International Biodeterioration & Biodegradation, 2017
Anaerobic mono-digestion and co-digestion of primary sludge and two organic wastes (namely food w... more Anaerobic mono-digestion and co-digestion of primary sludge and two organic wastes (namely food waste or paper pulp reject) were evaluated by biomethane potential assessment and kinetics modelling to elucidate the synergistic effect. The specific methane yields were 159, 652 and 157 mL/g VS added during mono-digestion of primary sludge, food waste and paper pulp reject, respectively. Co-digestion of primary sludge with either food waste or paper pulp reject resulted in much higher specific methane yields of 799 and 368 mL/g VS, respectively. pH and intermediate inhibitions (e.g. volatile fatty acids and ammonium-N) were not observed. The synergistic effect was also confirmed by examining the VS and COD removals. COD balance also identified and validated the enhanced specific methane yields from both primary sludge and organic waste (i.e. additional 32 and 19% of COD was converted to biogas during codigestion of primary sludge with food waste or paper pulp reject, respectively). The apparent first order rate constant derived from kinetics modelling increased from 0.18 to 0.63 d À1 during mono-digestion of paper pulp reject and co-digestion of primary sludge with paper pulp reject, which can be attributed to the initial high soluble biodegradable fraction in primary sludge.
Current research and development to lower the production cost of biodiesel by utilizing feedstock... more Current research and development to lower the production cost of biodiesel by utilizing feedstock derived from waste motivates the quest for developing catalysts with high performance in transesterification. This study investigates the performance of citric acid as a catalyst and support catalyst in transesterification of oil from black soldier fly (Hermetia illucens) larvae fed on organic kitchen waste. Two catalysts were prepared by synthesizing citric acid with NaOH and CaO by a co-precipitation and an impregnation method, respectively. The design of the experiment adopted response surface methodology for the optimization of biodiesel productivity by varying: the percentage loading weight of citric acid, the impregnation temperature, the calcinating temperature and the calcinating time. The characteristic activity and reuse of the synthesized catalysts in transesterification reactions were investigated. The morphology, chemical composition and structure of the catalysts were char...
Anaerobic digestion (AD) is one of the best alternative sustainable technologies for energy produ... more Anaerobic digestion (AD) is one of the best alternative sustainable technologies for energy production and recovery from organic solid wastes. Up to now dry AD has been commercialized in the treatment of municipal solid wastes. Little information could be found on the practical application of dry AD to manure wastes or waste activated sludge. This study aimed at testing the feasibility of using alkalinity to manage dry AD system for swine manure treatment and clarify its effect on the stability and efficiency of the newly-developed prototype cylindrical digester system. A prototype cylindrical digester with a diameter of 40 mm and a volume of 1.3 liters was designed and fabricated. It was operated under mesophilic conditions (38°C). The alkalinity of manure was increased by 3000 g/L (R 1) and 6000 g/L (R 2) by adding sodium bicarbonate with the raw swine manure as the control (R 0). Results showed that R 1 and R 2 maintained a relatively higher level of alkalinity during the whole operation compared to the control (R 0). Only one peak appeared in biogas production for the control reactor (R 0) which almost ceased on day 12, whereas R 1 and R 2 exhibited two biogas peaks. The 30 days' biogas yield for R 2 was 276.6 ml/g-VS added while R 1 was 204.8 ml/g-VS added which corresponds to an increase by 2.7-and 1.7-fold respectively as compared to the control (R 0). 2.2-and 4.1-fold increase in methane production was achieved in R 1 and R 2 respectively as compared to R 0. This difference is most probably attributable to the high alkalinity in R 1 and R 2 that stabilized the digestion process and minimized the influence of pH variations on methanogenesis.
