point is needed for optimum performance during hotter months. The highest demand reduction of 32% and a maximum temperature reduction of 3.7 °C were found in Mansa, Zambia (Cwa climate). The best results occur when average outdoor temperatures are within the temperature range of phase change. The higher the diurnal temperature range, the better the results. Our findings contribute to a better understanding of coconut oil in terms of its properties and potential for application in the building sector as PCM.

Design and Construction of Photochromic and Antileakage Reinforced Wood-Based Cellulose Microframework/Hexadecanol-Coconut Oil Composite Phase Change Material

The development of high-performance shape-stable phase change material composites (SPCMs) with high phase change enthalpy and high conversion efficiency, especially with good photochromic properties, is essential for thermal energy storage. Here, we report that one type of SPCMs with both photochromic and phase change energy storage is obtained by incorporating organic binary composite PCMs (hexadecanol/coconut oil, H/C) and photochromic phosphotungstic acid (PA) into Ochroma pyramidale wood-based cellulose microframe (DOW) through simple vacuum impregnation. When the ratio of hexadecanol to coconut oil is 3:7 and the ratio of phosphotungstic acid to N,N-dimethylacetamide is 4:13.6, the SPCM composite material (DOW-H3C7-4PA) represents a high phase transition enthalpy of 163.7 J/g and an appropriate phase transition temperature of 42.55 °C that can be applied to the environmental temperature adjustment of high-temperature areas (>40 °C) mentioned in this paper, in addition to the excellent thermal stability and photochromic stability; for example, even after 100 thermal cycles and UV radiation cycles, its phase transition enthalpy remains almost unchanged. The DOW-H3C7-4PA composite material also shows good shape stability and leakage resistance. In addition, the high photothermal conversion efficiency (65.71%) of DOW-H3C7-4PA is considered to be a promising candidate for photothermal energy storage applications. Therefore, the manufactured SPCMs (DOW-H3C7-4PA) have high latent heat, good melting/freezing cycle reliability, high photochromic stability, and remarkable light-to-heat energy conversion ability, making them show broad application prospects in energy conversion and storage devices.

Evaluation of thermal properties and acetaldehyde adsorption performance of sustainable composites using waste wood and biochar

In order to vitalize the use of wood, which is a sustainable resource, increase the utilization of resources through the recycling of wood waste, and reduce environmental pollution in the waste disposal process, biocomposite was manufactured by using biochar which can be produced with wood waste and is effective in carbon isolation. The thermal characteristics and acetaldehyde adsorption performance of the prepared biocomposite were evaluated based on the pore characteristics, surface functional groups, crystal structure, and elemental analysis results of the biochar. As a result of the experiment, as the content of biochar increased, the thermal conductivity of the biocomposite decreased and the specific heat was not affected. The acetaldehyde concentration tended to decrease as the content of biochar increased, adsorbed up to 4.4685 ppm of acetaldehyde more than the reference. From these results, it is judged that the biocomposite produced in this study can function as a sustainable composite that uses waste wood to improve indoor air quality and satisfies the performance as a building material.

Thermal, hygric, and environmental performance evaluation of thermal insulation materials for their sustainable utilization in buildings

As energy use in the building sector is increasing worldwide, building materials with characteristics that save energy are becoming increasingly important; in addition, there is an emerging need for high-performance insulation materials with low thermal conductivity. However, thermal insulation should consider thermal conductivity, which is the main performance parameter, in addition to the water adsorption rate, acidity, and deformation and expansion due to drying conditions. This study evaluated the main performance of 21 insulation materials used at construction sites to objectively and clearly evaluate their overall performance, including their thermal conductivity. Thermal conductivity was measured by the heat flow meter method according to ASTM C518 and ISO 8301 standards; it was also evaluated according to the drying conditions. The water absorption rate was evaluated by ISO 2896 to ensure the sustainability and long-term thermal conductivity performance of the material. Acidity was evaluated with ASTM E861 to reduce the environmental load of the buildings and soil. The results of this study reviewed an appropriate method to measure the main performance according to the type of insulation.

Conversion of tannery solid waste to an adsorbent for high-efficiency dye removal from tannery wastewater: A road to circular utilization

The high value-added use of tannery solid waste and elimination of tannery liquid waste in the leather-making industry have attracted widespread attention. In this study, a MgO-doped biochar (MgO/BC) adsorbent was successfully prepared by utilizing tannery solid waste (i.e., non-tanned hide wastes) as the biomass material for dye removal from tannery wastewater. Characterization results indicated that MgO was uniformly embedded into the porous BC structure. The adsorption capacity of acid orange II by MgO/BC reached up to 448.4 mg g^-1, which drastically exceeded the pure BC and other reported adsorbents. The adsorption behavior of acid orange II by MgO/BC matched nicely with Langmuir isotherm and pseudo-second-order kinetic model. This satisfactory adsorption capacity of MgO/BC for acid orange II was mainly due to the large specific surface area and the enhanced electrostatic interaction. According to the BET, zeta potential and XPS analysis, the possible mechanism towards acid orange II removal was attributed to the pore filling, surface complexation, electrostatic attraction and π-π interaction. In addition, MgO/BC showed the efficient removal towards anionic dyes from actual tannery wastewater. This work could provide guidance for the value-added utilization of tannery solid waste and a practical way to remove dyes from tannery wastewater.

