The Production Of Third-Generation Bioethanol From Eucheuma Cottonii Using Dowex (TM) DR-G8

Eucheuma cottonii (EC) adalah sejenis makroalga merah yang dianggap sebagai biomass generasi ketiga, dan mengandungi karbohidrat dalam jumlah yang besar and boleh difermentasi secara mudah menjadi bioethanol. Sehingga kini, penggunaan asid pemangkin cecair telah dilaporkan untuk menukar karbohidrat daripada pelbagai biomass kepada gula fermentasi melalui proses hidrolisis. Walau bagaimanapun, asid pemangkin pepejal yang boleh diasingkan secara mudah dan boleh diguna semula adalah dianggap penting dalam proses hidrolisis. Dalam kajian ini, Dowex (TM) Dr-G8 telah diterokai sebagai pemangkin berpotensi buat kali pertama bagi menghidrolisis karbohidrat daripada EC atau makroalga ekstrak (ME) kepada gula sebelum proses fermentasi. Sebanyak 43.2% and 49.4 % hasil gula optimum telah dicapai apabila dirawat dalam keadaan proses optimum iaitu bagi EC (6 % w/v Dowex (TM) Dr-G8, 120 oC, 1 Jam) dan ME (8 % w/v Dowex (TM) Dr-G8, 120 ºC, 1 Jam) (49.4 %). Keputusan ini adalah lebih rendah apabila berbanding dengan ME diguna sebagai bahan mentah. Kebolehgunaan Dowex (TM) Dr-G8 turut disiasat dalam kajian ini, hasil galactose yang dikekalkan iaitu kira-kira 46.7% sehingga larian kelima. Ini menunjukkan bahawa Dowex (TM) Dr-G8 tidak ketara dinyahaktifkan walaupun selepas berulang kali digunakan. Selain itu, Dowex (TM) Dr-G8 digunakan di proses prarawatan dijalankan untuk meningkat proses enzim bagi menukar MCR menjadi gula. Dalam keadaan yang optimum (10 % (w/v) Dowex (TM)-Dr G8, 120 oC, and 30 min), hasil gula optimum sebanyak 99.8 % telah dicapai apabila MCR yang dirawat (P-MCR) telah digunakan sebagai substrat untuk proses hidrolisis enzim selepas 30 jam. Di samping itu, satu konsep yang baru untuk mensintesis matriks polimer hibrid yang stabil telah dijalankan dalam kajian ini. Kajian ini telah mengimobilisasi enzim di κ-carrageenan dengan meggunakan kaedah kovalen melalui polyethyleneimine and glutaraldehid. Imobilisasi enzim itu telah digunakan untuk menghidrolisis P-MCR untuk menghasilkan gula yang sebanyak 73.4 %. Apabila asid hidrolisat yang mengandungi 35 g/L galaktosa telah difermentasi dengan jumlah yis yang sebanyak 16.0 g/L, nilai optimum boleh mencapai sebanyak11.63 g/L (64.6 % daripada nilai teori) selepas 72 jam. Bioetanol hasil daripada proses PSSF (prahidrolisis dan saccharification serentak dan penapaian) diperhatikan lebih berkesan daripada proses SHF (hidrolisis berasingan dan penapaian) yang menghasil bioetanol sebanyak 5.80 mg/mL (hasil teori sebanyak 91 %). Peningkatan jumlah proses SHF yang menggunakan acid hydrolysate telah dijalankan di 5 L fermenter telah menghasilkan sebanyak 61.6 % bioetanol, di mana dalam kajian proses PSSF telah dijalankan di 5 L fermenter dengan syarat-syarat yang optima menghasilkan sebanyak 87.1 % bioetanol adalah hampir sama seperti proses yang menggunakan kelalang kon. Keputusan ini menunjukkan bahawa proses penapaian menggunakan makroalga biomass boleh dipertingkatkan kepada jumlah besar dalam fermenter tanpa\ud menjejaskan prestasinya. Anggaran kos bagi penghasilan bioetanol dengan makroalga adalah sebanyak 0.77 USD /L. Berbanding dengan biomass yang lain, kos penghasilan bioetanol daripada makroalga dapat bersaing dari segi ekonomi. Penilaian kitar hayat (LCA) dan analisis exergy berasaskan makroalga-bioetanol telah dijalankan. Keputusan menunjukkan bahawa permurnian bioetanol (S6) didapati mempunyai kesan yang tertinggi dalam semua kategori kesan yang dipertimbangkan. Teknologi yang dicadangkan dalam kajian ini menggunakan asid pemangkin pepejal didapati sesuai untuk menghasilakan bioetanol dari