Energy Solution

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Browsing Energy Solution by Funder "National Research Fund"

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  • Publication
    Publication
    Energy recovery from biomethanation of vinasse and its potential application in ozonation post-treatment for removal of biorecalcitrant organic compounds
    (Elsevier, 2021) Otieno, Benton; Apollo, Seth
    Vinasse is characterized by a high chemical oxygen demand (COD) and dark brown colour, which requires abatement before disposal to prevent the pollution of receiving streams. Anaerobic digestion (AD) usually applied for vinasse treatment can only reduce the COD with the colour remaining unabated. This study investigated the feasibility of combining AD and ozonation for vinasse treatment. The AD process alone achieved high COD removal of 95 %, at a best organic loading rate of 15 kgCOD/m3/d. However, the anaerobic effluent still had an intense dark brown colour caused by a considerable amount of residual biorecalcitrant COD of 4.5 g/L. The ozonation post-treatment of the anaerobic effluent removed 80 % of the colour with up to 92 % ozone transfer at optimal parameters of pH 4, substrate dilution factor of 2, and 90 mg/L/min ozone dosage. Kinetic analysis showed that for a constant feed flow combined system, the ratio of the anaerobic reactor unit to the ozonation reactor unit is recommended to be 20:1. Also, from energy analysis, application of the bioenergy produced from AD to supplement the total energy requirement of the combined system could lead to 50 % savings on energy, and a carbon dioxide emission reduction of 122 kg CO2/m3 of vinasse treated. The combined system is thus a promising technology for vinasse treatment and can contribute to combating greenhouse gas emissions.
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    Publication
    Oil and Gas Exploration and Sustainable Environmental Management in Oil Block 13t South Lokichar Basin, Turkana County, Kenya
    (Kenyatta University, 2020) Mugendi, Kariuki David
    Commercial oil and gas was discovered in Kenya in 2012. Few academic studies have been done on the effects of the mentioned discovery to the environment.The oil and gas resources are expected to transform the economic wellbeing of the locals and the nation at large.However,land degradation, environmental pollution and socio-economic problems have always ensued oil and gas exporation ventures globally.This study aimed at determining the effects of oil and gas exploration on biophysical and socio-economic environments in Oil Block 13T South Lokichar Basin,Turkana South-subcounty and come up with sustainable environmental management strategies in the oil fields.The specific objectives were to review,constitutional,policy,legal and institutional framework governing environmental management in the backdrop of oil and gas exploration in Kenya and determination of oil and gas exploration effects on biophysical and socio-economic environments in the study area.The study adopted an exploratory mixed method research design.Purposive non-probability sampling was applied in determining the study area,sampling the boreholes,sampling the drill cutting samples and sampling the key informants.Probability sampling was used in identifying the manyattas,households and the villages for conducting focused group discussions.Questionnaires,documents review, photography,observation,landsat satellite imageries acquisition and analysis,laboratory analysis using XRF and AAS machines, for drill cuttings and water samples respectively to determine the levels of physicochemical properties were the data collection methods used.The questionnaires were coded into the Statistical Package for Social Sciences version 20.0 software and Excel 10.0.Descriptive and inferential statistics were used in data analysis.The study identified several gaps in the existing environmental policy and legal framework in relation to the oil fields environmental management coupled with poor enforcement of the laws by the relevant agencies.In addition, the study observed a decline in NDVI from 1 to 0.4329 for the rainy season and 0.4107 to 0.1217 jfor the dry season between 2006 and 2017 with a p-value of 0.0091< 0.05 on paired T-test implying a significant change on vegetation cover.The area under forest, shrubland and grassland had significantly reduced at 90% confidence interval with a,value of,0.0718,0.0738 and 0.0609.The drill cuttings whose levels of detected heavy metals concetration for Manganese(Mn),Copper(Cu),Nickel(Ni),Iron(Fe),Calcium(Ca),Lead(Pb),were;1.58,0.21,0.05,70.4,62.57,4.58 respectively were incorrectly being managed onsite.Mn, Feand Pb concentration levels in the drill cuttings were above the WHO and USEPA recommended standards for the reserve pit.The levels of Fe,Ni,Turbidity and Total Dissolved Solids of the sampled water from the study area,were all above the prescribed WHO standards.The study noted improved socio-economic characteristics, physical and social infrastructures in the study area.70% of the respondents felt that water provision, health facilities, education facilities, employment opportunities had improved since oil and gas exploration began with a Cohen kappa coefficient of agreement of 0.608.However,challenges such as population influx,land displacement,lack of adequate engagement of the locals, gender inequalities with a Cronbach’s Alpha of reliability of 0.735, health challenges of the locals and increased number of conflicts cases since 2012 with a statistical p-value of 0.005< 0.05 were noted.The study recommends enforcement of the existing environmental legislations and development of oil specific environmental laws,adoption of advanced oil drilling and drill waste management technologies, as well as participatory environmental management approach in the oil fields.
