Land and water degradation caused by soil erosion and climate change pose major environmental threats, particularly in agricultural watersheds. Soil erosion in a catchment leads to low crop yields due to declining soil quality (SQ), productivity and sustainability. However, very few studies have been done to assess soil health in Kenya, and none in Narok County. Thus, the aim of this study was to evaluate the soil sustainability status in Kakia-Esamburmbur catchment, based on the identification of key indicators (IKI) from a large dataset (LDS) of 23 indicators, across three land use types designated as grass land (GL), crop land (CL) and forest land (FL). To achieve the stated objective, two soil quality indexing methods were employed: the Additive Soil Quality Index (A-SQI) using the LDS; and the Weighted Soil Quality Index (W-SQI) using Principal Component Analysis (PCA) as a reduction tool to obtain the IKI set. The results show that at a depth of 20 cm, the catchment's soils characteristics did not differ significantly. The two methods (A-SQI and W-SQI) resulted in FL having the highest SQI mean values (0.61, 0.57), followed by CL (0.59, 0.55), while the lowest SQI mean value was recorded in GL (0.58, 0.53). Additionally, the sensitivity analysis showed W-SQI as the most sensitive and superior method in the evaluation of SQI changes due to its high sensitivity and coefficient of variation (CV), at 2.25 and >12 %, respectively. Among the ten IKI, CEC made the greatest contribution to SQ (18.68 %), followed by BD (15.61 %), BIR (14.71 %), Mg (14.26 %), MBN (8.30 %), MBC (8.26 %), Sand (6.77 %), Moisture (5.75 %), TOC (5.16 %), and PMN (2.63 %). The findings show that the catchment belongs to the "medium" category of SQ. The IKI can help save time and reduce the cost of intensive lab works for temporal assessment and monitoring of the effects of different land use on SQ.

The inefficient water use, and variable and low productivity in Kenyan public irrigation schemes is a major concern. It is, therefore, necessary to periodically monitor and evaluate the performance of public irrigation schemes. This prompted evaluation of performance of three rice growing irrigation schemes in western Kenya using benchmarking and principal component analysis. The aim of the study was to quantify and rank the performance of selected irrigation schemes. The performance of the irrigation schemes was evaluated for the period from 2012 to 2016 using eleven performance indicators under agricultural productivity, water supply and financial performance categories. The performance indicators were weighted using principal component analysis and combined to form a single performance score using linear aggregation method. The average performance in the Ahero, West Kano and Bunyala irrigation schemes was 48%, 49% and 56%, respectively. Based on performance score, the Bunyala irrigation scheme is the highest performing rice irrigation scheme in western Kenya. The three irrigation schemes have an average performance. Operation and management measures to improve the current performance of the irrigation schemes are needed.

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), anisidine value and fatty acid profile. The results showed that catalysts synthesized with CA retarded the decomposition of unsaturated fatty acids, resulting in a significant delay in the formation of hydroperoxides. Besides, 10-oxo-octadecanoic acid, an antioxidant, was present in biodiesel produced using catalysts synthesized with CA, hence enhancing the stability of biodiesel against oxidation. Catalysts synthesized with CA slowed the decomposition of monounsaturated fatty acids by 6.11–11.25%. Overall, biodiesel produced using catalysts synthesized with CA was observed to degrade at a slower rate than biodiesel produced using commercial calcium oxide. The reduced degradation rates demonstrate the effectiveness of the synthesized catalysts in enhancing the oxidation stability and consequently the fuel qualities of biodiesel from BSFL under accelerated storage.

