Synthesis of bioethanol from lignocellulosic materials: A focus on grass and waste paper as raw materials
- Authors: Vala, Mavula Kikwe
- Date: 2009-12
- Subjects: Ethanol as fuel , Biomass energy , Lignocellulose -- Biotechnology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24499 , vital:63049
- Description: Biofuels are currently recognized as not only a necessity, but an inevitable pathway to secure the planet future energy needs. Food crops have been used (so far) as the biomass for bioethanol and biodiesel production. This has increased concerns over food security and led to the search for diversification and alternative feedstocks for biofuel production. The use of lignocellulosic materials, the most abundant, low cost and easy feedstock to harvest for bioethanol purpose, involves challenging production processes. Several approaches have been used to facilitate the breakdown of the biopolymer structure to produce fermentable sugars that can be converted to ethanol. Most of the approaches have used high temperatures and pressures and have often led to the production of inhibitors of fermentation. In this study, lignocellulosic materials from grass and newsprint were investigated as sources of biomass for bioethanol production using a chemical route (sulfuric acid hydrolysis) which made use of temperatures below 100°C at normal atmospheric pressure. Fermentation of toxic lignocellulosic hydrolyzates was possible after the development of a method for inhibitors removal. The method used treated wood chips as a stationary phase in a chromatographic column to remove inhibitors. This method is expected to be extended to applications such as in municipal wastewater treatment. Sugar yields of 22.26 and 8.9 g/L of hydrolyzate; and an ethanol yield of 184.5 and 130.4 mg/mL of must were achieved for 5g grass and newsprint respectively using optimum conditions of 2percent H2SO4 at 97.5°C for grass and 0.5percent H2SO4 at 97.5°C for newsprint during the hydrolysis process. Pure cellulose was used as a control for the biomass where 254.1 g/L of fermentable sugars were recovered from soluble cellulose and the yield of ethanol was 201.8 mg/mL. , Thesis (MSc) -- Faculty of Science and Agriculture, 2009
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- Date Issued: 2009-12
The quantification of Pinus patula recovery and productivity of manually orientated biomass collection in post mechanised full tree and semi mechanised tree length harvesting operations
- Authors: Ncongwane, Thandekile Hazel
- Date: 2023-04
- Subjects: Pinus patula – south Africa , Forest ecology , Biomass energy
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61511 , vital:70692
- Description: The use of biomass as an alternate source of energy has grown in popularity. Different types of biomass are obtained from a variety of sources including natural forests, forestry plantations and agriculture residues. However, forestry residues have been identified as the most promising source, due to the wide variety of plant products including leaves, twigs, branches, merchantable stem, stumps and roots. The main sources of plantation forest biomass are residues from thinning, clearfell and conventional products such as pulpwood and sawn timber operations. These residues can accumulate between 4.3 to 9.4 billion tonnes annually around the world. The biomass availability in plantation forests has led to the development of different harvesting systems to help collect the products from infield to sawmill. Biomass harvesting has mainly been achieved through mechanised systems because of their high yields. However, the use of manual systems has been neglected due to technical limitations and financial viability. Thus, in South Africa, there is no scientific research looking at manual systems of collecting biomass from plantations. Because of this, different forestry stakeholders, including small growers and contractors using manual systems for biomass harvesting have limited knowledge regarding what to expect in terms of recoverable amounts, productivity and cost. This research examines the productivity of the manual biomass collection and the quantification of recovered and unrecovered residues after mechanised full tree (FT) and semi mechanised tree length (TL) harvesting operations in Pinus patula compartments. A total number of 8 plots with +/-200 standing trees were marked in each system. The diameter and height of all marked trees were measured to determine tree volume. Moreover, the quantification of recoverable woody biomass was determined, where after, a residues assessment method using plots and line transects was used to determine the amount of unrecovered residues. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
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- Date Issued: 2023-04
Evaluation of cellulase and xylanase production by two actinobacteria species belonging to the Micrococcus genus isolated from decaying lignocellulosic biomass
- Authors: Mmango-Kaseke, Ziyanda https://orcid.org/0000-0002-8936-1149
- Date: 2016-05
- Subjects: Lignocellulose , Biomass energy
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24197 , vital:62442
