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Advanced porous materials with uniform molecular scale apertures are highly desirable for energy related separations. Among them, zeolitic imidazolate frameworks (ZIFs) have received significant interest as separation membranes owing to their narrow apertures that can target small gases. ZIFs exhibit excellent gas transport properties, such as unprecedentedly high C3H6 permeability and remarkable C3H6/C3H8 selectivity, inaccessible by other porous inorganic materials and polymers. Deposition of ultrathin ZIFs on porous substrates to form gas-selective barriers has been a major focus in this area. There has been a significant development in the synthesis of ultrathin ZIF membranes for gas separations. In this review, we present a summary of current state-of-the-art in ZIF membrane processing and highlight unique microstructural features of the prepared membranes. Following this, we discuss level of separation performances of these advanced membranes focusing on three emerging/unsolved applications. Finally, we provide our perspectives on future research directions in the area.

Mankind’s quest to reduce its dependency on fossil fuel involves biomass as a promising alternative. However, direct application of raw biomass faces problems such as high moisture content, low heating value, and poor grindability. Pyrolysis is one of the pre-treatment methods to improve biomass properties particularly its energy density. This study is aimed at investigating the pyrolysis of oil palm trunk (OPT) into biocoal and its suitability for solid fuel applications in terms of slagging and fouling tendencies, bulk density, proximate and ultimate analysis, higher heating value, energy densification ratio, and mass and energy yield. The biocoal was produced using a top-lit, updraft reactor with a peak temperature of 550 °C and fixed air flowrate of 4.63 L/min. The bulk density of OPT biocoal was 87.7 kg/m3 which is 4.63% lower than that of original OPT due to the increased porosity. The elemental composition of our biocoal resembles lignite. The volatile matter content decreased by a factor of 1.87 while the fixed carbon content and higher heating value (HHV) increased from 4.29 to 30.9% and from 14.5 to 19.6 MJ/kg, respectively. The HHV of biocoal increased by a factor of 1.36 relative to that of raw OPT; however, the resulting energy yield was low (37.6 ± 1.9%) due to a low biocoal yield of 27.8 ± 1.4%. The ash content increased by a factor of 1.5, resulting in an ash content of 27.8 wt% for biocoal. This increment may exacerbate the slagging and fouling propensity in furnaces and boilers as indicated by the slagging and bed agglomeration index which increased from 2.0 to 5.2 and from 0.4 to 0.7, respectively. Demineralization, a lower pyrolysis temperature and subsequent briquetting of OPT biocoal are suggested to improve its fuel properties for co-combustion in coal-firing power plants.

The under-utilized legume Mucuna bracteata is a potential biomass resource in Malaysia. A 24-month study was conducted under 10-year-old mature oil palm trees to determine the effects of several harvesting frequencies of M. bracteata on the legume biomass and soil properties. The experimental design was a randomized complete block design (RCBD) for the biomass and a two-factorial RCBD for the soil properties. The treatments were the harvesting frequencies, which were once every two, four, six, and twelve months. The control treatment was without harvest. There were significant effects on the legume’s cumulative biomass, standing biomass, leaf area, nutrient contents, and total nutrient harvested for N, Ca, Mg, and cellulose content. Generally, the more frequent the harvest, the more biomass was obtained, but the more legume standing biomass and leaf area were reduced. Despite the reduction in legume growth and leaf area in the field, harvesting the legume did not affect any of the soil physicochemical properties. The biomass N, Ca, and Mg contents and nutrient harvested were also affected by harvesting. This was due to the production of relatively more young shoots after harvesting, which would remove most of the aboveground plant parts. The cellulose content in the legume also increased for the same reasons. Results showed that harvesting M. bracteata once every six months was an acceptable compromise between collecting large amounts of legume biomass and having a reduced legume growth recovery and leaf area in the field, but yet not detrimentally affecting the soil properties.

