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

Sustainable valorization of garlic byproducts: From waste to resource in the pursuit of carbon neutrality

Large-scale garlic planting and processing activities generate considerable amounts of agro-food waste and pose serious environmental and economic challenges. These byproducts are rich in bioactive compounds with promising applications in the food, medicine, and agriculture sectors. This review provides a comprehensive overview of the generation, classification, chemical composition, and valorization of garlic byproducts. Garlic agricultural waste is derived from all stages of garlic harvesting and post-harvest processing and contain abundant soluble polysaccharides, polyphenols, proteins, insoluble dietary fiber, and organic sulfur compounds. The valorization of garlic waste can be achieved through tailoring processing technologies to extract and utilize individual components or applying the whole matter. Using traditional and emerging extraction and modification technologies, a variety of bioactive constituents can be transformed into functional foods, nutraceuticals, or other high-value products with exceptional functional properties and health benefits. Moreover, garlic waste can be converted into N/S/O self-doped carbon dots and biochar or be utilized directly in applications such as biocomposite films for food packaging, fluorescence sensors for food safety detection, biosorbents for food wastewater purification, agricultural quality enhancers, or nutritional supplements. Despite these opportunities, there are still several knowledge gaps regarding assessment and grading of materials, clean and low-cost production, efficient applications, long-term performance evaluation of products, and well-establishment of a robust industrial chain. Therefore, more research is required to advance the valorization of garlic agricultural waste, fostering a win-win scenario for the effective utilization of garlic byproducts and progress toward carbon neutrality.

Improved Thermal Performance and Distillate of Conventional Solar Still via Copper Plate, Phase Change Material and CuO Nanoparticles

BACKGROUND

The world is currently facing a growing concern regarding freshwater scarcity, which has arisen as a result of a complex interplay of various factors. Renewable energy-powered water desalination is a feasible solution to address freshwater scarcity.

METHODS

This patent study presents a comprehensive investigation of the performance of a conventional solar still (CSS) and its modified versions, such as a still with copper plates, a still with PCM and a still with PCM and 3 wt% CuO nanoparticles blend. The experiments were carried out concurrently under identical circumstances for the CSS and the proposed stills. Prior to usage, the CuO nanoparticles and their blend with PCM were characterized through various analyses.

RESULTS

The investigation showcased the copper plate attached solar still with 3 wt% CuO nanoparticles blended with PCM significantly improved the distillate production, achieving approximately 6.85 kg/m2/day. This represents an increment of approximately 23.42% compared to the still with copper plate and PCM and 69.14% related to the CSS.

CONCLUSION

Moreover, the solar still with 3 wt% CuO nanoparticles blended with PCM demonstrated a thermal efficiency of 74.23% and an exergy efficiency of 9.75%. The production cost of distillate for all four stills remained at $0.03 per kg. These findings highlight the effectiveness of the proposed copper plate attached solar still with 3 wt% CuO nanoparticles blended with PCM as a viable method for producing potable water.

Nano-Biochar Prepared from High-Pressure Homogenization Improves Thermal Conductivity of Ethylene Glycol-Based Coolant

As an environmentally friendly material, biochar is increasingly being utilized in the field of heat transfer and thermal conduction. In this study, nano-biochar was prepared from high-pressure homogenization (HPH) using sesame stalks as the raw material. It was incorporated into ethylene glycol (EG) and its dispersion stability, viscosity, and thermal conductivity were investigated. The nano-biochar was stably dispersed in EG for 28 days. When the concentration of the nano-biochar added to EG was less than 1%, the impact on viscosity was negligible. The addition of 5 wt.% nano-biochar to EG improved the thermal conductivity by 6.72%, which could be attributed to the graphitized structure and Brownian motion of the nano-biochar. Overall, nano-biochar has the potential to be applied in automotive thermal management.

Thermo-kinetic behaviour of green synthesized nanomaterial enhanced organic phase change material: Model fitting approach

Metal, carbon and conducting polymer nanoparticles are blended with organic phase change materials (PCMs) to enhance the thermal conductivity, heat storage ability, thermal stability and optical property. However, the existing nanoparticle are expensive and need to be handle with high caution during operation as well during disposal owing to its toxicity. Subsequently handling of solid waste and the disposal of organic PCM after longevity usage are of utmost concern and are less exposed. Henceforth, the current research presents a new dimension of exploration by green synthesized nanoparticles from a thorny shrub of an invasive weed named Prosopis Juliflora (PJ) which is a agro based solid waste. Subsequently, the research is indented to decide the concentration of green synthesized nanoparticle for effective heat transfer rate of organic PCM (Tm = 35-40 °C & Hm = 145 J/g). Furthermore, an in-depth understanding on the kinetic and thermodynamic profile of degradation mechanism involved in disposal of PCM after usage via Coats and Redfern technique is exhibited. Engaging a two-step method, we fuse the green synthesized nanomaterial with PCM to obtain nanocomposite PCM. On experimental evaluation, thermal conductivity of the developed nanocomposite (PCM + PJ) increases by 63.8% (0.282 W/m⋅K to 0.462 W/m⋅K) with 0.8 wt% green synthesized nanomaterial owing to the uniform distribution of nanoparticle within PCM matrix thereby contributing to bridging thermal networks. Subsequently, PCM and PCM + PJ nanocomposites are tested using thermogravimetric analyzer at different heating rates (05 °C/min; 10 °C/min; 15 °C/min & 20 °C/min) to analyze the decomposition kinetic reaction. The kinetic and thermodynamic profile of degradation mechanism involved in disposal of PCM and its nanocomposite of PCM + PJ provides insight on thermal parameters to be considered on large scale operation and to understand the complex nature of the chemical reactions. Adopting thirteen different chemical mechanism model under Coats and Redfern method we determine the reaction mechanism; kinetic parameter like activation energy (Ea) & pre-exponential factor (A) and thermodynamic parameter like change in enthalpy (ΔH), change in Gibbs free energy (ΔG) and change in entropy (ΔS). Dispersion of PJ nanomaterial with PCM reduces Ea from 370.82 kJ/mol-1 to 342.54 kJ/mol-1 (7.7% reduction), as the developed nanomaterial is enriched in carbon element and exhibits a catalytic effect for breakdown reaction. Corresponding, value of ΔG for PCM and PCM + PJ sample within heating rates of 05-20 °C/min varies between 168.95 and 41.611 kJ/mol-1. The current research will unbolt new works with focus on exploring the pyrolysis behaviour of phase change materials and its nanocomposite used for energy storage applications. This work also provides insights on the disposal of PCM which is an organic solid waste. The thermo-kinetic profile will help to investigate and predict the optimum heating rate and temperature range for conversion of micro-scale pyrolysis to commercial scale process.

