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This study reviews the innovations and optimizations in biogas production from the biological perspective reported by recently published patents and research works. The proposed biological strategies can be categorized into three different groups, i.e., upstream, mainstream, and downstream approaches. In the first part of this review, upstream strategies, including pretreatments by fungal, microbial consortium, and enzymatic as well as some other biological methods including microaeration, composting, ensiling, and genetic and metabolic engineering are discussed in detail. The impacts of upstream strategies on biogas production as well as their potentials in further improving the biogas industry are comprehensively scrutinized. Despite their promising impacts on biogas production, such biological innovations are time-consuming and require extra equipment and facilities that should be addressed in future studies. Overall, most information on biogas production has been generated through lab-scale investigations and not by commercial plants, undermining the commercial value of these data for the right decision-making. Pilot data would be necessary for techno-economic analyses with acceptable accuracies. Therefore, the future efforts should be directed toward providing the missing data for re-engineering designs, calculations, and life cycle assessment (LCA) of the newly designed biogas plants.

This review is aimed at detailing and discussing biological innovations and optimizations including upstream, mainstream, and downstream approaches in biogas production elaborated in the recently published patents and research papers. In the first part of this review, upstream strategies including pretreatments by fungal, microbial consortium, and enzymatic as well as some other biological methods including microaeration, composting, ensiling, and genetic and metabolic engineering were comprehensively presented and duly discussed. Despite the fact that these approaches hold great promise for improving the quantity and quality of the evolved biogas, the need for more processing time and extra equipment are the main drawbacks of such strategies. In the second part of this review, mainstream and downstream strategies are reviewed, and their merits and limitations are outlined. Bioaugmentation, anaerobic co-digestion, and integrated biogas production are evaluated as mainstream strategies. Finally, downstream biological approaches used for removal of CO2, H2S, and other impurities are reviewed and discussed. Among the mainstream biological techniques, bioaugmentation is highly advised to accelerate start-up periods at commercial scale while anaerobic co-digestion is recommended to not only enhance biogas yield throughout the operation but also to take advantage of different waste streams. Such mainstream strategies could contribute to improving the economic facets of biogas plants. Despite their currently underdeveloped status, downstream techniques for biological removal of biogas impurities are expected to replace their physiochemical counterparts at industrial scale in future owing to increasingly stringent environmental regulations.

Waste cooking oil (WCO) disposal in landfills or discharge into sewer systems could cause severe environmental challenges. Therefore, extensive efforts are made to develop strategies for its effective management, aligned with circular bioeconomy and zero-discharge principles and the United Nations' Sustainable Development Goals. Among existing strategies, converting WCO into biodiesel is promising; however, biodiesel production from this waste stream could induce many direct and indirect environmental impacts, which should be scrutinized using advanced sustainability assessment tools. Life cycle assessment (LCA) is a powerful tool that can be applied to assess the environmental sustainability of WCO biodiesel production in comparison with diesel and first-generation biodiesel production. Accordingly, the present review aims to scrutinize the existing literature on the LCA analysis of WCO biodiesel production to shed light on the state-of-the-art of the application of this methodology in this domain, identify research gaps, and introduce future research opportunities. Although environmental assessment of biodiesel production by LCA is well-established, several limitations and concerns still exist. Overall, system boundaries have generally been clearly defined in the published literature; however, some studies have ignored waste management; for example, disposal of soap and other solid residues has usually been removed from the analysis. Furthermore, the “zero-burden assumption” applied to WCO (as biodiesel feedstock) in the published literature might not be a valid hypothesis since this waste stream could be a raw material for some other applications. At the inventory level, the inadequacy of the data, particularly information associated with the production of novel catalysts (including enzymes) and materials used for product purification, is also a problematic issue for the current and under development technologies used in WCO biodiesel production. Therefore, future studies should focus on decreasing the existing uncertainties mentioned throughout the present work. Moreover, efforts should be put into assessing the environmental impacts of WCO biodiesel production systems by employing innovative techniques, e.g., hydrodynamic cavitation reactors, integrating other renewable energy resources, and using green catalysts in the production and combustion stages of WCO biodiesel.

