The severe effects associated with global warming and the rapid increase in oil prices are the driving forces behind the demand for clean carbon–neutral and biofuels such as bioethanol. Research studies are now focusing on using lignocellulosic biomass for bioethanol production due to concerns about food security and inflation. The chosen feedstock for this study was maize stover, given that it is the most abundant agricultural residue in South Africa. Maize stover consists of structural carbohydrates that can be enzymatically converted into fermentable sugars. The major drawback in the production of bioethanol from lignocellulosic biomass has been its high equipment and operational costs due to the use of acids and high enzyme loadings. The aim of this study was to investigate the possibility of optimizing the enzyme hydrolysis of pre–treated maize stover without further increasing the amount of enzymes. The maximum glucose yield attained was 690 ± 35 mg of glucose per gram of substrate which is equivalent to a conversion efficiency of 119%. The preferred pre–treatment method used was 3% sulphuric acid for 60 minutes at 121oC and the enzymatic hydrolysis process was performed at a 5% substrate loading, 50oC and pH 5.0 using 30 FPU per gram of cellulose in the presence of 1.25 g.L–1 of Tween 80 for 48 hours. The addition of Tween 80 increased the glucose yields by 23 % and thus, it has the potential of lowering the overall process costs by increasing the glucose yield without further addition of enzymes. Keywords: Bioethanol, maize stover, lignocellulosic biomass, pre–treatment, enzymatic hydrolysis / Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

Paraffin is used as a main household energy source for cooking, lighting and heating by low-income communities in South Africa. It is highly inflammable and spillages from paraffin can be considered as one of the major causes of fires that lead to the destruction of dwellings in the informal settlement. The situation is made worse due to the close proximity of the dwellings to each other which cause the fires to spread very quickly from one dwelling to the next leaving suffering and most often death in its wake (Schwebel et al., 2009:700). It has been shown by Muller et al. (2003:2018) that most of the informal rural communities use paraffin in non-ventilated and windowless environments and this causes major respiratory problems. The government has made a huge effort towards replacing paraffin as main cooking fuel in rural and informal settlements with ethanol gel. Ethanol gel is a healthier, safer alternative to paraffin because ethanol gel does not burn unless it is contained within a cooking device that concentrates the flame. It also fails to emit lung irritants or other dangerous chemical vapours when burned indoors (Bizzo et al., 2004:67). Commercial ethanol gels are manufactured with imported gelling agents that make their costs unaffordable to the rural poor communities. It is the objective of this study to determine whether gelling agents extracted from the local endemic species of cactacea viz. Opuntia fiscus-indica and Cereus Jamacaru can be used to synthesise ethanol gel comparable or better than the commercial gels. The two species chosen have been declared pests (Nel et al., 2004:61) and are continuously uprooted from arable land and burned by local farmers (Van Wilgen et al., 2001:162) This study showed that Opuntia ficas-indica stems gave a better cellulose yield (15.0 ± 6.7 wt. %) than Cereus Jamacaru (11.5 ± 7.8wt %). Chemical composition analyses and FT-IR analyses showed that the hemicelluloses and lignin were completely removed from the extracted cellulose and the extraction was more effective for Opuntia ficasindica than for Cereus Jamacaru. Ethanol gel produced by using the extracted cellulose, as was investigated during this study, was compared to commercial gels with respect to viscosity, burn time, calorific values and residue and a good comparison was obtained. / Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.

The severe effects associated with global warming and the rapid increase in oil prices are the driving forces behind the demand for clean carbon–neutral and biofuels such as bioethanol. Research studies are now focusing on using lignocellulosic biomass for bioethanol production due to concerns about food security and inflation. The chosen feedstock for this study was maize stover, given that it is the most abundant agricultural residue in South Africa. Maize stover consists of structural carbohydrates that can be enzymatically converted into fermentable sugars. The major drawback in the production of bioethanol from lignocellulosic biomass has been its high equipment and operational costs due to the use of acids and high enzyme loadings. The aim of this study was to investigate the possibility of optimizing the enzyme hydrolysis of pre–treated maize stover without further increasing the amount of enzymes. The maximum glucose yield attained was 690 ± 35 mg of glucose per gram of substrate which is equivalent to a conversion efficiency of 119%. The preferred pre–treatment method used was 3% sulphuric acid for 60 minutes at 121oC and the enzymatic hydrolysis process was performed at a 5% substrate loading, 50oC and pH 5.0 using 30 FPU per gram of cellulose in the presence of 1.25 g.L–1 of Tween 80 for 48 hours. The addition of Tween 80 increased the glucose yields by 23 % and thus, it has the potential of lowering the overall process costs by increasing the glucose yield without further addition of enzymes. Keywords: Bioethanol, maize stover, lignocellulosic biomass, pre–treatment, enzymatic hydrolysis / Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

Paraffin is used as a main household energy source for cooking, lighting and heating by low-income communities in South Africa. It is highly inflammable and spillages from paraffin can be considered as one of the major causes of fires that lead to the destruction of dwellings in the informal settlement. The situation is made worse due to the close proximity of the dwellings to each other which cause the fires to spread very quickly from one dwelling to the next leaving suffering and most often death in its wake (Schwebel et al., 2009:700). It has been shown by Muller et al. (2003:2018) that most of the informal rural communities use paraffin in non-ventilated and windowless environments and this causes major respiratory problems. The government has made a huge effort towards replacing paraffin as main cooking fuel in rural and informal settlements with ethanol gel. Ethanol gel is a healthier, safer alternative to paraffin because ethanol gel does not burn unless it is contained within a cooking device that concentrates the flame. It also fails to emit lung irritants or other dangerous chemical vapours when burned indoors (Bizzo et al., 2004:67). Commercial ethanol gels are manufactured with imported gelling agents that make their costs unaffordable to the rural poor communities. It is the objective of this study to determine whether gelling agents extracted from the local endemic species of cactacea viz. Opuntia fiscus-indica and Cereus Jamacaru can be used to synthesise ethanol gel comparable or better than the commercial gels. The two species chosen have been declared pests (Nel et al., 2004:61) and are continuously uprooted from arable land and burned by local farmers (Van Wilgen et al., 2001:162) This study showed that Opuntia ficas-indica stems gave a better cellulose yield (15.0 ± 6.7 wt. %) than Cereus Jamacaru (11.5 ± 7.8wt %). Chemical composition analyses and FT-IR analyses showed that the hemicelluloses and lignin were completely removed from the extracted cellulose and the extraction was more effective for Opuntia ficasindica than for Cereus Jamacaru. Ethanol gel produced by using the extracted cellulose, as was investigated during this study, was compared to commercial gels with respect to viscosity, burn time, calorific values and residue and a good comparison was obtained. / Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.