UDOM IR :: Browsing by Author "Kombe, Godlisten G."

Browsing by Author "Kombe, Godlisten G."

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Do renewable energies contribute to enhancing environmental quality in Eastern Africa?
(Springer, 2022) Kombe, Godlisten G.; Mihayo, Isege Z.
East Africa has enormous renewable energy potential, but only a small portion of it has been exploited, and little is known on its role in improving environmental quality. Thus, this study empirically examines the impact of renewable energy on the environment using ecological footprint (EF; positive indicator) and CO2 emissions (negative indicator) as proxy indicators for environmental quality in a panel of ten East African countries from 1990 to 2015. These indicators were chosen due to their potential impact in the environment. The work used the pooled mean group (PMG) as the main panel estimator to determine the impact while controlling non-renewable energy consumption, GDP per capita, and foreign direct investment (FDI). PMG has been used as it forces the long-run coefficients to be equal across all panel groups. The findings show that in the long run, there is a significant negative relationship between CO2 emissions and renewable energy consumption, as well as a significant positive relationship (with a low impact) between EF and renewable energy consumption, suggesting that renewable energy use enhances the area’s environmental quality. Also, results indicate that non-renewable energy use degrades environmental quality in both metrics, whereas GDP degrades environmental quality through CO2 emissions and improves environmental quality through EF. This requires East African countries to focus a higher emphasis on accessible renewable energy sources to achieve quick and sustainable economic growth and minimize environmental effects. To accomplish this, strategic policies and legislation, as well as the promotion of green technology, are required.
The effects of pre-treatment and refining of high free fatty acid oil on the oxidation stability of biodiesel
(Taylor & Francis, 2017) Temu, Abraham K.; Kombe, Godlisten G.
Although non-edible oil feedstocks with high free fatty acid (FFA) are potential feedstocks for biodiesel production, their utilization may require refining or pre-treatment prior to the production of biodiesel by alkali catalyzed transesterification. In this study, the crude Jatropha curcas oil with 4.54% FFA was either refined (neutralized, deodorized, and fully refining) or pre-treated (acid esterifying and glycolysis) to lower the FFA to less than 1% prior to biodiesel production by homogeneous base catalyzed transesterification. The study revealed that the oxidation stability of the biodiesel varies significantly with the method of either refining or pre-treating the FFA in oil. It was further observed that the biodiesel from re-esterified oil presented the greatest stability, followed by the biodiesel from neutralized, deodorized, acid pre-treated, and fully refined oil in that order. Biodiesel produced from fully refined and acid esterified oil showed the poorest oxidation stability and fail to meet the minimum required induction time of 6 h and 3 h as recommended by the EN 14214 and ASTM D6751 standards, respectively. Both neutralized and re-esterified oil present superior biodiesel oxidation stability with oxidation induction time 8.18 h and 8.24 h, respectively. Although pre-treatment and refining process lowers the FFA in the oil to less than 1% and produces biodiesel with more than 96.5% fatty acid methyl ester content, the addition of antioxidants in the biodiesel from deodorized, acid esterified, and fully refined oil is inevitable due to poor oxidation stability of the produced biodiesel.
Factors influencing eco-industrial development in Africa: A SWOT analysis of a Tanzanian industrial park
(Taylor & Francis, 2022) Rweyendela, Amani George; Kombe, Godlisten G.
Eco-industrial parks (EIPS) have been proposed as a transformative model for assisting developing countries in upgrading their industrial systems to meet higher global environmental standards while boosting economic competitiveness. However, for many industrial settings, the requisite contextual requirements have yet to be clarified. This paper aims to contribute to filling this gap. It examines the potential of transforming a case study Tanzanian industrial park, an export processing zone (EPZ), into an EIP. The park was assessed against four criteria (roundput, locality, diversity and gradual change) using SWOT (strengths, weaknesses, opportunities, and threats) analysis. The paper draws upon key informant interviews, document reviews and physical site inspection. Findings reveal several strong and weak points of the EPZ, painting a scenario of a zone that is not based on the cycling of resources, does not have a diverse cooperation network arranged locally, and does not rely on the flow of renewables. However, the presence of a park management team, existing synergies, planned synergies and overall national and global development priorities make the park potentially strong as a whole. Our findings underscore the need for deliberate policy interventions. They can be applied to comparable contexts to pinpoint critical areas when planning the interventions.
Glycerolysis of high free fatty acid oil by heterogeneous catalyst for biodiesel production
(Elsevier, 2022) Selemani, Asumin; Kombe, Godlisten G.
The most widely used commercial biodiesel production technique, alkali-catalysed transesterification, requires only moderate temperatures and pressures to achieve a more than 98% conversion yield. Unfortunately, oil feedstock’s high free fatty acid (FFA) content limits the technology’s usefulness. A heterogeneous base catalysed glycerolysis process was investigated in this study to lower the FFA and meet these requirements. The response surface methodology (RSM) based on I-optimal design was used to model and optimize a CaO catalysed glycerolysis reaction under the influence of five reaction variables: temperature (60–180 ◦C), residence time (30–120 min), FFA concentration (6–50%), catalyst amount (0.4–0.6 wt (g/g)), and Glycerol to Oil ratio (G/O) (1–1.5). The data were fitted in a quadratic model, and R2 of 0.986 was observed, signifying that the model well defined the experimental data. The model was validated by running four replicates of the experiment, and a residual standard error of 2.7% was obtained, indicating the model would accurately predict future observations. The 48.584% FFA in oil was reduced to 0.98% under optimal conditions of 170 ◦C, 39.9 min of residence time, 0.591wt g catalyst concentration, and 1.026 g/g glycerol/oil (G/O) ratio. CaO catalysed glycerolysis has significantly reduced FFA to less than 3% in less than an hour in biodiesel feedstock for biodiesel production.