A large volume of oil palm empty fruit bunch (EFB) is generated as waste feedstock around the globe. This abundant waste containing 0.75% oil on average could be a promising feedstock for biodiesel production if oil recovery could be accomplished in an economically-viable and environmentally-friendly manner. To achieve that, a new method called High Pressure Water Spray (HPWS) system was introduced and performed by spraying pressurized water (500 psi) at 30 °C, 60 °C, and 90 °C and combination of water-steam at 120 °C and 150 °C onto the surface of the oil palm empty fruit bunches (EFB). The results obtained indicated that, the highest oil removal yield of 94.41 ± 0.02 wt% was obtained at 150 °C. Moreover, bioprospection of biodiesel properties based on fatty acid methyl ester (FAME) profile revealed that the biodiesels produced from the fresh crude palm oil and residual oil were comparable and were in accordance with international standards. In addition to that, the HPWS process led to an enhanced quality of the remaining lignocellulosic materials for conversion into other value added bio-products such as ligno-ethanol by decreasing lignin content and increasing cellulose content. In view of environmental impact assessment, the HPWS system showed favorable impacts on all the end-point damage categories especially in resources damage category. Moreover, economic assessment showed that the recovered CPO could be generated at a low price of USD 0.41 vs. USD 0.66 for CPO. Overall, this process could drastically increase the market value of an abundant type of waste in many parts of the world, i.e., EFB leading to the generation of additional wealth for the palm oil industry.

In order to develop a product sustainably, multiple analyses, including comprehensive environmental assessment, are required. Solar-assisted production of walnut husk methanolic extract (WHME) as a natural antioxidant for biodiesel was scrutinized by using the life cycle assessment (LCA) approach. More specifically, the environmental sustainability of WHME antioxidant was evaluated and compared to that of propyl gallate (PG), the most widely used synthetic biodiesel antioxidant, under two scenarios. Additionally, supplementary files including the inventory data consisting of raw data as well as elementary flows, mid-point, and end-point categories are presented. The analysis of scenarios revealed that the use of the natural antioxidant and the avoidance of the chemical antioxidant in biodiesel fuel could be regarded as an eco-friendly approach substantially enhancing the environmental friendliness of biodiesel in particular in terms of human health. Furthermore, given the waste-oriented nature of WHME, the scenario involved its application could serve as a promising strategy to simultaneously valorize the agro-waste and generate a value-added product; a move toward implementing the circular economy approach in the biodiesel industry.

Life-cycle assessment (LCA) is one of the most attractive tools employed nowadays by environmental policy-makers as well as business decision-makers to ensure environmentally sustainable production/consumption of various goods/services. LCA is a systematic, rigorous, and standardized approach aimed at quantifying resources consumed/depleted, pollutants released, and the related environmental and health impacts through the course of consumption and production of goods/service. Algal fuels are no exception and their environmental sustainability could be well scrutinized using the LCA methodology. In line with that, this chapter is devoted to present guidelines on the technical aspects of LCA application in algal fuels while elaborating on major standards used, i.e., ISO 14040 and 14044 standards. Overall, LCA practitioners as well as technical experts dealing with algal fuels in both the public and private sectors could be the main target audience for these guidelines.

Life-cycle assessment (LCA) is one of the most attractive tools employed nowadays by environmental policy-makers as well as business decision-makers to ensure environmentally sustainable production/consumption of various goods/services. LCA is a systematic, rigorous, and standardized approach aimed at quantifying resources consumed/depleted, pollutants released, and the related environmental and health impacts through the course of consumption and production of goods/service. Algal fuels are no exception and their environmental sustainability could be well scrutinized using the LCA methodology. In line with that, this chapter is devoted to present guidelines on the technical aspects of LCA application in algal fuels while elaborating on major standards used, i.e., ISO 14040 and 14044 standards. Overall, LCA practitioners as well as technical experts dealing with algal fuels in both the public and private sectors could be the main target audience for these guidelines.

This research mainly focuses on developing a natural cellulose nanofibre (CNF) from kenaf bast fibre and its potential for enzyme immobilization support. CNF was isolated by using a combination between chemical and mechanical treatments such as alkaline process and high-intensity ultrasonication process to increase the efficiency of hemicellulose and lignin removal, and to reduce its size into nano-order. The morphological study was carried out by using scanning electron microscope (SEM), indicating most of CNF diameter in range of 50-90 nm was obtained. The result of chemical analysis shows that cellulose content of raw bast fibre, bleached pulp fibre and CNF are 66.4 %, 83.7 % and 90.0 %, respectively. By decreasing the size of cellulose fibre, it increases the number of (O–H) group on the surface that plays as important role in enzyme immobilization. Covalent immobilization of cyclodextrin glucanotransferase (CGTase) onto CNF support resulted in about 95.0 % of protein loading with 69.48 % of enzyme activity, indicating high immobilization yield of enzyme. The enzymatic reaction of immobilized CGTase was able to produce more than 40 % yield of α-CD. Reusability profile of immobilized CGTase resulted in more than 60 % of retained activity up to 7 cycles. Therefore, the CNF is highly potential to be applied as enzyme immobilization support.

