With a growing global population and energy demand, there is increasing concern about the world’s reliance on fossil fuels, which have a negative impact on the climate, necessitating the immediate transition to a cleaner energy resource. This effort can be initiated in the rural areas of developing countries for a sustainable, efficient and affordable energy source. This study evaluated four types of renewable energy (solar, wind, biomass, and mini-hydro energy) using the integrated Life Cycle Assessment (LCA) and Analytical Hierarchy Process (AHP) approaches to select the best renewable energy source in Tatau, Sarawak. The criteria under consideration in this study included the environment, engineering and economics. The LCA was used to assess the environmental impact of renewable energies from gate-to-grave boundaries based on 50 MJ/day of electricity generation. The AHP results showed that solar energy received the highest score of 0.299 in terms of the evaluated criteria, followed by mini-hydro, biomass and wind energy, which received scores of 0.271, 0.230 and 0.200, respectively. These findings can be used to develop a systematic procedure for determining the best form of renewable energy for rural areas. This approach could be vital for the authorities that are responsible for breaking down multi-perspective criteria for future decision making in the transition into renewable energy.

The removal of carbon dioxide (CO₂) at offshore operation requires an absorption system with an environmentally friendly solvent that can operate at elevated pressure. Potassium carbonate promoted with glycine, PCGLY, is a green solvent that has potential for offshore applications. For high solvent concentrations at elevated pressure, the by-product of CO₂ absorption consists of precipitates that increase operational difficulty. Therefore, this study was done to assess the CO₂ absorption performance of non-precipitated PCGLY with concentration 15wt%PC+3wt%GLY, which is known to have comparable solubility performance with MDEA. A packed absorption column was used to identify the CO₂ removal efficiency, mass transfer coefficient in liquid film, $k_l{a}_e,$ and overall volumetric mass transfer coefficient, $K_G{a}_v$ . A simplified rate-based model was used to determine $k_l{a}_e$ and $K_G{a}_v$ based on the experimental data with a maximum MAE value, 0.057. The results showed that liquid flow rates and liquid temperature gives significant effects on the $k_l{a}_e$ and $K_G{a}_v$ profile, whereas gas flow rate and operating pressure had little effect. The CO₂ removal efficiency of PCGLY was found to be 77%, which was only 2% lower than 1.2 kmol/m³ MDEA. $K_G{a}_v$ of PCGLY is comparable with MDEA. The absorption process using PCGLY shows potential in the CO₂ sweetening process at offshore.

CO₂ removal is important for industrial flue gas treatment, biogas enhancement, and natural gas (NG) processing applications. Chemical absorption using an amine-based solvent is a proven technology for CO₂ removal from various gases. In recent years, various promising amine solvents have been investigated, either as single or blended solutions, to enhance the CO₂ absorption process at low and high CO₂ partial pressure conditions. Low CO₂ partial pressures (1 – 47 kPa) have been utilized in numerous research works focusing on flue gas treatment and biogas enhancement applications. On the other hand, high CO₂ partial pressures were instead applied in NG processing ranging between 750 and 1600 kPa. To provide more insight into the current trends, existing research on CO₂ absorption in amine-based solvents is presented in this review focusing on absorption performance in a packed column at low and high CO₂ partial pressures. Reports on the effect of different parameters, namely CO₂ partial pressure, gas, and liquid flow rates, amine concentrations, and liquid temperature, on the removal of CO₂ in the packed column are included. Based on the review, the future direction is further highlighted in this area.

In industrial scale, removal of CO₂ by chemical absorption from raw biogas represents an imperative treatment and the cutting-edge technology towards improvement of its quality and heat value. In this work, CO₂ absorption studies were conducted in an absorption column packed with Sulzer metal gauze packing with simulated biogas absorbed using 30 wt. % of monoethanolamine (MEA) solution. Experimental works were conducted to determine the influence of different CO₂ concentrations in feed gas (30 % and 40 %) and L/G ratio (0.6 and 0.7) and subsequently assessed in terms of CO₂ absorption efficiency along the column. The results showed that 30 % CO₂ in feed gas has higher removal efficiency as compared to 40 % CO₂ with the ability to remove 94 % CO₂ during the process. In addition, the CO₂ absorption studied on the L/G ratio proved that CO₂ removal was improved at higher L/G ratio of 0.7.

In this work, CO₂ absorption from simulated biogas is investigated using different blends of a PZ + AMP solution in an absorption system at CO₂ partial pressures ranging between 20 and 110 kPa. The collected data were presented as CO₂ removal profiles along the packed column and were evaluated in terms of CO₂ removal efficiency (%) and average overall volumetric mass transfer coefficient in the gas phase ($\overline{K_G{a}_v}$). An increased PZ concentration in the AMP solution was found to significantly increase the CO₂ removal efficiency and $\overline{K_G{a}_v}$ values. It was observed that, when conducted at different CO₂ partial pressures, gas and liquid flow rates, and chemical concentrations, the $L_{amine}/G_{C{O}_2}$ ratio strongly influenced the process behaviour in the packed column. Additionally, the optimal inlet liquid temperature was observed to be 35 ± 2 °C in this study.