Advances in Biocarbon and Soft Material Assembly for Enthalpy Storage: Fundamentals, Mechanisms, and Multimodal Applications

High-value-added biomass materials like biocarbon are being actively pursued integrating them with soft materials in a broad range of advanced renewable energy technologies owing to their advantages, such as lightweight, relatively low-cost, diverse structural engineering applications, and high energy storage potential. Consequently, the hybrid integration of soft and biomass-derived materials shall store energy to mitigate intermittency issues, primarily through enthalpy storage during phase change. This paper introduces the recent advances in the development of natural biomaterial-derived carbon materials in soft material assembly and its applications in multidirectional renewable energy storage. Various emerging biocarbon materials (biochar, carbon fiber, graphene, nanoporous carbon nanosheets (2D), and carbon aerogel) with intrinsic structures and engineered designs for enhanced enthalpy storage and multimodal applications are discussed. The fundamental design approaches, working mechanisms, and feature applications, such as including thermal management and electromagnetic interference shielding, sensors, flexible electronics and transparent nanopaper, and environmental applications of biocarbon-based soft material composites are highlighted. Furthermore, the challenges and potential opportunities of biocarbon-based composites are identified, and prospects in biomaterial-based soft materials composites are presented.

Structural characteristics and thermal performances of lauric-myristic-palmitic acid introduced into modified water hyacinth porous biochar for thermal energy storage

Water hyacinth (WH) was used to prepare biochar for phase change energy storage field to realize encapsulation and enhance thermal conductivity of phase change materials (PCMs) in this work. The maximum specific surface area of modified water hyacinth biochar (MWB) obtained by lyophilization and carbonization at 900 °C was 479.966 m²/g. Lauric-myristic-palmitic acid (LMPA) was used as phase change energy storage material, LWB900 and VWB900 were used as porous carriers respectively. Modified water hyacinth biochar matrix composite phase change energy storage materials (MWB@CPCMs) were prepared by vacuum adsorption method, with loading rates of 80 % and 70 % respectively. The enthalpy of LMPA/LWB900 was 105.16 J/g, which was 25.79 % higher than that of LMPA/VWB900, and the energy storage efficiency was 99.1 %. Moreover, the introduction of LWB900 increased the thermal conductivity (k) of LMPA from 0.2528 W/(m·K) to 0.3574 W/(m·K). MWB@CPCMs have good temperature control capability, and the heating time of LMPA/LWB900 was 15.03 % higher than that of LMPA/VWB900. In addition, after 500 thermal cycles, the maximum change rate of enthalpy of LMPA/LWB900 was 6.56 %, and it maintains a phase change peak, showing better durability than LMPA/VWB900. This study shows that the preparation process of LWB900 is the best, and the adsorption of LMPA has high enthalpy value and stable thermal performance, realizing the sustainable development of biochar.

Brewer’s Spent Grain Biochar: Grinding Method Matters

The present work is based on the principle of biomass waste valorization. Brewer’s spent grains (BSG) come from breweries as by-products. Their huge amount of production on an industrial scale should focus our attention on their valorization, which creates challenges as well as opportunities. One way to valorize BSG by-products is to convert them into biochar, a functional material with multiple potential applications. With an emphasis on sustainable development and the circular economy, in this work, we focused on a comparative study of the different mechanical processes of BSG grinding and their effect on the resulting biochar formed after pyrolysis. Home appliances such as blenders, coffee mills, and mortar and pestles were used for this purpose. FESEM images confirmed the successful creation of five different morphologies from the same BSG under the same pyrolysis conditions. Interestingly, a novel Chinese tea leaf egg-like biochar was also formed. It was found that a series of physical pretreatments of the biomass resulted in the reduced roughness of the biochar surface, i.e., they became smoother, thus negatively affecting the quality of the biochar. XRD revealed that the biomass physical treatments were also reflected in the crystallinity of some biochar. Via a Raman study, we witnessed the effect of mechanical pressure on the biomass for affecting the biochar features through pressure-induced modifications of the biomass’s internal structure. This induced enhanced biochar graphitization. This is a good example of the role of mechanochemistry. DSC revealed the thermochemical transformation of the five samples to be exothermic reactions. This study opens up an interesting possibility for the synthesis of biochar with controlled morphology, crystallinity, degree of graphitization, and heat capacity.