Biodiesel has a lower oxidation stability index (OSI) than mineral diesel fuel. Its consequential oxidation products and deteriorated physical and chemical properties of fuel are associated with engine operation challenges such as the formation of insoluble gums that can plug fuel filters. Given the fact that oxidation leads to barriers for commercial use of biodiesel, addition of appropriate antioxidants into biodiesel is a promising and cost-effective approach to overcome this challenge. Although synthetic antioxidants such as propyl gallate (PG) are frequently used to counter the oxidation process of biodiesel, PG is a designated carcinogen. In light of that, this study was conducted aiming at introducing walnut husk methanolic extract (WHME) as a more sustainable antioxidant to replace PG in waste cooking oil (WCO) methyl esters. Moreover, to facilitate the commercialization of the new product, a comprehensive environmental investigation and comparison with the conventional counterpart, i.e., PG, was performed using life cycle assessment (LCA) approach. To enhance the eco-friendly features of the natural antioxidant, a solar photovoltaic-driven extraction process based on methanol (as reagent) was used in extracting polyphenols from walnut husk. The results showed that the induction period of WCO methyl esters was prolonged from 1.2 h to more than 3 h (meeting the ASTM D6751 standards) using 5000 ppm and 250 ppm of WHME and PG, respectively. More specifically, 20-fold more natural antioxidants would be required to meet the international standards. However, since walnut-producing countries are responsible for 42.4% of global biodiesel production on one hand and the cost-effectiveness of walnut husks on the other hand, their valorization could attract the attention of the global biodiesel industry. Moreover, this study highlights the considerable environmental and health benefits of turning this bio-waste product into a value-added antioxidant fuel additive. The LCA results showed that the developed bio-antioxidant was more effective in different damage categories compared with PG, i.e., 0.32% in ecosystem quality, 12.13% in human health, 8.37% in climate change, and 614% in resource. Overall, the WHME obtained through solar photovoltaic-driven extraction process could outcompete PG from the environmental perspective.

Methanogenic anaerobic digestion (AD) is known as an alternative green technology, capable of converting different types of biomass and wastes into biogas. Various types of anaerobic reactors have been designed and implemented but regardless of the type of reactor use, it is necessary to thoroughly monitor the performance of such configurations and prevent any drastic change during biogas production process. Parameters such as pH, temperature, volatile fatty acids (VFAs), alkalinity, hydraulic retention time (HRT), organic loading rate (OLR), total solid (TS), volatile solid (VS), inhibitors such as ammonia, mixing and shear stress, etc., could potentially adversely affect the AD process efficiency if not managed. Hence, these parameters should be adjusted within a proper range to guarantee a favorable biogas production rate. The present chapter reviews the effects of major operational and non-operational parameters on AD process and summarize the most recent findings in this regard.

Biogas, a mixture of methane and carbon dioxide, is produced by anaerobic digestion of organic waste. Municipal and agroindustrial organic wastes are important feedstocks for producing biogas. Anaerobic digestion is a microbial process. It not only reduces the amount of waste to be disposed, but the methane produced can be burnt as fuel to provide energy. Anaerobic digestion is carried out in various kinds of bioreactors. This chapter is focused on the diverse bioreactor systems, or digesters, that are available for producing biogas. Depending on their design and operation, the different types of bioreactors are suited to different kinds of wastes, processing scenarios and other conditions. The following main types of bioreactors are discussed: the conventional anaerobic digesters (e.g. anaerobic sequencing batch reactor, continuous stirred tank reactor, anaerobic plug-flow reactor); the sludge retention reactors (e.g. anaerobic contact reactor, up-flow anaerobic sludge blanket reactor, expanded granular sludge blanket reactor, up-flow anaerobic solid-state reactor, anaerobic baffled reactor, internal circulation reactor, anaerobic fluidized bed reactor); the anaerobic membrane reactors; the anaerobic biofilm reactors; and the high rate reactors.

The oil palm Empty Fruit Bunch fibers (size in the range from 75 to 400 μm) have been prepared by wet and dry grinding methods. The prepared fibers were blended with polypropylene to achieve EFB-Polypropylene plastic composite denoted as EFB-PP plastic composite. Various weight contents (20, 35 and 50%) of the fibers were reinforced in the polypropylene matrix. The effect of the fiber weight contents on thermal and mechanical properties of the obtained EFB-PP plastic composite was investigated. The wet disk milled fiber reinforced EFB-plastic composite shows the superior mechanical properties.

