Analysis of energy supply, energy policies, and the final energy end-use consumption of the residential sector in Ethiopia.

The residential sector in Ethiopia heavily relies on biomass for cooking, using inefficient cookstoves. In order to assess energy policies and decision-making for better economic development, it is essential to have final energy consumption by end-use. However, there is a lack of readily accessible data on residential energy end-use. Our study fills this gap by using data collected from surveys of 590 urban households in Ethiopia, estimating their energy end-use consumption, and analyzing their determinants. The annual final energy consumption per household is about 7.2 MWh, where 90 % is for cooking, baking, tea/coffee boiling end-uses, and only 2.3 % for lighting. The analysis reveals that income has the strongest effect on energy consumption for Injera baking and on miscellaneous end-uses, both directly and partly indirectly as a mediating variable. The study highlights the importance of end-use consumption data to plan energy efficiency, mix technology options, and make suitable policy interventions.

Coupled adsorption-phytoremediation treatment of cellulose-reactive blue dye in a sustainable multi-step pilot-scale process.

A single-step dye removal strategy from wastewater is inadequate for concentrations above 100 mg/L. In order to address this limitation, the adsorption of high dye concentrations followed by phytoremediation is a potential approach for the treatment of dye-contaminated wastewater. This combined method utilizes physical adsorption and biological processes to remove dyes from wastewater. Herein, we investigated a pilot-scale multi-step cascaded process where batch adsorption and fixed-bed column adsorption were combined with phytoremediation to remove cellulose-reactive blue dye at 200 to 500 mg/L concentrations. The batch adsorption utilized low-cost water hyacinth root powder (WHRP) bioadsorbent having 670 m2/g surface area, whereas the fixed-bed column adsorption used sand having a surface area of 75 m2/g. The phytoremediation process utilized water hyacinth plants in a series of ponds. The effluent from one unit is fed to the next until the dye is removed to more than 98% for all concentrations considered in this study. Pilot-scale experimental data fitting to adsorption isotherms and kinetics were performed to gain insight into the pilot-scale adsorption mechanism. The fixed-bed sand column adsorption was conducted at different inlet dye concentrations, flow rates, and bed heights. The breakthrough curves were fit to the Thomas, Yoon-Nelson, and Bohart-Adams models. The effluent from the fixed-bed column was transferred to phytoremediation ponds, where complete dye removal was achieved. Overall, data collectively presented in this study demonstrated that the combined adsorption and phytoremediation approach offers a potential solution for the remediation of high dye concentration in wastewater, providing an effective and sustainable treatment option.

A systematic study of cellulose-reactive anionic dye removal using a sustainable bioadsorbent.

Cellulose-reactive anionic dyes are one of the dominant colorants used in textile finishing. Unfortunately, they also produce large quantities of wastewater that must be treated before discharge, demanding low-cost and sustainable adsorbents that can easily be implemented, especially for developing countries with thriving cotton-based textile sectors. In this study, a high specific surface area (670 m2/g) water hyacinth root powder (WHRP) bioadsorbent that is neither carbonized nor activated was prepared to remove cellulose-reactive anionic blue dye from an aqueous solution. The effect of adsorption pH (pH = 2-8), adsorbent dose (1 g/L-6 g/L), dye concentration (50 mg/L-500 mg/L), adsorbent particle size (50 µm-1000 µm), mixing speed (100 rpm -200 rpm), and adsorption temperatures (22 °C-60 °C) were systematically studied. It was found that the protonation of lignin polyphenols in WHRP at pH = 2 was responsible for the observed high (∼99%) adsorptive removal of reactive blue dye. The maximum equilibrium adsorption capacity was 128.8 mg/g when 1 g/L WHRP and 500 mg/L dye concentration were used. In addition, adsorption isotherms, kinetic models, and adsorption thermodynamics were investigated. Increasing adsorbent dose, decreasing adsorbent particle size, increasing mixing speed, and lowering temperature favored the adsorption of reactive dye to WHRP adsorbent. The batch adsorption data were best fitted with both Langmuir and Temkin models, especially at 22 °C, while the adsorption kinetic behavior was described best using pseudo-second-order kinetics. Adsorption of cellulose-reactive blue dye to WHRP was spontaneous as characterized by the negative Gibbs energy (-11 kJ/mol to -24 kJ/mol) and exothermic with negative enthalpy (-13 kJ/mol to -23 kJ/mol). The overall adsorption process was controlled by more than one mechanism since the intraparticle diffusion was not the only rate-limiting step under our experimental conditions. Taken together, the abundantly available and sustainable WHRP is an efficient adsorbent that could be scaled up for treating cellulose-reactive dye-contaminated water.