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- ItemFeasibility assessment of the production of bioethanol from lignocellulosic biomass pretreated with acid mine drainage (AMD)(Elsevier, 2020-09-01) Burman, N.W.; Sheridan, C.; Harding, K.G.A techno-economic evaluation of a lignocellulosic bioethanol facility that uses acid mine drainage for the pre-treatment of weeping love grass (Eragrostis curvula) was performed. Both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) reactor configurations were evaluated. Results were compared to an evaluation of the same process with biomass pre-treated with dilute H2SO4. Capital and operating costs were estimated and a simple economic evaluation was conducted. It was found that all scenarios made a loss except for biomass pre-treated with H2SO4 in the SHF reactor configuration, although the high capital cost resulted in a payback period of 80.7 years, which is unfeasible. SHF was found to produce more ethanol at a lower capital cost than SSF, indicating that it is more economically feasible. Incorporating the remediation of AMD into a simultaneous process could help improve process economics. It is thus recommended that a techno-economic evaluation be conducted on a process that produces bioethanol through SHF and simultaneously remediates AMD
- ItemLignocellulosic Bioethanol Production from Grasses Pre-treated with Acid Mine Drainage: Modeling and Comparison of SHF and SSF(Elsevier, 2019-09-01) Burman, N.W.; Sheridan, C.M.; Harding, K.G.Acid mine drainage (AMD) was used for the pre-treatment of indigenous South African grass (Eragrostis curvula), and compared to H2SO4 (1 wt%) pre-treatment. The optimal pre-treatment duration were investigated and found to be 1 day for H2SO4 and 3 days for AMD pre-treatment. The optimal biomass solid loadings were found to be 20 wt% for both pre-treatment methods. Additionally, enzymatic hydrolysis and fermentation to produce ethanol were investigated for both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). In both SHF and SSF, the H2SO4 pre-treatment obtained higher concentrations of glucose/ethanol compared to AMD pre-treatment. The concentration of glucose/ethanol obtained using AMD pre-treatment was 70–80% of that achieved using H2SO4 pre-treatment. Empirical equations modeling the glucose/ethanol concentration in all processes were determined using a least squares method. Concentrations predicted by the models were found to have a high correlation (r2 = 0.87–0.99) to concentrations determined experimentally
- ItemEvaluation of Fuel Quality of Invasive Alien Plants and Tropical Hardwoods as Potential Feedstock Materials for Pyro‑Gasifcation(Springer, 2021-09-01) Okoro, N.M.; Ikegwu, U.M.; Harding, K.G.; Daramola, M.O.INTRODUCTION: Despite several studies carried out on the efects of the fuel properties of raw biomass on the fnal fuel properties of the biofuel after a thermochemical conversion, an identifcation and grading of various biomass types with respect to the level of their viability for pyro-gasifcation has not been established. OBJECTIVES: The primary objective of this study was to identify and rank eight waste wood feedstocks based on the suitability of their fuel properties for an efcient pyro-gasifcation using experimental data. METHODS: The wood samples were characterized using standard experimental procedures to determine their fuel properties. Five fuel evaluators relevant to the efciency of a pyro-gasifcation process, were developed. The experimental data collated for each sample was used to carry out an evaluation exercise of the samples under each of the fve fuel evaluators. Finally, the result of this exercise was used to rank the wood samples based on their suitability as feedstock for pyro-gasifcation. RESULTS: The hardwoods such as the Eucalyptus and African mesquite exhibited high fuel ratios, heating value and energy density which was as result of their higher lignin content. However, they exhibited minimal char reactivity. Conversely due to its higher holocellulose-to-lignin ratio, the Bugweed exhibited high char reactivity but lower fuel ratio, heating value and energy density. In comparison to the literature, the experimental results in this study were somewhat consistent with those of other biomass samples previously reported. The Fuel characterization exercise reveals that no wood sample can be considered completely efcient for pyro-gasifcation. The Jacaranda was however ranked lowest across the board. CONCLUSION: The variations in the hierarchy of the samples under the diferent fuel evaluators due to the disparities in their fuel properties paves way for further studies on the blending of waste wood samples with contrasting fuel properties in diferent mix ratios. This would enable the production of feedstock with the right balance in fuel properties suitable for an efcient pyro-gasifcation process. This study provides stakeholders with a framework for blending diferent lignocellulosic biomass species for thermochemical conversion.
- ItemModelling of Low Temperature Dilute Sulfuric Acid Pre-treatment of South African Grass(Elsevier, 2018-12-01) Burman, N.W.; Sheridan, C.; van Dyk, L.; Harding, K.G.Dilute acid hydrolysis is an effective method of pre-treatment of lignocellulosic biomass. Although there are many studies modelling this pre-treatment at high temperature (120–210 °C), no studies were found modelling this reaction at low temperature. In this study, a long grass species was pre-treated with dilute sulfuric acid (pH 1, 2 & 3) at low temperatures (35 °C, 65 °C, 90 °C). The hydrolysis of xylan was found to obey a bi-phasic model in which there are two fractions of xylan, with significantly different hydrolysis rates. The rates of hydrolysis of the fast reacting fraction was found to obey Arrhenius type temperature dependence (Ea = 155.06 kJ/mol, A0 = 1.65 × 1019/min), which agrees with findings of similar studies at higher temperatures. A negligible rate of hydrolysis was determined for the slow fraction which differs from previous studies. The proportion of the slow reacting fraction (50%) which is lower than previously determined (55%–100%).
- ItemDealing with Under-Preparedness in Engineering Education Part 1: Defining the Goal: A Taxonomy of Engineering Competency.(American Society for Engineering Education., 2003) Woollacott, L.C.This paper emerges from work conducted on the problem of effectively addressing under-preparedness in entrants to university engineering programs in South Africa. Any educational curriculum is based on a conception of the developmental journey a learner must take in becoming a competent graduate. The conceptions underlying traditional engineering curricula do not match well with the journeys that under-prepared students with ability should take to reach their potential fully. To work towards a better match between conception and reality requires deeper understanding of the nature of under-preparedness, of engineering competency and of the determinants of engineering competency (that is, the underlying factors that determine the quality of the competencies). The first of these areas will inform the process of curriculum design by clarifying the starting point of the developmental journey. The second area will clarify the goal and the third will help to clarify what must be done to get there. This paper addresses the second of these issues –understanding engineering competency. Eight different perspectives on engineering competency have been extracted from the literature and a ninth is developed in the paper. Analysis of their similarities and differences provides a basis for developing a broader, integrated perspective that is presented as a taxonomy of engineering competency. How the taxonomy is used in acquiring a deeper understanding of competency determinants and under-preparedness will be explored in two follow up papers.