3D Lamellar Structure of Biomass-Based Porous Carbon Derived from Towel Gourd toward Phase Change Composites with Thermal Management and Protection

The practical application of shape-stable phase change composites (PCCs) is beneficial to thermal energy management and energy conservation due to their superior properties. A shape-stable PCC was fabricated by incorporating poly(ethylene glycol) (PEG) with biomass-based porous carbon that was produced via freeze-drying and carbonization using a low-cost and environmentally friendly fresh towel gourd. The towel gourd derived porous carbon with the characteristics of porosity, unique three-dimensional (3D) lamellar structure, and high specific surface area allowed a high encapsulation capacity (up to 94.5 wt %) for PEG. Structural morphologies, as well as the properties of latent heat storage, thermal reliability, thermal energy management, and thermal protection ability of the fabricated shape-stable PCC, were investigated. The micromorphologies revealed that PEG molecular chains were arranged in a 3D lamellar tissue structure. The shape-stable PCC demonstrated excellent thermal reliability and a high melting latent heat of ∼164.3 J/g. The analysis of infrared thermal images indicated that the shape-stable PCC exhibited remarkable strengths in thermal energy management. The result of the thermal insulation simulation experiment proved that the shape-stable PCC had superior thermal protection ability. This study provided an innovative strategy for the design and development of shape-stable PCCs for great potential in heat-insulating protective textiles, solar thermal energy storage, energy-saving buildings, and infrared stealth of military targets.

The Effect of Different Plant Oil Impregnation and Hardening Temperatures on Physical-Mechanical Properties of Modified Biocomposite Boards Made of Hemp Shives and Corn Starch

In this study, tung tree and linseed drying oils, as well as semi-drying hempseed oil, were analyzed as the protective coatings for biocomposite boards (BcB) made of hemp shives, corn starch binder, and the performance-enhancing additives. The hydrophobization coatings were formed at 40, 90, and 120 °C temperatures, respectively. The physical-mechanical properties such as the compressive strength, thermal conductivity, dimensional stability, water absorption, and swelling were tested. In addition, scanning electron microscopy (SEM) was employed for the analysis of the board microstructure to visualize the oil fills and impregnation in pores and voids. It was demonstrated that the compressive strength of oil-modified BcBs compared to uncoated BcBs (at 10% of relative deformation) increased by up to 4.5-fold and could reach up to 14 MPa, water absorption decreased up to 4-fold (from 1.34 to 0.37 kg/m²), swelling decreased up to 48% (from 8.20% to 4.26%), whereas the thermal conductivity remained unchanged with the thermal conductivity coefficient of around 0.085 W/m·K. Significant performance-enhancing properties were obtained due to the formation of a protective oil film when the tung tree oil was used.

Infiltration properties of n-alkanes in mesoporous biochar: The capacity of smokeless support for stability and energy storage

Biochar, also named biocarbon, is a solid particulate material produced from the thermal decomposition of biomass at moderate temperatures. It has progressively become the topic of scientific interest in energy storage and conversion applications due to its affordability, environment friendliness, and structural tunability. In this study, biochar (obtained 600 °C pyrolysis) was introduced as phase change materials (PCMs) support. Three different n-alkanes (such as dodecane, tetradecane, and octadecane) are used as PCMs. The PCMs were infiltrated in the biochar network via the vacuum impregnation method. Among the biochar/n-alkane composites, one from octadecane exhibited a high latent heat storage capacity of 91.5 kJ/kg, 15.7 % and 25.9 % higher than that of dodecane and tetradecane-based composites, respectively. The molecular length of the PCMs and intermolecular interaction between the functional groups play an imperative role. The infiltration ratio of PCM in the biochar reached 50.1 % with improved thermal stability and chemical compatibility. This is attributed to the favorable morphological and structural properties (e.g., large BET surface area and mesopore structure) of the biochar that resides the n-alkanes found in the nanosized chain length. Hence, this report will lay a foundation for the application of biochars in thermal energy management systems.

Biochar application for the improvement of water-soil environments and carbon emissions under freeze-thaw conditions: An in-situ field trial

There are few studies about biochar application in seasonally frozen soil areas. The regulatory mechanism of biochar on the water-soil environment and carbon emissions in seasonally frozen soil areas is unclear, which affects the study of nutrient migration and spring cropping systems under the control of biochar. For this purpose, we monitored the soil temperature (Ts), soil liquid moisture content (Ms) and soil respiration (Rs) rate during the freeze-thaw period under different application amounts of corn stover biochar (0 t∙ha^-1, 15 t∙ha^-1, 30 t∙ha^-1, 45 t∙ha^-1 and 60 t∙ha^-1). The results showed that biochar can reduce the thermal conductivity of soil, thus improving the thermal insulation effect of frozen thawed soil, and Ts increased by 1.8-5.7 °C. The Ts and Ms were more sensitive to the high biochar application amount than to the low application amount. At the same time, biochar changed the soil aggregate distribution, and Pearson correlation analysis indicated that the soil water retention capacity increased by increasing the macroaggregate content (>0.25 mm), and the Ms increased by 3.7-6.1%. Principal component regression (PCR) analysis showed that biochar can promote soil carbon emission, and Rs of soil treated with biochar was 0.01-0.58 μmol m^-2 s^-1 higher than that of the control. The Ms and Ts were the most important factors promoting the carbon emissions of freeze-thaw soil under the synergistic effect of biochar and freeze-thaw conditions. However, biochar may promote soil CO₂ emissions by affecting the water-soil environment. Considering the soil moisture, seed germination and growth conditions in spring, the suitable biochar application amount was determined to be 44-51 t∙ha^-1. This study provides theoretical support for determining reasonable and effective biochar control measures and improving the soil productivity of farmland soil in seasonally frozen soil areas.