Post Graduate Profiles

Waste management and energy supply are among the most persistent setbacks facing the world today. Anaerobic breakdown of plant and animal waste has both the advantages of managing garbage and also addresses the energy shortage in developing countries. The cost of energy (electricity, firewood and liquefied petroleum gas) in Kenya is high and there is a need to come up with renewable and sustainable energy. This work focuses on the production of biogas and electricity from vegetable market waste as a substrate using rumen fluid and cow dung as inoculum at optimized psychrophilic, mesophilic and thermophilic conditions. The market wastes were analyzed for proximate and ultimate composition using standard techniques. The elemental composition was done to determine pesticide residues, macro and micronutrients and heavy metals. Bacterial studies of the inoculum involved microbial counts, isolation and culturing in anaerobic conditions. Influence of acidic and alkaine waste pretreatments, pH, temperature, C: N ratio, inoculum to substrate ratio and proximate properties was also investigated. Biogas composition analysis was done using Biogas analyzer GP180 from Henan, China. Bio-methane potential and kinetic studies of substrate conversion to biogas were done by fitting data to different mathematical models. Biogas upgrade was studied using zeolite rocks, desulphurizer,
maize cobs, steel wire and worn out tyres cartridges. A portable digester was fabricated which incorporated agitation, pH monitoring and temperature regulation mechanism. Biogas leakage and safety usage were set using Arduino based microcontrollers. Pilot-scale biogas production was set up using 5 – 350l capacity digesters. A 1450l Ferro-cement and a 14000l bricks digesters were
constructed. Bio-slurry was employed in vegetable and maize farming. Finally, waste conversion to
electricity was studied using microbial fuel cell technology at optimized conditions.

The results obtained in this research works show that fruits and vegetable wastage in Wakulima and Kangemi markets are high resulting in the accumulation of landfills. The wastage levels depend on seasons and products properties. The wastes contain high levels of proximate properties like carbohydrates, fat and proteins. Heavy metals were reported at 15.20±2.70ppm lead.The microbial counts in cow dung and rumen fluid were 3.15±0.01 * 10 10 cfu/ml and 1.50 ±0.02* 10 10 cfu/ml respectively. The volatile solids were found to be 81.69±1.52 and 73.50±2.20% of the total solids while the C: N ratio was 29.62±0.51 and 17.06±0.50 in rumen fluid and cow dung respectively. Biogas production at mesophilic conditions was highest in waste mixtures inoculated with rumen fluid at 3500ml and lowest in cucumber wastes at 400ml for 500ml reactors. Thermophilic biogas production was highest in waste mixtures at 4700ml for the same reactor capacity. The general trend was a reduction in retention time for waste degradation at thermophilic conditions compared to psychrophilic and mesophilic temperatures. The thermochemical pretreatment results in more cumulative biogas production at 6200ml, followed by thermal at 4900ml and then chemical pretreatments at 3750ml for 500g mixed fruits and vegetable market wastes for 500ml -1500ml digester capacity. Alkaline pretreatment is more efficient compared to acidic hydrolysis though highly influenced by proximate properties of the wastes and operation pH. The pilot scale (10l) pretreatment resulted in 34500ml and 31400ml cumulative biogas from HCl and NaOH pretreatment.

The optimal pH observed in this study was 6.70 – 7.23. Biogas production was highly dependent on proximate properties like moisture, carbohydrates, fat and protein levels. The best working range for C:N ratio was 19 – 30, with higher levels significantly reducing biogas production. The biochemical methane potential studies revealed that generated biogas was 1000 to 3500ml with
CH 4 levels of 56 – 60%. The measured level of raw biogas was 227ppm H 2 S, >20% CO 2 and 52-56% CH 4 . The most efficient upgrade material was zeolite rocks with upgrade levels of 89 – 93% methane.

The total removal for zeolite was observed to be 75% for CO 2 and 95.34% for H 2 S.
Re-engineered digesters were fabricated and biogas yields studied from the pilot scale studies. The data obtained indicated that the cumulative biogas produced from the 120l automated digester is 26400ml, while the un-agitated digester is 4700ml. Temperature and pH regulation was observed to influence biogas production with the aggregate production being 11800ml and 15300ml for pH and temperature regulated 120l digesters, respectively. Agitation increases biogas production six-fold in comparison to the un-agitated digester.

A portable biogas safety device was designed and developed using Arduino micro-controller. The
device alerts the user in the event of excess smoke or fire breakout via a call or SMS using the SIM900 GSM module.
Microbial fuel cell technology was employed in direct conversion of market wastes to electricity. The results obtained from the MFC indicated that voltage recovered increased with time. On average, avocado and watermelon produced 0.357V and 0.009V, respectively. The power density generated was 0.060856 to 22.53043μW/MW/M 2, while the current density was 0.751315 to 63.11044 mA/m 2 . ClostridiumSpp., Proteus and rumen fluid generated 0.622V, 0.465V and 0.759V, respectively. The results obtained from bioremediation of pesticide residues in market wastes show that on day 9 of degradation, the highest voltage readings were recorded, ranging from 0.463 to 0.537V at 0.002 to 0.076 mA current range. The data obtained from varying MFC operating parameters indicates that 6.6668 * 10 -3 m 2 electrode S/A produced 0.00399m 2 and 0.01331m 2 voltage and power, respectively. Tomato wastes generated 0.385V, 0.038mA and 0.01463Mw, voltage, current and power, respectively across 45KΩ resistor.