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    Publication
    Quantifying Greenhouse Gas Emissions and Carbon Stocks in Maize-Soybean Cropping Systems in Siaya County, Kenya
    (Kenyatta University, 2020) Karanja, Anne Njeri
    As climate change continues to threaten ecosystems’ functions, agriculture remains one of the major source of greenhouse gas (GHG) emissions that are responsible for global warming. The major GHG in agriculture are; carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). Unfortunately, agriculture is also one of the most affected sectors by climate change. There is therefore need to reduce emissions by adopting agricultural practices with mitigation potential. This is by enhancing soil carbon sequestration to offset emissions, or reducing emissions while safeguarding crop yields. However, little is still known about GHG quantities and intensities that major cropping systems in Kenya emmit. Site specific studies on GHG emissions to establish interventions for mitigation of climate change and enhanced crop production is therefore of essence. The objective of this study was to examine the effect of reduced tillage, crop residue retention and use of controlled release urea (CRU) in maize-soybean cropping systems on GHG emissions, soil N mineralization, organic carbon stocks and yields. Field measurements were carried out in a 13 year old researcher-managed trial in Siaya county, Kenya between March 2016 and January 2017. Four treatment combinations: ZT M-S NU (reduced tilage+maize soybean rotation+normal urea), ZT M-S CRU (reduced tillage+maize soybean rotation+controlled release urea), ZT M/S (reduced tillage+maize soybean intercrop without urea), CT M-S NU (Conventional tillage+maize soybean rotation+normal urea) were tested. The treatments were laid out in a randomized complete block design. DAYCENT model was used to simulate soil carbon, N2O emissions and maize yields. Results showed that daily fluxes of N2O ranged between -0.5-26 g ha-1 d-1 and -2-10 g ha-1 d-1 in the long and short rainy seasons respectively. Cumulatively, N2O emissions were between 0.2 - 0.7 kg ha-1 and 0.2 - 0.4 kg ha-1 in the long and short rainy seasons respectively. In the long rainy season, ZT M-S CRU had significantly higher N2O fluxes than the other treatments (P=0.05). In the short rainy season there were no significant effects of treatment on N2O emissions. In the long rainy season, CO2 daily fluxes were between 9 to 42 kg ha-1 while the cumulative emissions ranged between 2.5 to 2.8 t ha -1. In the short rainy season daily CO2 fluxes ranged between 6 to 30 kg ha-1 while cumulative emissions were 1.8- 2.5 t ha -1. There was no significant effect of treatment on CO2 emissions. Methane emissions were largely negative, and did not differ significantly among treatments. Yield was significantly low for ZT M/S but N2O emission intensities were not significantly different among treatments. DAYCENT simulated soil carbon and maize yield within the same ranges observed by measurement. N2O emissions by DAYCENT were higher during the peak of the seasons, but were comparable with observed measurements later in the seasons. Even though the long rainy season had higher N2O and CO2 emissions, the difference was not significant. These results indicate that emissions in the study area were low.These results further indicate that the current soil management practices in Siaya County influence GHG emissions, and the higher emissions observed with ZT M-S CRU in the long rainy season calls for further investigations of the effect of CRU on N2O emissions. The lower emission intensity shown by ZT M/S despite having lower yield points to the need of evaluating cropping systems for climate change mitigation and adaptation. These results indicated that DAYCENT model can be used to simulate soil carbon and yield but not N2O emissions in the study area.