As the world grapples with an imminent energy crisis brought on by the depletion of nonrenewable resources, such as petroleum, the necessity for alternative and eco-friendly power sources becomes increasingly apparent. In this regard harnessing knowledge gained from natural microorganisms to produce electricity using economical substrates is a promising solution through microbial fuel cells (MFCs). Microbial fuel cells leverage microbes' catabolic abilities to break down organic matter and release electrons that are subsequently transported across an external circuit for electricity generation. This article delves into the fundamental components involved in MFC construction and explores crucial factors that impact their performance including substrate oxidation, electron transfer, and internal resistance. Additionally, it offers a comprehensive analysis of existing microbial fuel cell designs while highlighting their respective strengths and weaknesses. Finally, the article showcases cost-effective MFC models based on thorough studies conducted worldwide while illuminating potential practical applications of this renewable energy technology.

Steel slag is a by-product of steelmaking which has emerged as a potential CO₂ sequestration material due to its high reactivity and abundance. This research investigates the use of steel slag waste for the direct capture of carbon from air and its storage through mineral carbonation. Two abundant wastes, blast-furnace slag (BFS) and ladle slag (LS), were tested for their carbon sequestration potential, and the effects of operational parameters such as reaction time between CO₂ and slag waste, temperature, liquid-solid ratio, and pressure on CO₂ sequestration were determined. Quantitative and qualitative results reveal that much higher CO₂ sequestration was achieved using LS compared to BFS after exposure to CO₂ for 1 day at room temperature. By increasing the exposure time to four days, levels of CO₂ sequestration increased gradually from 2.71% to 4.19% and 23.46%-28.21% for BFS and LS respectively. Increasing the temperature from 20 ± 2 °C to 90 ± 2 °C positively influenced CO₂ sequestration in BFS, resulting in an enhancement from 3.45% to 13.21%. However, the impact on LS was insignificant, with sequestration levels rising from 27.72% to 29.90%. Moreover, better CO₂ sequestration was observed for BFS than LS when the liquid-to-solid ratio increased from 3:1 to 4:1, whereupon the sequestration potential reached approximately 15% for BFS and 30% for LS at 90 ± 2 °C. Meanwhile, higher pressure reduced the sequestration potential of slag. The results of this study suggest that there is potential for scaling up the process to industrial applications and contributing to the reduction of CO₂ emissions in the steelmaking industry.

Solar air heaters (SAHs) are renewable energy systems that utilise solar radiation to heat air, offering sustainable solutions for space heating, agricultural drying, and industrial processes. These systems are simple in design, cost-effective, and environmentally friendly, making them essential to the renewable energy landscape. However, challenges such as low thermal efficiency, dependency on climatic conditions, and significant thermal losses limit their adoption. Recent advancements in design, materials, and operational strategies have significantly improved their performance. This review explores the principles of SAHs, innovations in design, thermal storage integration, and efficiency enhancement techniques. Applications in various sectors are discussed, highlighting ongoing research to maximise efficiency while maintaining economic viability and ecological benefits.