The consistent use of household water treatment and storage (HWTS) technologies is necessary for ... more The consistent use of household water treatment and storage (HWTS) technologies is necessary for human health. However, most HWTS options are designed for typical household use as opposed to emergency contexts, where use is less consistent. To investigate ways to improve the consistency of HWTS use in emergencies, we conducted in-person surveys with 108 households in northern Kenya and comparatively analyzed factors that influenced the use of household filters during a protracted drought. Findings showed that about 50% of respondents used their filter consistently over the course of the study. The main limitation to usability was that none of the filters were well-suited for the indoor living environment of the survey respondents. The factors associated with consistency of use varied by filter design. For one-bucket filters, consistent use was associated with ease of assembly, reported availability of spare parts, and peer approval of HWTS use. For two-bucket filters, consistent use was best explained by the certainty regarding when the filter was functioning or not. We suggest that filter manufacturers should reduce the number of parts to mitigate assembly difficulties and should develop flexible filter designs to improve compatibility across households in terms of space and height requirements. Those disseminating filters during protracted emergencies should conduct user training on the assembly and disassembly of unfamiliar filters and ensure affordable access to necessary replacement parts. Finally, to improve consistency of use of new types of filters, implementers should assess the peer approval of these HTWS options among the target population.
Kajiado County is an arid and semi-arid area in Kenya that experiences frequent flash floods. Mos... more Kajiado County is an arid and semi-arid area in Kenya that experiences frequent flash floods. Most of the water evaporates due to the high temperatures experienced in the area. However, to attain reasonable crop yield the soil moisture can be conserved for longer provision to the plants. The objective of this research was to assess the best technique in retaining the soil moisture content of a spate-irrigated sorghum field in Ewaso Nyiro South Drainage Basin. The conservation techniques used were Chloris gayana grass-mulch, ridges and ridge-furrow mulch. The techniques were then compared to the control which was the traditional way of growing sorghum in the area. The experiment was set-up in a Randomized Complete Block Design (RCBD) of three blocks of 10m by 10m. The blocks were further subdivided into four equal plots of 5m by 5m. The effect of the treatments on moisture retention was monitored using YL-69 sensors installed at depths 20 cm and 40 cm respectively for 125 days. At the 20-cm depth, there was no significant difference in terms of moisture retention from the different treatments. However, at the 40cm depth, mulch treatment had the highest moisture retention value of 31.69%. This was closely followed by the combined ridges and mulch, ridges and control which had means of 31.61%, 31.59% and 30.39% respectively. These findings are important as they can be used by agriculturalists, farmers and relevant stakeholders in prioritizing soil moisture conservation techniques for increased crop production.
Journal of engineering in agriculture & the environment, 2020
Growing of Algae for biodiesel production has gained popularity in recent times. This is because ... more Growing of Algae for biodiesel production has gained popularity in recent times. This is because biodiesel from algae has an economic advantage over other oil crops. The oil content that can be extracted from microalgae biomass depends on the culture conditions and microalgae species. This means that besides selecting the best microalgae species, it is also necessary to ensure and maintain the best culture conditions for optimal biodiesel production. Optimum algae growth conditions can be best be provided by a Controlled Environment Bioproduction System (CEBS) for the algae called as photobioreactor (PBR). This paper reports design and fabrication of a PC based control system for a PBR production system for algae being developed at the School of Biosystems and Environmental Engineering (SoBEE) in Jomo Kenyatta University of Agriculture and Technology (JKUAT) in Kenya. The control system is intended to ensure that optimum PH, temperature, nutrients content; light intensity/duration and salinity of growth medium for algae are maintained. The paper covers the design and fabrication of the PC control and monitoring system. The control and monitoring system consists of a computer program and a microcontroller connected to sensors and actuators. The computer program (master) provides the graphical user interface (GUI) consisting of control buttons and means for real time data logging and analysis as well as real-time simulation of PBR activities. It is available in executable file that can be run in any windows OS computer. The microcontroller program (slave) provides the means for connecting sensors and is used to measure as well as monitor the conditions in the PBR tanks. Communication between the computer program and the microcontroller is achieved through the universal serial bus (USB). The control system consists of both open and closed loop systems. The open loop system is used to control the light duration at predetermined intervals of time. The closed loop system is used to control the nutrient concentration, light intensity, PH and oxygen: carbon dioxide ratio.