EC. ________________________________________________________________________________________________________________________ The red macroalgae, Eucheuma cottonii (EC) is a third-generation biomass, and it contains large amount of carbohydrate that can be readily fermented into bioethanol. Up to now, the use of the liquid acid-catalyst have been reported for the hydrolysis of carbohydrates from various biomass to fermentable sugar. However, the need of easily separable and reusable solid acid catalyst is considered essential in the hydrolysis process. In this study, for the first time, Dowex (TM) Dr-G8 was explored as a potential solid catalyst to hydrolyze carbohydrates from dried raw EC or macroalgae extract (ME) and pretreatment of macroalgae cellulosic residue (MCR), to simple reducing sugar prior to the fermentation process. The reaction condition for hydrolysis of EC (6 % w/v Dowex (TM) Dr-G8, 120 ºC, 1 h) and ME (8 % w/v Dowex (TM) Dr-G8, 120 ºC, 1 h) resulted to a galactose yield of 43.2 % and 49.4 %, respectively. This result was slightly lower compared with the feedstock by using ME. However as for MCR, the solid acid catalyst (Dowex (TM) Dr-G8) was used in the pretreatment process to enhance enzymatic conversion of MCR to reducing sugar. Reusability of Dowex (TM) Dr-G8 was also investigated in this study, the galactose yield maintained at around 46.7 % till the fifth run. This shows that Dowex (TM) Dr- G8 was not significantly deactivated even after repeated used. The pretreatment condition for MCR is 10 % (w/v) Dowex (TM)-Dr G8, 120 oC, and 30 min. An optimum sugar yield of 99.8 % was attained when pretreated MCR (P-MCR) was used as substrate for enzymatic hydrolysis after 30 h. Catalyst recyclability study were performed and a sixth-times reuse was accomplished without any loss of catalytic activity. In addition, a novel concept for the synthesis of stable polymer hybrid matrix was developed. In this study, glutaraldehyde crosslinked κ-carrageenan was used for the immobilization of β-glucosidase using the covalent method via polyethyleneimine and glutaraldehyde. The immobilized β-glucosidase was then used to hydrolyze PMCR for the production of reducing sugar and a hydrolysis yield of 73.4% was obtained. When a solid acid hydrolysate containing 35 g/L of galactose were fermented with an inoculums amount of 16.0 g/L, an optimum bioethanol production of 11.63 g/L was achieved (64.6 % of the theoretical value) after 72 h. Bioethanol production by PSSF (prehydrolysis and simultaneous saccharification and fermentation) process was observed to be more effective than the SHF (separate hydrolysis and fermentation) process, producing 5.80 mg/mL of bioethanol, with a theoretical yield of 91 %. Scale up of SHF of solid acid hydrolysate was carried out in a 5 L fermenter resulting to 61.6 % of bioethanol yield, while scale up study of PSSF process was carried out in a 5 L fermenter conducted with optimized conditions resulting to 87.1 % of bioethanol yield, which is almost the same as in shaking flasks. This result indicated that the fermentation process using macroalgae biomass could be easily scaled-up to large fermenter without compromising its performance. On the other hand, the estimated bioethanol production cost using macroalgae was 0.77 USD /L. Compared to other feedstocks, bioethanol production cost from macroalgae are competitive and economically viable. A consequential life cycle assessment (LCA) and exergy analysis of macroalgae-based bioethanol were performed. Results suggested that the purification of bioethanol (S6) is found to have the highest impact in all the impact categories considered. The proposed technology in this study using solid acid catalyst was found feasible for the production of bioethanol from EC

