One of the viable solutions to the fossil fuel energy crisis was to seek alternative sources of environmentally friendly energy with the same or better quality such as bioethanol. It was possible to produce bioethanol from organic waste, e.g., corncob. This research aimed to obtain the lowest exhaust emission levels of CO and CO2 generated from a gasoline motor that used a mixture of bioethanol containing 96 % corncob and RON 90 fuel. This research was experimental using Anova statistical data analysis method. The results showed that the lowest average of CO emissions was 0.177 vol% using E100 fuel, and the highest average was 2.649 vol% using 100 % RON 90 fuel, displaying a significant difference. The lowest average of CO2 emissions was 6.6 vol% using E100 fuel, and the highest was 7.51 vol% using 100 % RON 90 fuel, which was insignificantly different. The mixture variation with the lowest CO and CO2 emissions was E100.

-Along with the development of the era and the technology, which are rapidly growing every time, the global communities receive both positive and negative impacts from these advancements. One of the negative effects is the issue of waste. Physically, there are three types of waste: solid, liquid, and gas. In general, organic waste is contributing the most to the amount of waste currently. One of the examples of solid waste, which comes from the agricultural process, is corncob. Corncob is often only used for animal feed or as a substitute for firewood in the absence of further treatment. These simple utilization of corncob, decrease either value of its usability or its economic value. One of the efforts to improve the usability and economic value of corncob is by processing it into bioenergy, such as bioethanol. The purpose of this study is to explore the bioethanol production process from corncob and to find out the level of purity of the ethanol, which is resulted from the same bioethanol production process. This study employed experimental as its design. The results expose that corncob can be used as the raw material for producing bioethanol which underwent several processes; pretreatment, hydrolysis for a day, fermentation for seven days, and four times of distillation process with the temperature of 52 -72,5 0 C and the pressure of 95,5 -107,3 mBar, which produce ethanol of 96%.