The exploration of groundwater resources has considerable potential for boosting water supplies i... more The exploration of groundwater resources has considerable potential for boosting water supplies in Kericho County, Kenya. However, it is underused due to limited knowledge caused by lack of adequate research in this field. As a way to fill this gap, this study aimed to characterize hydraulic and hydrogeological parameters controlling groundwater occurrence in the Kericho aquifer in Kericho County, Kenya. To achieve this objective, the study utilized a combination of geophysical and pumping test data. Consequently, fifty Vertical Electric Soundings (VES) were carried out to determine the aquifer properties of the study area. Further, seven out of fifty surveyed sites were drilled to depths ranging between 30m and 230m, and test pumping was done for 24 hours. Geophysical results show that the average hydraulic conductivity in the study area varies from 1.96 m day-1 to 6.2 m day-1 . The transmissivity ranged from 35.83 m2 day-1 to 5166.4 m2 day-1 , while the yield ranged between 0...
African Journal of Science, Technology and Social Sciences
Solid waste management is a cross-cutting issue impacting many aspects of the environment, societ... more Solid waste management is a cross-cutting issue impacting many aspects of the environment, society and economic development. Cities of low- and middle-income countries are currently facing severe challenges in management of the increasing amount of solid waste produced, particularly the organic waste fraction. This review presents information in literature about the utilization of Black soldier fly (BSF) in managing organic waste. It summarizes the approaches in organic waste management, use of BSF in organic waste management, life cycle and growth conditions of BSF and the benefits of utilizing BSF for resource recovery. Organic waste treatment using BSF is an emerging waste management technology with minimal global warming potential. The BSF larvae helps in carbon sequestration and is a protein source which can help alleviate the raising global demand for animal feed. The BSF larval model provides for nutrient recycling, waste reduction and value addition significantly contributin...
In biodegradable waste management, use of Black Soldier Fly Larvae (BSFL) is a promising method f... more In biodegradable waste management, use of Black Soldier Fly Larvae (BSFL) is a promising method for bioconversion of waste into crude insect fat as feedstock for biodiesel production. Biodiesel is a renewable alternative to fossil fuel, but it is more susceptible to oxidative degradation over long-term storage. This study investigates the effectiveness of NaOH and CaO catalysts synthesized with citric acid (CA) in improving the oxidative stability of biodiesel. The biodiesel and biodiesel/diesel blends derived from BSFL were stored at 63 °C for 8 days. The quality of biodiesel was determined by analysis of the physicochemical and fuel properties by: Fourier transform infrared (FTIR) spectroscopy, ultraviolet visible spectrophotometer (UV-Vis), gas chromatography-mass spectroscopy (GC-MS), bomb calorimeter and titration methods. Properties that were analyzed included: peroxide value, acid value, iodine value, refractive index, density, calorific value, total oxidation (TOTOX), anisid...
Expeditious situational analysis of the enabling regulatory environment (ERE) of faecal sludge ma... more Expeditious situational analysis of the enabling regulatory environment (ERE) of faecal sludge management (FSM) is vital for strengthening sanitation systems. However, existing diagnostic tools employ broad indicators, neglecting the detailed assessment of the policy, legal and institutional frameworks for each step along the FSM chain. This paper presents a web-based integrated diagnostic tool for evaluating the quality and adequacy of policy in guiding equity, targeting of resources, quality of service, financial considerations and institutional roles and responsibilities. The tool evaluates the legal framework based on laws, standards and regulations emphasizing on means of enforcement. It evaluates the institutional framework based on investors, service providers, regulators and consumers as guided by the literature. Each indicator is assigned a score of 1: green (effective), 0.5: yellow (limited) and 0: red (poor) for the user interface, containment, emptying, transport, treatm...
This is a self-archived version of an original article. This version may differ from the original... more This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details.