An optimization framework for sandstone acidizing using design of experiment (DOE) and mathematical modelling

Fluoroboric acid (HBF4) serve as one of the alternatives for conventional mud acid in the application of sandstone wells stimulation. Various parameters such as formation temperature and acid injection velocity would significantly affect the performance of sandstone acidizing and hence determine the success rate of well stimulation. It is therefore undeniable that a deep understanding of the effects of these major parameters are of paramount importance. However, there is a scarcity of data available in the literature regarding the use of HBF4 in sandstone acidizing in comparison to the use of mud acid. In this work, an optimization framework is developed to study the combined effects of formation temperature and acid injection velocity to the change in porosity and pressure drop. Apart from porosity improvement, a pressure drop across the sandstone core would also give an indication to the acidizing performance. The optimization approach is achieved by using design of experiment (DOE) and response surface methodology, coupled with a mechanistic model for sandstone acidizing. The design of experiment used in this work is central composite design (CCD). Meanwhile, the mechanistic model that simulate a flow in porous media is being developed using COMSOL Multi-physics, which is a computational fluid dynamics (CFD) software that uses finite element method (FEM). In this optimization tool, a range of formation temperature was set between 41˚C and 88˚C, whereas the range of acid injection velocity was set between 1.79×10-5 m/s to 3.78×10-5 m/s. According to the results, the optimum condition studied was found out to be 88˚C and 3.78×10-5 m/s. Under such an operating condition, the favourable maximum porosity enhancement and pressure drop profile were obtained. The maximum porosity and pressure drop were up to 17% and 16.6979 kPa respectively. The porosity enhancement and pressure drop in the sandstone core showed an excellent agreement with the data predicted by the model. In general, this optimization study had proven that response surface methodology (RSM) could be applied to determine the acid performance in sandstone acidizing

Investigating the Effectiveness of Emulsified Acid on Sandstone Formation under High Temperature Conditions

Acid stimulation supports the oil and gas industry as a versatile mean in enhanced oil recovery to fulfill the world energy demand. Although hydrochloric acid can significantly improve the reservoir permeability, its rapid reaction rate at high temperature has created a barrier for acid penetration. Subsequently, emulsified acid has slowly gain its popularity due to its retardation effect which allows deeper penetration of acid into the formation and achieves minimal corrosion issues. Nonetheless, emulsified acid has rarely applied on sandstone formation. Since a large portion of reservoirs are made up of sandstone, the effects of emulsified acid on sandstone under high temperature conditions should be studied to unlock the effective usage of emulsified acid in restoring the hydrocarbon recovery from the potential sandstone reservoirs. Besides, it is also crucial to explore cheaper and greener substitute to formulate innovative emulsified acid in minimizing the high acidizing budget along with environmental concerns. In this project, 10 different emulsified acid combinations are prepared using hydrofluoric acid, hydrochloric acid, phosphoric acid, formic acid, acetic acid, cationic surfactant, diesel and waste oil. The pre-flush treatment (5 % CH3COOH: 10 % HCl) is followed by the main flush (emulsified acids) saturation for 3 days. The thermal stability of emulsified acids and their effect on the Berea sandstone properties are evaluated. Major outcome is that the emulsified acids have the capability to remain stable at 275 °F up to 6 hours with uniform and fine droplet size. It is also proven that most of the emulsified acids can improve the porosity and permeability of Berea sandstone core samples except for HF: H3PO4. Regardless of the types of oil used for emulsified acid formulation, HF: HCl acid combination shows the best performance enhancement for both diesel-based and waste oil-based emulsified acids. In sandstone acidizing, emulsified acid dissolves the minerals and create acid transport pathway with close connectivity between pore spaces, causing the formation of large and conductive channels within the rock. Hence, these positive results clearly reflect on the feasibility of emulsified acid application in sandstone matrix acidizing and the effectiveness of waste oil as a replacement fluid for diesel

A mini-investigation on enhanced oil recovery evolution (2007 – 2020)

Energy plays an important role in sustaining humanity. With rising worldwide energy demand and the great dependence of energy generation on fossil fuels, it is inevitable that enhanced oil recovery must be deployed to recover more possible reserves. This report focuses on reviewing publications related to enhanced oil recovery from 2007 to 2020 through the utilization of bibliometric analysis. Of the 5498 documents retrieved from Web of Science, 569 journals, 90 countries, 2025 organizations, and 8684 authors are involved. China, the United States, Iran, Canada, and India published the most documents. The United States has the highest h-index at 61. The analysis of keywords had shown that the hot issues lie around four main domains namely carbon capture, utilization, and sequestration (CCUS), microbial enhanced oil recovery (MEOR), development of unconventional reserves, and chemical enhanced oil recovery. This study provides some useful insights for future research directions. From there, discussions were subsequently placed on chemical EOR

