A new variant of stirring mechanism for agitating contents of an anaerobic digester that makes
use of vertical and horizontal directed jets of liquid reactor content being re-circulated by and
electric pump, is reported. In order to demonstrate its working, a thermophilic pilot scale reactor
using waste water is described and various parameters analysed. As a sample run, raw
(untreated) waste water from the treatment works in Nairobi was used as the nutrient source,
while sludge from an anaerobic pond in the same treatment works was used as source of bacteria.
Measurement of various parameters like organic loading rate and characteristics of feed
wastewater (BOD, COD, pH, TS), biogas production rate in thermophilic anaerobic digester,
maximum gas yield and biogas quality were undertaken. The reactor was fed at a controlled
organic loading rate of 0.5 L/min. The reactor contained substrate to inoculums in the ratio 3:1
with the temperature was controlled using a thermostated heating coil. Digestion was carried out
in a pilot scale digester (with a capacity of 210 litres) under thermophilic (at 55 0C) anaerobic
conditions for a period of 15 days. The final average yield of biogas was 1.225 x 10-2 m3.
Average percentage composition of biogas produced by thermophilic digester was 66.6 vol. %
CH4, 30.4 vol. % CO2.
Extensive work has been done on Anaerobic digestion of single substrates and using codigestion.
In a number of cultures around the world, the wastes that are discarded as
household waste may not easily fit in the biogas models that have been developed so far. It is
therefore necessary to analyse the biogas produced from food mixtures found in unique
settings and compare them with literature values of individual substrates. In the current study,
food mixture found at waste bin at a cafeteria used by StudentsofUniversity of Nairobiwas
analysed. The purposes of this study were to investigate adjusted modes of substrate pretreatment
(Mechanical, thermal and thermo-chemical) and their role in maximizing the
process of anaerobic digestion through speeding up hydrolysis. The experiments were carried
out on waste samples consisting of carbohydrate food waste (ugali+Rice),potato peels, banana
peels and a mixture of the substrates mixed with rumen slurry in the ratio 3:1 under controlled
mesophilic anaerobic conditionsin the lab scale digester. Thermo-chemical pre-treatment was
the most effective for speeding up hydrolysis with the co digested substrates producing
maximum biogas. The desired C:N ratio of 31 was obtained when all the four substrates were
combined. Similarly, the biogas produced from the mixture of the four substrates was higher
than from any of the substrates.
Microalgae has had a number of applications. This study explores the formation of biodiesel from lipids and
formation of charred biomass fuel from the algae species found at Ruai Wastewater facility at Ruai, Nairobi. The resulting biomass after solvent extraction was carbonized and the gross calorific value determined using a constant volume bomb calorimeter. The bio-oil obtained from the algae was transesterified and the calorific value determined. In one of the cases, carbon dioxide was bubbled through fresh algae from the waste water facility and the biodiesel from this sample which was later sun-dried, crushed, then subjected to solvent extraction and subsequent transesterification had the highest calorific value of 27,620 KJ/g compared to 22,758KJ/g in algae sample which was not subjected to such a treatment. In the case of the charred biomass fuel, the gross calorific value was found to be approx 23,132 KJ/g which makes it a medium calorific value fuel. GC-MS analysis was performed on one of the transesterification samples and methyl esters of the isolated fatty acids were identified as methyl esters of polyunsaturated fatty acid α-linolenic acid (18:3, n-3; ALA), Hexadecanoic acid and cis-9-hexadecenoic acid. In addition an alkane heptadecane was also isolated. This study shows that algae, which is present in many water systems in Kenya can be used as a valuable source of fatty acids that are taken in diet by animals and humans thus building a healthy nation.