International Biodeterioration & Biodegradation, 2017
Anaerobic mono-digestion and co-digestion of primary sludge and two organic wastes (namely food w... more Anaerobic mono-digestion and co-digestion of primary sludge and two organic wastes (namely food waste or paper pulp reject) were evaluated by biomethane potential assessment and kinetics modelling to elucidate the synergistic effect. The specific methane yields were 159, 652 and 157 mL/g VS added during mono-digestion of primary sludge, food waste and paper pulp reject, respectively. Co-digestion of primary sludge with either food waste or paper pulp reject resulted in much higher specific methane yields of 799 and 368 mL/g VS, respectively. pH and intermediate inhibitions (e.g. volatile fatty acids and ammonium-N) were not observed. The synergistic effect was also confirmed by examining the VS and COD removals. COD balance also identified and validated the enhanced specific methane yields from both primary sludge and organic waste (i.e. additional 32 and 19% of COD was converted to biogas during codigestion of primary sludge with food waste or paper pulp reject, respectively). The apparent first order rate constant derived from kinetics modelling increased from 0.18 to 0.63 d À1 during mono-digestion of paper pulp reject and co-digestion of primary sludge with paper pulp reject, which can be attributed to the initial high soluble biodegradable fraction in primary sludge.
Current research and development to lower the production cost of biodiesel by utilizing feedstock... more Current research and development to lower the production cost of biodiesel by utilizing feedstock derived from waste motivates the quest for developing catalysts with high performance in transesterification. This study investigates the performance of citric acid as a catalyst and support catalyst in transesterification of oil from black soldier fly (Hermetia illucens) larvae fed on organic kitchen waste. Two catalysts were prepared by synthesizing citric acid with NaOH and CaO by a co-precipitation and an impregnation method, respectively. The design of the experiment adopted response surface methodology for the optimization of biodiesel productivity by varying: the percentage loading weight of citric acid, the impregnation temperature, the calcinating temperature and the calcinating time. The characteristic activity and reuse of the synthesized catalysts in transesterification reactions were investigated. The morphology, chemical composition and structure of the catalysts were char...
Anaerobic digestion (AD) is one of the best alternative sustainable technologies for energy produ... more Anaerobic digestion (AD) is one of the best alternative sustainable technologies for energy production and recovery from organic solid wastes. Up to now dry AD has been commercialized in the treatment of municipal solid wastes. Little information could be found on the practical application of dry AD to manure wastes or waste activated sludge. This study aimed at testing the feasibility of using alkalinity to manage dry AD system for swine manure treatment and clarify its effect on the stability and efficiency of the newly-developed prototype cylindrical digester system. A prototype cylindrical digester with a diameter of 40 mm and a volume of 1.3 liters was designed and fabricated. It was operated under mesophilic conditions (38°C). The alkalinity of manure was increased by 3000 g/L (R 1) and 6000 g/L (R 2) by adding sodium bicarbonate with the raw swine manure as the control (R 0). Results showed that R 1 and R 2 maintained a relatively higher level of alkalinity during the whole operation compared to the control (R 0). Only one peak appeared in biogas production for the control reactor (R 0) which almost ceased on day 12, whereas R 1 and R 2 exhibited two biogas peaks. The 30 days' biogas yield for R 2 was 276.6 ml/g-VS added while R 1 was 204.8 ml/g-VS added which corresponds to an increase by 2.7-and 1.7-fold respectively as compared to the control (R 0). 2.2-and 4.1-fold increase in methane production was achieved in R 1 and R 2 respectively as compared to R 0. This difference is most probably attributable to the high alkalinity in R 1 and R 2 that stabilized the digestion process and minimized the influence of pH variations on methanogenesis.