Emerging technologies for conversion of sustainable macroalgal carrageenan biomass into L-lactic acid: A state-of-the-art review

The environmental awareness and concerns (plastic pollution) worldwide have driven the development of sustainable and environmentally friendly biopolymer derived from renewable materials. Biopolymers, especially L-lactic acid (L-LA) have played a crucial role in manufacturing polylactic acid, a biodegradable thermoplastic. Recently, L-LA production from non-edible macroalgal biomass has gained immense attraction due to it offers the simplest saccharification process for the biorefinery route. However, the commercialization of macroalgal-based L-LA is still limited due to high production costs. This paper has comprehensively reviewed the potential and development of third-generation feedstock for L-LA production, including significant technological barriers to be overcome for potential commercialization purposes. Then, an insight into the state-of-the-art hydrolysis and fermentation technologies using macroalgae as feedstock are also deliberated in detail. Furthermore, this review provides a conceivable picture of macroalgae-based L-LA biorefinery and future research directions that can be served as an important guideline for scientists, policymakers, and industrial players

The impact of using recycled culture medium to grow Chlorella vulgaris in a sequential flow system: Evaluation on growth, carbon removal, and biochemical compositions

Excessive of carbon dioxide (CO2) emission and water pollution have been identified as the two primary challenges to humans and environment. Hence, biological carbon sequestration by microalgae is recommended as an environmentally friendly approach to capture and convert this CO2 into value-added products. However, research related to the development of efficient system to concurrently overcome low CO2 solubility in water and reduction of water footprint in microalgae cultivation is still limited in the literature. In this study, the CO2 capture by Chlorella vulgaris in a recycled cultivation medium was exploited using a sequential flow photobioreactor system. The study revealed that nutrient replenished recycled medium did not significantly affect the growth performance and lipid content of C. vulgaris. It was also observed that the CO2 capture efficiency and protein content were gradually increased from the first (SFB-RWN1) to the third (SFB-RWN3) cycle of cultivation due to the increment of carbon and nitrogen content in the microalgae cell. Besides, the lipid profile of C. vulgaris cultivated in the recycled medium comprised of high concentration of saturated (up to 32.41%) and polyunsaturated (up to 43.21%) fatty acid methyl ester (FAME). The present study suggested that growing C. vulgaris in a recycled medium is a feasible solution to fix CO2 from the atmosphere and help to reduce water footprint in the microalgae cultivation system

Production of biodiesel through transesterification of sunflower oil using SiO2/50% H2SO4 solid acidic catalyst

A renewable fuel such as biodiesel, with lesser exhaust emissions, is the need of the day. Hence, researchers and scientific community worldwide have focused on development of biodiesel and the optimization of the processes to meet the standards and specifications needed for the fuel to be used commercially without compromising on the durability of engine parts. Based on the intricacies associated with the homogeneously catalyzed transesterification process, the purpose of the present work is to study biodiesel production by transesterification of sunflower oil with methanol in a heterogeneous system, using silica gel loaded with sulfuric acid (SiO2/50%H2SO4) as a solid acidic catalyst. The catalyst prepared by loading of 50v/v% H2SO4 on silica gel followed by drying it at 110°C. The catalysts were characterized by FTIR, TGA and SEM. The reaction between sunflower oil and methanol is carried out in a 3-necked round bottom flask heated by a rotamantle. The sample is withdrawn at certain time interval and is analyzed using gas chromatography. The dependence of the conversion of sunflower oil on the reaction variables such as the molar ratio of methanol to oil, reaction temperature and catalyst loading was studied. The catalyst has exhibited maximum oil conversion (84wt.%) under the conditions of 100°C, methanol/oil molar ratio of 6:1 and catalyst amount 10%. Kinetic study of reaction was also done. The experimental data is well fitted to the Pseudo-homogeneous model. This optimum operating condition and kinetic model are very important for producing biodiesel fuel effectively in a larger scale

