Feedstock is one of the key resources for the production of hydrogenation derived renewable diesel (HDRD). Used cooking oil is a waste oil generated from vegetable oil after frying and can be easily sourced from domestic, restaurant outlet and food processing industries within the Durban metropolis. The right selection of feedstock contributes to the high yield and quality of HDRD. Current works on several vegetable oil sources for potential feedstock applications are reviewed. Good quality and optimal yields of HDRD can be obtained by proper selection of potential feedstock, the right catalyst, and optimal process parameters for desirable reaction pathway etc. The literature on vegetable oil as potential feedstock is discussed. Literature regarding the selection of catalysts for hydrogenation is reviewed. Biomass-based thermal power plants fly ash (BBTPPFS) and calcium oxide sourced from eggshell are identified as viable catalysts for the HDRD process.

Growing anxieties about the continued depletion of fossil fuel reserves, improving the performance of diesel engines, and mandates to reduce greenhouse gas emissions have made the search for alternative fuels for diesel engines more imperative. Hydrogenation Derived Renewable Diesel (HDRD) is recognized as a sustainable, reliable, and cost-effective alternative to petroleum-based diesel (PBD) fuel for compression ignition (CI) engines. This may be because the physicochemical properties of HDRD are similar to that of PBD fuel. The current effort examines the performance and emission characteristics of HDRD in unmodified CI engines. Performance emissions characteristics such as power, torque, brake specific fuel consumption, thermal efficiency, nitrogen oxides, carbon monoxide, carbon dioxide, particulate matter, and exhaust gas temperature were interrogated and compared with that of PBD fuel in a CI engine. The outcome of the study shows that HDRD is better than biodiesel and a sustainable replacement for PDB fuel to achieve improved performance and reduced emissions of CI engines. Going forward, more investigations are needed to further simplify the preparation and democratize the utilization of HDRD as CI fuels for various applications.

The high cost of commercial catalysts has hampered the commercialization and cost-effective production of renewable diesel in recent times. This research investigates the effect of silica (SiO2) reinforcement on bio-based thermal power plant fly ash (BBTPPFS) for hydrogenation. The BBTPPFS and the SIO2 were pulverized, calcinated, and subjected to various characterization processes. The value of micropore volume, surface area, and external surface area of sample due to the reinforcement by SiO2. These results show that the addition of SiO2 to BBTPPFS improved the potential of the BBTPPFS as a heterogeneous catalyst for hydrogenation.

The search for clean energy for transportation fuel across the globe has grown in intensity. The use of biodiesel as a fuel for compression ignition (CI) engines has shown some deficiencies, e.g., poor storage, and poor pour point. The carbon chain of biodiesel is one of the factors to be considered; the longer carbon chain length leads to decreased ignition delay, which leads to the formation of OH during the premixed combustion phase. The major challenges that render biodiesel inefficient are discussed, like higher viscosity, lower energy content, higher nitrogen oxide (NOX) emissions, lower engine speed and power, injector coking, engine compatibility, high cost, and higher engine wear. The novelty of this work is that it shows that biodiesel conversion to green diesel is possible using a biowaste heterogeneous catalyst to obtain quality and high yield of HDRD with lower cost. This renewable energy (HDRD) possesses properties that are directly compatible with CI engines and transportation engines. This research reviewed biodiesel and UCO as feedstocks for the production of HDRD, including the cost–benefit of these feedstocks. Hydrogenation of biodiesel has the potential to overcome the drawbacks of conventional chemically catalyzed processes.