Bioethanol is likely to be a large contributor to the fuel sector of industry in the near future. Current research trends are geared towards utilizing food crops as substrate for bioethanol fermentation; however, this is the source of much controversy. Utilizing food crops for fuel purposes is anticipated to cause massive food shortages worldwide. Cellulose is the most abundant renewable resource on earth and is subject to a wide array of scientific study in order to utilize the glucose contained within it. Waste paper has a high degree of cellulose associated with it, which makes it an ideal target for cellulose biotechnology with the ultimate end goal of bioethanol production. This study focussed on producing the necessary enzymes to hydrolyse the cellulose found in waste paper and using the sugars produced to produce ethanol. The effects of various printing inks had on the production of sugars and the total envirorunental impact of the effluents produced during the production line were also examined. It was found that the fungus Trichoderma longibrachiatum DSM 769 grown in Mandel's medium with waste newspaper as the sole carbon source at 28 °C for 6 days produced extracellular cellulase enzymes with an activity of 0.203 ± 0.009 FPU.ml⁻¹, significantly higher activity as compared to other paper sources. This extracellular cellulase was used to hydrolyse waste newspaper and office paper, with office paper yielding the highest degree of sugar production with an end concentration of 5.80 ± 0.19 g/1 at 40 °C. Analysis by HPLC showed that although glucose was the major product at 4.35 ± 0.12 g/1, cellobiose was also produced in appreciable amounts (1.97 ± 0.71 g/1). The sugar solution was used as a substrate for Saccharomyces cerevisiae DSM 1333 and ethanol was produced at a level of 1.79 ± 0.26 g/1, the presence of which was confirmed by a 600 MHz NMR spectrum. It was found that cellobiose was not fermented by this strain of S. cerevisiae. Certain components of inks (the PAHs phenanthrene and naphthalene) were found to have a slight inhibitory effect (approximately 15% decrease) on the cellulase enzymes at very high concentrations (approximately 600 μg/1 in aqueous medium), while anthracene had no effect. Whole newsprint ink was shown not to sorb glucose. The environmental analysis of the effluents produced showed that in order for the effluents to be discharged into an aqueous ecosystem they would have to be diluted up to 200 times. They were also shown to have the potential to cause severe machinery damage if reused without proper treatment.

PhD (Geography) / Department of Geography and Geo-Information Sciences / Improved access to modern affordable, sustainable and reliable energy supply is fundamental in the development of any economy and in the achievement of sustainable development goals. However, energy as a resource is increasingly and becoming scare in many countries and subsequently expensive, with a substantial impact on the socio-economic progress, especially in any country that lacks the financial, physical, social and human capital to secure its energy supply. Energy can also be produced though the anaerobic fermentation of biological waste, such as animal excrement, which is methane-rich. Fermentation also produces a nutrient-rich digestate. Biogas can be used for domestic purposes, such as cooking and heating. Furthermore, it can be converted into electricity. Biogas technology is of particular significance in rural households, where energy crisis are common. This thesis therefore aimed at developing an adoption and sustainable utilisation framework of biogas as an alternative source of energy for greenhouse gases emission reduction in the Limpopo Province. The sample involved 72 households with biogas digesters, which were purposively sampled and 128 households without digesters, which were randomly selected. The study was based on the primary data that were elicited using open and closed-ended questionnaires. Empirically, the results of this thesis developed a sustainable, simplified, appropriate and comprehensive framework for biogas adoption and utilisation, including an analysis of important factors that could influence the adoption of this desired technology, for cost-effectiveness and sustainability. / NRF

This project is primarily focused on improving the storage stability of bio-oils or pyrolysis oils by varying feedstock, reactor, and storage conditions. Pyrolysis oil is a complex medley of oxygenated chemicals (aliphatic and aromatic) that are well known to undergo unstable polymeric reactions (auto-catalyzed) if suitable additives are not utilized. These reactions can be severely detrimental to the long-term storage stability of pyrolysis oils. Hence, a detailed investigation was conducted in four phases namely: 1) pyrolysis oil production 2) additive prescreening 3) concentration optimization and 4) stability testing. During the first phase a lab-scale semi-continuous auger reactor is utilized to produce 16 pyrolysis oils. The reactor variables include pyrolysis temperature and vapor residence time. The feed stocks include pine wood, pine bark, oak wood, and oak bark. During the second phase a range of chemical additives (26) are prescreened to obtain three best performing additives. Anisole, glycerol, and methanol are consequently utilized to perform concentration optimization studies during the third phase. Viscosity, water content, and pH of pyrolysis oils are timely measured to assess the accelerated storage stability of pyrolysis oils during the phases 2-3. During the fourth phase, pyrolysis oils produced from three different reactor systems (lab-scale auger, large-scale auger, and entrained flow) were tested for their storage stability. Viscosity, water content, pH, density, and acid value are timely measured to assess the ambient and accelerated storage stability of pyrolysis oils during phase 4. Extrinsic variables such as light and filtration are utilized during the experimental testing of phase 4. The rheological data (Newtonian/non-Newtonian) enhanced the understanding of pyrolysis oil storage stability both qualitatively and quantitatively. The stability performance of a chemical additive is very much dependent on the concentration and its organic functional group. Consequently, alcohols fared above all the other functional groups in stabilizing the pyrolysis oils. Glycerol is observed to have special blending and homogenizing properties compared to all other additives. Feedstock seems to be the single most important factor affecting storage stability of pyrolysis oils. Consequently, pine wood resulted in the most stable pyrolysis oil whereas pine bark resulted in the least stable pyrolysis oil.