In this study, d-limonene as green solvent was used as an alternative to n-hexane to recover the residual crude palm oil (RCPO) from the OPDC. The OPDC obtained from the palm oil mill contained about 12.55±3.15% (dry basis) of RCPO. Similar as n-hexane, the results proved that d-limonene as solvent was able to recover 100% of the RCPO from the OPDC successfully. The recyclable of d-limonene was 90%, higher than n-hexane (70%) and not much variation on fatty acids composition of extracted RCPO were observed. To ensure complete RCPO recovery, microscopic observation and FTIR spectra analysis on OPDC before and after the extraction were performed. This study concludes that d-limonene is comparable to n-hexane. However, the residual oil is classified as non-edible as it is not extracted via mechanical method. Therefore, further analysis is necessary in order to determine the potential use of the residual oils in other industries such as pharmaceutical, food packaging, fiberboard manufacturing and others.

The development of new, low-cost technology to increase the oil recovery in the palm oil mill especially from the palm oil wastes has been an important goal for the industry to increase OER. According to preliminary oil detection, the residual oil is mainly located on the surface of spikelet, about 73.73 ± 0.05% from total residual oil. The combined water-steam shows the best oil extraction process, indicating 82 ± 0.13% of oil may be removed from the EFB spikelet. Thus, this method is chemical free and environmentally friendly residual CPO recovery process using EFB.

Agitation speed is an important factor in the industrial application for the mixing efficiency in order to increase productivity. In this study, the effect of agitation speed was investigated in a stirred bioreactor for hydrolysis of tapioca slurry into glucose by using encapsulated enzymes within calcium alginate-clay (alg-clay) beads. The hydrolysis process was tested at various agitation speeds from 40 to 200 rpm. The stability of alg-clay beads was examined in term of morphology of beads, enzyme leaching behavior and enzymes activity. The morphology of the alg-clay beads was investigated by Field Emission Scanning Electron Microscopy (FESEM). It was found that vigorous speed ruptured the beads structure. The result also showed that by increasing the agitation speed, the leakage of enzymes also increased. Therefore, it can be concluded that there was a strong correlation between the speed of agitation and the beads morphology. The optimum agitation speed which gave the highest amount of enzymes activity was 120 rpm.

In this study, the recovery of residual oil from the spikelet of oil palm empty fruit bunches (OPEFB) was conducted. Residual oil was present in the OPEFB due to mechanical processes such as the loading of fruit into the sterilizer cage, sterilization and threshing, in which a certain portion of the oil from the fruitlet was impregnated mainly on the surface of the spikelet rather than on the stalk of OPEFB. The highest residual oil content was found mainly in the small OPEFB (28.49 ± 5.20% dry basis). The oil extraction process was introduced as hydro solvent-assisted steam extraction, which comprises of four main steps, i.e., flooding, injection, soaking and draining. The overall process resulted in above 83% residual oil removal from the spikelet. The proposed method can be an option to be implemented in the palm oil mill because it is a chemical-free, environment-friendly and novel process.

Abundant oil palm empty fruit bunches (OPEFB) generated from the palm oil mill industry create huge problems for the environment and the palm oil mill itself. Despite the importance of determining the amount of oil left in the OPEFB, little research of that nature has been reported. This study describes the oil content and physicochemical characteristics of OPEFB fibers, detection of oil attachment on the fiber’s surface using sudan red dye, contact angle values, and also the quality of the residual oil. The OPEFB fibers, which are normally used as mulch for the palm oil mill, have been found to be a rich source of lignocellulosic materials, especially cellulose, which constitutes 33.70 to 35.10% for a press-shredded fiber. Residual oil (3 to 7% on dry basis) extracted from the OPEFB exhibits good quality parameters such as deterioration of bleachability index (DOBI), free fatty acid (FFA), and peroxide value (PV). The DOBI values were still in the acceptable range, which is from 1.94 to 2.43, while the PV results are within the range of about 1.84 to 2.80 meq/kg. The major fatty acids of the residual fiber oil were palmitic and oleic acids, at 39.77% to 39.89% and 39.55% to 42.60%, respectively. There were no significant changes in the macronutrients and quality of the OPEFB residual oil. Therefore, the residual oil from the OPEFB should be recovered and reused as a raw material for industrial applications, boosting the oil extraction rate (OER) in the palm oil industry.