Blue colored essential oil samples were obtained from chamomile flowers by a Solvent Extraction Clevenger Distillation (SECD) method and by the standard Clevenger distillation of Chamomile flowers. The solvents used were hexane, acetone, dichloromethane (DCM), ethyl acetate and methanol. The solvents were evaluated in terms of the yield of extract, and the quality of extract (determined by Gas Chromatography-Mass Spectrometry). Of all the SECD extracts, the DCM extract gave the highest yield of the essential oil while the hexane extract gave the lowest yield of the blue essential oil
Anaerobic digestion was conducted at mesophilic (37oC) and thermophilic (55oC) conditions using sewage
wastewaters as the substrate and sludge and/or rumen fluid as the inoculum, with a view to optimize biogas
production. The substrate and inoculum were mixed in the ratios 1:1, 1:3, and 3:1 (volume by weight (where
sludge was used) or volume by volume (where rumen fluid was used).At mesophilic conditions for both
inocula, the 3:1 substrate/inoculum mixture produced the most biogas in a 24 hour period, with the rumen
mixture producing the highest yield (20 ml). At thermophilic conditions the 3:1 wastewater/sludge mixture
had the highest biogas yield (58 ml), whereas when rumen fluid was used as inoculum, the 1:3 mixture
produced the most biogas (66 ml). The thermophilic experiments using rumen as the inoculum were
repeated for a 10 day period and the 3:1 mixture achieved the maximum yield (140 ml) faster than the other
two (1:1 and 1:3 mixtures) indicating that the 3:1 substrate/inoculum ratio is the best.
Chalcones, flavanones and other flavonoids have been shown to have varied anti-plasmodium activity. In this work, chalcones were synthesized from corresponding flavanones extracted from Senecio roseiflorus, Erythina abysinica and Polygonum senegalense, using conventional organic reagents and green chemistry approach.Dihydrochalcones were converted to homoisoflavones using the Kostanecki reaction. Characterization and bioassay on the synthetic derivatives was also undertaken.
Ground chamomile flowers were mixed with distilled acetone in a large conical flask, kept under varying period of days without agitation/shaking, yielded an organic extract, which when concentrated, mixed with water and Clevenger distilled produced the blue essential oil. Thin layer chromatography, Nuclear Magnetic Resonance spectra and Gas Chromatography analysis of the oil obtained from the direct Clevenger distillation of chamomile flowers and that from the Solvent Extraction-Clevenger Distillation (SECD) revealed similar components of essential oil extracted, though in varying proportions. The SECD method offers a cheaper method of producing chamomile essential oil on large scale without the use of expensive high-pressure steam systems currently being used for the extraction of the essential oil on industrial scale. The yield of the essential oil produced on a 400 g scale of flowers after eight days of contact between solvent and flowers (extraction) is comparable with that of Clevenger distillation on a laboratory scale (1.1% yield).
The waste chamomile flowers from solvent extraction of fresh chamomile flowers. were compacted into cylindrical shapes with and without added binder (Calcium Sulphate), then carbonised using an electric oven to avoid contamination. The gross fuel content of the carbonised biomass fuel determined using a constant volume bomb calorimeter was found to be 29,379 KJ kg-1, while the Net Calorific value was calculated as 26,661 KJ Kg-1.
Ground Flowers of Matricaria Recutita (German Chamomile) Banat Variety grown in Kenya, were subjected to Clevenger distillation under varying temperature, distillation, pressure conditions and the yields assessed. An inert solvent being present in the collecting column of the Clevenger apparatus increases the yield of the oil by reducing dispersion of the blue oil; its presence however, in the distillation flask inhibits the production of the essential oil. Distillation under reduced pressure leads to a decrease in the yield of the oil produced. A break in distillation time especially during the first three hours of distillation also leads to a decrease in the yield of the oil produced.
Reduction of ethyl 3-methyl-, 3-isopropyl- and 3-n-pentyl-3-[dimethyl(phenyl)silyl]propanoates with DIBAL to the aldehydes, enol trifluoromethanesulfonate (triflate) formation using trifluoromethanesulfonic (triflic) anhydride and 2,6-di-tert-butylpyridine, and elimination using LDA, gives the propargyl silanes . The esters could also be prepared enantiomerically enriched, and the final products are the enantiomerically enriched propargyl (homochiral) silanes.