- Description: Bacteria were isolated from sawdust and screened for cellulase and xylanase production on carboxyl methyl cellulose (CMC) and birchwood xylan agar. The bacteria showing halo forms around the colony were selected for further analyses and those isolates with the highest cumulative halozone size (isolate PLY1 and MLY10) were chosen for detailed studies. Evaluation of cellulase and xylanase production by saw dust actinobacterial species whose 16S rDNA nucleotide sequences were deposited in GenBank as Micrococcus luteus strain SAMRC-UFH3 with accession number KU171371 and Micrococcus yunnanensis strain SAMRC-UFH4 with accession number KU171372. Optimum culture conditions for the production of cellulase for respective axenic culture include incubation period (96 h), incubation temperature (25oC), agitation speed (50 rpm), and pH 5. For xylanase production, the optimum culture conditions in the presence of 1percent (w/v) birchwood xylan include incubation period (84 h), incubation temperature (25oC), agitation speed (200 rpm), and pH 10. For Micrococcus yunnanensis strain SAMRC-UFH4 cellulase production was optimal under such conditions as, incubation temperature (30oC), agitation speed (0 rpm), and pH 5, while xylanase production was optimal at, incubation temperature (30oC), agitation speed (150 rpm), and pH 10. The high cellulase and xylanase activity obtained from these isolates suggest suitability of the organisms as important candidates for commercial application. , Thesis (MSc) -- Faculty of Science and Agriculture, 2016
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- Date Issued: 2016-05
Nutrient removal and biofuel potential of MaB-floc biomass from an integrated algal pond system treating domestic sewage
- Authors: Sibelo, Linda
- Date: 2020
- Subjects: Biomass energy , Waste products as fuel , Algal biofuels , Sewage -- Purification -- Nutrient removal
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/144955 , vital:38395
- Description: Integrated algal pond systems (IAPS) are a passive water treatment technology derived from the Oswald designed advanced integrated wastewater pond systems (AIWPS®) and effect wastewater treatment based on biological activity of microorganisms within the system, solar energy and gravity. The technology consists of an advanced facultative pond (AFP), a series of interconnected high rate algal oxidation ponds (HRAOP) and algal settling ponds. The symbiotic relationship between microalgae and bacteria facilitated by paddlewheel mixing of HRAOP results in the formation of biomass aggregates known as MaB-flocs. MaB-floc formation enhances nutrient abstraction, gravitational sedimentation and separation from water hence forming two product streams; recyclable water and biomass, both with valorisation potential. This work aimed to determine the suitability of MaB-floc biomass generated in the HRAOP of an IAPS treating domestic sewage as feedstock for biofuel production based on the content of carbohydrate and lipid. Nutrient removal efficiency, biomass productivity and bulk lipid and carbohydrate concentration were monitored for two consecutive three-month periods in the winter and summer seasons of 2018/19. Maximum removal efficiencies of nitrogen and phosphorus were determined as 71% and 75% respectively, demonstrating the efficiency of IAPS as a wastewater treatment technology. MaB-floc biomass productivity in winter and summer was 9.4 g/m2/d and 16.5 g/m2/d respectively indicating the heavy influence of seasonal temperature, possibly day length, and solar irradiation on biomass productivity in the HRAOP. Summer productivity was lower than the maximum theoretical productivity of 25 g/m2/d possibly due to photoinhibition of photosynthesis as well as grazing pressures caused by the proliferation of rotifers mainly of the Brachionus genus. MaB-floc biomass consistently contained higher amounts of carbohydrate than lipid despite the changes in species dominance from Scenedesmus sp. and Desmodesmus sp. in winter to Pediastrum sp. in summer. Variations in MaB-floc biomass carbohydrate content were linked to changes in nitrogen concentration, mainly in the form of nitrates. Lower nitrogen concentration significantly increased the carbohydrate content of MaB-floc biomass from 17.5 ± 0.15% to 33.5 ± 0.3 % recorded in summer. In winter, biomass carbohydrate increased from 18.3 ± 1.2% to 35.8 ± 0.3%.To induce accumulation of carbohydrates through nitrogen starvation, isolated microalgal species native to the HRAOPs of the IAPS at Institute for Environmental Biotechnology Rhodes University(EBRU) were used. The outcome from the laboratory studies showed that carbon partitioning within isolated strains could be altered from carbohydrate to lipid which is more energy-rich. Hence, exploring the biodiesel production option using HRAOP MaB-floc biomass, which had a lipid content ranging between 12.1 ± 0.64 % and 13.9 ± 0.5 %, would require a preconditioning step in the form of nitrogen starvation to enhance its lipid content. Overall, the outcome of outdoor monitoring studies on biomass biochemical composition indicated that HRAOPs operating under natural environmental conditions preferentially generated a biomass rich in carbohydrate. Therefore, anaerobic digestion may be a more viable option for HRAOP MaB-floc biomass because of the high carbohydrate levels ranging between 24.9 ± 0.6 % and 25.6 ± 1.3 % of the dry MaB-floc biomass weight. Despite the low biomass C/N ratio (7.1 to 7.8), the MaB-floc biomass can be anaerobically co-digested with a higher C/N ratio (24) substrate such as in-pond digester sludge, to improve methane yields calculated to be between 0.31 m3 CH4/ kg MaB-floc biomass and 0.33 m3 CH4/ kg MaB-floc biomass. Anaerobic digestion of biomass also produces CO2 which can be recovered and added to HRAOPs to enhance MaB-floc biomass productivity while lowering greenhouse gas emissions from a wastewater treatment plant. The digestate from the anaerobic process, which is rich in nitrogen and phosphorus can be used as a biofertiliser. Thus, a potential MaB-floc biomass biorefinery consisting of biogas and bio-fertiliser pathways can be established using IAPS treating sewage as the platform technology. IAPS is a system designed to operate in a way that is passive and without substantial environmental impact but technological innovations and a reduction in the size of the system are required to make the technology more acceptable.