The effect of different aeration rates on the organic matter (OM) degradation during the active phase of oil palm empty fruit bunch (EFB)-rabbit manure co-composting process under constant forced-aeration system has been studied. Four different aeration rates, 0.13 L min(-1) kg(DM)(-1),0.26 L min(-1) kg(DM)(-1),0.49 L min(-1) kg(DM)(-1) and 0.74 L min(-1) kg(DM)(-1) were applied. 0.26 L min(-1) kg(DM)(-1) provided enough oxygen level (10%) for the rest of composting period, showing 40.5% of OM reduction that is better than other aeration rates. A dynamic mathematical model describing OM degradation, based on the ratio between OM content and initial OM content with correction functions of moisture content, free air space, oxygen and temperature has been proposed.

Waste clay recovered from palm oil mill effluent (POME) was characterized and used as an enzyme-supporting material for the cassava saccharification process. The clay was treated by the Soxhlet extraction method to remove the residual oil and then characterized using a BET surface area analyser, XRF, XRD, FTIR, TGA, and FESEM. The chemical analysis showed that the sample had a high amount of CaO (93%) with a minor content of SiO2 (1.378%) and Al2O3 (0.707%), with a surface area of 1.15 m2/g. The XRD analysis revealed the major mineral presence to be calcite, as confirmed by FESEM analysis. The FTIR results also attested to the presence of a calcite phase and carbonate groups. To study the performance of the waste clay for enzyme immobilization application, the recovered waste clay was further used as an enzyme supporting material for enzyme immobilization in the cassava saccharification process. Results showed that the enzymes were successfully encapsulated and gave the highest immobilization yield of 70% with 2% clay concentration. In addition, the encapsulated enzymes also enhanced the reusability, where the enzyme retained 32% of its activity after seven cycles of saccharification processing.

This paper provides an overview of the use of green solvents for oil extraction from natural product using soxhlet extraction and supercritical fluid extraction (SFE) methods. In terms of qualitative and quantitative determinations on the extracted oils, the use of green solvents was comparable with n-hexane. For soxhlet extraction method, the integration of microwave application into the soxhlet at their optimum conditions has shown improvement in oil yield, oil quality, solvent consumption and extraction time. SFE using CO2also revealed promising results as soxhlet extraction but apparently it involved high operating cost and difficult to control. Despite of that, all the studies successfully demonstrated the suitability of green solvent as an alternative to petroleum driven solvents for extraction of oils from natural products.

Alpha-amylase, glucoamylase and cellulase were immobilized onto calcium alginate-waste clay (alg-WC) beads by using encapsulation technique. The clay was obtained from palm oil mill clay bath processing waste that was collected from FELDA Serting Hilir Palm Oil Mill, Malaysia. The aim of this study is to characterize and investigate the performance of waste clay as a supporting material for the tapioca starch hydrolysis. The encapsulated enzymes were characterized by using analytical equipment such as Fourier Transform Infrared Spectroscopy (FTIR) and Field Emission Scanning Electron Microscopy (FESEM). The FTIR results showed the interaction of functional groups between alginate and waste clay in the alg-WC beads. The alginate beads characterized at peaks 1615 cm-1, 1417 cm-1and 1027 cm-1, and peaks 1396 cm-1, 873 cm-1and 712 cm-1characterized the waste clay. The FESEM analysis also revealed that the different surface morphology of alginate beads and alg-WC beads. It also showed that the enzymes were successfully encapsulated within the alg-WC beads. The activity of the immobilized enzymes was studied at different clay concentrations. The highest immobilization yield was obtained at 2% (w/v) of clay concentration and the highest enzyme loading was 98.29 %. The immobilized enzymes also retained 33% of its activity after seven usage cycle with 1 hour of each reaction time.

Article history: Cassava is very popular in Nigeria, Brazil, Thailand and Indonesia. The global cassava production is currently estimated at more than 200 million tons and the trend is increasing due to higher demand for food products. Together with food products, huge amounts of cassava wastes are also produced including cassava pulp, peel and starchy wastewater. To ensure the sustainability of this industry, these wastes must be properly managed to reduce serious threat to the environment and among the strategies to achieve that is to convert them into biosugars. Later on, biosugars could be converted into other end products such as bioethanol. The objective of this paper is to highlight the technical feasibility and potentials of converting cassava processing wastes into biosugars by understanding their generation and mass balance at the processing stage. Moreover, enzyme immobilization technology for better biosugar conversion and future trends are also discussed.

