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Optimization of the enzymatic conversion of maize stover to bioethanol / by Nombongo MabentselaMabentsela, Nombongo January 2010 (has links)
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.
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Optimization of the enzymatic conversion of maize stover to bioethanol / by Nombongo MabentselaMabentsela, Nombongo January 2010 (has links)
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.
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Evaluation of restoration and management actions in the Molopo savanna of South Africa :|ban integrative perspective / Christiaan Johannes HarmseHarmse, Christiaan Johannes January 2013 (has links)
The loss of ecosystem resilience and rangeland (often referred to as veld in South
Africa) productivity is a major problem in the semi-arid Savanna environments of
southern Africa. The over-utilization of rangelands in the Molopo region of the North-
West Province in South Africa has resulted in profound habitat transformations. A
common regional indicator of rangeland degradation is the imbalance in the grasswoody
ratio, characterized by a loss of grass cover and density with increased shrub
or tree density. This can result in major reductions of rangeland productivity for the
grazing animal, forcing land users to apply active or passive restoration actions to
improve rangeland condition, control the thickening of woody species (bush
thickening), mitigate economic losses and restoring the aesthetical value of the
Savanna environment for ecotourism and game hunting aspects.
This study formed part of the multinational EU-funded PRACTICE project
(“Prevention and restoration actions to combat desertification: an integrated
assessment”). The first aim of the study was to evaluate locally applied restoration
actions using a participatory approach, followed by interviews with certain
stakeholders that formed part of a multi-stakeholder platform (MSP) related to the
livestock and game farming community in the Molopo. Participants of the MSP
ranked indicators according to their relative importance regarding the restoration
actions on an individual basis. The individual ranking results were combined with
quantitative bio-physical and qualitative socio-economic measurements for each
indicator in a multi-criteria decision analysis (MCDA), whereby the alternative actions
were ranked according to their relevancy and performance. The results were then
shared with members of the MSP in order to stimulate discussion among the
members and contribute to the social learning of the project outcome.
The overall positive response and acceptance of results by members of the MSP
changed the perceptions and objectives of the land users regarding rangeland
management. This type of participatory assessment was therefore found to be very
promising in helping to identify more sustainable actions to mitigate rangeland
degradation in the Molopo Savanna region. There is, however, still an urgent need to
create legal policy frameworks and institution-building, to support local-level implementation in all socio-ecological and economic settings, particularly in
communal areas.
The second aim was to evaluate the effect of two chemical bush control actions
(chemical hand- (HC) and aeroplane control (AC)) as well as rotational grazing
(RGM) on the Molopo Savanna vegetation.
Results show that rangeland productivity, i.e. forage production and grazing
capacity, was found to be negatively related to the woody phytomass in the savanna
system studied. Bush thickening influenced grass species composition which was
commonly associated with a decline in the abundance of sub-climax to climax
grasses, respectively. All three actions (HC, AC & RGM) significantly reduced the
woody phytomass and increased forage production and grazing capacity.
Although AC resulted in the highest reduction of woody phytomass, the highest
forage production and grazing capacity was found under RGM. The second highest
grazing capacity was found in HC sites, which was due to a high abundance of
perennial, palatable climax grass species. Results from this study also show that the
patterns and compositions of grass species, grass functional groups (GFGs) and
woody densities indicated by RGM and chemical HC, best resemble a productive
and stable savanna system that provides important key resources to support both
grazing and browsing herbivores. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014
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Evaluation of restoration and management actions in the Molopo savanna of South Africa :|ban integrative perspective / Christiaan Johannes HarmseHarmse, Christiaan Johannes January 2013 (has links)
The loss of ecosystem resilience and rangeland (often referred to as veld in South
Africa) productivity is a major problem in the semi-arid Savanna environments of
southern Africa. The over-utilization of rangelands in the Molopo region of the North-
West Province in South Africa has resulted in profound habitat transformations. A
common regional indicator of rangeland degradation is the imbalance in the grasswoody
ratio, characterized by a loss of grass cover and density with increased shrub
or tree density. This can result in major reductions of rangeland productivity for the
grazing animal, forcing land users to apply active or passive restoration actions to
improve rangeland condition, control the thickening of woody species (bush
thickening), mitigate economic losses and restoring the aesthetical value of the
Savanna environment for ecotourism and game hunting aspects.
This study formed part of the multinational EU-funded PRACTICE project
(“Prevention and restoration actions to combat desertification: an integrated
assessment”). The first aim of the study was to evaluate locally applied restoration
actions using a participatory approach, followed by interviews with certain
stakeholders that formed part of a multi-stakeholder platform (MSP) related to the
livestock and game farming community in the Molopo. Participants of the MSP
ranked indicators according to their relative importance regarding the restoration
actions on an individual basis. The individual ranking results were combined with
quantitative bio-physical and qualitative socio-economic measurements for each
indicator in a multi-criteria decision analysis (MCDA), whereby the alternative actions
were ranked according to their relevancy and performance. The results were then
shared with members of the MSP in order to stimulate discussion among the
members and contribute to the social learning of the project outcome.
The overall positive response and acceptance of results by members of the MSP
changed the perceptions and objectives of the land users regarding rangeland
management. This type of participatory assessment was therefore found to be very
promising in helping to identify more sustainable actions to mitigate rangeland
degradation in the Molopo Savanna region. There is, however, still an urgent need to
create legal policy frameworks and institution-building, to support local-level implementation in all socio-ecological and economic settings, particularly in
communal areas.
The second aim was to evaluate the effect of two chemical bush control actions
(chemical hand- (HC) and aeroplane control (AC)) as well as rotational grazing
(RGM) on the Molopo Savanna vegetation.
Results show that rangeland productivity, i.e. forage production and grazing
capacity, was found to be negatively related to the woody phytomass in the savanna
system studied. Bush thickening influenced grass species composition which was
commonly associated with a decline in the abundance of sub-climax to climax
grasses, respectively. All three actions (HC, AC & RGM) significantly reduced the
woody phytomass and increased forage production and grazing capacity.
Although AC resulted in the highest reduction of woody phytomass, the highest
forage production and grazing capacity was found under RGM. The second highest
grazing capacity was found in HC sites, which was due to a high abundance of
perennial, palatable climax grass species. Results from this study also show that the
patterns and compositions of grass species, grass functional groups (GFGs) and
woody densities indicated by RGM and chemical HC, best resemble a productive
and stable savanna system that provides important key resources to support both
grazing and browsing herbivores. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014
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