Advances of macroalgae biomass for the third generation of bioethanol production

In recent years, utilization of renewable sources for biofuel production is gaining popularity due to growing greenhouse gas (GHG) emissions which causes global warming. There has been a great effort in exploring alternative feedstock for bioethanol production. In this context, the production of third-generation bioethanol from macroalgae has emerged as an alternative feedstock to food crop-based starch and lignocellulosic biomass. This is mainly due to the fast growth rate of macroalgae, no competition with agricultural land, high carbohydrate content and relatively simple processing steps compared to lignocellulosic biomass. This review paper provides an insight of recent innovative approaches for macroalgae bioethanol production, including conventional and advanced hydrolysis process to produce fermentable sugar, various fermentation technologies, economic analysis and life cycle assessment. With the current technology maturity, efficient utilization of macroalgae as sustainable source for bioethanol and other value-added chemicals production could be achieved in the near future

Insights and utility of cycling-induced thermal deformation of calcium-based microporous material as post-combustion CO2 sorbents

© 2019 Elsevier Ltd On the quest of finding ideal sorbent for post-combustion CO2 capture, calcium-based sorbent seems to have the potential, but often it cannot sustain its reactivity, especially after repeated cycle of sorption. This work aims to unravel the controlling factors in carbonation reaction and thermal-induced deformation of skeleton pore network that limits the CO2 absorptivity of calcium-based sorbent. Through precise measurement of CO2 absorption activity using TGA/DSC and a series of characterization, this study paves the way for the development of next-generation CaO sorbent that has high CO2 uptake capacity and thermal stability. Key findings include CaO particles with severe point defects contribute to fast CO2 absorption activity. The transformation from CaCO3 phase to CaO phase from organic precursor is 4 times higher than the inorganic precursor. Decomposition of calcium formate is thermally stable regardless of calcination temperature. Citrate-based structure precursor is able to produce homogeneous nanosized CaO particle. Shifting of reaction controlling regime from fast carbonation reaction to diffusion limited stage happened at Thiele modulus of 1.35. Lastly, first stage of fast carbonation reaction will take place at CaO sorbent's surface with proximate zero activation energy and second stage of slow carbonation reaction is controlled by high activation energy of ion diffusion behavior in CaCO3 ionic crystals at product diffusion layer. Future research direction can focus on reproducing long periodical citrate-like structural precursor using sol-gel method to mimic the behavior of calcium formate and calcium citrate to form nano-sized CaO particles with thermally stable crystal structure

Valorisation of Chlorella vulgaris biomass for multi-products synthesis via hydrothermal processing

Microalgal-based biofuel such as hydrochar has gained popularity in recent years owing to the high lipid content and fast growth rate of microalgal cells. However, commercial scale production of microalgal-based biofuel is not feasible due to the high processing cost of microalgal itself. One possible solution to overcome this limitation is to obtain other value-added byproducts to enhance the economic feasibility of the entire process in which such nature of research work is still very limited in the literature. Thus, in the present study, a two-step sequential hydrothermal carbonization (SEQHTC) was used to produce polysaccharides and hydrochar (potential solid fuel) from Chlorella vulgaris biomass. In the first step, whole algal (WA) biomass was subjected to hydrothermal subcritical extraction of polysaccharides whereas in the second step, the solid residue from the first step or identified as treated algal residue (TAR) was subjected to hydrothermal carbonization to produce hydrochar. The yield of hydrochar using WA biomass through SEQHTC process was 39.3 wt% with 12.5 wt% of polysaccharides. Apart from using WA, lipid-extracted algal (LEA) biomass was also used as feedstock for SEQHTC. The total extracted lipid, hydrochar and polysaccharides were 15.2 wt%, 41.5 wt% and 13.4 wt%, respectively. For comparison purposes, the conventional direct hydrothermal carbonization (DHTC) method was also carried out on both biomass. This study successfully demonstrated the realization of microalgal biorefinery concept, in which value-added products (polysaccharides) could be extracted along with the production biofuel such as biodiesel and hydrochar as sustainable renewable energy sources from microalgal biomass