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 characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray fluorescence (XRF) and X-ray diffraction (XRD). High citric acid loading on NaOH and a small amount of citric acid on CaO resulted in improved dispersion and refinement of the particle sizes. Increasing citric acid loading on NaOH improved the CaO and SiO₂ composition of the modified catalyst resulting in higher biodiesel yield compared to the modified CaO catalyst. A maximum biodiesel yield of 93.08%, ±1.31, was obtained when NaOH was synthesized with a 130% weight of citric acid at 80 °C and calcinated at 600 °C for 240 min. Comparatively, a maximum biodiesel yield of 90.35%, ±1.99, was obtained when CaO was synthesized with a 3% weight of citric acid, impregnated at 140 °C and calcinated at 900 °C for 240 min. The two modified catalysts could be recycled four times while maintaining a biodiesel yield of more than 70%.

Urbanization has caused limitations on water resources, while climate change has reduced amounts of surface water in some parts of the world. Kikuyu, a suburban area in Kiambu county, Kenya, is facing this challenge. The major challenge in the study is scarcity of potable water, resulting in inadequate water supply to Kikuyu residents. Currently, only 63.6% of the population is being supplied with water by Kikuyu Water Company, the company mandated to supply water to the area. Water demand was 2972 m³/day in 2015 and was projected to be 3834 m³/day by 2025. This has put pressure on the already exploited clean water resources, making it necessary to seek additional sources of domestic water. Storage capacity and water quality of surface water bodies, especially small reservoirs whose water can be used to ease the demand, need to be assessed for supplemental water supply. This study aimed at assessing the suitability of the abandoned quarry reservoir as a source of potable urban water by determining its storage capacity characteristics and water quality status. Volume characteristics were determined using bathymetry survey in January 2019. Water samples were collected in January and August 2019 and analyzed for chemical, physical, and bacteriological quality, as per the American Public Health Association (APHA) standard methods for water and wastewater. Parameters were evaluated based on World Health Organization (WHO) and Kenya Bureau of Standards (KEBS) guidelines for drinking water, and rated based on the drinking water quality index (WQI). The reservoir’s maximum storage capacity was found to be 128,385 m³, the surface area was 17,699 m², and the maximum depth was 15.11 m. Nineteen of the twenty-five investigated parameters were within the acceptable standards. However, the concentrations of manganese (Mn), cadmium (Cd), iron (Fe), turbidity, total coliforms, and Escherichia coli (E. coli) were above the acceptable limits. Manganese and iron levels increased with depth. The overall WQI of the reservoir was 82.51 and 85.85 in January and August, respectively. Therefore, based on WQI rating, the water scored a good quality rating and could be used for domestic supply upon treatment. The original achievement of this study is establishment of the volume of the water in the quarry as an additional source of water to the nearby community, along with water quality status.

The study assessed the impact of land-use types on the groundwater quality of the mid River Njoro catchment, Kenya. Groundwater samples were collected from eight boreholes between the period of October 2017 to February 2018 and analyzed for pH, temperature, electrical conductivity, dissolved oxygen, nitrate, ammonium, and total phosphorus. These parameters were used to calculate the Groundwater Quality Index (GQI) value of the study area. The concentration maps (primary maps I) were constructed using Kriging interpolation of ArcGIS software from the seven groundwater quality parameters. The primary maps I were standardized with the KEBS and WHO standards to the primary maps II for ease of integration into a GIS environment. The primary maps II were then rated and weighted using a polynomial function to generate rank maps before calculating the GQI using spatial analyst tools of ArcGIS software. The land use map was prepared from a high-resolution Google earth satellite imagery of 2015. The mean GQI values for the different land use polygons were calculated and compared using GIS techniques. The GQI ranged from 68.38 to 70.92, indicating a high groundwater quality of mid River Njoro catchment. The major land-use types identified include settlement area, forest cover, agricultural land and mixed area. The agricultural land dominated the study area, followed by settlement area, forest cover and finally mixed area. The mean GQI value in each land use type varied minimally and this could be because of the diffuse nature of the land use types of the study area. Settlement area had low GQI, followed by agricultural land, mixed area and the forest cover had the highest mean GQI value, which corresponds to good quality of groundwater. Even though the variation is insignificant in this particular study, it somehow indicates the adverse effects of different land use on the quality of groundwater.