Palm oil industry produces huge amount of oil palm decanter cake (OPDC). Currently it is not yet commercialized however due to its characteristics, it can be used to produce oil palm decanter cake natural polymer composite (OPDC-NPC). NPC is a type of material made by combining natural fiber with polymer. Therefore the objective of this paper is to produce NPC from OPDC and then determine its mechanical and physical properties such as elasticity, stiffness, tensile strength and water absorption rate. The OPDC samples were collected from Felda Trolak Palm Oil Mill. Prior to NPC development, the oil was removed from OPDC using hexane soxhlet extraction method. OPDC-NPC was fabricated using molding method where the mixture of 95% polypropylene (PP) and 5% OPDC were mixed using twin-screw extruder. The results showed that OPDC-NPC has an elasticity of 2231 MPa, stiffness of 30 MPa, tensile strength of 32 MPa and water absorption rate of 0.16 % which was slightly better with the other types of fibers.

For decades agricultural waste materials have been a subject of study for the production of sustainable bioproducts such as biodegradable composite. In Malaysia millions of tonnes of palm oil biomass are produced annually including Oil Palm Decanter Cake (OPDC). In this study, the objective was to characterize the delignified OPDC for potential biodegradable composite development. Chemical delignification is a process of removing the lignin from the plant biomass by using chemicals. Delignification process was performed by treating the raw OPDC with 10% NaOH (alkaline treatment) followed by 25% H 2 SO 4 (acid treatment) and finally 10% H 2 O 2 (bleaching). The result of the treated OPDC showed that cellulose content had increased from 29.4 to 87.6%, while hemicellulose had decreased from 11.2 to 3.1% and finally lignin had decreased from 25.3 to 9.3%. TGA, FTIR and XRD analysis of the raw and treated OPDC samples supported the findings as well. Through morphological analysis of the treated OPDC using FESEM, it showed that the chemical treatment had caused the raw OPDC fibre surface to break-up and open its structure. At the end of this study, the treated OPDC was also exposed to lauric acid for hydrophilic properties study and the result showed that the hydrophobic properties had been developed in the treated OPDC and thus made it suitable for biodegradable composite development.

The effects of hydrochloric acid (HCL) modification of the surface area, morphology and physico-chemical properties of Sayong kaolinite clay was investigated in this study. Sayong kaolinite clay was refluxed with different concentration of HCL (1M, 5M and 10M) at 100 °C for 4 hours and followed by calcination at 500 °C at 1 hour. The samples of untreated and treated clay were characterized by different analytical equipment such as BET Surface Area Analyzer, X-Ray Fluorescence (XRF), Fourier Transform Infrared (FTIR), Thermogravimetric Analyzer (TGA) and Field Emission Scanning Electron Microscopy (FESEM). The acid treatment increased the surface area of the Sayong kaolinite clay almost three times from 24.46 m2/g to the maximum value which is 64.04 m2/g once treated with 5M HCL. The increasing of the surface area is due to the formation of amorphous silica phase and removal of the octahedral Al3+cations and other impurities (such as Mg2+, K+, Ca+etc.) when the acid strength is increasing as reported in XRF analysis. FTIR study shows the change of the peak intensity of several types of structural OH groups that presently in the untreated and acid treated samples. TGA-DTA profiles shows that acid treatment increased the amount of physisorbed water as the acid concentration is increased. There are three of endothermic peaks was observed in the untreated sample which centered at 49 °C, 275 °C and 520 °C. However, when the clay samples treated with acid, it has increased the physisorbed water and decreased the structural and coordinated water which caused the change in the endothermic curves in the treated sample.

This study analyzed the effects of sulphuric acid (H2SO4) treatment on pysico-chemical properties and morphological changes of clay obtained from Sg. Sayong, Perak. The clay was ground and sieved to 2SO4. The treatment was completed by refluxing the clay with different concentration of H2SO4 (1M, 5M and 10M ) at 100 °C for 4 hours and followed by calcination at 500 °C for 1 hour. The physic-chemical properties and morphological changes of the untreated and treated clay were compared using Surface Area Analyser, X-Ray Diffraction (XRD), Field Emission Scanning Electron Micrograph (FESEM), X-Ray Diffraction (XRD) and Fourier Transformed Infrared Spectroscopy (FTIR). The results showed that acid treatment of 5M increased the surface area from 25 m2/g to 75 m2/g and the pore volume increased from 0.1518 cc/g to 0.3546 cc/g. The nanopore size of the clay decreased from 24.8 nm to 19.4 nm after treated with acid. This can be explained due to the elimination of the exchangeable cations and generation of microporosity. The results of XRF showed SiO2 increased from 58.34% to 74.52% and Al2O3 reduced from 34.6% to 18.31%. The mineral oxides such as Fe2O3, MgO, CaO, K2O and TiO2 also reduced. This concluded that H2SO4 treatment has led to significant removal of octahedral Al3+, Fe3+ cations and other impurities. In conclusion, this study showed the physico-chemical properties and morphology of Sayong clay were improved once treated with H2SO4 and therefore suggests better supporting material for enzyme immobilization.