Biomass-derived biochar emerges as a potential green bio-coal candidate for power generation. Microwave-assisted pyrolysis has been proven to be an efficient and economical technique for biomass conversion into biochar. The process can be further improved by utilising susceptor. This research focuses on producing biochar from microwave pyrolysis of empty fruit bunch (EFB) in an alumina susceptor. EFB pellet (PEFB) and EFB short fibre (FEFB) were pyrolysed in a 14L bench scale microwave pyrolyser at temperatures between 200 and 400 °C. The pyrolyser performance (biochar yield, energy efficiency) and biochar properties (proximate analyses, ultimate analyses, calorific value and ash content) were analysed. The results showed that temperature of 300 °C demonstrated the optimised conditions for biochar production. FEFB produced 5.2% higher biochar yield and exhibited better biochar properties compared to PEFB. FEFB-derived biochar (FEFBC) overall characteristics were better than PEFB-derived biochar (PEFBC), with higher heating value (25.19 MJ/kg), fixed carbon (64.52%), volatile matter (13.38%) and carbon content (59.83%). However, FEFBC has high tendency of forming slagging and fouling in the combustor as the ash indexes was >0.34 kg/GJ and RB/A > 1.75.

Biomass is a promising alternative for the reduction of global dependency on fossil fuels. However, there are some issues with the direct application of raw biomass such as high moisture content, low heating value, and poor grindability. To alleviate the problems, biomass-derived biocoal is introduced and utilised as fuel in power plants. Oil palm trunk biocoal (OPTC) is produced from pyrolysis of oil palm trunk biomass (OPTB) in a top-lit, updraft reactor at a constant air flowrate of 4.63 L/min and maximum temperature of 550 °C. OPTC is co-combusted at temperatures between 600 and 900 °C with sub-bituminous coal (SBC). Pollutant emission and ash production from combustion of fuel blends containing 20% and 50% biocoal are analysed and compared with pure SBC, OPTB and OPTC. NOx and SO2 emission profiles from all tested fuel blends are well below the limits imposed under Environmental Quality (Clean Air) Regulation 2014 of 296 and 190 ppm respectively. Response surface methodology (RSM) analysis indicates that the operation of combustion is optimised with 92.16% efficiency at 774 °C and air flowrate of 16.6 SCFH to emit 16.38% CO2, and the findings are validated against experimental results. The optimised combustion process produces ash with 67.9% silicon compounds.

Mullite-based ceramics were prepared by utilizing agriculture by-product called as rice husk ash (RHA) from untreated rice husk (RH) and commercial alumina powdermixtures. Various samples were prepared accordingly with the mullite stoichiometric composition and subjected to the uniaxial hydraulic press. The green bodies, then were sintered to various temperatures at 1200 °C, 1300 °C, 1350 °C, 1400 °C, 1450 °C and 1500 °C in an electric furnace. Physical and microstructural characterization were done such as bulk density (BD), linear shrinkage (LS), X-ray fluorescence (XRF), X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). The sample M1, which composed the slightest RHA (40 %) was considered the optimum composition which produced the highest densification, 3.101 g/cm3 and the lowest linear shrinkage, 8.62 % which compareswith the theoretical mullite density. Besides, it is supported by the evidence of the presenceof mullite in the samples sintered 1300 °C (shown as elongated shape) as primary mullite and continued to grow at higher temperatures at 1400 °C (shown as equiaxed shape) as secondary mullite. The sintered samples showno evidence of mullite inearly at 1200 °C due to insufficient energy to diffuse for mullitization. As the sintering temperature increased, mullitization increased while decreasing the distribution of glassy phase and voids. The results revealed the high dependency of bulk density and linear shrinkage on the Al2O3 content and the values were gradually increased with the increase of sintering temperature. These findingsmay lead to the extended study ofthermal insulationmaterials as mullite ceramic is an excellent candidate for this application due to its properties.

Since the industrialisation of Malaysia, the energy demand which mainly relied on fossil fuels has risen continuously. Therefore, all parties including the government, academic society and communities have explored alternative fuel resources to improve the reliability and security of energy supply to meet the future energy. In recent years, biomass has been identified as one of the most promising renewable energy resources compared to hydro, solar, wind, etc. It is projected that energy crops could potentially supply around 200-400 EJ/year in Malaysia at a competitive cost by 2050. Perennial grass is one type of energy crop that could address the above mentioned challenge. In this work, Napier grass (NG) is chosen as the subject due to its desirable characteristics (availability, high growth rates, carbon neutrality and high volatility). In order to investigate the feasibility of NG for heat and power application, the thermal decomposition characteristics, reactivity, and kinetic of NG needed were tested via thermogravimetric analysis (TGA) under inert (nitrogen) and air atmosphere conditions, respectively. The results indicated that NG biomass has great potential as sustainable energy fuel source for energy generation via gasification process.

