Biodiesel has several environmental benefits, such as biodegradability, renewability and lower soot emissions. However, biodiesel has undesirable properties such as higher viscosity and density and low calorific value compared to petroleum diesel, resulting in high Brake Specific Fuel Consumption (BSFC), reduced Brake Power (BP) and increased NO_X emissions creating an environmental concerns in biodiesel development. This study investigated the effects of synthesizing transesterification catalysts (CaO and NaOH) with Citric Acid (CA) on the quality of biodiesel and biodiesel blends produced from Black Soldier Fly Larvae (BSFL) (Hermetia Illucens). The quality of biodiesel and blends was determined based on fuel properties, engine performance and emission composition characteristics. The tests were performed on a single-cylinder, four-stroke, Compression Ignition (CI) diesel engine at five loads at a constant speed of 1500 rpm. The results showed that synthesizing the catalysts with CA significantly affected the fatty acid profile of the biodiesel compared to physical fuel properties. B100 (pure BSFL biodiesel) exhibited higher BSFC by 10.57–13.97 % and lower BP by 4.21–7.83 % than diesel fuel. However, the Brake Thermal Efficiency (BTE) of biodiesel was higher than that of diesel fuel by 0.82–4.34 % at maximum load. Synthesizing catalysts with CA improved the viscosity of biodiesel by 0.93–2.81 % and effectively reduced NO_X, HC and Smoke opacity by 2.23–3.16 %, 4.95–5.83 % and 20.51–41.15 %, respectively.

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%.

Hydropower in the United Kingdom (UK) remains underexplored due to its dependence on site‐specific geographical and hydrological conditions. This study aims to assess the technical and economic feasibility of installing a small‐scale hydropower system at an existing weir on the River Colne. Hydrological assessment was conducted using a 95% dependable flow duration curve (FDC) to estimate available flow and power output, while system performance and economic viability were evaluated using RETScreen modelling and sensitivity analysis. Results indicate a maximum capacity of 76.5 kW and annual generation of 284,384 kWh, offsetting approximately 3235 tonnes of CO ₂ . Economic analysis yields a net present value (NPV) of £322,769, a benefit‐cost ratio of 4.5, an internal rate of return of 9.4% and a levelised cost of electricity (LCOE) of £0.132/kWh, with simple and equity payback periods of 15.3 and 17.2 years, respectively. The findings confirm technical and economic viability and provide a replicable framework for site‐specific hydropower assessment in the UK.