In this paper, the kinetic parameters of free and encapsulated enzymes in the calcium alginate-clay beads were determined using Lineweaver-Burk plot. The Michaelis constant, Kmof free alpha-amylase, glucoamylase and cellulase were 2.0831, 1.8326 and 7.8592 mg/mL, respectively, whereas for the encapsulated system, the Kmvalues were 3.1604, 2.1708 and 9.2791 mg/mL, respectively. The results showed encapsulation enzymes gave higher Kmvalue than the free enzymes. Comparatively the encapsulated alpha-amylase was 1.5 times higher and the glucoamylase and cellulase were 1.18 times higher. This suggests that the affinity of encapsulated enzymes for substrate was lower which might be due to the diffusional limitation of the substrate and enzymes. Amongst the three in both systems, glucoamylase was determined to have highest affinity followed by alpha-amylase and cellulase enzymes.

In order to accelerate the bioconversion process of press-shredded empty fruit bunches (EFB), the effect of high-pressure steam pre-treatment (HPST) in degrading the lignocellulosic structure was investigated. HPST was carried out under various sets of temperature/pressure conditions such as 170/0.82, 190/1.32, 210/2.03, and 230 °C/3.00 MPa. It was noted that after HPST, the surface texture, color, and mechanical properties of the treated EFB had obviously altered. Scanning electron micrographs of the treated EFB exhibited effective surface erosion that had occurred along the structure. Moreover, the Fourier transform infrared and thermogravimetric analyses showed the removal of silica bodies and hemicellulose ingredients. X-ray diffraction profiles of the treated EFB indicated significant increases in crystallinity. These results reveal that HPST is an effective pre-treatment method for altering the physicochemical properties of the EFB and enhancing its biodegradability characteristics for the bioconversion process.

This paper proposes a new approach for integrated technology of biogas energy and compost production for a palm oil mill. This study evaluated the economic viability based on the changes of materials flow and energy balance when a palm oil mill introduces this approach. A palm oil mill processing 54 tonnes fresh fruit bunch (FFB) per hour has the potential to produce 8.2 GWh per year of electricity using biogas captured during anaerobic treatment of palm oil mill effluent (POME). Compost production using shredded empty fruit bunch (EFB) and POME anaerobic sludge obtained from the anaerobic digester is equivalent of 579 tonnes, 151 tonnes and 761 tonnes per year of nitrogen, phosphorus and potassium respectively. The integrated technology is a more attractive solution compared to the case when the palm oil mill installs either biogas energy or compost technology individually. The result of economic analysis suggests that this integrated approach is the most economically effective in comparison to the other two cases. Interestingly, even without Clean Development Mechanism (CDM), the integrated technology can still be economically viable, which can be a good solution for sustainable palm oil industry management in the near future.

This study was conducted to characterize Sg. Sayong clay so that it can be applied as a supporting material for the immobilization of biocatalyst in the bioconversion of wastewater into biofuel. The clay sample was physically and chemically characterized using Nitrogen Adsorption, X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Fourier Transform Infrared Spectroscopy (FTIR), Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and Field Emission Scanning Electron Microscopy (FESEM). The results obtained showed that the clay composed of SiO2 (57.4%), followed by Al2O3 (32.5%), K2O (4.9%), Fe2O3 (3.8%) and traces amount of Ca, Mg, Ma, and Ti. The results also showed the clay type was kaolinite with some presence of quartz, illite, montmorillonite and microcline. The clay was also successfully coated onto the wire-mesh and immobilized with biocatalyst for further bioconversion study.

The effectiveness of superheated steam pretreatment on the enzymatic saccharification of oil palm mesocarp fiber (OPMF) was investigated by varying the temperature (140 to 210 °C) and the retention time (20 to 90 minutes). The results showed that superheated steam pretreatment at 180 °C for 60 minutes is the optimum condition for enzymatic saccharification of OPMF. Scanning electron microscopy (SEM) images of the OPMF show that superheated steam pretreatment is able to remove silica bodies. Further characterization by FTIR and TG/DTG analysis of the raw and treated OPMF indicates that the solubilization and removal of hemicelluloses took place after the pretreatment. This suggested that superheated steam pretreatment is an effective method for the alteration of the OPMF structure and enhances the digestibility of the biomass, hence improving enzymatic saccharification.