Fuel resource diversification is a global effort to deviate from non-renewable fossil fuels. Biomass has been identified as an alternative solid biofuel source due to its desirable properties and carbon neutrality. As reported in the literature, biomass can positively contribute towards combating climate change while providing alleviation for energy security issue. As part of efforts to diversify biomass resources, this work intends to explore the potential of Napier grass, one type of energy crop, for the production of renewable syngas via gasification. This energy crop is originally from Africa, which is highly productive with low cost (40 tonnes per year per hectare). Limited studies were conducted to analyze the potential of such an energy crop as a fuel source, which is the subject of this work. In order to analyze the full potential of such energy crop, the physical and chemical characteristics of this biomass was first analyzed. To determine the productivity of syngas from this biomass, fluidized bed gasifier was used in this work. The effects of gasification process parameters (i.e., equivalence ratio and temperature) on product yield and producer gas compositions were examined. Besides, the effects of equivalence ratio towards higher heating value of syngas and carbon conversion efficiency were analyzed. Based on the ultimate analysis results, the molecular formula of Napier gas was CH1.56O0.81N0.0043. Meanwhile, the higher heating value of such biomass was determined as 16.73 MJ/kg, which was comparable to other biomasses. It is noted that in this work, the volatile matter was determined as 85.52% and this promoted gasification process remarkably. The dynamics of the reactions involved were observed as a significant variation in product yield and biogas components were recorded at varying equivalence ratio and gasifier operating temperature.

This paper describes a batch study on four different mixture ratios of household organic waste and cow manure. The biomethane potential test is used to evaluate the suitability of high solid anaerobic co-digestion of household organic waste and cow manure and its biodegradability. The maximum methane yield was observed for both co-digestions in R3 (247 mL/g VS) and R4 (244 mL/g VS). The percentages of mass recovery were 65-80% (based on VS removal). The biodegradability of each reactor was recorded as 97.7%, 10.7%,71.6% and 76.8% for R1, R2, R3, and R4, respectively. High solid co-digestion of household organic waste and cow manure in different mixture ratios increase the specific methane yields compared to mono-digestion. Hence, this clearly demonstrates a synergistic effect on the stability of anaerobic digestion. Upon correcting the results of the theoretical method with experimental data, an agreement ranged 70-90% was achieved.

Different mixture ratio of household organic waste (HOW) and cow manure (CM) were investigated for biogas production. The objective was to explore possible significant synergistic effect obtained from the combination of these different substrates in Reactor 1 – 4 (R1 – 4) batch experiment. The highest methane yield, 247mL/g VS was obtained from R3 and 243mL/g VS in R4. Co-digestion in R4 increased to 9% for CM and 78% for HOW in methane production. The results clearly demonstrate synergistic effect from nutrient balanced that improves the stability of anaerobic process.

The accumulation of organic fraction in municipal solid waste (OFMSW) is now becoming scarce globally due to population and economic boosts, especially in Malaysia. Municipal solid waste (MSW) landfills remain the predominant end-state for waste disposal in most developing countries. Unsustainable MSW management accelerates environmental degradation through landfill gaseous (LFG) emissions of mainly methane (CH4) and carbon dioxide (CO2), which promote global warming that finally is affecting human health. Recently, harnessing CH4 from anaerobic digestion of solid waste has attracted more interest and promised betterment in MSW management. With its current amount of more than 50%, organic material in landfills is estimated to emit 310,225 CH4/year with carbon credit of US$ 85.93, which can potentially generate 2.20×10 9 kWh of electricity valued at US$ 220 million. This present work is a review manuscript that discusses the state-of-the-art anaerobic digestion of OFMSW as treatment in term of waste diversion from a landfill. The study also estimates the renewable energy potentials from OFMSW waste diversion. Finally, this paper discusses the benefits of harnessing biogas from the perspectives of environmental benefits, energy recovery, and economics.

Introducing a highly technical multidisciplinary design problem to first year students can be a daunting task. First, their knowledge experience revolves only about basic mathematics, science and its application to technological problem. If mishandled, exposing them to complex design process at this stage can pose a disastrous effect. The intent of this paper is to share the facilitative teaching approach performed onto the first year students at the Department of Chemical & Environmental Engineering, UPM. This facilitative teaching approach is specifically adopted in the Material Balances courses (2+1) where a multidisciplinary conceptual design project is embedded as part of its content. The teaching team is responsible to plan and design instruction, assessment and evaluation materials, coach team during design activities by providing assistance and on time feedback, and maintain teams' vibrancy. A highly committed teaching team is required to materialize this approach because the efforts and time spent to conduct the activities for learning is not equivalent in number to the given credit loading. Furthermore, time and energy for other activities related to key performance indicators are usually sacrificed. However, excellent students' engagement, enthusiasm and participation to learn indicate that the efforts and time were worth spent.