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- Date Issued: 2020
Pyrolysis of algal biomass and coal in a rotary kiln reactor: Pyrolysis behaviour, product distribution and kinetic analysis
- Authors: Nyoni, Bothwell
- Date: 2023-12
- Subjects: Algal biofuels , Biomass energy , Coal -- South Africa
- Language: English
- Type: Doctorate theses , text
- Identifier: http://hdl.handle.net/10948/62550 , vital:72823
- Description: There are two primary reasons why the global economy is gradually reducing its dependence on coal as an energy source. Firstly, coal reserves are finite, and while some argue that current reserves will last for generations, the reality is that coal is a non-renewable resource. Secondly, the emissions associated with coal usage have adverse effects on both the environment and human health. While European countries have adopted seemingly aggressive strategies to replace coal and other fossil fuels, South Africa and other developing nations face economic constraints that limit such actions. Fortunately, there are more conservative approaches that can be employed, one of which involves a gradual introduction of renewable energy sources into the energy grid. Wind, solar, and biomass currently stand as the major renewable energy sources under consideration. However, it's worth noting that the intermittent nature of wind and solar energy production poses a significant challenge. Biomass holds the potential to replace coal in retrofitted coal-fired plants. However, the unchecked utilisation of biomass can lead to deforestation and have adverse effects on the human and animal food supply chain, as many essential food items are derived from plants. The debate over using biomass as a fuel source, especially when some types of biomasses can serve as food for humans and animals, has been a subject of ongoing discussion. Furthermore, biomass exhibits a lower energy density when compared to coal. Combustion stands as the primary technology for converting coal into energy and is widely used in most coal-based power plants. Gasification, on the other hand, has been employed for years in South Africa as a coal-to-liquids technology to supplement transportation fuel requirements and reduce reliance on crude oil imports. Pyrolysis, too, has found application as a key method for obtaining high-energy coal char, serving both as an energy source and a reducing agent in blast furnaces for the steelmaking industry. Pyrolysis technologies are gaining popularity in biomass-to-liquids processes due to their simplicity. Currently, there is growing research interest in simultaneous pyrolysis of coal and biomass. The study presented in this thesis focuses on investigating the pyrolysis of Scenedesmus algae biomass and low-grade coal in a small-scale rotary kiln, with particular emphasis on the synthesised liquid products. Algae represent a unique type of biomass that can be cultivated in photo-bioreactors with minimal use of agricultural land. This suggests significant potential for large-scale cultivation of algae, and ongoing efforts are exploring strategies for the mass production of algal biomass.Firstly, pyrolysis studies were carried out via thermogravimetric analysis instruments. It was revealed that because of algae’s considerably higher volatile content and lower carbon content when compared to coal, the pyrolysis process of algal biomass occurred at a faster rate. The highest pyrolytic reactivity of algae was 0.41 mg/min occurring at approximately 290 ᵒC in comparison with coal’s 0.06 mg/min occurring in the approximate temperature range of 550 – 600 ᵒC. The magnitude of the reactivity of the blends depended on the coal/algae ratios used. Furthermore, kinetics analysis revealed that the overall pyrolytic decomposition of coal followed 2nd order kinetics with an activation energy of 81.8 kJ/mol. The decomposition of algae and coal-algae blends occurred in two stages; the first stage decomposition followed 2nd order kinetics with activation energies in the range 130.3 – 145.5 kJ/mol. The second stage decomposition of algae followed 1st order kinetics with an activation energy of 27.3 kJ/mol, whilst coal-algae blends followed 2nd order decomposition with an activation energy range of 69.4 – 74.2 kJ/mol. Secondly, pyrolysis studies were carried out in a rotary kiln reactor wherefrom the char products were collected, and pyrolytic gases condensed to obtain pyroligneous liquid. It was found that the composition of oils synthesised from the pyrolysis of coal was rich