Changes in the lignocellulosic structure of oil palm empty fruit bunches (OPEFB) during composting treatment using an in-vessel composter was investigated in this work. The composting process was completed within 40 days of treatment, and the final C/N ratio achieved was 13.85. Scanning electron microscopy (SEM) revealed that the structure of OPEFB material was severely degraded, especially during the thermophilic phase where the biodegradation process was most active. Close examination of the physicochemical and thermal analysis using X-ray diffraction (XRD), Fourier transform infrared (FTIR), and thermogravimetric and differential thermal analysis (TG/DTA) showed that the crystallinity size of the OPEFB structure decreased. This result was attributed to the removal of silica bodies from OPEFB materials. Also, the functional groups of cellulose, hemicelluloses, and lignin structures had changed throughout the composting period, and the most extensive degradation of cellulose was detected in the thermophilic phase. It was also found that the exothermic peak of the matured compost reduced most significantly compared to the raw OPEFB. In conclusion, the in-vessel composting system was able to enhance the degradation process of OPEFB materials for producing compost.

This article is a case study to compare the economic viabilities of biogas generation and compost projects in a palm oil mill in Malaysia with and without clean development mechanism (CDM). Biogas is captured from anaerobic ponds or digester tanks treating palm oil mill effluent (POME) and converted to green renewable electricity for grid connection, while compost is produced from the shredded empty fruit bunch and raw untreated POME. The both technologies were compared by considering the changes of the materials flow and energy balances. A palm oil mill with a capacity of 54 t fresh fruit bunch per hour has the potential to produce either 6.9 GWh of electricity from biogas or fertilizer equivalent to 488 t of nitrogen, 76 t of phosphorus and 1,065 t of potassium per year. The economic analysis for 10 years project term analysis indicated that CDM gave a significant impact and ensured economic viability for both projects with 25 % of internal rate of return (IRR), RM 12.39 million of net present value (NPV) and 3.5 years of payback period (PBP) for biogas project, whereas 31 % of IRR, RM 10.87 million of NPV and 2.9 years of PBP for compost project, respectively. In addition, sensitivity analysis indicated that the profitability of both projects will vary depending on the economic situation, such as electricity price which is based on the government policy, whereas compost price that depend on fertilizer market price with 43 % NPV change in 20 % range of fertilizer value.

The effect of superheated steam treatment on oil palm empty fruit bunches (OPEFB) was investigated in terms of physicochemical property changes and enzymatic hydrolysis enhancement. The experimental treatment was carried out at different temperatures (140-210°C) and durations (20-90 min). Results showed that as the superheated steam temperature and time increased, the size distribution also changed, resulting in more small particles. Analysis on the surface texture, color, and mechanical properties of the treated OPEFB also showed that significant changes resulted due to the superheated steam treatment. In support to this, Fourier Transform Infrared (FTIR) spectroscopy and thermogravimetric (TG) analyses showed that solubilization and removal of the hemicelluloses component also took place. As a result of this phenomenon, higher total sugar and glucose yield was achieved once the treated OPEFB was subjected to enzymatic hydrolysis. This suggests that superheated steam treatment could enhance OPEFB structure degradation for the preparation of a suitable substrate in order to produce a higher glucose yield in the enzymatic hydrolysis process.

The biogas and biomethane production in a 50 litre closed stirred tank anaerobic bioreactor treating palm oil mill effluent (POME) supplemented with oil palm biomass in the form of oil palm empty fruit bunch (OPEFB) under mesophilic condition was evaluated. With OPEFB supplementation, the biogas and biomethane generation increased by 63% and 52%, respectively. During this process, we found changes in the OPEFB morphology and microbial community through microbiota analysis using 16S rRNA gene clone library method, after OPEFB was added, suggesting that the increased biogas and biomethane production would be due to enhanced lignocellulosic biomass degradation.

Methane derived from anaerobic treatment of organic wastes has a great potential to be an alternative fuel. Abundant biomass from various industries could be a source for biomethane production where combination of waste treatment and energy production would be an advantage. This article summarizes the importance of the microbial population, with a focus on the methanogenic archaea, on the anaerobic fermentative biomethane production from biomass. Types of major wastewaters that could be the source for biomethane generation such as brewery wastewater, palm oil mill effluent, dairy wastes, cheese whey and dairy wastewater, pulp and paper wastewaters and olive oil mill wastewaters in relevance to their dominant methanogenic population are fully discussed in this article.