Makori Benard Onsase

Makori Benard Onsase

Project Title: Integrable Dufferential equations from Quantum Field theory

Project/ Thesis Abstract

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.

Master of Science in Physics Student.

He is an accomplished theorical Physicist and who enjoy using his expertise and experience in teaching and research. He is a graduate student at the University of Nairobi.