• Energy Research

A huge amount of palm waste generated daily represents a problematic high-moisture waste to be disposed of, yet it also represents a promising biomass resource to be transformed into a value-added product. A single-mode microwave hydrothermal carbonization process incorporating steam purging was developed and utilised to convert high-moisture palm waste into hydrochar over a range of process temperatures from 150 to 300 °C. The microwave hydrothermal carbonization recorded a shorter process duration (10 min) and prevented the occurrence of hot spots within the reactor. The resulting hydrochar showed up to 94.3 wt% of mass yield, 69.2 wt% of fixed carbon, and 412.3 m2/g of surface area. The subsequent application of the hydrochar in de-chlorination of domestic water demonstrated an impressive removal performance of up to 98.9% of free chlorine, exhibiting 435 min of breakthrough time, and 40.0 mg/g of bed capacity in continuous column operation. The results show great promise of microwave hydrothermal carbonization as a desirable approach to produce desirable hydrochar for de-chlorination application.

Abstract The heating performance of empty fruit bunch pellets (EFBPs) has been limited by its low energy density, high moisture, and ash content. Hence, microwave co-torrefaction (MCT) was performed with microwave heating unto waste oil mixed EFBP to produce high-energy biofuel. However, the non-homogeneous electromagnetic fields distribution in the microwave cavity results in an uneven heating behavior, producing the hot and cold spots. Hence, MCT coupled with helical lift was examined for its potential to improve heat distribution. The effect of temperature and types of waste oil on the proximate analysis and surface properties were studied. In comparison to the conventional torrefaction using a furnace (>30 min), MCT provided rapid heating (50–80°C·min−1) and a shorter process time (10 min). The use of helical lift with 2-dimensional movement – rotational (24 rpm·min−1) and vertical motion (5 cm·min−1) simultaneously, distributed microwave radiation uniformly for rapid heating. The proximate analysis demonstrated that the ash content was reduced from 8 to 3 wt%, and the highest fuel ratio of 2.0 was achieved. Additionally, the highly porous structure of EFBP biochar can act as an activated carbon precursor. MCT coupled with helical lift represents a promising approach to prevent hot spots during microwave heating.

Abstract The growing health and environmental concerns associated with the consumption of fossil energy sources catalyze the production of biofuels as renewable energy carriers for heat and electricity generation. Production of biofuels from biomass, being the most available renewable feedstock, is advantageous as it results in increased mitigation of GHGs (greenhouse gas) emissions. Co-firing biomass pellet in power plants is a promising way of using biomass for renewable energy generation. Among the various thermochemical conversion routes, torrefaction represents an efficient low-temperature pyrolysis technology to produce co-firing biofuel at 200–300 °C with low conversion losses. However, the current practice of using conventional heating in batch operation adversely affects oil palm torrefaction, leading to low throughput, low biomass processing rate, and poor heat transfer rate. Integration of microwave technology has emerged as a promising solution to enhance the upscaling capacity of torrefaction technology, offering higher production rates and better volumetric heat transfer. The present work critically reviews and discusses the latest developments in the torrefaction of oil palm waste to produce energy-dense biochar with reduced moisture content (for better water resistivity and durability). The use of microwave radiation as a heating method could also catalyze the torrefaction reaction with lower activation energy. In conclusion, microwave systems incorporated into continuous reactors seem to have great potential in streamlining torrefaction processes, thereby producing environmentally friendly energy.

Climate change, food crisis, energy generation and environmental pollution are among the greatest threats and challenges faced by mankind today. Biochar production from various biomass sources has gained a lot of interests since its addition to degraded agricultural soils not only improve soil fertility and biomass yield, but also mitigate climate change through soil carbon sequestration and reduction in greenhouse gas emissions. There are enormous amounts of oil palm biomass generated along with the main palm oil production streams. A lot of research has been carried out to convert oil palm biomass into value-added products, but none except biochar has come close to be labeled as carbon negative products. In this paper, a review about production and application potential of biochar from oil palm biomass in Malaysia is given. Besides, some of the challenges in promoting biochar production and application, such as nature of the feedstocks, economic and logistical factors and market acceptance are highlighted as well. Producing biochar from oil palm biomass can potentially lead to a healthier environmental, societal and economic growth for the oil palm industry specifically, and enhances sustainability in worldwide context.

