Biomass is considered one of the prospective alternatives to energy and environmental challenges. The use of biomass as bioenergy has gained global interest due to its environmentally benign, renewable, and abundant characteristics. Numerous conversion technologies have been developed over time to convert biomass into various energy products. This review presents a summary of the different biomass conversion technologies used for bioenergy production. These include thermochemical, biological, physical, biochemical, and hybrid system technologies. It summarizes the production of different bioenergy products such as bio-oil, biodiesel, and fuel via various conversion technologies. The competitive advantages, potential environmental impacts, and challenges of these biomass conversion technologies are discussed. The recycling of biomass can solve a lot of current energy challenges. However, conversion technologies exhibit some challenges relative to upscaling and commercialization due to their immense operational and investment expenses and high energy usage.

Zinc oxide (ZnO) has been widely studied over the last decade for its remarkable properties in optoelectronic and photovoltaic devices because of its high electron mobility and excitonic properties. It has probably the broadest range of nanostructured forms that are also easy and cheap to synthesize using a wide variety of methods. The volume of recent work on ZnO nanostructures and their devices can potentially overshadow significant developments in the field. Therefore, there is a need for a concise description of the most recent advances in the field. In this review, we focus on the effect of ZnO nanostructure morphologies on the performance of ZnO-based solar cells sensitized using methylammonium lead iodide perovskite. We present an exhaustive discussion of the synthesis routes for different morphologies of the ZnO nanostructure, ways of controlling the morphology, and the impact of morphology on the photoconversion efficiency of a given perovskite solar cell (PSC). We find that although the ZnO nanostructures are empirically similar, one-dimensional structures appear to offer the most promise to increasing photoconversion efficiency (PCE) by their proclivity to align and form vertically stacked layers. This is thought to favor electron hopping, charge mobility, and conductivity by allowing multiple charge conduction pathways and increasing the effective junction cross-sectional area. The combined effect is a net increase in PCE due to the reduced surface reflection, and improved light absorption.

This review provides detailed information on perovskite solar cell device background and monitors stepwise scientific efforts applied to improve device performance with time. The work reviews previous studies and the latest developments in the perovskite crystal structure, electronic structure, device architecture, fabrication methods, and challenges. Advantages, such as easy bandgap tunability, low charge recombination rates, and low fabrication cost, are among the topics discussed. Some of the most important elements highlighted in this review are concerns regarding commercialization and prototyping. Perovskite solar cells are generally still lab-based devices suffering from drawbacks such as device intrinsic and extrinsic instabilities and rising environmental concerns due to the use of the toxic inorganic lead (Pb) element in the perovskite (ABX₃) light-active material. Some interesting recommendations and possible future perspectives are well articulated.

The properties of untreated sugar cane bagasse (SCB) and soft wood (SW) and their respective celluloses were investigated. The celluloses indicated improved crystallinity index values and decreased concentration of lignin and hemicellulose compared to their untreated counterparts. Three degradation models, Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (OFW), and Kissinger (KGR) methods were employed to determine apparent activation energy values. Generally, the thermal degradation processes of both sugarcane bagasse and soft wood included dehydration, degradation of hemicellulose and cellulose, whereas the lignin degraded from the degradation temperature of hemicellulose to the end of the cellulose. The apparent activation energy values obtained from the OFW and KAS models vary with the degree of conversion, and showed similar trends. The activation energies obtained by KGR were relatively lower than those obtained from the KAS and OFW methods.

The viability of large-scale biodiesel production ultimately boils down to its cost of commercialisation despite other very important factors such as the negative environmental and health effects caused by the direct combustion of fossil diesel. How much each country’s economy will be influenced by the production of biodiesel will be determined by the commitment of various stakeholders to the much-needed transition from petroleum-based resources to renewable resources. Biodiesel production is largely determined by the cost of the feedstock (>70%) and this review focuses on the use of waste oil resources as biodiesel feedstock with a special focus on waste cooking oil (WCO). Generating value from waste oil provides an alternative waste management route as well as a positive environmental and economic contribution. The transesterification process for biodiesel production, its catalysis and some important technical and economic aspects are covered in this communication with a special focus on the South African framework. An overview of the current research and its implications going forward is discussed.