Institutional influences on circular economy: a Tanzanian perspective
(Elsevier Inc., 2021) Rweyendela, Amani G.; Kombe, Godlisten G.
The shift towards circular economy (CE) is strongly linked to institutions, particularly laws and regulations, whose primary aim is to minimise uncertainties and align economic actors’ incentives. However, the literature is inconclusive about the factors within legislative environments and what kind of influences they produce, especially in the African context. Thus, this study sought to analyse and describe holistically the factors within Tanzania's current legislative context that may stimulate or hinder CE development. The authors conducted a narrative literature review and document review using the SWOT (strengths, weaknesses, opportunities and threats) analysis approach. The results suggest that there are several strengths and opportunities that may have created a CE enabling context. But also several weaknesses and threats impede the circular transformation. Based on the results, the authors discuss what they mean for policymakers and what is needed for the current and future legislation to support CE better. This ground-breaking Tanzanian-based study adds to the existing body of knowledge on CE's institutional antecedents in developing countries. It stands out for offering a broad view of the Tanzanian legislative environment, identifying opportunities for facilitating CE and clarifying directions for further research.
Low temperature glycerolysis as a high FFA pre-treatment method for biodiesel production
(Scientific Research, 2013) Kombe, Godlisten G.; Temu, Abraham K.; Rajabu, Hassan M.; Mrema, Godwill D.; Lee, Keat Teong
A novel low temperature glycerolysis process for lowering free fatty acid (FFA) in crude jatropha oil for alkali cata-lyzed transesterification has been developed. The response surface methodology (RSM) based on central composite design was used to model and optimize the glycerolysis efficiency under three reaction variables namely; reaction time, temperature and glycerol to oil mass ratio. The optimum conditions for highest glycerolysis efficiency of 98.67% were found to be temperature of 65°C, reaction time of 73 minutes and 2.24 g/g glycerol to oil mass ratio. These conditions lower the high free fatty acid of crude jatropha oil from 4.54% to 0.0654% which is below 3% recommended for alkali catalyzed transesterification. The pre-treated crude jatropha oil was then transesterified by using homogeneous base transesterification resulting to a conversion of 97.87%. The fuel properties of jatropha biodiesel obtained were found to be comparable to those of ASTM D6751 and EN 14214 standards. The process can also utilize the crude glycerol from the transesterification reaction, hence lowering the cost of biodiesel. The glycerolysis is easier implemented than acid esterification thereby avoiding the need for neutralization and alcohol removal step.
Pre-treatment of high free fatty acids oils by chemical re-esterification for biodiesel production—a review
(Scientific Research, 2013) Kombe, Godlisten G.; Temu, Abraham K.; Rajabu, Hassan M.; Mrema, Godwill D.; Kansedo, Jibrail; Lee, Keat Teong
Non edible oil sources have the potential to lower the cost of biodiesel. However, they usually contain significant high amounts of free fatty acids (FFA) that make them inadequate for direct base catalyzed transesterification reaction (where the FFA content should be lower than 3%). The present work reviews chemical re-esterification as a possible method for the pre-treatment of high FFA feedstock for biodiesel production. The effects of temperature, amount of glycerol, type and amount of catalyst have been discussed. Chemical re-esterification lowers FFA to acceptable levels for transesterification at the same time utilizing the glycerol by product from the same process. Further researches have been proposed as a way forward to improve the process kinetics and optimization so as to make it more economical.
Steam deacidification of high free fatty acid in Jatropha oil for biodiesel production
(ACS Publications, 2017) Temu, Abraham K.; Kombe, Godlisten G.
Although non-edible oil feedstocks are available at a lower price than edible oil feedstocks, their high free fatty acid (FFA) content hinders their direct utilization in the production of biodiesel by alkali-catalyzed transesterification. In this study, the steam deacidification process has been employed in reducing the FFA of crude Jatropha oil before alkali-catalyzed transesterification. The response surface methodology (RSM) established on the central composite design (CCD) was used to model and optimize the steam deacidification efficiency under two process variables, namely, temperature and amount of steam. The optimum conditions for deacidification efficiency of 98.74% were found to be the temperature of 235 °C and the amount of steam of 3.4% (w/w) of the feedstock. These conditions reduce the high FFA of crude Jatropha oil from 4.54 to 0.09%, which is below 1% recommended for base-catalyzed transesterification. The deacidified crude Jatropha oil was then transesterified using a homogeneous base catalyst and gave a conversion of 97.45%. The tested fuel properties of biodiesel, such as viscosity at 40 °C, acid value, gross calorific value, iodine value, fatty acid methyl ester (FAME) content, and density at 15 °C, were found to be comparable to those of ASTM D6751 and EN 14214 standards.

Browsing by Author "Kombe, Godlisten G."

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