Recent advances in functional utilisation of environmentally friendly and recyclable high-performance green biocomposites: A review

Humans have relied on biomass for survival and development since the Stone Age. All aspects of human needs for materials are covered by tools, fuel, and buildings. Nowadays, metals and petroleum-based materials are widely used in highly developed industries. Unfortunately, environmental contamination and the loss of natural resources have led to the reemergence of biomass resources as efficient and sustainable energy sources. Notably, simple and direct applications can no longer meet the demand for functionalization, high performance of materials and construction materials. Therefore, it is imperative to modify biomass and combine its utilisation to produce functionalization and high performance materials. For example, construction materials with superior mechanical properties and water resistance can be produced by reinforcing fibres to facilitate crosslinking. Water-oil separation or adsorption effects of hydrogels and aerogels are determined by the porosity and lightness of biomass, biocomposite conductor is prepared by chimaeric conductive material. Here, we review the approaches that have been taken to devise an environmentally friendly yet fully recyclable and sustainable functionalised biocomposites from biomass and its potential directions for future research.

Microwave physicochemical activation:an advanced approach to produce activated biochar for palm oil mill effluent treatment

Empty fruit bunch(EFB)is an industrial waste that is abundantly available in Malaysia.Traditionally,EFBs were burned and dumped on the plantation site,resulting in global warming pollution from methane and carbon dioxide.In this study,the EFB was transformed into a high-surface area of activated biochar through a microwave physicochemical approach involving the combination of steam followed by a hydroxide mixture for palm oil mill effluent(POME)treatment.It was found that BET(Brunauer-Emmett-Teller)surface area and total pore volume of activated biochar were 365.60 m^(2)/g and 0.16 cm^(3)/g,respectively.The surface morphology of activated biochar revealed the formation of well-developed pores that can potentially be used as adsorbents to treat POME.The removal efficiency of biochemical oxygen demand(BOD)and chemical oxygen demand(COD)of POME achieved 75%-55%,respectively.This study offers insight into the transformation of industrial waste into value-added products for sustainable environmental remediation.

Utilization of microwave steam pyrolysis to produce biochar for thermal energy storage

Microwave steam pyrolysis(MSP)is an innovative thermochemical approach to converting biomass into high-quality biochar using steam to improve the dielectric heating of microwave radiation.Biochar shows high fixed carbon and carbon contents at a maximum temperature of 550℃in 10 min.The MSP achieved a heating rate of 112℃/min from 200℃to 400℃to produce biochar effectively.Furthermore,the thermal properties of biochar in microwave heating were investigated in this study to explore its potential as a microwave heat-absorbent material.Microwave is able to perform volumetric and controllable heating to the biochar.Moreover,biochar shows good microwave heat absorbency,storing and transferring heat effectively.The temperature profile of three different sizes of biochar was investigated to examine the efficiency of biochar in heat absorption from microwave radiation.It was found that the powder form of biochar showed a higher heat transfer rate of 40℃/min and a low cooling rate of 7.5℃/min.The presented results are useful for evaluating the application of biochar as a promising medium for heat storage systems.

Microwave torrefaction of empty fruit bunch pellet:Simulation and validation of electric field and temperature distribution

Microwave simulation is significant in identifying a reactor design allowing the biomass to be heated and processed evenly.This study integrated the radio frequency and transient heat transfer modules to simulate the microwave distribution and investigated the performance of microwave heating in the cavity.The simulation results were compared with the experimental findings us-ing the finite element analysis software of COMSOL MULTIPHYSICS to predict the temperature profile and electric field of microwave in the biomass(empty fruit bunch pellets).The higher temperature distribution was observed at the bottom and centre section of the empty fruit bunch pellet bed in the reactor,showing the uniqueness of microwave heating.According to the simula-tion results,the temperature profile obtained through the specific cavity geometry and dielectric properties agreed with the experimental temperature profile.The simulated temperature profile demonstrated a logarithmic increase of 120°C/min at the first 50 s followed by 50°C/min until 350 s.The experimental temperature profile showed three different heating rates before reaching 300°C,including 78.3°C/min(50-120°C),30.6°C/min(121-250°C),and 105°C/min(250-300°C).The results of this study might contribute to the improvement of microwave heating in biomass torrefaction.