in paraffins (52.6 % at 550 ᵒC), however the yield of oil from the pyrolysis of coal was low (6.9 %). Oils from algae and coal-algae blends were dominated by alcohols, fatty acids, fatty acid esters and poly-cyclic aromatic compounds. For example, the most abundant compounds in algae oil produced at 550 ᵒC were fatty acid esters (28.8 %), alcohols (17.6 %), fatty acids (10.8 %) and unsaturated aliphatics (10.7 %); the oil yield obtained from pyrolysis of algae was 40 %. The yields and composition of oils obtained from coal-algae blends were linked to individual contributions from coal and algae, especially at 550 ᵒC; however, the contributions were not proportional due to synergistic effects. This kind of study will contribute to the already existing but limited literature on coal-algae pyrolysis. Furthermore, this study demonstrates the potential of using low-grade coals (an abundant resource in Southern Africa) in conjunction with algal biomass (a renewable resource), in large-scale synthesis of liquid fuels and valuable chemicals via a simple pyrolysis process. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2023
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- Date Issued: 2023-12
Investigation of brewery waste grains and microbial fuel cells as value-additive technologies improving solvent production yields in Clostridium acetobutylicum (ATCC 824) fermentation
- Authors: Du Toit, Ryan Guillaume
- Date: 2023-10-13
- Subjects: Biomass energy , Butanol , Fermentation , Microbial fuel cells , Brewery waste , Clostridium acetobutylicum
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424643 , vital:72171
- Description: The production of the solvent compounds acetone, ethanol and butanol through fermentation of organic feedstocks using Clostridia species could be a promising route for biofuel production. However, the cost of raw materials, low yields and the complexity of anaerobic fermentation continue to hinder this means of generating these compounds. The research presented in this Thesis investigated low-cost interventions that could decrease the costs of production and to direct the synthesis of fuel compounds using microbial fuel cells. Low-cost anaerobic chambers were designed and constructed for the propagation and manipulation of Clostridium acetobutylicum, selected as a low-risk microbial catalyst. Fermentation was monitored using in situ pH measurements and a combination of turbidity measurements, nutrient assays (especially total carbohydrates) and HPLC-RI detection as a means of monitoring the consumption of nutrients (glucose), production of precursor compounds (butyric acid) and the formation of solvent molecules (acetone/ethanol and butanol) during fermentation by this organism. Brewer’s spent grains were tested as a sustainable and low-cost feedstock for solvent production, comparing the effects of sterilising before fermentation, or allowing resident microflora to remain during Clostridium-catalysed solvent production. Sterilised spent grains significantly improved the production of solvent molecules (e.g. 12.97 ± 0.38 g/L of butanol yielded, compared to 0.40 ± 0.33 g/L for defined media sampled during the solventogenic phase); compared to these, the use of non-sterilised brewer’s grain decreased both the reproducibility and yields of fermentation (8.66 ± 1.6 g/L of butanol). Microbial fuel cells were studied as a possible means of altering electron transfer to/from electrode-attached Clostridia to control the metabolic shift in bacteria from acidogenesis to solventogenesis. The base line MFC (11.00 ± 4.69 g/L) fermentation experiment did produce higher acetone/ethanol than the baseline batch experiment MB (5.47 ± 4.48 g/L), indicating an improvement to solvent production in C. acetobutylicum (ATCC 824) in a MFC fermentation. In this study, MFC-1 demonstrated remarkable superiority over MB in terms of butyric acid production, yielding significantly higher concentrations while also improving acetone and ethanol production. However, the enhanced butyric acid production did not correspond to significantly increased butanol yields when compared to batch fermentation of chemically defined media. These findings highlight the potential of MFC-1 as an efficient approach for enhancing the fermentative production of valuable compounds, with a particular focus on butyric acid and acetone/ethanol. , Thesis (MSc) -- Faculty of Science, Biotechnology Innovation Centre, 2023
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- Date Issued: 2023-10-13