Thermal co-processing of lignocellulosic and aquatic biomass, such as algae and shellfish waste, has shown synergistic effects in producing value-added energy products with higher process efficiency than the traditional method, highlighting the importance of scaling up to pilot-scale operations. This article discusses the design and operation of pilot-scale reactors for torrefaction, pyrolysis, and gasification, as well as the key parameters of co-processing biomass into targeted and improved quality products for use as fuel, agricultural application, and environmental remediation. Techno-economic analysis reveals that end product selling price, market dynamics, government policies, and biomass cost are crucial factors influencing the sustainability of thermal co-processing as a feasible approach to utilize the biomass. Because of its simplicity, pyrolysis allows greater energy recovery, while gasification has the highest net present value (profitability). Integration of liquefaction, hydrothermal, and fermentation pre-treatment technology has the potential to increase energy efficiency while reducing process residues.

As the world’s second largest producer and exporter of palm oil, Malaysia’s palm oil industry leaves behind huge amounts of biomass waste from its plantation and milling activities such as empty fruit bunch, palm kernel shell (PKS), palm frond and palm trunk. Generally, most of the waste generated is disposed of via open dumping, used as solid fuel in boilers, or used as fertilizers. To enhance the use of the abundant biomass generated by the oil palm industry in Malaysia, conversion of biomass to biochar could be a promising alternative. Biochar has the strength in improving long term soil productivity and capable of sequestering carbon in soils to reduce the emission of carbon dioxide to atmosphere. This research project aims to investigate and optimize the use of PKS for biochar production through slow pyrolysis by using the Biochar Experimenter’s Kit (BEK) from All Power Labs, California. PKS was pyrolyzed at 400 °C for an hour. Biochar and the pyrolysis by-products were then collected. The biochar was then selectively characterized for its physicochemical properties such as proximate and ultimate analysis, pH, water holding capacity and BET surface area.

AbstractBACKGROUNDOil palm shell (OPS) is a biomass widely available from palm oil mills. Self‐purging microwave pyrolysis (SPMP) was performed to produce carbon‐rich biochar from OPS for the adsorption of methylene blue dye. The effect of feedstock amount on the pyrolysis temperature, yield and characteristics of the biochar were investigated.RESULTThe amount of feedstock was directly proportional to the final pyrolysis temperature. The pyrolysis reached a maximum final temperature of 760 °C when ≥300 g of OPS was loaded into the reactor without microwave absorbent. A heating rate of up to 105 °C min−1 was recorded, producing a yield of 40 wt% of biochar at a short processing time of 20 min. The biochar obtained at 700 °C showed relatively low volatile matter (24 wt%), higher fixed carbon content (66 wt%), carbon (78.5 wt%), oxygen (17.7 wt%), a highly porous structure with high BET surface area of 410 m2 g−1 and pore volume of 0.16 cm3 g−1, and recorded a methylene blue dye adsorption efficiency of 20 mg g−1.CONCLUSIONThe SPMP approach showed exceptional promise to produce biochar with low H/C ratio (0.5) and O/C ratio (0.2), which indicated a high degree of carbonization and stability of the biochar to act as a durable agent in wastewater treatment. © 2018 Society of Chemical Industry

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 using 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 simulation 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.

Traditional disposal of animal manures and lignocellulosic biomass is restricted by its inefficiency and sluggishness. To advance the carbon management and greenhouse gas mitigation, this review scrutinizes the effect of pyrolysis in promoting the sustainable biomass and manure disposal as well as stimulating the biochar industry development. This review has examined the advancement of pyrolysis of animal manure (AM) and lignocellulosic biomass (LB) in terms of efficiency, cost-effectiveness, and operability. In particular, the applicability of pyrolysis biochar in enhancing the crops yields via soil remediation is highlighted. Through pyrolysis, the heavy metals of animal manures are fixated in the biochar, thereby both soil contamination via leaching and heavy metal uptake by crops are minimized. Pyrolysis biochar is potentially use in soil remediation for agronomic and environmental co-benefits. Fast pyrolysis assures high bio-oil yield and revenue with better return on investment whereas slow pyrolysis has low revenue despite its minimum investment cost because of relatively low selling price of biochar. For future commercialization, both continuous reactors and catalysis can be integrated to pyrolysis to ameliorate the efficiency and economic value of pyrolysis biochar.