Keywords: Arduino, Biogas, Bio-methane, Market wastes, Microbial fuel cells.

Correlation functions of certain types of quantum fields are solutions to integrable partial differential equations. This is useful in two ways: in evaluating correlation functions, and in describing solutions to integrable PDEs. Simple cases of this relation are known since a long time, but the understanding is still largely incomplete. This project is for learning about this relation and the techniques of integrable QFT involved, and exploring new avenues to further the understanding.

Maize is an essential staple food crop in Kenya, including Narok County, whose productivity is often constrained by marked variability in the biophysical and socio-economic factors within the production environment. Climate variability and change threaten the sustainability of smallholder agricultural systems and food security in the county. Thus, strategies that can deliver enhanced and sustainable maize yields and food security are of urgent priority to Kenya and Narok County in particular.

This study therefore, aimed to assess the impacts of climate variability and change on maize productivity in Narok county of Kenya. The study used observed daily rainfall, maximum and minimum temperature data for eleven stations in Narok County for the period 1981-2018 from Kenya Meteorological department, annual maize yield data in MT/ha from the Ministry of Agriculture, Livestock and Fisheries Development and CNRM model outputs. Intra-seasonal climate characteristics of onset and cessation dates, number of rainy days, wet spell length, dry spell length, length of the growing season, seasonal total rainfall, maximum temperature, minimum temperature, temperature range and Growing Degree Days (GDD) were analyzed. The double mass curve was used to test for data homogeneity. Time series analysis was employed to determine temporal distribution of the data sets. The Instat Plus statistical package Version 3.36 was used to determine rainfall characteristics at station level. Pearson’s correlation analysis was used to determine the relationship among the study variables. The combined effect of intra-seasonal climate characteristics on maize yields was assessed using the multivariate linear regression analysis.

Rainfall onset dates for most stations indicated an increasing trend, implying late onset of rains in recent years. The cessation dates for the rainy season depicted a decreasing trend hence early rainfall cessation in most of the study stations. The length of growing season indicated a decreasing trend, implying shorter/ reduced length of the growing season. The season total rainfall for MAM season decreased over most stations. Dry spell length increased over the study period. On the contrary, the season wet spell length indicated decreasing trend, signifying shorter lengths of wet spell over the study area. The number of rainy days during MAM season indicated a decreasing trend, implying reduced rainy days within the season. GDD, temperature range, maximum and minimum temperatures indicated an increasing trend over the study period 1981-2018 for all the study stations.

The results further revealed increased climate variability under future climate (2021-2050) based on both RCP4.5 and RCP8.5 emission scenarios; with more increased climate variability based on RCP8.5 compared to RCP4.5. Both emission scenarios project increased temperature and rainfall during the period 2021-2050. Climate change will severely impact maize yields under RCP8.5 as compared to RCP4.5. By the year 2050, maize yields are projected to decline by 2.5% based on RCP4.5 and 10.3% based on RCP8.5 emission scenarios. Hence, effective adaptation strategies to climate variability and change impacts will be key in ensuring sustainable and increased maize productivity and food security in Narok County and Kenya as a whole.

Project Summary

There has been a drastic plastics pollution in the environment and it is a growing problem globally. In previous studies, plastic pollution in the aquatic environment (marine and freshwater) has been well documented. Due to their unique characteristic, that is light weight, plastics are easily transported by water and wind to the freshwater bodies. When exposed in different environmental conditions, these plastics break down to microplastics. Microplastics are nano-size in nature and due to their physical characteristics and chemical compositions, they absorb a cocktail of contaminants such as organochlorine pesticides, organic pollutants, herbicides and other hazardous chemicals which pose higher environmental risks and potential risk to human health.

In some cases, bottled water is basically tap water from aquatic sources. Microplastics have conclusively been identified in bottled water and in samples collected at drinking water treatment plants in several countries such as China and Mexico. In Kenya as at now, there are no maximum allowable microplastic concentration guidelines yet. It means microplastic contamination may be prevalent in drinking water given that the current water treatment processes and water regulating programs do not take this into account.

Therefore, in this project, water samples from different water bottling companies will be collected randomly and oxidized using 30% H2O2. The component will be filtered through a Whatman filter paper, dried at room temperature for 24hrs and later examined under a dissecting microscope. Fourier Transform Infrared Spectrometer will be used for identification and chemical characterization of the particles. Concentration will be determined by the use of the One-Way ANOVA.

The result of this study will identify the abundance and distribution of microplastics in bottled drinking water products and as a consequence, to formulate priorities for water safety.