The consistent use of household water treatment and storage (HWTS) technologies is necessary for ... more The consistent use of household water treatment and storage (HWTS) technologies is necessary for human health. However, most HWTS options are designed for typical household use as opposed to emergency contexts, where use is less consistent. To investigate ways to improve the consistency of HWTS use in emergencies, we conducted in-person surveys with 108 households in northern Kenya and comparatively analyzed factors that influenced the use of household filters during a protracted drought. Findings showed that about 50% of respondents used their filter consistently over the course of the study. The main limitation to usability was that none of the filters were well-suited for the indoor living environment of the survey respondents. The factors associated with consistency of use varied by filter design. For one-bucket filters, consistent use was associated with ease of assembly, reported availability of spare parts, and peer approval of HWTS use. For two-bucket filters, consistent use was best explained by the certainty regarding when the filter was functioning or not. We suggest that filter manufacturers should reduce the number of parts to mitigate assembly difficulties and should develop flexible filter designs to improve compatibility across households in terms of space and height requirements. Those disseminating filters during protracted emergencies should conduct user training on the assembly and disassembly of unfamiliar filters and ensure affordable access to necessary replacement parts. Finally, to improve consistency of use of new types of filters, implementers should assess the peer approval of these HTWS options among the target population.
Kajiado County is an arid and semi-arid area in Kenya that experiences frequent flash floods. Mos... more Kajiado County is an arid and semi-arid area in Kenya that experiences frequent flash floods. Most of the water evaporates due to the high temperatures experienced in the area. However, to attain reasonable crop yield the soil moisture can be conserved for longer provision to the plants. The objective of this research was to assess the best technique in retaining the soil moisture content of a spate-irrigated sorghum field in Ewaso Nyiro South Drainage Basin. The conservation techniques used were Chloris gayana grass-mulch, ridges and ridge-furrow mulch. The techniques were then compared to the control which was the traditional way of growing sorghum in the area. The experiment was set-up in a Randomized Complete Block Design (RCBD) of three blocks of 10m by 10m. The blocks were further subdivided into four equal plots of 5m by 5m. The effect of the treatments on moisture retention was monitored using YL-69 sensors installed at depths 20 cm and 40 cm respectively for 125 days. At the 20-cm depth, there was no significant difference in terms of moisture retention from the different treatments. However, at the 40cm depth, mulch treatment had the highest moisture retention value of 31.69%. This was closely followed by the combined ridges and mulch, ridges and control which had means of 31.61%, 31.59% and 30.39% respectively. These findings are important as they can be used by agriculturalists, farmers and relevant stakeholders in prioritizing soil moisture conservation techniques for increased crop production.
Journal of engineering in agriculture & the environment, 2020
Growing of Algae for biodiesel production has gained popularity in recent times. This is because ... more Growing of Algae for biodiesel production has gained popularity in recent times. This is because biodiesel from algae has an economic advantage over other oil crops. The oil content that can be extracted from microalgae biomass depends on the culture conditions and microalgae species. This means that besides selecting the best microalgae species, it is also necessary to ensure and maintain the best culture conditions for optimal biodiesel production. Optimum algae growth conditions can be best be provided by a Controlled Environment Bioproduction System (CEBS) for the algae called as photobioreactor (PBR). This paper reports design and fabrication of a PC based control system for a PBR production system for algae being developed at the School of Biosystems and Environmental Engineering (SoBEE) in Jomo Kenyatta University of Agriculture and Technology (JKUAT) in Kenya. The control system is intended to ensure that optimum PH, temperature, nutrients content; light intensity/duration and salinity of growth medium for algae are maintained. The paper covers the design and fabrication of the PC control and monitoring system. The control and monitoring system consists of a computer program and a microcontroller connected to sensors and actuators. The computer program (master) provides the graphical user interface (GUI) consisting of control buttons and means for real time data logging and analysis as well as real-time simulation of PBR activities. It is available in executable file that can be run in any windows OS computer. The microcontroller program (slave) provides the means for connecting sensors and is used to measure as well as monitor the conditions in the PBR tanks. Communication between the computer program and the microcontroller is achieved through the universal serial bus (USB). The control system consists of both open and closed loop systems. The open loop system is used to control the light duration at predetermined intervals of time. The closed loop system is used to control the nutrient concentration, light intensity, PH and oxygen: carbon dioxide ratio.
