The purpose of this paper is to evaluate the research on biodiesel manufacturing, combustion, efficiency, and emissions. This research is based on the results of about 130 scientists who published their findings between 1980 and 2008. As fossil fuels deplete, there is a pressing need to develop an alternative fuel to meet the world's energy demands. Biodiesel is one of the finest accessible options for meeting the global energy needs. More than 350 oil-bearing crops have been discovered, with some only being evaluated as possible diesel engine alternative fuels. Several oils and their mixes with diesel were used in the experiments by the scientists and researchers. Short-term engine experiments utilizing vegetable oils as fuels were extremely promising, according to the vast majority of scientists, but long-term test results revealed increased carbon buildup and lubrication oil pollution, culminating in engine failure. Vegetable oils, either chemically changed or mixed with diesel, were shown to be effective in preventing engine failure. Biodiesel has been shown to have comparable combustion properties as diesel, with shorter ignition timing, greater ignition temperature, higher ignition pressure, and higher overall heat release in blends. The power output of the engine was found to be comparable to that of diesel fuel. Furthermore, it was discovered that base catalysts and enzymes are more effective than acid catalysts and enzymes.