In this study, hydrogel-(rice husk) biochar composite (HBC-RH) was prepared using acrylamide (AAm) as monomer, with N.N’-methylenebisacrylamide (MBA) as crosslinker, ammonium persulfate (APS) as initiator and rice husk biochar (RHB). The synthesized hydrogel-(rice husk) biochar composite was characterized for swelling capacity andthen utilized for the removal of zinc from wastewater. The optimum batch experimental conditions for this study were determined by evaluating the effect of solution pH, adsorbent dosage, adsorbate initial concentration and contact time. Langmuir isotherm best fitted the HBC-RH sorption of Zinc whereas the kinetic data were best described by pseudo second-order. The maximum monolayer sorption capacity of HBC-RH for zinc was 35.75mg/g.

Biochars have received increasing attention because of their potential environmental applications such as soil amending and atmospheric C sequestration. In this study, biochar was produced from waste rubber-wood-sawdust. The produced biochars were characterized by Brunauer–Emmett–Teller (BET) gas porosimetry, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). Pyrolysis temperature was shown to have a strong influence on both thermal and chemical characteristic of biochar samples. The experimental data shows that the biochar samples can absorb around 5% water by mass (hydrophilic) at lower temperatures ( 650 °C), biochar samples were thermally stable and became hydrophobic due to the presence of aromatic compounds. Carbon content (over 85%) increased with increasing temperature, and showed an inverse effect to the elemental ratios of H/C and O/C. The very low H/C and O/C ratios obtained for the biochar indicated that carbon in this material is predominantly unsaturated. BET results showed that the sawdust derived biochars have surface areas between 10 and 200 m2 g−1 and FTIR indicated an aromatic functional group about 866 cm−1 in most of the samples. The rate of CO2 adsorption on sawdust derived biochar generally increased with increasing temperature from 450 to 650 °C but then decreased with increase in the production temperature. Derived biochar represents a potential alternative adsorbent for C sequestration.

Fischer-Tropsch Synthesis (FTS) is a process which converts synthesized gas (a mixture of H2 and CO) to synthetic liquid fuels and valuable chemicals with the existence of metal catalysts and suitable operational conditions. Less costly and plentiful biomass from agricultural waste can be converted into synthesized gas by thermal gasification. FTS derived Biofuel is a high quality, clean fuel and have a very low sulfur content in comparison to conventional fuel. In this study, FTS reaction was investigated in a tubular fixed bed reactor on prepared Co-Ni bimetallic catalysts supported by walnut shells derived activated carbon (AC) to study the synergistic effect of the active metals on the catalyst’s physical properties as well as hydrocarbon liquid product distribution. Employed catalysts were synthesized by wet impregnation method and were characterized afterwards by XRD, TPR-H2, BET surface area and FESEM-EDX techniques to identify the morphology and physical properties of the catalysts. Maximum gasoline selectivity of 69% was achieved on the 7Co7Ni/AC bimetallic catalyst, which was considered as the best bimetallic catalyst among others. Temperature increase from 220°C to 300°C enhanced gasoline selectivity from 69% to 92%. In addition, carbon monoxide (CO) conversion increased as well from 43% to 65% on the 7Co7Ni/AC bimetallic catalyst. On the contrary, increased reaction pressure from 1 bar to 9 bar decreased gasoline selectivity from 92% to 36% but increased CO conversion is from 65% to 84% on the 7Co7Ni/AC bimetallic catalyst. The optimum reaction conditions were considered based on the maximum selectivity of gasoline which was 300°C reaction temperature and 1 bar reaction pressure. In conclusion, the employing of bimetallic Co-Ni catalysts supported by AC in Fischer-Tropsch reaction has significantly enhanced the catalytic activity and improved gasoline selectivity due to the achieved high metal dispersion, better reduction degree and large surface area. Higher reaction temperatures increased gasoline selectivity whereas, higher reaction pressures decreased gasoline selectivity.