The exploration of groundwater resources has considerable potential for boosting water supplies i... more The exploration of groundwater resources has considerable potential for boosting water supplies in Kericho County, Kenya. However, it is underused due to limited knowledge caused by lack of adequate research in this field. As a way to fill this gap, this study aimed to characterize hydraulic and hydrogeological parameters controlling groundwater occurrence in the Kericho aquifer in Kericho County, Kenya. To achieve this objective, the study utilized a combination of geophysical and pumping test data. Consequently, fifty Vertical Electric Soundings (VES) were carried out to determine the aquifer properties of the study area. Further, seven out of fifty surveyed sites were drilled to depths ranging between 30m and 230m, and test pumping was done for 24 hours. Geophysical results show that the average hydraulic conductivity in the study area varies from 1.96 m day-1 to 6.2 m day-1 . The transmissivity ranged from 35.83 m2 day-1 to 5166.4 m2 day-1 , while the yield ranged between 0...
African Journal of Science, Technology and Social Sciences
Solid waste management is a cross-cutting issue impacting many aspects of the environment, societ... more Solid waste management is a cross-cutting issue impacting many aspects of the environment, society and economic development. Cities of low- and middle-income countries are currently facing severe challenges in management of the increasing amount of solid waste produced, particularly the organic waste fraction. This review presents information in literature about the utilization of Black soldier fly (BSF) in managing organic waste. It summarizes the approaches in organic waste management, use of BSF in organic waste management, life cycle and growth conditions of BSF and the benefits of utilizing BSF for resource recovery. Organic waste treatment using BSF is an emerging waste management technology with minimal global warming potential. The BSF larvae helps in carbon sequestration and is a protein source which can help alleviate the raising global demand for animal feed. The BSF larval model provides for nutrient recycling, waste reduction and value addition significantly contributin...
In biodegradable waste management, use of Black Soldier Fly Larvae (BSFL) is a promising method f... more In biodegradable waste management, use of Black Soldier Fly Larvae (BSFL) is a promising method for bioconversion of waste into crude insect fat as feedstock for biodiesel production. Biodiesel is a renewable alternative to fossil fuel, but it is more susceptible to oxidative degradation over long-term storage. This study investigates the effectiveness of NaOH and CaO catalysts synthesized with citric acid (CA) in improving the oxidative stability of biodiesel. The biodiesel and biodiesel/diesel blends derived from BSFL were stored at 63 °C for 8 days. The quality of biodiesel was determined by analysis of the physicochemical and fuel properties by: Fourier transform infrared (FTIR) spectroscopy, ultraviolet visible spectrophotometer (UV-Vis), gas chromatography-mass spectroscopy (GC-MS), bomb calorimeter and titration methods. Properties that were analyzed included: peroxide value, acid value, iodine value, refractive index, density, calorific value, total oxidation (TOTOX), anisid...
Expeditious situational analysis of the enabling regulatory environment (ERE) of faecal sludge ma... more Expeditious situational analysis of the enabling regulatory environment (ERE) of faecal sludge management (FSM) is vital for strengthening sanitation systems. However, existing diagnostic tools employ broad indicators, neglecting the detailed assessment of the policy, legal and institutional frameworks for each step along the FSM chain. This paper presents a web-based integrated diagnostic tool for evaluating the quality and adequacy of policy in guiding equity, targeting of resources, quality of service, financial considerations and institutional roles and responsibilities. The tool evaluates the legal framework based on laws, standards and regulations emphasizing on means of enforcement. It evaluates the institutional framework based on investors, service providers, regulators and consumers as guided by the literature. Each indicator is assigned a score of 1: green (effective), 0.5: yellow (limited) and 0: red (poor) for the user interface, containment, emptying, transport, treatm...
This is a self-archived version of an original article. This version may differ from the original... more This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details.
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